Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3687_Библиотеки_им_академика_М_И_Перельмана
.pdf
92 Chapter 9/Pathophysiology of Chronic Venous Insuffi ciency
https://t.me/med1917
investigators trying to seek a causal relationship between
hypoxia, stagnant blood fl ow, and the development of CVI.
The fi rst investigator to address the question of hypoxia
and CVI scientifi cally was Alfred Blalock.31 He obtained
venous samples from the femoral, greater saphenous, and
varicose veins in 10 patients with CVI isolated to one limb
and compared their oxygen content to samples taken from
corresponding veins in the opposite limb. Seven of the
patients had active ulcers at the time. All samples were collected in the recumbent and standing positions. He reported
that in patients with unilateral CVI the oxygen content was
higher in the femoral vein of the affected limb. He speculated that this observation may be refl ective of increased
venous fl ow rather than stagnation.
Arteriovenous Fistula Theory
The concept of increased venous fl ow in the dermal
venous plexus was expanded upon by Pratt who reported
that increased venous fl ow in patients with CVI could be
clinically observed.32 He attributed the development of
venous ulceration to the presence of arteriovenous connections and coined the term arterial varices. He reported that
in a series of 272 patients with varicose veins who underwent vein ligation, 24% had arteriovenous connections. Of
the 61 patients who developed recurrences, 50% occurred in
patients with arteriovenous communications identifi ed clinically by the presence of arterial pulsations in venous conduits. Pratt hypothesized that increased venous fl ow shunted
nutrient and oxygen rich blood away from the dermal plexus
leading to areas of ischemia and hypoxia and resulting in
venous ulceration. Pratt’s clinical observations however,
have never been confi rmed with objective scientifi c evidence. Experiments with radioactively labeled microspheres
have never demonstrated shunting and have therefore cast
serious doubts on the validity of this theory.
ment in the number of capillaries with experimentally
induced hypertension.34 This important investigation was
one of the fi rst studies to demonstrate a direct effect of
venous hypertension on the venous microcirculation. In a
later study, Browse and Burnand noted that the enlarged
capillaries observed on histologic examination exhibited
pericapillary fi brin deposition and coined the term fi brin
cuff.35 They speculated that venous hypertension led to wid-
ening of endothelial gap junctions with subsequent extravasation of fi brinogen leading to the development of fi brin
cuffs. These authors theorized that the cuffs acted as a barrier
to oxygen diffusion and nutrient blood fl ow, resulting in
epidermal cell death. Although pericapillary cuffs do exist,
it has never been demonstrated that they act as a barrier to
nutrient fl ow or oxygen diffusion.
LEUKOCYTE ACTIVATION
Dissatisfaction with the fi brin cuff theory and subsequent
observations of decreased circulating leukocytes in blood
samples obtained from the greater saphenous veins in
patients with CVI led Coleridge Smith and colleagues to
propose the leukocyte trapping theory.36 This theory proposes that circulating neutrophils are trapped in the venous
microcirculation secondary to venous hypertension. The
subsequent sluggish capillary blood fl ow leads to hypoxia
and neutrophil activation. Neutrophil activation leads to
degranulation of toxic metabolites with subsequent endothelial cell damage. The ensuing heterogenous capillary perfusion causes alterations in skin blood fl ow and eventual skin
damage. The problem with the leukocyte trapping theory is
that neutrophils have never been directly observed to obstruct
capillary fl ow, therefore casting doubt on its validity.
However, there is signifi cant evidence that leukocyte activation plays a major role in the pathophysiology of CVI.
Hypoxia and alterations in nutrient blood fl ow again were
proposed as the underlying etiology of CVI in 1982 by
Burnand et al.33 These authors performed a study in which
skin biopsies were obtained from 109 limbs of patients with
CVI and 30 limbs from patients without CVI. Foot vein
pressures were measured in the CVI patients at rest and after
5, 10, 15, and 20 heel raises. Vein pressure measurements
were then correlated with the number of capillaries observed
on histologic section. The authors reported that venous
hypertension was associated with increased numbers of capillaries in the dermis of patients with CVI. Whether the
histologic sections represented true increases in capillary
quantity or an elongation and distension of existing capillaries was not answered by this study. However, in a canine
hind limb model, the authors were able to induce enlarge-
Diffusion Block Theory
ROLE OF LEUKOCYTE ACTIVATION
AND FUNCTIONAL STATUS IN CVI
In 1988, Thomas et al. reported that 24% fewer white
cells left the venous circulation after a period of recumbency
in patients with CVI as compared to normal patients.37 They
studied three groups of 10 patients each. Group 1 consisted
of patients with no signs of venous disease. Group 2 were
patients with uncomplicated primary varicose veins, and
group 3 were patients with long-standing CVI as determined
by Doppler ultrasonography, strain-gauge plethysmography,
and foot volumetry. Patients had the greater saphenous vein
cannulated just above the medial malleolus. Venous samples
were obtained at various time points with patients in the
sitting and supine position. Samples were then placed in an
automated cell counter and the number of leukocytes and
Role of Leukocyte Activation and Functional Status in CVI 93
https://t.me/med1917
erythrocytes determined. The ratio of white cells to red cells
at the various time points, were then compared. The authors
reported that with leg dependency, packed cell volume signifi cantly increased in patients with CVI as compared to
normal controls whereas patients with primary varicose
veins showed no difference from controls. They also noted
that the relative number of white cells were signifi cantly
decreased compared to control and primary varicose vein
patients (28% vs 5%, p < 0.01). The authors concluded that
the decrease in white cell number was due to leukocyte trapping in the venous microcirculation secondary to venous
hypertension. They further speculated that while trapped,
leukocytes may be activated and release toxic metabolites
causing damage to the microcirculation and the overlying
skin. These important observations were the fi rst to implicate abnormal leukocyte activity in the pathophysiology of
CVI.
The importance of leukocytes in the development of
dermal skin alterations was empahsized by Scott et al.38
These authors obtained punch biopsies from patients with
primary varicose veins, lipodermatosclerosis, and patients
with lipodermatosclerosis and healed ulcers, and determined
median number of white blood cells (WBCs) per high power
fi eld (40× magnifi cation) in each group. No patients with
active ulcers were included and no attempt to identify the
type of leukocytes was made. The authors reported that in
patients with primary varicose veins, lipodermatosclerosis,
and healed ulceration there was a median of 6, 45, and 217
WBCs per mm2, respectively. This study demonstrated that
with clinical disease progression and increasing severity of
CVI, there was a progressive increase in the number of
leukocytes in the dermis of CVI patients.
