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.pdf
326
https://t.me/med1917
R. Roy et al.
331. Erdem Büyükkiraz M, Kesmen Z. Antimicrobial peptides
(AMPs): a promising class of antimicrobial compounds. J Appl
Microbiol. 2022;132(3):1573–96.
332. Da Silva J, Leal EC, Carvalho E.Bioactive antimicrobial peptides as therapeutic agents for infected diabetic foot ulcers.
Biomolecules. 2021;11(12):1894.
333. Chen CH, Lu TK.Development and challenges of antimicrobial
peptides for therapeutic applications. Antibiotics. 2020;9(1):24.
334. Duplantier AJ, van Hoek ML. The human cathelicidin antimicrobial peptide LL-37 as a potential treatment for polymicrobial
infected wounds. Front Immunol. 2013;4:143.
335. Grönberg A, Mahlapuu M, Ståhle M, Whately-Smith C, Rollman
O.Treatment with LL-37 is safe and effective in enhancing healing of hard-to-heal venous leg ulcers: a randomized, placebocontrolled clinical trial. Wound Repair Regen. 2014;22(5):613–21.
336. Peschel A.How do bacteria resist human antimicrobial peptides?
Trends Microbiol. 2002;10(4):179–86.
337. El Shazely B, Yu G, Johnston PR, Rolff J. Resistance evolution against antimicrobial peptides in Staphylococcus aureus
alters pharmacodynamics beyond the MIC. Front Microbiol.
2020;11:103.
338. Kakasis A, Panitsa G.Bacteriophage therapy as an alternative
treatment for human infections. A comprehensive review. Int J
Antimicrob Agents. 2019;53(1):16–21.
339. Furfaro LL, Payne MS, Chang BJ.Bacteriophage therapy: clinical trials and regulatory hurdles. Front Cell Infect Microbiol.
2018;8:376.
340. Morozova VV, Vlassov VV, Tikunova NV.Applications of bacteriophages in the treatment of localized infections in humans. Front
Microbiol. 2018;9:1696.
341. Fish R, Kutter E, Bryan D, Wheat G, Kuhl S.Resolving digital
staphylococcal osteomyelitis using bacteriophage—a case report.
Antibiotics. 2018;7(4):87.
342. Fish R, Kutter E, Wheat G, Blasdel B, Kutateladze M, Kuhl
S.Bacteriophage treatment of intransigent diabetic toe ulcers: a
case series. J Wound Care. 2016;25(Suppl 7):S27–33.
343. Fish R, Kutter E, Wheat G, Blasdel B, Kutateladze M, Kuhl
S. Compassionate use of bacteriophage therapy for foot ulcer
treatment as an effective step for moving toward clinical trials. In:
Bacteriophage therapy. Springer; 2018. p.159–70.
344. Chanishvili N. Bacteriophages as therapeutic and prophylactic
means: summary of the Soviet and post Soviet experiences. Curr
Drug Deliv. 2016;13(3):309–23.
345. Ghanaim AM, Foaad MA, Gomaa EZ, Dougdoug KAE, Mohamed
GE, Arisha AH, Khamis T.Bacteriophage therapy as an alternative technique for treatment of multidrug-resistant bacteria causing diabetic foot infection. Int Microbiol. 2023;26:343–59.
346. Nilsson AS.Pharmacological limitations of phage therapy. Ups J
Med Sci. 2019;124(4):218–27.
347. Lin J, Du F, Long M, Li P.Limitations of phage therapy and
corresponding optimization strategies: a review. Molecules.
2022;27(6):1857.
348. Clark SC, Kamen R.The human hematopoietic colony- stimulating
factors. Science. 1987;236(4806):1229–37.
349. Wakeeld PE, James WD, Samlaska CP, Meltzer MS. Colonystimulating factors. J Am Acad Dermatol. 1990;23(5):903–12.
350. Bussolino F, Wang JM, Delippi P, Turrini F, Sanavio F, Edgell
C-J, Aglietta M, Arese P, Mantovani A.Granulocyte-and granulo-
cyte–macrophage-colony stimulating factors induce human endothelial cells to migrate and proliferate. Nature. 1989;337:471–3.
351. Bhattacharya P, Budnick I, Singh M, Thiruppathi M, Alharshawi
K, Elshabrawy H, Holterman MJ, Prabhakar BS. Dual role
of GM-CSF as a pro-inammatory and a regulatory cytokine: implications for immune therapy. J Interf Cytokine Res.
2015;35(8):585–99.
352. Geissmann F, Manz MG, Jung S, Sieweke MH, Merad M, Ley
K.Development of monocytes, macrophages, and dendritic cells.
Science. 2010;327(5966):656–61.
353. Dale DC, Boxer L, Liles WC.The phagocytes: neutrophils and
monocytes. Blood. 2008;112(4):935–45.
354. Mehta HM, Malandra M, Corey SJ.G-CSF and GM-CSF in neutropenia. J Immunol. 2015;195(4):1341–9.
355. Barrientos S, Brem H, Stojadinovic O, Tomic-Canic M.Clinical
application of growth factors and cytokines in wound healing.
Wound Repair Regen. 2014;22(5):569–78.
356. Luster AD, Alon R, von Andrian UH. Immune cell migration
in inammation: present and future therapeutic targets. Nat
Immunol. 2005;6(12):1182–90.
357. He HQ, Liao D, Wang ZG, Wang ZL, Zhou HC, Wang MW, Ye
RD. Functional characterization of three mouse formyl peptide
receptors. Mol Pharmacol. 2013;83(2):389–98.
358. Zibert A, Balzer S, Souquet M, Quang TH, Paris-Scholz C,
Roskrow M, Dilloo D. CCL3/MIP-1 α is a potent immunostimulator when coexpressed with interleukin-2 or granulocytemacrophage colony-stimulating factor in a leukemia/lymphoma
vaccine. Hum Gene Ther. 2004;15(1):21–34.
359. Hamilton JL, Mohamed MF, Witt BR, Wimmer MA, Shakhani
SH. Therapeutic assessment of N-formyl-methionyl-leucylphenylalanine (fMLP) in reducing periprosthetic joint infection.
Eur Cell Mater. 2021;41:122–38.
