Effect of Brain-Derived Neurotrophic Factor on Mesenchymal Stem Cell-Seeded Electrospinning Biomaterial for Treating Ischemic Diabetic Ulcers via Milieu-Dependent Differentiation Mechanism

Great challenges in transplantation of mesenchymal stem cells (MSCs) for treating ischemic diabetic ulcers (IDUs) are to find a suitable carrier and create a beneficial microenvironment. Brain-derived neurotrophic factor (BDNF), a member of neurotrophin family, is considered angiogenic and neuroprotective. Given that IDUs are caused by vascular disease and peripheral neuropathy, we used BDNF as a stimulant, and intended to explore the role of new biomaterials complex with MSCs in wound healing. BDNF promoted the proliferation and migration of MSCs using MTT, transwell, and cell scratch assays. The activity of human umbilical vein endothelial cells (HUVECs) was also enhanced by the MSC-conditioned medium in the presence of BDNF, via a vascular endothelial growth factor-independent pathway. Since proliferated HUVECs in the BDNF group made the microenvironment more conducive to endothelial differentiation of MSCs, by establishing co-culture systems with the two cell types, endothelial cells derived from MSCs increased significantly. A new biomaterial made of polylactic acid, silk and collagen was used as the carrier dressing. After transplantation of the BDNF-stimulated MSC/biomaterial complex, the ulcers in hindlimb ischemic mice healed prominently. More blood vessel formation was observed in the wound tissue, and more MSCs were co-stained with some endothelial-specific markers such as cluster of differentiation (CD)31 and von Willebrand Factor (vWF) in the treatment group than in the control group. These results demonstrated that BDNF could improve microenvironment in the new biomaterial, and induce MSCs to differentiate into endothelial cells indirectly, thus accelerating ischemic ulcer healing.