The types of leukocytes involved in dermal venous stasis
skin changes are controversial. In a study performed by
Wilkerson et al., skin biopsies were obtained from 23
patients who required surgical ligation, stripping, and/or
avulsion for their varicose veins.39 The condition of the skin
was recorded as liposclerotic, eczematous, or normal. Lipodermatosclerosis was defi ned clinically as palpable induration of the skin and subcutaneous tissues and eczema as
visible erythema with scaling of the skin. Using immunohistochemical techniques, the authors stained for leukocytespecifi c cell surface markers and reported that macrophages
and lymphocytes were the predominant leukocytes observed
in this patient population. Neutrophils and B-lymphocytes
rarely were observed. T-lymphocytes and macrophages
were predominantly observed perivascularly and in the epidermis. However, Pappas et al. performed a quantitative
morphometric assessment of the dermal microcirculation
using electron microscopy and reported that macrophages
and mast cells were the predominant cells observed in
patients with CVI dermal skin changes.
40
Furthermore, lymphocytes were never observed. This discrepancy may refl ect
the types of patients that were studied. Wilkerson et al.
biopsied patients with erythematous and eczematous skin
changes, whereas Pappas predominantly evaluated older
patients with dermal fi brosis. Patients with eczematous skin
changes may have an autoimmune component to their CVI,
whereas patients with dermal fi brosis may refl ect changes
consistent with chronic infl ammation and altered tissue
remodeling.
Given the predominant role of leukocytes in CVI pathology, there has been great interest in the activation state and
functional status of leukocytes in CVI patients. Pappas et al.
explored the hypothesis that circulating leukocytes in CVI
patients were in an altered state of activation and therefore
may be involved in leukocyte-mediated injury. They measured the expression of cell surface activation markers of
41
circulating leukocytes using fl uorescence fl ow cytometry.
Relative to normal individuals, patients with chronic venous
stasis ulcers had a decreased expression of the CD3+/DR+
and CD3+/CD38+ markers on T-lymphocytes and an
increased expression of CD14+/CD38+ markers on monocytes. Circulating neutrophils demonstrated no evidence of
activation.
Although Pappas et al. identifi ed a population of circulating cells demonstrating altered activation markers their
results did not test the functional status of these cells. In a
follow-up study, Pappas et al. tested the hypothesis that
circulating mononuclear cells in CVI patients were dysfunctional by challenging monocytes with test mitogens.42 Lymphocyte and monocyte cell function was measured as the
degree of proliferation in response to a mitogenic challenge.
Fifty patients were separated into four groups: Group 1, 14
patients with normal limbs; Group 2, 10 patients with class
II CVI (stasis dermatitis only); Group 3, 15 patients with
active venous ulcers; Group 4, 11 patients with healed
venous ulcers and current evidence of lipodermatosclerosis.
Systemically circulating lymphocytes and monocytes were
obtained by antecubital venipuncture from Groups 1–4.
Cells were cultured in the presence of staphylococcal enterotoxins (SEs) A, B, C1, D and E (mitogens) and PHA,
a control mitogen (Phytohemagglutinin). Proliferative
responses to PHA indicated that lymphocytes and monocytes from CVI patients were not globally depressed.
However, patients in Group 2 did not exhibit the same
degree of proliferation to PHA as did Groups 1, 3, and 4.
Differences in proliferative responses between Goup 2 and
1 (44.38 ± 43.9 versus 118.87 ± 27.1, p < 0.05) and Groups
2 and 3 (44.38 ± 43.9 versus 105.95 ± 60.99, p < 0.05) were
signifi cant. Challenges with staphylococcal enterotoxin A
and B revealed signifi cant diminution of proliferative
responses in Groups 2 (42.73 ± 11.55, p < 0.05) and 3 (45.57
± 9.1, p < 0.05) and Groups 3 (36.81 ± 6.9, p < 0.05) and 4
(35.04 ± 7.5, p < 0.05), compared to SEA controls (68.68 ±
9.9) and SEB controls (66.25 ± 13.56), respectively. A trend
toward diminished cellular function with progression of CVI
was observed with staphylococcal enterotoxins B, C
, D, and
1
94 Chapter 9/Pathophysiology of Chronic Venous Insuffi ciency
https://t.me/med1917
E, strongly suggesting biologic signifi cance. Furthermore,
patients with LDS and a history of healed ulcers uniformly
exhibited the poorest proliferative responses. This study
indicated that deterioration of mononuclear cell function
was associated with CVI and suggested that lymphocyte and
monocyte function diminished with clinical disease progression. The authors speculated that the decreased capacity for
mononuclear cell proliferation in response to various challenges may manifest itself clinically as poor and prolonged
wound healing.
THE VENOUS MICROCIRCULATION
Numerous investigations have attempted to evaluate the
microcirculation of patients with CVI.
these investigations were qualitative descriptions of vascular
abnormalities, which lacked uniformity of biopsy sites and
patient stratifi cation. Prior to 1997 it was widely accepted
that endothelial cells from the dermal microcirculation
appeared abnormal, contained Weibel-Palade bodies, were
edematous, and demonstrated widened interendothelial gap
junctions.45 Based on these descriptive observations it was
assumed that the dermal microcirculation of CVI patients
have functional derangements related to permeability and
ulcer formation. It was not until 1997 that a quantitative
morphometric analysis of the dermal microcirculation was
reported.40 The objectives of this investigation were to quantify differences in endothelial cell structure and local cell
type with emphasis on leukocyte cell type and their relationship to arterioles, capillaries, and post-capillary venules
(PCVs). Variables assessed were number and types of leukocytes, endothelial cell thickness, endothelial vesicle
density, interendothelial junctional width, cuff thickness,
and ribosome density. Thirty-fi ve patients had two fourmillimeter punch biopsies obtained from the lower calf
(gaiter region) and lower thigh. Patients were separated
into one of four groups according to the 1995 ISCVS/SVS
(International Society for Cardiovascular Surgery/Society
for Vascular Surgery) CEAP classifi cation.
sisted of fi ve patients with no evidence of venous disease.
Skin biopsies from these patients served as normal controls.
Groups 2 through 4 consisted of patients with CEAP Class
4 (n = 11), Class 5 (n = 9), and Class 6 (n = 10) CVI.
40,43–46
The majority of
5
Group 1 con-
ENDOTHELIAL CELL
CHARACTERISTICS
No signifi cant differences were observed in endothelial
cell thickness of arterioles, capillaries, and PCVs from either
gaiter or thigh biopsies.
appeared metabolically active. Many nuclei exhibited a
euchromatic appearance, implying active mRNA transcrip-
40
Qualitatively, endothelial cells
tion. In most instances ribosome numbers were so abundant
that they exceeded the resolution capacity of the image
analysis system and were unable to be quantifi ed. The prominence in ribosome content and the euchromatic appearance
of the endothelial cell nucleus strongly suggested active
protein production. No signifi cant differences in vesicle
density were observed in gaiter biopsies between groups.
Class 6 patients exhibited an increased number of vesicles
in arterioles and PCV endothelia from thigh biopsies but did
not differ compared to gaiter biopsies. Mean interendothelial
junctional width varied within a normal range of 20–50 nm.
Signifi cantly widened interendothelial gap junctions were
not observed and thus confl icted with the reports of Wenner
et al.45 Mean basal lamina thickness differed signifi cantly at
the capillary level in both gaiter and thigh biopsies. Differences were most pronounced in patients with Class 4 disease.