360. Pouget C, Dunyach-Remy C, Pantel A, Boutet-Dubois A,
Schuldiner S, Sotto A, Lavigne J-P, Loubet P. Alternative
approaches for the management of diabetic foot ulcers. Front
Microbiol. 2021;12:747618.
361. Knödler A, Schmidt SM, Bringmann A, Weck MM, Brauer KM,
Holderried TAW, Heine AK, Grünebach F, Brossart P. Posttranscriptional regulation of adapter molecules by IL-10 inhibits
TLR-mediated activation of antigen-presenting cells. Leukemia.
2009;23(3):535–44.
362. Curtale G, Mirolo M, Renzi TA, Rossato M, Bazzoni F, Locati
M. Negative regulation of Toll-like receptor 4 signaling by
IL-10-dependent microRNA-146b. Proc Natl Acad Sci U S A.
2013;110(28):11499–504.
363. Murray PJ.The primary mechanism of the IL-10-regulated antiinammatory response is to selectively inhibit transcription. Proc
Natl Acad Sci U S A. 2005;102(24):8686–91.
364. Wang P, Wu P, Siegel M, Egan R, Billah M.Interleukin (IL)-10
inhibits nuclear factor B activation in human monocytes. IL-10
and IL-4 suppress cytokine synthesis by different mechanisms. J
Biol Chem. 1995;270:9558–63.
365. Mahmud F, Roy R, Mohamed MF, Aboonabi A, Moric M,
Ghoreishi K, Bayat M, Kuzel TM, Reiser J, Shakhani
SH. Therapeutic evaluation of immunomodulators in reducing
surgical wound infection. FASEB J. 2022;36(1):e22090.

Biomarkers ofDiabetic Foot Ulcers
https://t.me/med1917
andIts Healing Progress
MonikaA.Niewczas andHetalShah
18
Abstract
There are urgent, unmet needs in the eld of biomarkers
of diabetic wound healing. Rapidly developing molecular
technologies supported by the parallel, robust progress in
biostatistical and machine learning approaches are offering more granular insights into the disease processes and
unraveling potential biomarkers. These methodological
and computational innovations are tremendously accelerating biomarker research. National Institute of Diabetes
and Digestive and Kidney Diseases has recently funded
the Diabetic Foot Consortium, the largest initiative to date
aiming to develop and validate biomarkers of diabetic
foot ulcers; whereas the Food and Drug Administration
and the National Institutes of Health offer an important
glossary of nomenclature to help researchers navigate
through different types of biomarkers. Multi-molecule
signatures rather than single biomarker measurements
will likely guide the diabetic wound healing course in the
near future.
Denition ofBiomarkers andUnmet Needs
The U.S. Food and Drug Administration and the National
Institutes of Health (FDA-NIH) Working Group for
Biomarkers, EndpointS and other Tools (BEST) denes a
biomarker as “a dened characteristic that is measured as an
indicator of normal biological processes, pathogenic processes, or responses to an exposure or intervention, including
therapeutic interventions. Molecular, histologic, radiographic or physiologic characteristics are types of biomarkers. A biomarker is not an assessment of how an individual
M. A. Niewczas (*) · H. Shah
Section on Genetics and Epidemiology, Joslin Diabetes Center,
Boston, MA, USA
Department of Medicine, Harvard Medical School,
Boston, MA, USA
e-mail: Monika.Niewczas@joslin.harvard.edu
feels, functions, or survives.” FDA-NIH BEST denitions of
categories of biomarkers are outlined in Table18.1 [1].
To set the stage for the discussion on biomarkers of diabetic foot ulceration (DFU), it is important to understand different types of biomarkers. In individuals without the clinical
manifestations of the disease, a risk biomarker is associated
with an increased (or sometimes decreased) likelihood of
developing the disease, and is detected at a time preceding
the onset of clinical signs and symptoms [1]. For example,
certain vascular or neuropathic indices are clinically recognized risk factors or risk biomarkers of developing new foot
ulcer [2–4], whereas the HLA DR3/DR4-DQ8 risk alleles
identify people at high risk of developing type 1 diabetes [5].
By early identication of individuals at risk, these biomarkers can help guide effective preventive strategies against disease onset.
Prognostic markers, on the other hand, are associated
with an increased likelihood of a future clinical event, disease progression, or recurrence among individuals who have
already been diagnosed with the disease [1]. Prognostic biomarkers of the diabetic wound healing course and of the
DFU recurrence are of particular interest to the DFU community [6, 7]. According to current clinical guidelines, initially all patients with DFU are uniformly treated with the
standard of care. A limited improvement in wound healing
after approximately 4weeks prompts more specialized care.
This tier-based approach is ineffective and generates a nancial burden for the healthcare system. Thus, biomarkers
prognostic for the diabetic wound healing course that could
differentiate, early in the disease course, subjects whose
ulcers will successfully heal from those whose ulcers will
likely fail to heal are urgently needed [6]. Percent change in
wound area at 4weeks is one traditional biomarker prognostic for the DFU course [8]. Robust prognostic biomarkers
have the potential to optimize clinical algorithms and support clinical trials for DFU.Moreover, after the foot ulcer
resolution, more than half of patients will suffer from the
DFU recurrence within 5years. For more details on the natural history of the disease and current clinical guidelines,
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
A. Veves et al. (eds.), The Diabetic Foot, Contemporary Diabetes, https://doi.org/10.1007/978-3-031-55715-6_18
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Table 18.1 Biomarker nomenclature
Category of biomarker FDA-NIH BEST denition
Diagnostic A biomarker used to reveal or verify the presence of a disease or condition of interest or to identify those
with a disease subtype
Monitoring A biomarker assessed at regular intervals to determine the burden of disease or extent of the medical
condition; or one that is used to indicate exposure to an environmental agent or a medical product
Pharmacodynamic/response A biomarker that demonstrates occurrence of a biological response following exposure to a medical product
or environmental agent
Susceptibility/risk A biomarker that signals the likelihood of developing a disease or medical condition in a person that is
asymptomatic or without any clinical evidence of the disease or medical condition
Prognostic A biomarker that indicates the potential occurrence of a clinical event, progression or recurrence of disease
in individuals that already have the disease or medical condition
Predictive A biomarker that discerns individuals who are more likely (than those without the biomarker) to experience
a differential effect (favorable or unfavorable) of a medical product or environmental agent
Safety A biomarker that assesses toxicity after exposure to a medical product or environmental agent
Surrogate endpoint An endpoint that is used as a substitute for a direct measure of a clinical benet
M. A. Niewczas and H. Shah
please refer to the American Diabetes Association Standards
of Foot Care, other chapters of this book and other publications [2–4].
