Mechanical stretch loading of BMSCs-PLCL composite scaffolds accelerate diabetic wound healing by protecting endothelial cells and promoting angiogenesis.

BACKGROUND: Impaired angiogenesis is a critical factor that delays diabetic wound healing. Although bone marrow mesenchymal stem cells (BMSCs) have therapeutic potential, their paracrine functions are suppressed in hyperglycemic environments. This study aimed to construct a stem cell-scaffold construct by integrating BMSCs with poly(L-lactic-co-ε-caprolactone) (PLCL) nanofiber scaffolds and applying cyclic mechanical stretch to enhance the function of BMSCs, thereby promoting angiogenesis and tissue repair in diabetic wounds.

METHODS: The efficacy of mechanically stretched BMSCs-PLCL (MS-BMSCs-PLCL) composite scaffolds was evaluated in a full-thickness skin defect model using diabetic rats. Immunofluorescence staining was used to assess the expression of CD31, α-SMA and vascular endothelial growth factor (VEGF) to evaluate angiogenesis and vascular maturation. The in vivo fate of PKH26-labeled BMSCs was tracked post-transplantation. Additionally, CCK-8 assay, EdU staining, scratch assay, Transwell assay, and tube formation assay analyzed the effects of mechanical stretch-preconditioned BMSCs and their conditioned medium (CM) on high-glucose-injured rat umbilical vein endothelial cells (RUVECs). RNA-seq was performed to elucidate the mechanism underlying the pro-angiogenic enhancement of BMSCs under mechanical stretch, followed by functional validation via knockdown of the identified Postn gene.

RESULTS: The MS-BMSCs-PLCL composite scaffolds significantly enhanced the healing process of diabetic wounds. Immunofluorescence staining showed that MS-BMSCs-PLCL upregulated CD31, α-SMA, and VEGF expression, promoting angiogenesis and vascular maturation. Cell tracing confirmed the transplanted BMSCs were co-localized with the endothelial marker CD31. In vitro, both mechanically stretched BMSCs and their CM improved the proliferation, migration, and tube formation of high glucose-injured RUVECs. RNA-seq analysis identified key genes involved in angiogenesis and tissue repair that were altered by mechanical stimulation. Functional analysis confirmed that silencing Postn attenuated the pro-angiogenic function of mechanically stretched BMSCs.

CONCLUSION: Mechanical stretch enhanced the paracrine function of BMSCs, thereby promoting angiogenesis in diabetic wounds and reversing endothelial cells damage from high glucose. These findings support a novel strategy that combines mechanical preconditioning, biomaterials, and stem cells for improving diabetic wound healing.