These data indicated that endothelial cells from the dermal
microcirculation of CVI patients were far from normal.
They demonstrated increased metabolic activity suggestive
of active cellular transcription and protein production. Most
surprising was the observation of uniformly tight gap junctions. Previously these gap junctions were reported to be as
wide as 180 nanometers and it was assumed that these
widened junctions were responsible for macromolecule
extravasation and edema formation.
33,45
Pappas et al. suggested that alternate methods for tissue edema like increased
transendothelial vesicle transport, formation of transendothelial channels, and alterations in the glycocalyx lining the
junctional cleft may be involved in CVI edema and macromolecule transport.
40
TYPES AND DISTRIBUTION
OF LEUKOCYTES
The most striking differences in cell type and distribution
were observed with mast cells and macrophages (see Figure
9.3). In both gaiter and thigh biopsies, mast cell numbers
were two to four times greater than control in Class 4 and 5
patients around arterioles and PCVs (p < 0.05). Class 6
patients demonstrated no difference in mast cell number
compared to controls. Mast cell numbers around capillaries
did not differ across groups in either gaiter or thigh biopsies.
Macrophages demonstrated increased numbers in Class 5
and 6 patients around arterioles and PCVs, respectively
(p < 0.05). Differences in macrophage numbers around capillaries were observed primarily in Class 4 patients in both
gaiter and thigh biopsies. Surprisingly, lymphocytes, plasma
cells, and neutrophils were not present in the immediate
perivascular space. Fibroblasts were the most common cells
observed in both gaiter and thigh biopsies. It was speculated
that mast cells and macrophages may function to regulate
tissue remodeling resulting in dermal fi brosis.
cell enzyme chymase is a potent activator of matrix metal-
40
The mast
Extracellular Matrix (ECM) Alterations 95
https://t.me/med1917
Migrating
Pericapillary
Cuff
Fibroblast
Postcapillary
Venule
FIGURE 9.4 Electron micrograph (Mag 4300×) of a well-developed
perivascular cuff in close proximity to a fi broblast in a patient with CEAP
class 6 chronic venous insuffi ciency. Long arrow points to macrophages
that appear to be entering a lymphatic lumen.
FIGURE 9.3 Electron micrograph (Mag 4300×) of mast cells (MC),
macrophages (MP) and fi broblast (F) surrounding a central capillary
from dermal biopsy of a patient with CEAP class 4 chronic venous
insuffi ciency.
Macrophages
Lymphatic
(ECM) proteins and forms a perivascular cuff. Adjacent to
these perivascular cuffs and throughout the dermal intersti-
33,40
loproteinase-1 and -3 (collagenase and stromelysin).
47–49
In
an in vitro model using the human mast cell line HMC-1,
these cells were reported to spontaneously adhere to fi bronectin, laminin, and collagen types I and III, all components
of the perivascular cuff (see later).49 Chymase also causes
release of latent TGF-β1 secreted by activated endothelial
cells, fi broblasts, and platelets from extracellular matrices.50
Release and activation of TGF-β1 initiate a cascade of
events in which macrophages and fi broblasts are recruited
to wound healing sites and stimulated to produce fi broblast
mitogens and connective tissue proteins, respectively.51
Mast cell degranulation leading to TGF-β1 activation and
macrophage recruitment may explain why decreased mast
cell and increased macrophage numbers were observed in
Class 6 patients. Macrophage migration, as evidenced by the
frequent appearance of cytoplasmic tails in perivascular
macrophages, further substantiates the concept of infl ammatory cytokine recruitment (see Figure 9.4).
tium is an intense and disorganized collagen deposition.
Perivascular cuffs and the accompanying collagen deposition are the sine qua non of the dermal microcirculation in
CVI patients (see Figure 9.4). The perivascular cuff originally was thought to be the result of fi brinogen extravasation
and erroneously referred to as a fi brin cuff.5 It is now known
that the cuff is a ring of ECM proteins consisting of collagen types I and III, fi bronectin, vitronectin, laminin, tenascin, and fi brin.52 The role of the cuff and its cell of origin is
not completely understood. The investigation by Pappas
et al. suggested that the endothelial cells of the dermal
microcirculation were responsible for cuff formation.40 The
cuff was once thought to be a barrier to oxygen and nutrient
diffusion; however, recent evidence suggests that cuff formation is an attempt to maintain vascular architecture in
response to increased mechanical load.
53
Although perivascular cuffs may function to preserve microcirculatory architecture, several pathologic processes may be related to cuff
formation. Immunohistochemical analyses have demonstrated transforming growth factor-β1 (TGF-β1) and ±2macroglobulin in the interstices of perivascular cuffs.54 It has
EXTRACELLULAR MATRIX
(ECM) ALTERATIONS
been suggested that these “trapped” molecules are distributed abnormally in the dermis leading to altered tissue
remodeling and fi brosis. Cuffs may also serve as a lattice
Once leukocytes have migrated to the extracellular space
they localize around capillaries and postcapillary venules.
The perivascular space is surrounded by extracellular matrix
for capillary angiogenesis explaining the capillary tortuosity
and increased capillary density observed in the dermis of
CVI patients.
96 Chapter 9/Pathophysiology of Chronic Venous Insuffi ciency
https://t.me/med1917
PATHOPHYSIOLOGY OF STASIS
DERMATITIS AND DERMAL FIBROSIS
The mechanisms modulating leukocyte activation, fi broblast function, and dermal extracellular matrix alterations
have been the focus of investigation in the 1990s. CVI is a
disease of chronic infl ammation due to a persistent and
sustained injury secondary to venous hypertension. It is hypothesized that the primary injury is extravasation of
macromolecules (i.e., fi brinogen and ±2-macroglobulin) and
red blood cells (RBCs) into the dermal interstitium.
33,34,44,45,54
RBC degradation products and interstitial protein extravasation are potent chemoattractants and presumably represent
the initial underlying chronic infl ammatory signal responsible for leukocyte recruitment. It has been assumed that
these cytochemical events are responsible for the increased
expression of ICAM-1 (intercellular adhesion molecule-1)
on endothelial cells of microcirculatory exchange vessels
39,55
observed in CVI dermal biopsies.
ICAM-1 is the
activation-dependent adhesion molecule utilized by macrophages, lymphocytes, and mast cells for diapedesis. As
stated earlier, all these cells have been observed by immunohistochemistry and electron microscopy in the interstitium
of dermal biopsies.