It is important to acknowledge that both susceptibility/
risk and prognostic markers are unrelated to the effects of an
intervention. In contrast, predictive biomarkers can identify
those who may or may not respond to treatment or may experience either benecial or adverse effects from an intervention [1]. In other words, when comparing an experimental
group to a control group in a randomized clinical trial, the
effects of treatment are different among those who are positive for the predictive biomarker compared to those who are
biomarker-negative. For example, variants in the glucose
transporter gene SLC2A2 are associated with differential
glycemic response to metformin treatment [9]. In the Action
to Control Cardiovascular Disease Risk in Diabetes
(ACCORD) clinical trial, a genetic risk score discriminated
individuals who experienced cardiovascular benets from
intensive glycemic treatment versus those who adversely
experienced increased cardiac mortality from this regimen
[10]. A randomized clinical trial (PRIORITY) evaluating a
mineralocorticoid receptor antagonist (spironolactone)
guided by a proteomics biomarker (CKD273 classier) for
diabetic kidney endpoints is an excellent example of incorporating prognostic and predictive biomarkers into the study
[11]. Statistically speaking, a formal test of interaction
between the treatment group and predictive biomarker
should be signicant when examined in relation to the outcome as the dependent variable. In contrast, if only the biomarker is signicant and not the interaction term, the
biomarker is considered prognostic and not predictive. It is
important to distinguish these terms from statistical nomenclature where predictive models are used, in order to determine if a predictor or independent variable (any biomarker in
this case) has an association with the disease outcome or a
dependent variable [12]. In fact, the nomenclature traditionally used in epidemiology and biostatistics will refer to the
predictive models in a number of scenarios, which, in light of
the BEST criteria, would be considered risk, prognostic, or
predictive biomarkers.
Diabetic Foot Consortium
To accelerate advances toward the development of validated
biomarkers for DFUs, the National Institute of Diabetes and
Digestive and Kidney Diseases (NIDDK) established a large,
national, multi-site framework of multidisciplinary and
renowned experts forming the Diabetic Foot Consortium
(DFC) in 2018 [6, 7]. The Consortium is led by Dr. Rodica
Pop-Busui (University of Michigan, Ann Arbor, MI) under
the NIDDK guidance of Dr. Teresa Jones. It comprises clinical sites dedicated to patient recruitment, a Data Coordinating
Center led by Dr. Catherine Spino (University of Michigan,
Ann Arbor, MI), a biorepository committee spearheaded by
Dr. Brian Schmidt (University of Michigan, Ann Arbor, MI),
and relevantly, a few Biomarker Analyses Units. This rstin- kind national initiative focuses solely on foot ulcerations
in diabetes. Top priorities of the initiative include efforts to
develop: (1) biomarkers to identify subjects with DFU who
are unlikely to respond to standard therapies; (2) biomarkers
monitoring the disease course; (3) biomarkers representing
molecular heterogeneity; or (4) biomarkers of DFU recurrence in subjects who had their DFU recently healed. The
initiative supports human translational studies to validate
candidate biomarkers detecting the therapeutic response,
rening the eligibility criteria, monitoring the disease course,
or offering surrogate endpoints for more long-term outcomes, ultimately accelerating drug development strategies.
Early DFC Biomarker Studies One of the two earliest studies of the Consortium is a project led by Dr. Marjana TomicCanic (University of Miami, Miami, FL), entitled “C-myc
Biomarker Study for Diabetic Foot Ulcers”; a clinicaltrials.

18 Biomarkers ofDiabetic Foot Ulcers andIts Healing Progress
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329
gov identier: NCT04591691. This prospective study
includes subjects with DFU from whom the tissue specimen
from the wound edge is obtained at baseline, and the subjects
are subsequently followed for their disease course for up to
12weeks. C-myc and phosphorylated glucocorticoid receptor (p-GR) are being tested by immunostaining. The study is
built upon a substantial knowledge base coming from functional studies that demonstrate an activation of the Wnt pathway in non-healing wounds, with consequential increases in
its downstream molecules: c-myc and p-GR [13–16].
Another early study of the Consortium is a project led by
Dr. Chandan Sen (recently: Indiana University, Indianapolis,
IN; now University of Pittsburgh, Pittsburgh, PA), entitled
“TEWL Biomarker Study for Diabetic Foot Ulcer Recurrence”
(NCT04558775, also [6, 7]). This prospective study aims to
evaluate a trans-epidermal water loss (TEWL) with a semiopen probe as a local biomarker of recurrent DFU within
16weeks of follow-up. The currently recognized clinical outcome is based on the reepithelization of the skin with no discharge, which may not speak well to DFU recidivism. TEWL
is considered an early and sensitive measure of skin barrier
function and integrity and has been employed in studies of
multiple skin diseases [17, 18]. Promising preclinical, functional studies suggest that TEWL may also be a valuable biomarker of DFU recurrence [19, 20]. Results of these projects
should be available in the near future.
R61-Supported Biomarker Studies of the DFC Currently,
ve ongoing ancillary DFC studies are funded in response to
the NIDDK funding opportunity: RFA-DK-21-001 via NIH
R61 award mechanism (Table 18.2). All are investigating
candidate biomarkers prognostic for the diabetic wound
healing course. These projects are excellent examples of
diverse molecular phenotyping approaches as they study
proteins, metabolites, coding, and non-coding RNA in a
range of biospecimens relevant for the clinical phenotype of
DFU (local wound tissue and uid, serum and urine) to
develop composite biomarker signatures.
R61 Project on Inammatory Transcriptomics The project
entitled “Inammation-related gene biomarkers in human
diabetic foot ulcer healing” led by Dr. Kara Spiller (Drexel
University, Philadelphia, PA) proposes to evaluate changes
over time in seven inammatory candidate gene expressions
in the debrided wound tissue by using a ratio of early inammation phase to late phase of inammation resolution genes
involved. Molecular phenotyping entails quantitative
RT-PCR measurements in the debrided wound tissue. The
candidate roster stems from the discovery functional studies
on inammation involving macrophage subtypes M1 and
M2, and small longitudinal data in humans built upon bulk
transcriptomics data [21–27].
