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6 The Association Between Telomere Length and Sensitivity to Apoptosis of HUVEC

49

6.2.3 Measurement of Apoptosis Rates and Telomere Lengths

 

Fluorescent microscopy was used to determine apoptosis. The apoptosis

rate

of HUVEC with fluorescent stain was calculated by the amount of apoptotic HUVEC/(the amount of apoptosis HUVEC + the amount of normal HUVEC). MTL was measured by using Southern Blot.

6.2.4 Statistics Analysis

Chi-Square, random T test and Q test were performed using SAS software.

6.3 Results

6.3.1Relationship Between the Time of Culture and the Telomere Length

HUVEC that were cultured for 1 month, which represented the group with less cell division, had significantly longer telomeres (5.43 ± 0.45 kb) than the telomeres (4.57 ± 0.21 kb) in HUVEC that were cultured for 3 months, which represented group with more cell division (p <0.05) (Table 6.1, Figs. 6.1 and 6.2).

Table 6.1 Mean telomere length of human umbilical endothelial cells that were cultured for 1 or 3 months

 

Mean telomere

 

 

Groups

length (kb)

t

p

 

 

 

 

1 month

5.43 ± 0.45

3.022

0.0391

3 months

4.57 ± 0.21

 

 

6.3.2Relationship Among Apoptosis Rates, Culture Times and Oxidation

Apoptosis rates in the control group (without oxidation) were 0.5% at 1 month and 1.0% at 3 months (p >0.05), indicating that apoptosis rates of HUVEC without oxidation were not affected by culture time (Table 6.2). While the oxidation group exposed to 0.2 mmol/l FeSO4/0.0001 mmol/l H2O2 had apoptosis rates of 8.0% at 1 and 17.5% at 3 months (p = 0.054) and the oxidation group exposed to 0.2 mmol/l FeSO4/0.005 mmol H2O2 had rates of 17.4% at 1 and 36.0% at 3 months (p <0.05). These data indicate that the apoptosis rate was affected by the oxidation and as culture time increased (cell division amounts). Thus, HUVEC with shorter telomere length had a higher apoptosis rate than the apoptosis rate in HUVEC with shorter

50

J. Zhang et al.

Fig. 6.1 Southern Blot of telomere lengths of HUVEC that were cultured

1 month. 1: normal (control);

2:apoptosis group cultured in 0.2 mmol/l

FeSO4/0.0001 mmol/l H2O2;

3:apoptosis group cultured in 0.2 mmol/l

FeSO4/0.005 mmol/l H2O2

Table 6.2 The apoptosis rate of human umbilical endothelial cells that were cultured for 1 or 3 months and induced by free radicals

FeSO4/H2O2

 

 

 

 

concentrations

 

 

χ2

 

(mmol/l)

1 month (%)

3 months (%)

p

Control

0.5

1.0

0.168

>0.05

0.2/0.0001

8.0

17.5

3.703

0.054 (<0.1)

0.2/0.005

17.4

36.0

8.733

<0.05

 

 

 

 

 

culture time and longer telomeres. We conclude that HUVEC with shorter telomeres are sensitive to free radicals.

6.3.3 Oxidation Enhances the Telomere Shortening

There are significant differences between the telomere lengths influenced by different oxidation concentrations (p <0.05) at which HUVEC were cultured for 1 or 3 months. As the free radical concentration increased, MTL decreased, indicating the increasing oxidation can enhance the telomere shortening (Table 6.3, Figs. 6.1 and 6.2).