39,40
CYTOKINE REGULATION
AND TISSUE FIBROSIS
Leukocyte recruitment, ECM alterations, and tissue
fi brosis are characteristic of chronic infl ammatory diseases
caused by alterations in TGF-β1 gene expression and protein
production. To determine the role of TGF-β1 in CVI, dermal
biopsies from normal patients and CEAP class 4, 5, and 6
CVI patients were analyzed for TGF-β1 gene expression,
protein production, and cellular location.56 Quantitative RTPCR for TGF-β1 gene expression was performed on 24 skin
biopsies obtained from 24 patients. Patients were separated
into four groups according to the ISCVS/SVS classifi cation
for CVI: normal skin (n = 6), CEAP class 4 (n = 6), CEAP
class 5 (n = 5), and CEAP class 6 (n = 7). TGF-β
transcripts for controls, Class 4, 5, and 6 patients were 7.02
± 7.33, 43.33 ± 9.0, 16.13 ± 7.67, and 7.22 ± 0.56 × 10
moles/g total RNA, respectively. The differences in TGF-β1
gene expression in Class 4 patients was signifi cantly elevated compared to control and Class 5 and 6 patients (p <
0.05).56 An additional 38 patients had 54 biopsies from the
lower calf (LC) and lower thigh (LT) analyzed for TGF-β1
protein concentration. The amounts of active TGF-β1 in
picograms/gram (pg/gm) of tissue from LC and LT biopsies
compared to normal skin biopsies were as follows: Normal
skin (<1.0 pc/gm), Class 4 (LC, 5061 ± 1827, LT 317.3 ±
277), Class 5 (LC, 8327 ± 3690, LT 193 ± 164), and Class
6 (LC, 5392 ± 1800, LT, 117 ± 61) (see Figure 9.5). Differ-
gene
1
−14
Results: Active TGF-
Levels From CVI Dermal Skin
15000
10000
*,#
*
CON C4 LC C4 LT C5 LC C5 LT C6 LC C6 LT
#
CVI Patient Classification
tissue
1 levels in pg/gm of
5000
β
TGF-
0
* Control vs Class 4 and 6 (p
# LC vs LT biopsies within each class (p
FIGURE 9.5 Active TGF-β1 levels indicating increased levels in
class 4, 5, and 6 patients compared to controls and ipsilateral thigh biopsies.
Con-Control patients without venous disease, LT-Ipsilateral thigh, LCIpsilateral diseased skin.
Biopsies
#
≤
0.05)
β
1 Protein
#
*,
≤
#
#
0.02)
ences between normal skin and Class 4 and 6 patients were
signifi cant (p < 0.05 and p < 0.01, respectively). No differences between Class 4, 5, and 6 patients were observed.
Differences between LC and LT within each CVI group
were signifi cant (Class 4, p < 0.003, Class 5, p < 0.008, Class
6, p < 0.02). These data demonstrate that in areas of clinically active CVI, increased amounts of active TGF-β
present compared to normal skin. Furthermore, active TGF-
β1 protein concentrations of biopsies from the LT did not
differ from normal skin demonstrating a regionalized repsonse to injury.
56
Immunohistochemistry and immunogold labeling exper-
iments were performed to identify the sources of active
TGF-β1 protein production. Immunohistochemistry of
normal skin and ipsilateral thigh biopsies of CVI patients
demonstrated mild TGF-β1 in the basal layer of the epidermis. The dermis demonstrated few capillaries, ordered collagen architecture, and no interstitial leukocytes. CVI dermal
biopsies from areas of clinically active disease demonstrated
staining of the basal layer of the epidermis, interstitial leukocytes, and fi broblasts. Many perivascular leukocytes demonstrated positive staining of intracellular granules and
appeared morphologically similar to previously reported
56
mast cells (see Figures 9.3 and 9.6).
Numerous capillaries
with perivascular cuffs were observed; however, cuffs did
not stain positively for TGF-β1.56 This study confl icts with
the observations reported by Higley et al. in which they
reported positive TGF-β1 staining in perivascular cuffs and
an absence of TGF-β1 in the provisional matrix of the venous
ulcer compared to healing donor skin graft sites.54 They
concluded that TGF-β1 was therefore abnormally “trapped”
in the perivascular cuff and therefore unavailable for normal
LC=Lower Calf
LT=Lower Thigh
are
1
Cytokine Regulation and Tissue Fibrosis 97
https://t.me/med1917
an alteration in the storage and release of growth factors.
The latent form of TGF-β1 is secreted from cells bound to
one of three latent TGF-β1 binding proteins (LTBP). Once
secreted, LTBPs mediate binding of latent TGF-β1 to matrix
proteins. Matrix release of TGF-β1 is mediated by multiple
serine proteinases including plasmin, mast cell chymase,
and leukocyte elastase.
50,58–60
An increase in the number of
mast cells and circulating leukocyte elastase have been
reported previously in CVI patients.
40,61
The increase in
active TGF-β1 observed in Class 5 and 6 patients therefore
may result from ECM release of latent TGF-β1, resulting in
tissue fi brosis. This hypothesis is consistent with the demonstration of immunogold labeling to collagen fi brils in the
FIGURE 9.6 Immunohistochemistry (Mag 575×) of dermal skin biopsy
demonstrating transforming growth factor-β1 positive granules (long
arrow) in leukocytes surrounding a perivascular cuff and leukocytes migrating through a perivascular cuff (short arrow).
ECM of CVI patients. The modulation of TGF-β1 release
from the ECM may therefore provide a faster means of
signal transduction than simple control of gene expression,
and therefore may explain the sustained increase of TGF-β1
in Class 5 and 6 patients in the absence of increased gene
expression. This study did not demonstrate increased TGF-
β1 staining in the ECM by ICC because the primary antibody
granulation tissue development. Differences between the
two studies may relate to biopsy site selection. Higley et al.
biopsied chronic, nonhealing venous ulcer edges and ulcer
bases, whereas patients with active ulcers in the study by
Pappas et al. were biopsied fi ve to ten centimeters away
from an active ulcer. Therefore, the former study refl ects the
biology of chronic wound healing and our data suggest
active tissue remodeling in response to a chronic injury
stimulus.
Immunogold labeling confi rmed the presence of TGF-β1
in dermal leukocytes. Positive labeling of gold particles
similarly were observed in collagen fi brils of the ECM. This
observation may explain why the molecular regulation of
TGF-β1 in CVI patients demonstrates differential gene and
protein production according to disease classifi cation. As
stated earlier, the gene expression of TGF-β1 was increased
in Class 4 patients only, and the protein production essentially was increased in Class 4, 5, and 6 patients. These
differences may be related to disease severity and the pluripotential responses of TGF-β
. TGF-β1 can have inhibitory
1
and stimulatory effects that are primarily dependent on local
concentration, cell source, and surrounding ECM. In the
study by Pappas et al., Class 4 patients were younger than
the other study groups, never experienced an episode of
venous stasis ulceration, and clinically demonstrated less
dermal tissue fi brosis. TGF-β1 in these patients therefore
may be involved in limiting the response to injury. Indeed,
one could speculate that early on in the disease process, a
low-grade production of TGF-β1 is a normal wound-healing
response and may serve to prevent the onset and development of tissue fi brosis. With continued and prolonged exposure, an imbalance in tissue remodeling in patients with
Class 5 and 6 disease clinically manifests itself as dermatofi brosis. A pathologic effect of increased ECM deposition is
used was specifi c only for active TGF-β1 and therefore may
have missed LAP and LTBP associated TGF-β1.