R61 Project on Proteomics The project entitled “Proteomic
Biomarkers Prognostic for Diabetic Wound Healing” co-led
by Drs. Aristidis Veves and Monika Niewczas (Harvard
Medical School, Boston, MA) aims to rene and validate a
multi-protein biomarker signature in serum prognostic for
diabetic wound healing. The project is built upon the scientic premise of the importance of circulating biomarkers
coming from the targeted protein studies in DFU [28–30]
further enhanced by recently developed robust, highthroughput proteomics approaches that have already demonstrated their value in studies of other diabetic complications
[31–34].
Table 18.2 Diabetic Foot Consortium studies provide an excellent example of diverse molecular approaches to DFU biomarker research
Biomarker category
Prognostic for DFU course
C-myc biomarker study for diabetic foot ulcers Dr. Marjana Tomic-Canic, Univ. of
Inammation-related gene biomarkers in human
diabetic foot ulcer healing
Proteomic biomarkers prognostic for diabetic
wound healing
Diabetic foot ulcer wound uid biomarker Dr. Sashawati Roy, Indiana Univ. Metabolite Focused Local—wound uid
Microbiome-based biomarkers of wound healing Drs. Meghan Brennan and Lindsay
Circulating urinary microRNAs as systemic
biomarkers of healing outcomes in diabetic foot
ulcers
Prognostic for DFU recurrence
TEWL biomarker study for diabetic foot ulcer
recurrence
Project
title
Molecule
PI
Miami
Dr. Kara Spiller, Drexel Univ. mRNA Focused Local—debrided
Drs. Aristidis Veves and Monika
Niewczas, Harvard Medical School
Kalan, Univ. of Wisconsin
Drs. Rivka Stone and Marjana
Tomic-Canic, Univ. of Miami
Dr. Chandan Sen, Univ. of
Pittsburgh
type Method scale Specimen
Protein Focused Local—wound edge
wound tissue
Protein High
throughput
Microbiome High
throughput
microRNA High
throughput
Water loss Focused Local—skin
Biouid—serum
Local—wound swab
Biouid—urine
physiological property

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https://t.me/med1917
M. A. Niewczas and H. Shah
R61 Project on Metabolites The project entitled “Diabetic
Foot Ulcer Wound Fluid Biomarker” led by Dr. Sashawati
Roy (Indiana University, Indianapolis, IN) aims to validate a
cysteine-to-cystine ratio (Cys/CysS) as a wound uid biomarker prognostic for non-healing diabetic foot ulcers. This
candidate two-metabolite biomarker is derived from a
metabolomics study of over 500 metabolites [6, 7]. A ratio of
Cys to its disulde derivative, CysS, is a biomarker of the
oxidative stress, which has been shown to be associated with
diabetic complications including wound healing [35, 36].
R61 Project on Skin Microbiome Another project co-led
by Drs. Meghan Brennan and Lindsay Kalan entitled
“Microbiome Based Biomarkers of Wound Healing”
(University of Wisconsin, Madison, WI) proposes to
investigate the wound microbiome with metatranscriptomics
tools with a particular focus on the anaerobic species. This
novel, culture-independent method will utilize a wound
swab. Existing evidence has already demonstrated that the
microbiome of non-healing wounds comprises persistent
mixed populations of bacteria with a marked proportion of
anaerobic species [37–41].
R61 Project on miRNA The project entitled “Circulating
urinary microRNAs as systemic biomarkers of healing outcomes in diabetic foot ulcers” led by Drs. Rivka Stone and
Marjana Tomic-Canic (University of Miami, Miami, FL)
aims to identify candidate miRNAs in the urine prognostic
for the DFU course based on the initial high-throughput
miRNA proling. Several functional studies have strongly
implicated miRNAs involvement in the diabetic wound healing process [42–46].
Precision Medicine andDFU Biomarkers
Diabetic wound healing over time varies among individuals.
The heterogeneity of the disease course justies precision
medicine approaches to capture molecular phenotypes in a
high-throughput manner to best inform on the disease course
[47, 48].
Proteins asBiomarkers
Proteomics is one such approach that holds particular promise. Proteins are closer to the clinical phenotype than genes
or transcripts, so they may impact the disease course more
directly than other types of -omics [49, 50]. Proteomics correlate only moderately with transcriptomics [51] and, as
such, can arguably offer additional information. Mass spec-
trometry (MS) proteomics remains an important tool to study
proteins in tissue. Indeed, studies at the local site of injury
(diabetic wound) have been done [52, 53]. An untargeted
MS-based study of wound biopsies in a medium-size study
group of subjects with DFU pointed to SERPINB3 as a
potential biomarker of the DFU course, which was subsequently validated in the study group subset [52]; whereas
another MS-based study of wound uid biospecimens
pointed to inammatory S100 proteins or metalloproteinases, among others [53].
Proteins measured in biouids (serum, plasma or urine)
are frequent biomarkers. Early targeted biomarker studies
have utilized enzyme-linked immunosorbent assays
(ELISAs) or low multiplex solutions. One such study of
over 100 subjects with diabetes prospectively followed for
18months for their DFU incidence and subsequent DFU
course identied that TNF, MCP1, MMP9, and FGF2
increased in subjects who failed to have their DFU healed
from among 20 circulating cytokines examined [30].
Overall, a few targeted biomarker studies have demonstrated that select inammatory cytokines in circulation are
associated with DFU development and course [28–30],
with a closely related clinical phenotype of diabetic neuropathy [54], and other diabetic complications [55–57].
However, the predominance of classical plasma proteins
(albumin, immunoglobulins), broad dynamic ranges of circulating proteins (several orders of magnitude), or a possible cross-reactivity limits the applicability of MS and/or
ELISA and other low multiplex solutions in studies of the
circulating proteome.
