Ultrasound-Stimulated BMSCs Promote Regenerative Healing in Refractory Foot Ulcer by Paracrine Effect

Diabetic foot ulcer (DFU) is a common and serious complication of diabetes, often leading to infection, amputation and poor quality of life. Bone marrow mesenchymal stem cells (BMSCs) have shown promise in treating chronic wounds, but their therapeutic efficacy is limited due to poor survival and low regenerative activity. Low-intensity pulsed ultrasound (LIUS), a non-invasive physical modality, has been shown to enhance the biological behavior of BMSCs. LIUS in combination with BMSCs shows promising potential to promote healing of refractory foot ulcer wounds.

Several methods were compared to establish an optimal DFU rat model. Based on screening results, a model involving femoral nerve transection, femoral artery ligation and full-thickness skin removal on the dorsum of the foot was selected. the DFU model of SD (Sprague-Dawley rats) was established and divided into groups. Ulcer wound healing, histopathological changes and collagen fiber formation were observed in each group after treatment. The expression of inflammatory cells and inflammatory factors, pro-angiogenic factors and related genes and healing-related cytokines was detected.

The rat DFU model established by cutting the femoral nerve, ligating the femoral artery and removing the full-thickness skin on the dorsum of the foot could simulate the clinical state of incomplete ischemia and neuropathy of the lower limbs in DFU. In addition, delayed wound healing, blocked deposition of collagen fibers, reduced angiogenesis and delayed expression of healing-related factors were more severe than in the other groups. LIUS pretreated BMSCs enhanced wound repair by promoting M2 macrophage polarization, reducing pro-inflammatory cytokine expression and increasing anti-inflammatory factors. Additionally, they upregulated VEGF-A, SDF-1, CXCR4 and NGF to stimulate angiogenesis and nerve regeneration and improved re-epithelialization and collagen fiber formation.

A robust DFU rat model mimicking clinical pathology has been established. LIUS pretreatment significantly enhances the therapeutic potential of BMSCs in promoting DFU healing via multiple regenerative and immunomodulatory mechanisms. This study provides a promising strategy for improving stem cell therapy in diabetic wound management.