The distribution and location of several other growth
factors in the skin of CVI patients have also been investigated. Peschen et al. reported on the role of platelet-derived
growth factor receptor alpha and beta (PDGFR-± and -β)
and vascular endothelial growth factor (VEGF).62 Skin biopsies from 30 patients were separated into fi ve groups: Group
1, patients with reticular veins; Group 2, venous eczema;
Group 3, skin pigmentation; Group 4, lipodermatosclerosis;
and Group 5, patients with active leg ulcers; with a total of
six patients in each group. Biopsies were studied with immunohistochemistry and the degree of immunoreactivity
assessed with a scoring system by two blinded reviewers.
Peschen et al. reported that PDGFR-± and -β and VEGF
expression was strongly increased in the stroma of CVI
patients with eczema and active ulcers compared to patients
with reticular veins and pigmentation changes only.62 To a
lesser degree, patients with lipodermatosclerosis demonstrated immunoreactivity to PDGFR-± and -β and VEGF as
well. PDGFR-± and -β expression was elevated considerably in the capillaries and surrounding fi broblasts and
infl ammatory cells of venous eczema patients. In addition,
immunoreactivity was increased in dermal fi broblasts,
smooth muscle cells, and vascular cells of lipodermatosclerosis patients compared to patients with reticular veins only.
The greatest expression of PDGFR-± and -β was observed
in mesenchymal cells and vascular endothelial cells of
patients with active venous ulcers. VEGF immunoreactivity
correlated with disease severity. VEGF positive capillary
endothelial cells and pericapillary cells increased in patients
with venous eczema, lipodermatosclerosis, and active venous ulceration, respectively. In a subsequent investigation,
these authors reported that with progression of CVI dermal
57
98 Chapter 9/Pathophysiology of Chronic Venous Insuffi ciency
https://t.me/med1917
pathology the endothelial cell adhesion molecules intercelluar and vascular adhesion molecules (ICAM-1, VCAM-
1) and their corresponding leukocyte ligands LFA-1 and
VLA-4 were upregulated on leukocytes and endothelial
cells.55 Based on these observations, the authors speculated
that leukocyte recruitment, capillary proliferation, and interstitial edema in CVI patients may be regulated through
PDGF and VEGF by upregulation of adhesion molecules
leading to leukocyte recruitment, diapedesis, and release of
chemical mediators.
55
In summary, these investigations indicate that progression
of CVI dermal pathology is mediated by a cascade of infl ammatory events. Venous hypertension causes extravasation of
macromolecules like fi brinogen and red blood cells that act
as potent infl ammatory mediators. These mediators cause an
upregulation of adhesion molecules and the expression of
growth factors like PDGF and VEGF, which result in leukocyte recruitment. Monocytes and mast cells travel to the site
of injury, which activate or release TGF-β1 and probably
other undiscovered chemicals as well. What effect growth
factor binding has on fi broblast and endothelial cell function
has been the focus of numerous investigations in the 1990s.
DERMAL FIBROBLAST FUNCTION
Several studies have reported aberrant phenotypic behavior of fi broblasts isolated from venous ulcer edges when
compared to fi broblasts obtained from ipsilateral thigh biopsies of normal skin in the same patients. Hasan et al. compared the ability of venous ulcer fi broblasts to produce ±I
procollagen mRNA and collagen after stimulation with
TGF-β1.63 These authors were not able to demonstrate differences in ±I procollagen mRNA levels after stimulation
with TGF-β1 between venous ulcer fi broblasts and normal
fi broblasts (control) from ipsilateral thigh biopsies. However,
collagen production was increased by 60% in a dosedependent manner in controls whereas venous ulcer fi broblasts were unresponsive. This unresponsiveness was
associated with a four-fold decrease in TGF-β
tors. In a follow-up report, Kim et al. indicated that the
decrease in TGF-β1 type II receptors was associated with a
decrease in phosphorylation of the TGF-β1 receptor substrates SMAD 2 and 3 as well as p42/44 mitogen activated
protein kinases.64 A similar investigation reported a decrease
in collagen production from venous ulcer fi broblasts and
similar amounts of fi bronectin production when compared
to normal controls.
65
Fibroblast responsiveness to growth factors was further
delineated by Stanley et al.66 These investigators characterized the proliferative responses of venous ulcer fi broblasts
when stimulated with basic fi broblastic growth factor
(bFGF), epidermal growth factor (EGF), and interleukin 1-β
(IL-1β). In their initial study, they reported that venous ulcer
type II recep-
1
fi broblast growth rates were markedly suppressed when
stimulated with bFGF, EGF, and IL-1β. In a follow-up
investigation these authors noted that the previously observed
growth inhibition could be reversed with bFGF.67 Lal et al.
reported that the proliferative responses of CVI fi broblasts
to TGF-β1 correlated with disease severity.68 Fibroblasts
from patients with CEAP Class 2 and 3 disease retain their
agonist-induced proliferative capacity. Class 4 and 5 fi broblasts demonstrated diminished agonist-induced proliferation, whereas Class 6 (venous ulcer fi broblasts) did not
proliferate after TGF-β1 stimulation, confi rming the observations made by the previous investigators. Phenotypically,
venous ulcer fi broblasts appeared large and polygonal with
varied nuclear morphologic features, whereas normal fi broblasts appeared compact and tapered with well-defi ned
nuclear morphologic features. Venous ulcer fi broblasts
appeared morphologically similar to fi broblasts undergoing
cellular senescence. Therefore, the blunted growth response
of CVI venous ulcer fi broblasts appears related to development of cellular senescence.
66,69
Other characteristics of senescent cells are an overexpres-
sion of matrix proteins such as fi bronectin (cFN) and
enhanced activity of β-galactosidase (SA-β-Gal). In an evaluation of seven patients with venous stasis ulcers, it was
noted that a higher percentage of SA-β-Gal positive cells in
venous ulcers compared to normal controls (6.3% vs 0.21%,
p < 0.0.6).67 It was also reported that venous ulcer fi broblasts
produced one to four times more cFN by Western blot analysis compared to controls.69 These data support the hypothesis that venous ulcer fi broblasts phenotypically behave like
senescent cells. However, senescence is probably the end
manifestation of a wide spectrum of events that leads to
proliferative resistance and cellular dysfunction. Telomeres
and telomerase activity are the sine qua non of truly senescent cells. To date, there are no reported studies indicating
an abnormality in CVI fi broblast telomere or telomerase
activity. Absent these investigations, the true role of senescence in CVI remains ill-defi ned.