An unparalleled opportunity for proling of the circulating proteome has recently become feasible. Innovative afnity proteomics outperforms other technologies by a number
of critical features. It incorporates components of the
genomic technologies that allow for a broad dynamic range
and high level of multiplexing (a few thousand proteins). The
two main technologies mainly differ by the recognition system. One method (SOMAscan platform, Somalogic Inc.) utilizes aptamers—small nucleic acids capable of specic
protein binding, and another method (proximity extension
assay (PEA) by Olink Inc.) utilizes dual antibody recognition system [58, 59]. Note that PEA proteomics is used as a
reference for one of the major Human Protein Atlas projects—the Secretome [60, 61]. Afnity proteomics has
already been employed in a number of studies of the circulating proteome of diabetes [62], and diabetic complications
other than foot ulceration, including neuropathy [33, 63, 64],
kidney [31, 32, 65], non-diabetic wound healing [66], as well
as other clinical phenotypes. Ongoing studies of the DFC as
discussed above shall unravel more insights into the circulating proteomics signatures of the diabetic wound healing
processes.

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Metabolites asBiomarkers
Metabolites are low molecular weight analytes (<1800Da)
that stem from biological processes occurring in various cells
or external exposures present in tissues. Furthermore, circulating metabolites released extracellularly into biouids (plasma,
serum, or urine) can be measured non-invasively through various relatively accessible techniques, such as mass spectrometry or nuclear resonance imaging, further enhancing their
value as biomarkers of disease. As end- products of regulatory
processes, metabolites, similar to proteins, are among the closest molecules to the disease phenotype [50, 67, 68].
Metabolomics assesses a wide range of metabolite classes
using high-throughput methods such as high-resolution
tandem mass spectrometry, often preceded by liquid or gas
chromatography. However, in these high-throughput
approaches, several metabolites remain with only a partially
known structure or metabolites that are unannotated in the
pathway databases [69].
Given the metabolic nature of diabetes, it is not surprising
that metabolic alterations are involved in the pathogenesis of
diabetic complications [35]. However, there are only few
metabolomics studies in DFU.These point to phospholipids
and select amino acids as candidate metabolites involved in
the process [70, 71]. Nonetheless, metabolomics studies
have already advanced our understanding of other diabetic
complications. For example, a targeted metabolomics study
revealed an impairment of amino acid and tricarboxylic acid
cycle metabolism, as reected by changes in circulating
metabolites associated with the course of the cardiovascular
autonomic neuropathy in subjects with diabetes [72]. Two
global metabolomics proling studies reported that higher
levels of uremic solutes and other modied metabolites were
associated with risk of progression of diabetic kidney disease
in both types of diabetes [73, 74], while circulating short and
medium chain fatty acids were reported as protective factors
[75]. Another study identied orotidine as a novel biomarker
of cardiovascular disease risk [76]. An ongoing DFC study is
evaluating two metabolites as a potential biomarker measure
of an oxidative stress and the DFU course.
Coding RNA asaPotential Biomarker
Coding RNA is a plausible biomarker as it directly reects the
biological processes of transcriptions within the tissue. Indeed,
some data suggest the potential value of this molecule type
and is supported by published data and an ongoing DFC study.
A number of bulk transcriptomics studies identied genes
activated during an early and late phase of the wound healing
process and demonstrated that the initial inammatory
response is crucial for wound healing, but its prolonged persistence contributes to unfavorable DFU outcomes [21–27].
Next-generation RNA sequencing comparing human skin and
oral acute wounds (the latter as a model of an “ideal” tissue
repair) points to the importance of the transcription factors:
FOXM1 and STAT3in the healing processes [77].
Nevertheless, RNA expression may be subject to variability due to biology, sampling techniques, and data normalization schemes. In addition to bulk transcriptomics,
novel technologies emerged to offer an even higher resolution at the single level and/or in the context of the tissue/
cellular location. Single-cell or single nucleotide RNA
sequencing (scRNAseq or snRNAseq) and/or spatial transcriptomics tremendously accelerate, without any doubt, the
discovery of relevant pathways and processes. Indeed,
important advances have been made in many areas including the DFU eld. Two scRNAseq studies in DFU point to
the importance of select broblast clusters, select metalloproteinases (MMPs), tumor necrosis factor (TNF) or interferon gamma (IFNG)-related molecules differentiating
tissues between subjects who had their ulcers successfully
healed vs. those who had not [28, 78]. More in-depth
insights on this topic have been described in previous
reviews [79, 80]. Further research is needed to evaluate
whether these great tools for discovery research provide a
satisfactory benchmark performance as biomarkers.
MicroRNAs asPotential Biomarkers
MicroRNAs are endogenously produced short non-coding
RNAs (~22 nucleotides long) that may play critical roles in
pathophysiological processes by affecting gene regulation at
the posttranscriptional level. By inhibiting translation of proteins or inducing mRNA degradation, miRNAs can obstruct
target gene expression. There are over 2500 known human
miRNAs that regulate at least 60% of the protein-coding
genes. Studies have suggested that miRNAs play a vital role
in cell proliferation, differentiation, development and
immune responses, as well as modulation of disease-related
genes [13, 81–84]. MiRNAs are potentially attractive biomarkers, as they are protected from degradation, and amenable to be studied in stored biospecimens [85].
Substantial evidence exists showing that miRNAs are
involved in the mechanisms underlying diabetic wound healing [13, 43, 45, 46, 86, 87]. In an integrated miRNA-mRNA
genomic approach, an induction of select miRNAs, namely:
miR-21-5p, miR-34a-5p, and miR-145-5p in dermal broblasts inhibited healing processes of the diabetic wound [43].
Bacterial pathogen, Staphylococcus aureus, has been shown
to induce miR-15b-5p suppressing inammatory response
and DNA repair resulting in an impaired DFU healing [46].
The ongoing DFC study evaluating miRNA proling in
urine, as described above, will soon shed light on this potential biomarker application for DFUs.

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Skin Microbiome asPotential Biomarkers
The skin microbiome is recognized for its diversity and
importance in health and disease states [40]. DFU infections
develop in approximately 50% of patients [41]. Culturedependent techniques take time, thus delaying targeted antibiotic therapies. Emerging novel molecular techniques like
metagenomics can now comprehensively examine the skin
microbiome [39, 41].
Recent, high-throughput sequencing studies performed in
prospective cohorts of subjects with DFU offered a much
higher resolution of the DFU microbiome and revealed the
importance of select strains of S. aureus, of other bacteria
such as Corynebacterium, Enterobacteriaceae, anaerobes
and of fungal communities associated with the diabetic
wound healing outcomes [88–90]. This topic has been discussed in-depth in recent reviews [37, 39, 41]. Skin microbi-
ome studies have the potential to deliver prognostic
biomarkers for DFU outcomes, and also diagnostic biomarkers for DFU infections that cannot be detected clinically or
with culture-dependent techniques. An ongoing study supported by DFC is discussed above.
