Transverse tibial bone transfer accelerates healing of foot ulcers in a rabbit model of type 2 diabetes mellitus: involvement and regulation of circular RNA

Abstract

BACKGROUND: Transverse tibial bone transfer is an emerging surgical technique that enhances local blood circulation and promotes angiogenesis, thereby accelerating the healing of diabetic foot ulcers. Although this technique has demonstrated positive clinical outcomes, its specific molecular mechanisms remain unclear. Recently, the role of circular RNA in angiogenesis and wound healing has gained increasing recognition. Circular RNA may influence the healing process by regulating the expression of related genes; however, its involvement in the treatment of diabetic foot ulcers through transverse tibial bone transfer has yet to be explored. OBJECTIVE: To investigate the therapeutic effects of transverse tibial bone transfer on diabetic foot ulcers in a rabbit model and the mechanism of action. METHODS: Eighteen 3-month-old male New Zealand rabbits, weighing 2.8–3.6 kg, were included in this study. After being fed a high-sugar, high-fat diet for 1 month, type II diabetic rabbit models were induced by intravenous injection of alloxan monohydrate. After successful modeling, the right femoral artery at the mid-upper segment was ligated, and full-thickness skin on the ipsilateral foot dorsum was excised to simulate the pathological features of diabetic foot ulcers. Subsequently, the successfully modeled rabbits were randomly divided into 4 groups (4 rabbits per group): blank group (no additional treatment), dressing change group (routine iodophor disinfection after modeling), sham surgery group (installation of transverse tibial bone transfer scaffold without bone transfer), and surgery group (installation of scaffold and bone transfer). At 7 and 14 days post-surgery, the healing of foot ulcer wounds was observed. At 7, 14, and 21 days post-surgery, serum levels of vascular endothelial growth factor A (VEGF-A) and CD31 were measured by enzyme-linked immunosorbent assay. At 14 days post-surgery, ulcer tissue samples were collected for hematoxylin-eosin staining, CD31 immunofluorescence staining, and western blot analysis of VEGF-A and CD31 protein expression. At 7, 14, and 21 days post-surgery, venous blood from the surgery group was collected for whole-genome sequencing to analyze differential expression of circular RNAs. RESULTS AND CONCLUSION: At 7 and 14 days post-surgery, the surgery group showed significantly better recovery of diabetic foot ulcers compared to the other three groups, with superior promotion of epidermal repair, collagen fiber deposition, and angiogenesis. At 14 and 21 days post-surgery, serum levels of VEGF-A and CD31 in the surgery group were significantly higher than those in the other three groups (P < 0.01). Gene sequencing analysis revealed that the most significant changes in circular RNAs occurred at 21 days post-surgery, especially the expression of circular RNA PDS5B (circPDS5B) adhesion-related factor B, which gradually decreased over time, suggesting that circPDS5B may be closely related to angiogenesis and tissue repair. These results indicate that transverse tibial bone transfer can effectively promote the healing of diabetic foot ulcer wounds in rabbits. Gene sequencing results showed differential expression of circular RNAs, especially significant downregulation of circPDS5B, suggesting that transverse tibial bone transfer may promote wound repair and angiogenesis by activating related molecular pathways.

1. Introduction

Diabetic foot ulcer (DFU) is one of the common and severe complications of diabetes mellitus, significantly reducing patients' quality of life and, in severe cases, leading to amputation. The pathological mechanisms of DFU primarily involve diabetic vasculopathy and neuropathy. Chronic hyperglycemia-induced neuropathy causes loss of protective sensation, making patients unaware of foot injuries, while vasculopathy leads to impaired lower limb blood circulation, particularly microvascular dysfunction, resulting in chronic ischemia of foot tissues and impaired wound healing. The healing process of DFU is often slow and prone to recurrence, frequently complicated by infection and gangrene. Current treatment modalities often fail to achieve satisfactory outcomes, prolonging the disease course and increasing patient suffering. Therefore, exploring novel therapeutic approaches to improve the prognosis of diabetic foot patients has become a crucial direction in medical research.

Transverse tibial bone transfer (TTBT) is an innovative surgical technique that has been increasingly applied in the treatment of DFU in recent years. TTBT has the potential to improve local blood flow, promote angiogenesis, and enhance tissue repair, thereby offering a new therapeutic avenue for DFU. By mechanically distracting the bone segment, TTBT stimulates local vascular endothelial cell proliferation and promotes neovascularization. However, the precise molecular mechanisms underlying its therapeutic effects remain largely unknown. Recent studies have highlighted the role of circular RNAs (circRNAs) in angiogenesis and wound healing. CircRNAs may regulate the expression of related genes and influence the healing process. Nevertheless, the involvement of circRNAs in TTBT treatment of DFU has not been explored. This study aims to investigate the therapeutic effects of TTBT on DFU in a rabbit model and to elucidate the underlying molecular mechanisms, focusing on the differential expression of circRNAs.