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.