Building Biomarker Signature
Single Biomarker or Biomarker Signature? The DFU
course is multi-factorial, thus it is plausible that a multiplex
biomarker signature, rather than a single biomarker, will
offer the most optimal prognostication [91].
The recent boom of rapidly developing molecular technologies offers a plethora of methods ranging from untargeted or high-throughput semi-quantitative platforms to
scaled-down, quantitative panels built with low multiplex
solutions suitable for biomarker advances. Afnity proteomics platforms, which are great tools of discovery, were
discussed earlier in this chapter. Low multiplex platforms are
great for biomarker signature renement and nal development. Meso Scale Discovery platform is one example of a
high-precision protein quantication for multiplex biomarker detection. This unique electrochemiluminescent
technology offers high sensitivity while assuring high reproducibility across the assays thanks to a non-uidic detection
system. This technology has already been used to translate a
multi-biomarker panel into clinical practice [92].
How to Identify Candidate Biomarkers? There are multiple approaches to identify candidate biomarkers. They may
be hypothesis-driven, often focused and well-invested in
biology, for example, the c-myc biomarker study [15].
Another approach is an untargeted one, resulting from an
unbiased, comprehensive screen of certain types of molecules, like proteomics or metabolomics. They can conrm
associations for molecules or pathways known to be
involved, offering a “proof of concept”, but they often point
to novel molecules or pathways that have not yet been
investigated with hypothesis-driven approaches [31, 73,
93]. For example, the Joslin Kidney Study identied circu-
lating TNF receptors 1 and 2 robustly associated with the
10-year risk of kidney failure in both types of diabetes
using a targeted approach based on the hypothesis that
inammation is involved in the loss of kidney function [56,
57]. Subsequently, the two targeted biomarkers were vali-
dated for their associations with the kidney outcomes in
diabetes in multiple cohorts totaling over 5000 subjects followed for 5–10years [55]. Impressively, a proteome-wide
scan of circulating inammation in three prospective
cohorts conrmed associations for TNF receptors with the
kidney outcome (“proof of concept”), but it also unraveled
several new molecules that have never been considered
before [31]. Moreover, an integrated approach informed by
more than one -omics can be an efcient tool of candidate
biomarker discovery. Successful examples of integrated
approaches were already reported in DFU [43, 94] and
other diabetic complications [95].
Local Versus Systemic Biomarkers Mainstream DFU
research has been focused on studying biomarkers at the
wound site. Local biomarkers are of a particular interest as
they reect molecular processes of diabetic wound healing at
its core [13]. Specimens include: wound uid for highthroughput or targeted protein or metabolite studies; wound
swabs for transcriptomics, metabolomics, or microbiome
studies; tissue specimens for histology, immunostaining, or
different types of -omics [13, 79]. Specic examples include
ongoing biomarker studies of the Consortium [6]: C-myc
protein staining in the edge of the wound tissue [14–16],
inammatory transcriptomic signature of the debrided tissue
[23–25], or microbiome study of wound swab [88, 89].
However, local specimens (e.g., tissue from the surgical
debridement) are mostly invasive, and often affected by high
variability of the specimen collection process [96]. Ongoing,
non-invasive biomarker studies of the Consortium include
TEWL measurements of the density gradient of water evaporation from the skin [19, 20], or other imaging studies currently under evaluation [97, 98].
The systemic, circulating biomarkers may include molecules (often proteins or metabolites) that are actively secreted
into the bloodstream, some of which can be upstream regulators of the disease process, as well as downstream in the process proteins that leak into the blood as a result of cell
damage (for example from the wound site) [61]. Speaking to

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that, two studies of atopic dermatitis demonstrated at least a
partial overlap between circulating and local protein changes
[99, 100]. Nevertheless, to date, very few circulating molecules have been translated to clinical practice. Hemoglobin
A1c (circulating protein) and creatinine (circulating metabolite) are two, well-established, clinical legacy measures of
poor glycemic control and kidney function, respectively, that
constitute risk factors of DFU [2]. In addition, there have
been research advances in the search of relevant circulating
molecules. A few targeted biomarker studies have demonstrated that select circulating proteins are associated with
DFU development and course [28–30], with other diabetic
complications [54–57], and other disorders of the skin
[99–101].
Biomarker Signature Renement Forming a biomarker
signature from the identied candidate biomarkers relies on
several important components: (1) data-driven associations
with the outcome of interest; (2) correlations among each
other; (3) independence from clinical covariates; (4) reection of relevant biological processes and pathways; (5) analytical performance; and (6) choices possibly also informed
by longitudinal trajectories within individual over time.
Single or Repeated Biomarker Measurement How stable
the biomarker is over time, impacts the decision on the number of times the biomarker should be measured. Albuminuria,
a well-established risk factor for diabetic complications, is
known to be highly variable and clinical guidelines recommend its measurements multiple times to determine albuminuria status [2]. On the other hand, a number of omics
studies have shown that a marked proportion of molecules
(proteins or metabolites) track well within individual over
time. These are desired features of risk or prognostic biomarkers [74, 102]. On the other hand, the diabetic wound
healing is a dynamic process as it has been shown in targeted
protein biomarker studies [29] as well as in transcriptomic
studies [25, 27]. These longitudinal trajectories may offer
additional insights serving as surrogate biomarkers or supporting the development of the prognostic biomarkers.
Biostatistical andMachine Learning
Approaches
After various preprocessing steps of the molecular data that
are often specic to the platform and include screening for
outliers, ltering, normalization, and transformation or controlling for batch effect, the omics data can then be analyzed
using biostatistical multivariate approaches. These processes
test the relationships of the relative abundance of each molecule one at a time with the outcome of interest using methods
such as t-tests, fold-change analysis, analysis of variance, or
Wilcoxon rank-sum tests [49, 69]. However, it is paramount
to correct for multiple hypotheses testing given that hundreds
or thousands of molecules are being assayed. This may be
done via Bonferroni corrections for the number of independent tests or controlling for the false discovery rate by various
methods to produce a q-value, the minimum threshold at
which an analyte is considered signicant [103]. Volcano plot
is a highly informative tool to visualize the results of the multivariate screen. Ratios of molecules between the two groups
(x axis) are typically plotted against the strengths of the signicance (p value adjusted for multiple testing) on the y axis.