ROLE OF MATRIX
METALLOPROTEINASES (MMPS)
AND THEIR INHIBITORS IN CVI
The signaling event responsible for the development of
a venous ulcer and the mechanisms responsible for prolonged wound healing are poorly understood. Wound healing
is an orderly process that involves infl ammation, re-epithelialization, matrix deposition, and tissue remodeling. Tissue
remodeling and matrix deposition are processes controlled
by matrix metalloproteinases (MMPs) and tissue inhibitors
of matrix metalloproteinases (TIMPs). In general, MMPs
and TIMPs are not constitutively expressed. They are
induced temporarily in response to exogenous signals such
Conclusion 99
https://t.me/med1917
as various proteases, cytokines or growth factors, cell-matrix
interactions, and altered cell-cell contacts. TGF-β1 is a potent
inducer of TIMP-1 and collagen production and inhibitor of
MMP-1 through regulation of gene expression and protein
synthesis. Several studies have demonstrated that prolonged
and continuous TGF-β1 production causes tissue fi brosis by
stimulating ECM production and inhibiting degradation by
affecting MMP and TIMP production. Alterations in MMP
and TIMP production may similarly modulate the tissue
fi brosis of the lower extremity in CVI patients. Several
investigators have reported that the gelatinases MMP-2 and
-9 as well as TIMP-1 are increased in the exudates of patients
with venous ulcers compared to acute wounds.
70–72
However,
analyses of biopsy specimens have demonstrated variable
results. Herouy et al. reported that MMP-1, and -2 and
TIMP-1 are increased in patients with lipodermatosclerosis
compared to normal skin.73 In a subsequent investigation,
biopsies from venous ulcer patients were found to have
increased levels of the active form of MMP-2 compared to
normal skin74 as well as increased immunoreactivity to
EMMPRIN (Extracelluar inducer of MMP), MT1-MMP
(Membrane Type 1), and MT2-MMP in the dermis and
perivascular regions of venous ulcers.75 Saito et al. were
unable to identify differences in overall MMP-1, -2, and -9
and TIMP-1 protein levels or activity in CVI patients with
CEAP Class 2 through 6 disease compared to normal controls or CVI groups.76 However, within a clinical class,
MMP-2 levels were elevated compared to MMP-1, and -9
and TIMP-1 in patients with Class 4 and Class 5 disease.
These data indicate that active tissue remodeling is occurring in patients with CVI. Which matrix metalloproteinases
are involved and how they’re activated and regulated are
currently unclear. It appears that MMP-2 may be activated
by urokinase plasminogen activator (uPA). Herouy et al.
observed increased uPA and uPAR mRNA and protein
levels in patients with venous ulcers compared to normal
skin.77 The elevated levels of active TGF-β1 in the dermis of
CVI patients suggests a regulatory role for TGF-β1 in MMP
and TIMP synthesis and activity. However, there is currently
no direct evidence indicating such a relationship.
CONCLUSION
The mechanisms regulating varicose vein development
and the subsequent dermal skin sequelae caused by chronic
ambulatory venous hypertension only recently have been
investigated. It is clear that varicose vein formation has a
genetic component that is linked to environmental stimuli.
Susceptible patients develop vein wall fi brosis and loss of
valvular competence that leads to venous hypertension. The
transmission of high venous pressures to the dermal microcirculation causes extravasation of macromolecules and red
blood cells that serve as the underlying stimulus for infl am-
matory injury. Activation of the microcirculation results in
cytokine and growth factor release leading to leukocyte
migration into the interstitium. At the site of injury, a host
of infl ammatory events is set into action. TGF-β
appears to
1
be a primary regulator of CVI induced injury. TGF-β1 secretion from leukocytes with subsequent binding to dermal
fi broblasts is associated with intense dermal fi brosis and
tissue remodeling. In addition, decreased TGF-β1 type II
receptors on venous ulcer fi broblasts are associated with
diminished fi broblast proliferation. Fibroblast proliferation
diminishes with disease progression ultimately leading to
senescence and poor ulcer healing. In addition, increases in
MMP-2 synthesis appear to increase tissue remodeling and
further impede ulcer healing. As our understanding of the
underlying cellular and molecular mechanisms that regulate
CVI and ulcer formation increase, therapeutic interventions
for treatment and prevention will ultimately follow.
References
1. White GH. Chronic Venous Insuffi ciency. In: Veith F, Hobson RW II,
Williams RA, Wilson SE, eds. Vascular Surgery. New York: McGrawHill Inc. 1993. 865–888.
2. Callam MJ. Epidemiology of varicose veins, Br J Surg. 1994. 81:
167–173.
3. Hume M. Presidential address: A venous renaissance? J Vasc Surg.
1992. 6: 947–951.
4. Lawrence PF, Gazak CE. Epidemiology of chronic venous insuffi ciency. In: Gloviczki P, Bergan JJ, eds. Atlas of endoscopic perforator
vein surgery. London: Springer-Verlag. 1998. 31–44.
5. Porter JM. International Consensus Committee on Chronic Venous
Disease. Reporting Standards in venous disease: An update, J Vasc
Surg. 1995. 21: 635–645.
6. Varicose veins: Pathology. In: Browse NL, Burnand KG, Irvine AT,
Wilson NM, eds. Diseases of the veins. London and New York: Oxford
University Press, Inc. 1999. 145–162.
7. Gunderson J, Hauge M. Hereditary factors in venous insuffi ciency,
Angiology. 1969. 20(6): 346–355.
8. Cornu-Thenard A, Boivin P, Baud MM, De Vincenzi I, Carpentier PH.
Importance of the familial factor in varicose disease: Clinical study of
134 families, J Derm Surg Onc. 1994. 20: 318–326.
9. Labropoulos N, Giannoukas AD, Delis K, Mansour MA, Kang SS,
Nicolaides AN et al. Where does the venous refl ux start? J Vasc Surg.
1997. 26: 736–742.
10. Wakefi eld TM, Strietert RM, Prince MR, Downing LJ, Greenfi eld LJ.
Pathogenesis of venous thrombosis: A new insight, Cardiovasc Surg.
1997. 5(1): 6–15.
11. Takase S, Bergan JJ, Schmid-Schönbein G. Expression of adhesion
molecules and cytokines on saphenous veins in chronic venous insuffi ciency, Ann Vasc Surg. 2000. 14: 427–435.
12. Rose A. Some new thoughts on the etiology of varicose veins, J Cardiovasc Surg. 1986. 27: 534–543.
13. Pappas PJ, Gwertzman GA, DeFouw DO, Padberg FT, Jr., Silva MB,
Jr., Duran WN et al. Retinoblastoma protein: A molecular regulator of
chronic venous insuffi ciency, J Surg Res. 1998. 76: 149–153.
14. Travers JP, Brookes CE, Evans J, Baker DM, Kent C, Makin GS et al.
Assessment of was structure and composition of varicose veins with
reference to collagen, elastin and smooth muscle content, Eur J Vasc
Endovasc Surg. 1996. 11: 230–237.
100 Chapter 9/Pathophysiology of Chronic Venous Insuffi ciency
https://t.me/med1917
15. Jurukova Z, Milenkov C. Ultrastructural evidence for collagen degradation in the walls of varicose veins, Exp and Molec Path. 1982. 37:
37–47.
16. Venturi M, Bonavina L, Annoni F, Colombo L, Butera C, Peracchia
A et al. Biochemical assay of collagen and elastin in the normal and
varicose vein wall, J Surg Res. 1996. 60: 245–248.
