Diabetic foot ulcer (DFU) stands out as a notably prevalent and critical health issue of diabetes, significantly contributing to patient morbidity and mortality.1 Approximately 15 % of individuals with diabetes are affected by DFU globally, with up to 24 % developing chronic non-healing ulcers, which frequently result in lower limb amputation.2,3 The economic burden of DFU is significant, including prolonged hospitalizations, repeated treatments, and extensive rehabilitation.4 Despite advancements in wound care and diabetes management,5 the healing of DFU remains a major clinical challenge due to its complex and multifactorial etiology of DFU.

Multiple factors contribute to the pathogenesis of DFU, including peripheral neuropathy, peripheral arterial disease, and immune dysfunction.6,7 Peripheral neuropathy leads to a loss of protective sensation, rendering the foot vulnerable to injury.8 Ischemia, which arises from peripheral arterial disease, diminishes blood flow and nutrient delivery to the affected area, thereby hindering the wound healing process.9 Immune dysfunction, particularly chronic inflammation and impaired immune responses, further complicate healing, often leading to an infection that exacerbates tissue damage.10 Studies have found that specific immune-related gene polymorphisms are associated with susceptibility to DFUs. These genes include human leukocyte antigen (HLA) genes,11 cytokine genes such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α),12 and chemokine genes such as C C motif ligand 2 (CCL2,13). Besides, in patients with DFU, the expression levels of some immune-related genes change significantly, which may lead to the persistence of inflammatory responses. Liu et al.14 indicated that a high matrix metallopeptidase-9 (MMP-9) content environment may indicate inflammation and poor wound healing. Measuring MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), and transforming growth factor-beta (TGF-β) in wound fluid can help identify ulcers at risk for poor healing. Li et al.15 have demonstrated that the serum MMP-9/TIMP-1 ratio at admission may predict healing and provide new targets for future DFU treatment. Alterations in serum levels of complement C3 and interleukin-1β (IL-1β) levels may contribute to suppressed immune responses, leading to delayed wound healing and recurrent infections.16

It follows that immune regulatory genes play a crucial role in the development of DFU.11 Identifying immune-related genes and their associated pathways can provide valuable insights into the immune mechanisms underlying DFU. This knowledge can improve early diagnosis, help develop personalized treatment strategies, monitor and evaluate treatment effects, and discover new therapeutic targets. In this study, we aimed to develop and validate an immune-related diagnostic model for diabetic foot ulcers by utilizing gene expression datasets from the Gene Expression Omnibus (GEO) database. We utilized weighted gene co-expression network analysis (WGCNA) to pinpoint gene modules connected to diabetic foot ulcers and performed differential gene expression analysis to highlight immune-related candidate genes. A functional enrichment analysis was conducted, shedding light on the key biological processes and pathways involved. Using the Least Absolute Shrinkage and Selection Operator (LASSO) regression, we formulated a risk score to predict the presence of DFU and validated its diagnostic performance across multiple datasets. Furthermore, we investigated the infiltration patterns of immune cells between high- and low-risk subgroups of diabetic foot ulcer patients and identified potential drug targets for key genes implicated in the etiology of DFU.

This integrative bioinformatics approach aims to deepen our comprehension of the molecular mechanisms of DFU, provide powerful diagnostic tools, and identify potential therapeutic targets. The insights gained from this study could pave the way for improved management strategies and therapeutic interventions for patients with DFU, ultimately reducing the burden of this debilitating disease.