This graph has been utilized multiple times in omics studies
of diabetic complications [31, 74].
Classical biostatistical tools like logistic or Cox regression
models are highly interpretable. Effect estimates are in clinically meaningful units. In addition, one can quantitatively
evaluate independence from clinical covariates via confounding or effect modication. Nevertheless, biostatistical tools
may fall short in studies with multiple and possibly correlated
high-throughput omics-based biomarkers. Machine learning
is a rapidly developing computer science eld that aims to
address these challenges. Although machine learning methods
have lower interpretability, they are better at overcoming the
challenges of correlations or non-linearity, offering the potential for superior model accuracy [104–106].
Data redundancy among molecules measured in a highthroughput manner is a common phenomenon. Spearman
or Pearson correlation matrices are biostatistical approaches
to examine such data and continue to be relevant methods.
Among machine learning models, principal component
analysis is one of the early approaches to leverage correlated data in an unsupervised way, meaning disregarding
the outcome. Principal component analysis uses orthogonal
projection directions to capture the data’s maximal variance, clustering subjects (score plot) and molecules (loading plot) accordingly, grouping molecules in the loading
vectors of the principal components. Other unsupervised
methods include hierarchal clustering, or two-mode clustering [73, 76].
Among machine learning models that are supervised,
meaning those that take the outcome into account, elastic net
model is an example of penalized regression well-suited for
a large number of continuous variables featuring correlated
data and is an “elastic compromise” between ridge and lasso
regressions. Ridge regression welcomes correlated data
whereas lasso regression discriminates against them [107].
On the other hand, generalized boosting model and random
forest belong to the decision tree family and are applicable

334
Symbols credit to Biorender.com
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M. A. Niewczas and H. Shah
for detecting threshold effects and interactions. Neural network, an example of deep learning, is primed for complex
non-linear relationships. Novel computational methods to
address the needs of omics-based biomarker research are
rapidly developing.
Limitations
We shall mention some limitations in scope. This chapter
focuses on research advances of molecular biomarkers
derived from targeted or high-throughput approaches. We do
not discuss in greater detail risk or prognostic values of clinical characteristics (indices of diabetes, neuropathy, or
peripheral vascular disease). We also do not discuss other
potential types of biomarkers (e.g., social determinants of
health, or imaging biomarkers). We do not discuss in-depth
methodological assay aspects of the biomarker performance
(detectability, cross-reactivity) or model accuracy metrics
(sensitivity, specicity, positive predictive value) as those
gold standard methods for biomarker evaluation are readily
available elsewhere.
Into theBright Future
These are truly exciting times in biomarker research
(Fig. 18.1). Increased awareness and ongoing research
advances combine to address the molecular heterogeneity
of the disease course with an increasing appreciation for
the molecular underpinnings of these processes. Rapidly
developing technologies support these efforts by offering
high- resolution phenotyping of a variety of molecules
moving toward single-cell or spatial -omics data. The
efforts have begun to integrate data across multiple -omics
layers that will further enhance biomarker discovery.
Technical advances team with rapid development of computational tools in responding to the needs of these big
data [47, 108, 109].
Biomarker research is an extremely relevant and active
area of investigation in the diabetic wound healing eld. An
important NIH-funded initiative supports multiple projects
under an umbrella of a multi-site consortium. These and
other advances should soon result in biomarker solutions
supporting the ultimate goal of improving patient
outcomes.
Fig. 18.1 Biomarker
research in DFU—past,
current, and future. (Symbols
credit to Biorender.com)

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References
1. FDA-NIH Biomarker Working Group. BEST (Biomarkers E,
and other Tools) Resource [Internet]. Silver Spring, MD: Food
and Drug Administration (US); 2016. Co-published by National
Institutes of Health (US), Bethesda, MD.Created: 28 Jan 2016;
Updated: 25 Jan 2021.
2. ElSayed NA, Aleppo G, Aroda VR, etal. 12. Retinopathy, neuropathy, and foot care: standards of care in diabetes—2023.
Diabetes Care. 2023;46(Suppl 1):S203–s215. (In eng). https://doi.
org/10.2337/dc23- S012.
3. Armstrong DG, Boulton AJM, Bus SA.Diabetic foot ulcers and
their recurrence. N Engl J Med. 2017;376(24):2367–75. (In eng).
https://doi.org/10.1056/NEJMra1615439.
4. Armstrong DG, Tan TW, Boulton AJM, Bus SA. Diabetic foot
ulcers: a review. JAMA. 2023;330(1):62–75. (In eng). https://doi.
org/10.1001/jama.2023.10578.
5. DiMeglio LA, Evans-Molina C, Oram RA. Type 1 diabetes. Lancet. 2018;391(10138):2449–62. (In eng). https://doi.
org/10.1016/s0140- 6736(18)31320- 5.
6. Jones TLZ, Holmes CM, Katona A, etal. The NIDDK Diabetic
Foot Consortium. J Diabetes Sci Technol. 2023;17(1):7–14. (In
eng). https://doi.org/10.1177/19322968221121152.
7. The Diabetic Foot Consortium (DFC). https://diabeticfootconsor-
tium.org/researchers/.
8. Sheehan P, Jones P, Caselli A, Giurini JM, Veves A. Percent
change in wound area of diabetic foot ulcers over a 4-week period
is a robust predictor of complete healing in a 12-week prospective
trial. Diabetes Care. 2003;26(6):1879–82. (In eng). https://doi.
org/10.2337/diacare.26.6.1879.
9. Zhou K, Yee SW, Seiser EL, etal. Variation in the glucose transporter gene SLC2A2 is associated with glycemic response to
metformin. Nat Genet. 2016;48(9):1055–9. (In eng). https://doi.
org/10.1038/ng.3632.
10. Shah HS, Gao H, Morieri ML, etal. Genetic predictors of cardiovascular mortality during intensive glycemic control in type
2 diabetes: ndings from the ACCORD clinical trial. Diabetes
Care. 2016;39(11):1915–24. (In eng). https://doi.org/10.2337/
dc16- 0285.