17. Maurel E, Azema C, Deloly J, Bouissou H. Collagen of the normal and
the varicose human saphenous vein: A biochemical study, Clinica
Chimica Acta. 1990. 193: 27–38.
18. Ascher E, Jacob T, Hingorani A, Gunduz Y, Mazzariol F, Kallakuri
S. Programmed cell death (apoptosis) and its role in the pathogenesis
of lower extremity varicose veins, Ann Vasc Surg. 2000. 14: 24–30.
19. Ascher E, Jacob T, Hingorani A, Tsemekhin B, Gunduz Y. Expression
of molecular mediators of apoptosis and their role in the pathogenesis
of lower-extremity varicose veins, J Vasc Surg. 2001. 33: 1080–
1086.
20. Gandhi RH, Irizarry E, Nachman GB, Halpern JJ, Mulcare RJ,
Tilson MD. Analysis of the connective tissue matrix and proteolytic
activity of primary varicose veins, J Vasc Surg. 1993. 18: 814–
820.
21. Parra JR, Cambria RA, Hower CD, Dassow MS, Freischlag JA,
Seabrook GR et al. Tissue inhibitor of metalloproteinase-1 is increased
in the saphenofemoral junction of patients with varices in the leg,
J Vasc Surg. 1998. 28: 669–675.
22. Kosugi I, Urayama H, Kasashima F, Ohtake H, Watanabe Y. Matrix
metalloproteinase-9 and urokinase-type plasminogen activator in varicose veins, Ann Vasc Surg. 2003. 17(3): 234–238.
23. Woodside KJ, Hu M, Burke A, Murakami M, Pounds LL, Killewich
LA et al. Morphologic characteristics of varicose veins: Possible role
of metalloproteinases, J Vasc Surg. 2003. 38: 162–169.
24. Shireman PK, McCarthy WJ, Pearce WH, Shively VP, Cipollone M,
Kwaan HC et al. Plasminogen activator levels are infl uenced by location and varicosity in greater saphenous vein, J Vasc Surg. 1996. 24(5):
719–724.
25. Badier-Commander C, Verbeuren T, Lebard C, Michel J, Jacob M.
Increased TIMP/MMP ratio in varicose veins: A possible explanation
for extracellular matrix accumulation, J Path. 2000. 192: 105–112.
26. Lowell RC, Gloviczki P, Miller VM. In vitro evaluation of endothelial
and smooth muscle function of primary varicose veins, J Vasc Surg.
1992. 16: 679–686.
27. Rizzi A, Quaglio D, Vasquez G, Mascoli F, Amadesi S, Calo G et al.
Effects of vasoactive agents in healthy and diseased human saphenous
veins, J Vasc Surg. 1998. 28: 855–861.
28. Barber DA, Wang X, Gloviczki P, Miller VM. Characterization of
endothelin receptors in human varicose veins, J Vasc Surg. 1997. 26:
61–69.
29. Nemcova S, Gloviczki P, Rud KS, Miller VM. Cyclic nucleotides and
production of prostanoids in human varicose veins, J Vasc Surg. 1999.
30: 876–884.
30. Homans J. The etiology and treatment of varicose ulcer of the leg,
SG&O. 1917. 24: 300–311.
31. Blalock A. Oxygen content of blood in patiens with varicose veins,
Arch Surg. 1929. 19: 898–905.
32. Pratt GH. Arterial varices: A syndrome, Am J Surg. 1949. 77: 456–
460.
33. Burnand KG, Whimster I, Naidoo A, Browse NL. Pericapillary fi brin
deposition in the ulcer bearing skin of the lower limb: The cause of
lipodermatosclerosis and venous ulceration, Br Med J. 1982. 285:
1071–1072.
34. Burnand KG, Clemenson G, Gaunt J, Browse NL. The effect of sustained venus hypertension in the skin and capillaries of the canine hind
limb, Br J Surg. 1981. 69: 41–44.
35. Browse NL, Burnand KG. the cause of venous ulceration, The Lancet.
1982. 2: 243–245.
36. Smith PDC, Thomas P, Scurr JH, Dormandy JA. Causes of venous
ulceration: A new hypothesis, Br Med J. 1988. 296: 1726–1727.
37. Thomas P, Nash GB, Dormandy JA. White cell accumulation in
dependent legs of patients with venous hypertension: A possible
mechanism for trophic changes in the skin, Br Med J. 1988. 296:
1693–1695.
38. Scott HJ, Smith PDC, Scurr JH. Histological study of white blood cells
and their association with lipodermatosclerosis and venous ulceration,
Br J Surg. 1991. 78: 210–211.
39. Wilkinson LS, Bunker C, Edward JCW, Scurr JH, Smith PDC.
Leukocytes: Their role in the etiopathogenesis of skin damage in
venous disease, J Vasc Surg. 1993. 17: 669–675.
40. Pappas PJ, DeFouw DO, Venezio LM, Gorti R, Padberg FT, Jr., Silva
MB, Jr. et al. Morphometric assessment of the dermal microcirculation
in patients with chronic venous insuffi ciency, J Vasc Surg. 1997. 26:
784–795.
41. Pappas PJ, Fallek SR, Garcia A, Araki CT, Back TL, Duran WN et al.
Role of leukocyte activation in patients with venous stasis ulcers, J
Surg Res. 1995. 59: 553–559.
42. Pappas PJ, Teehan EP, Fallek SR, Garcia A, Araki CT, Back TL et al.
Diminished mononuclear cell function is associated with chronic
venous insuffi ciency, J Vasc Surg. 1995. 22: 580–586.
43. Leu AJ, Leu HJ, Franzeck UK, Bollinger A. Microvascular changes in
chronic venous insuffi ciency: A review, Cardiovasc Surg. 1995. 3:
237–245.
44. Leu HJ. Morphology of chronic venous insuffi ciency-light and electron
microscopic examinations, Vasa. 1991. 20: 330–342.
45. Wenner A, Leu HJ, Spycher M, Brunner U. Ultrastructural changes of
capillaries in chronic venous insuffi ciency, Expl Cell Biol. 1980. 48:
1–14.
46. Scelsi R, Scelsi L, Cortinovis R, Poggi P. Morphological changes of
dermal blood and lymphatic vessels in chronic venous insuffi ciency of
the leg, Int Angiol. 1994. 13: 308–311.
47. Saarien J, Lalkkinen N, Welgus HG, Kovannen PT. Activation of
human interstitial procollagenase through direct cleavage of the Leu
Thr84 bond by mast cell chymase, J Biol Chem. 1994. 269: 18134–
18140.
48. Lees M, Taylor DJ, Woolley DE. Mast cell proteinases activate precursor forms of collagenase and stromelysin, but not of gelatinases A and
B, Eur J Biochem. 1994. 223: 171–177.
49. Kruger-Drasagakes S, Grutzkau A, Baghramian R, Henz BM.
Interactions of immature human mast cells with extracellular matrix:
Expression of specifi c adhesion receptors and their role in cell binding
to matrix proteins, J Invest Dermatol. 1996. 106: 538–543.
50. Taipale J, Keski-Oja J. Growth factors in the extracellular matrix,
FASEB J. 1997. 11: 51–59.
51. Roberts AB, Flanders KC, Kondaiah P, Thompson NL, Van
Obberghen-Schiling E, Wakefi eld L et al. Transforming growth
factor β: Biochemistry and roles in embryogenesis, tissue repair and
remodeling, and carcinogenesis, Recent Prog Horm Res. 1988. 44:
157–197.
52. Herrick S, Sloan P, McGurk M, Freak L, McCollum CN, Ferguson WJ.
Sequential changes in histologic pattern and extracellular matrix
deposition during the healing of chronic venous ulcers, Am J Pathol.
1992. 141: 1085–1095.
53. Bishop JE. Regulation of cardiovascular collagen deposition by
mechanical forces, Molec Med Today. 1998. 4: 69–75.
54. Higley HR, Kassander GA, Gerhardt CO, Falanga V. Extravasation of
macromolecules and possible trapping of transforming growth factorβ1 in venous ulceration, Br J Surg. 1995. 132: 79–85.
55. Peschen M, Lahaye T, Gennig B, Weyl A, Simon JC, Wolfgang V.
Expression of the adhesion molecules ICAM-1, VCAM-1, LFA-1
and VLA-4 in the skin is modulated in progressing stages of chronic
venous insuffi ciency, Acta Derm Venereol. 1999. 79: 27–32.
83
-
References 101
https://t.me/med1917
56. Pappas PJ, You R, Rameshwar P, Gorti R, DeFouw DO, Phillips CK
et al. Dermal tissue fi brosis in patients with chronic venous insuffi ciency is associated with increased transforming growth factor-β1 gene
expression and protein production, J Vasc Surg. 1999. 30: 1129–1145.
57. Taipale J, Saharinen J, Hedman K, Keski-oja J. Latent transforming
growth factor-β1 and its binding protein are components of extracellular matrix microfi birls, J Histochem Cytochem. 1996. 44: 875–889.
58. Border WA, Noble NA. Transforming growth factor β in tissue fi brosis, N Engl J Med. 1994. 331: 1286–1292.
59. O’Kane S, Ferguson WJ. Transforming growth factor βs and wound
healing, Int J Biochem Cell Biol. 1997. 29: 63–78.
60. Grande JP. Role of transforming growth factor-β in tissue injury and
repair, PSEBM. 1997. 214: 27–40.
61. Shields DA, Sarin AS, Scurr JH, Smith PDC. Plasma elastase in venous
disease, Br J Surg. 1994. 81: 1496–1499.
62. Peschen M, Grenz H, Brand-Saberi B, Bunaes M, Simon JC, Schopf
E et al. Increased expression of platelet-derived growth factor receptor
alpha and beta and vascular endothelial growth factor in the skin of
patients with chronic venous insuffi ciency, Arch Dermatol Res. 1998.
290: 291–297.
63. Hasan A, Murata H, Falabella A, Ochoa S, Zhou L, Badiavas E et al.
Dermal fi broblasts from venous ulcers are unresponsive to the action
of transforming growth factor-β1, J Dermatol Sci. 1997. 16: 59–66.
64. Kim B, Kim HT, Park SH, Cha J, Yufi t T, Kim S et al. Fibroblasts from
chronic wounds show altered TGF-β signaling and decreased TGF-β
type II receptor expression, J Cell Physiol 2003. 195: 331–336.
65. Herrick SE, Ireland GW, Simon D, McCollum CN, Ferguson MW.
Venous ulcer fi broblasts compared with normal fi broblasts show
differences in collagen but not in fi bronectin production under
both normal and hypoxic conditions, J Invest Dermatol. 1996. 106:
187–193.
66. Stanley AC, Park H, Phillips TJ, Russakovsky V, Menzoian JO.
Reduced growth of dermal fi broblasts from chronic venous ulcers can
be stimulated with growth factors, J Vasc Surg. 1997. 26: 994–1001.
67. Mendez MV, Stanley A, Park H, Shon K, Phillips TJ, Menzoian JO.
Fibroblasts cultured from venous ulcers display cellular characteristics
of senescence, J Vasc Surg. 1998. 28: 876–883.
68. Lal BK, Saito S, Pappas PJ, Padberg FT Jr., Cerveira JJ, Hobson RW
II et al. Altered proliferative responses of dermal fi broblasts to TGF-β1
may contribute to chronic venous stasis ulcers, J Vasc Surg. 2003.
37: 1285–1293.
69. Mendez MV, Stanley A, Phillips TJ, Murphy M, Menzoian JO, Park
H. Fibroblasts cultured from distal lower extremities in patients with
venous refl ux display cellular characteristics of senescence, J Vasc
Surg. 1998. 28: 1040–1050.
70. Weckroth M, Vaheri A, Lauharanta J, Sorsa T, Konttinen YT. Matrix
metalloproteinases, gelatinase and collagenase, in chronic leg ulcers, J
Invest Dermatol. 1996. 106: 1119–1124.
71. Wysocki AB, Staiano-Coico L, Grinell F. Wound fl uid from chronic
leg ulcers contains elevated levels of metalloproteinases MMP-2 and
MMP-9, J Invest Dermatol. 1993. 101: 64–68.
72. Bullen EC, Longaker MT, Updike DL, Benton R, Ladin D, Hou Z
et al. Tissue inhibitor of metalloproteinases-1 is decreased and activated gelatinases are increased in chronic wounds, J Invest Dermatol.
1995. 104: 236–240.
73. Herouy Y, May AE, Pornschlegel G, Stetter C, Grenz H, Preissner KT
et al. Lipodermatosclerosis is characterized by elevated expression and
activation of matrix metalloproteinases: Implications for venous ulcer
formation, J Invest Dermatol. 1998. 111: 822–827.
74. Herouy Y, Trefzer D, Zimpfer U, Schopf E, Vanscheidt W, Norgauer
J. Matrix metalloproteinases and venous leg ulceration, Eur J Dermatol. 2000. 9: 173–180.
75. Norgauer J, Hildenbrand T, Idzko M, Panther E, Bnademir E,
Hartmann M et al. Elevated expression of extracellular matrix
metalloproteinase inducer (CD 147) and membrane-type matrix
metalloproteinases in venous leg ulcers, Br J Dermatol. 2002. 147:
1180–1186.
76. Saito S, Trovato MJ, You R, Lal BK, Fasehun F, Padberg FT, Jr. et al.
Role of matrix metalloproteinases 1, 2, and 9 and tissue inhibitor of
matrix metalloproteinase-1 in chronic venous insuffi ciency, J Vasc
Surg. 2001. 34(5): 930–938.
77. Herouy Y, Trefzer D, Hellstern MO, Stark GB, Vanscheidt W, Schopf
E et al. Plasminogen activation in venous leg ulcers, Br J Dermatol.
2000. 143: 930–936.
Соседние файлы в папке Библиотека им академика М.И. Перельмана