11. Tofte N, Lindhardt M, Adamova K, etal. Early detection of diabetic
kidney disease by urinary proteomics and subsequent intervention
with spironolactone to delay progression (PRIORITY): a prospective observational study and embedded randomised placebocontrolled trial. Lancet Diabetes Endocrinol. 2020;8(4):301–12.
(In eng). https://doi.org/10.1016/s2213- 8587(20)30026- 7.
12. Ballman KV. Biomarker: predictive or prognostic? J Clin
Oncol. 2015;33(33):3968–71. (In eng). https://doi.org/10.1200/
jco.2015.63.3651.
13. Eming SA, Martin P, Tomic-Canic M.Wound repair and regeneration: mechanisms, signaling, and translation. Sci Transl
Med. 2014;6(265):265sr6. (In eng). https://doi.org/10.1126/
scitranslmed.3009337.
14. Sawaya AP, Pastar I, Stojadinovic O, etal. Topical mevastatin promotes wound healing by inhibiting the transcription factor c-Myc
via the glucocorticoid receptor and the long non-coding RNA
Gas5. J Biol Chem. 2018;293(4):1439–49. (In eng). https://doi.
org/10.1074/jbc.M117.811240.
15. Stojadinovic O, Brem H, Vouthounis C, et al. Molecular pathogenesis of chronic wounds: the role of beta-catenin and c-myc
in the inhibition of epithelialization and wound healing. Am J
Pathol. 2005;167(1):59–69. (In eng). https://doi.org/10.1016/
s0002- 9440(10)62953- 7.
16. Stojadinovic O, Pastar I, Nusbaum AG, Vukelic S, Krzyzanowska
A, Tomic-Canic M. Deregulation of epidermal stem cell niche
contributes to pathogenesis of nonhealing venous ulcers.
Wound Repair Regen. 2014;22(2):220–7. (In eng). https://doi.
org/10.1111/wrr.12142.
17. Berardesca E, Loden M, Serup J, Masson P, Rodrigues LM.The
revised EEMCO guidance for the invivo measurement of water
in the skin. Skin Res Technol. 2018;24(3):351–8. (In eng). https://
doi.org/10.1111/srt.12599.
18. Klotz T, Ibrahim A, Maddern G, Caplash Y, Wagstaff M.Devices
measuring transepidermal water loss: a systematic review of measurement properties. Skin Res Technol. 2022;28(4):497–539. (In
eng). https://doi.org/10.1111/srt.13159.
19. Roy S, Elgharably H, Sinha M, etal. Mixed-species biolm compromises wound healing by disrupting epidermal barrier function.
J Pathol. 2014;233(4):331–43. (In eng). https://doi.org/10.1002/
path.4360.
20. Sen CK, Roy S.The hyperglycemia stranglehold sties cutaneous epithelial–mesenchymal plasticity and functional wound closure. J Invest Dermatol. 2021;141(6):1382–5. (In eng). https://doi.
org/10.1016/j.jid.2020.11.021.
21. Bajpai A, Nadkarni S, Neidrauer M, Weingarten MS, Lewin PA,
Spiller KL. Effects of non-thermal, non-cavitational ultrasound
exposure on human diabetic ulcer healing and inammatory gene
expression in a pilot study. Ultrasound Med Biol. 2018;44(9):2043–
9. https://doi.org/10.1016/j.ultrasmedbio.2018.05.011.
22. Lurier EB, Dalton D, Dampier W, et al. Transcriptome analysis of IL-10-stimulated (M2c) macrophages by next-generation
sequencing. Immunobiology. 2017;222(7):847–56. (In eng).
https://doi.org/10.1016/j.imbio.2017.02.006.
23. Miao M, Niu Y, Xie T, Yuan B, Qing C, Lu S.Diabetes-impaired
wound healing and altered macrophage activation: a possible pathophysiologic correlation. Wound Repair Regen. 2012;20(2):203–
13. (In eng). https://doi.org/10.1111/j.1524- 475X.2012.00772.x.
24. Mirza RE, Fang MM, Weinheimer-Haus EM, Ennis WJ, Koh
TJ. Sustained inammasome activity in macrophages impairs
wound healing in type 2 diabetic humans and mice. Diabetes.
2014;63(3):1103–14. (In eng). https://doi.org/10.2337/
db13- 0927.
25. Nassiri S, Zakeri I, Weingarten MS, Spiller KL.Relative expression of proinammatory and antiinammatory genes reveals differences between healing and nonhealing human chronic diabetic
foot ulcers. J Invest Dermatol. 2015;135(6):1700–3. (In eng).
https://doi.org/10.1038/jid.2015.30.
26. Spiller KL, Anfang RR, Spiller KJ, etal. The role of macrophage phenotype in vascularization of tissue engineering scaffolds. Biomaterials. 2014;35(15):4477–88. (In eng). https://doi.
org/10.1016/j.biomaterials.2014.02.012.
27. Spiller KL, Nassiri S, Witherel CE, etal. Sequential delivery of
immunomodulatory cytokines to facilitate the M1-to-M2 transition of macrophages and enhance vascularization of bone scaffolds. Biomaterials. 2015;37:194–207. (In eng). https://doi.
org/10.1016/j.biomaterials.2014.10.017.
28. Theocharidis G, Baltzis D, Roustit M, et al. Integrated skin
transcriptomics and serum multiplex assays reveal novel mechanisms of wound healing in diabetic foot ulcers. Diabetes.
2020;69(10):2157–69. https://doi.org/10.2337/db20- 0188.
29. Tecilazich F, Dinh T, Pradhan-Nabzdyk L, etal. Role of endothelial progenitor cells and inammatory cytokines in healing of
diabetic foot ulcers. PLoS One. 2013;8(12):e83314. https://doi.
org/10.1371/journal.pone.0083314.
30. Dinh T, Tecilazich F, Kafanas A, etal. Mechanisms involved in
the development and healing of diabetic foot ulceration. Diabetes.
2012;61(11):2937–47. https://doi.org/10.2337/db12- 0227.
31. Niewczas MA, Pavkov ME, Skupien J, etal. A signature of circulating inammatory proteins and development of end-stage renal
disease in diabetes. Nat Med. 2019;25(5):805–13. https://doi.
org/10.1038/s41591- 019- 0415- 5.
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