In Situ-formed Fibrin Hydrogel Scaffold Loaded With Human Umbilical Cord Mesenchymal Stem Cells Promotes Skin Wound Healing

Abstract Background: Full-thickness skin wound healing remains a major challenge. Recently, human umbilical cord mesenchymal stem cells (hUC-MSCs) have exerted their brilliant potential to promote skin repair in clinical applications. However, low survival rate of hUC-MSCs after transplantation limits their therapeutic efficiency in treating full-thickness skin wound. The fibrin hydrogel is considered an ideal cell transplantation vectors owing to its three-dimensional mesh structure and low cytotoxicity. The objective of this study was to investigate the skin wound healing effect of fibrin hydrogel scaffold loaded with hUC-MSCs.Methods: The cytotoxicity of the fibrin hydrogel was determined via cell counting kit-8 (CCK-8) assay. A total of 36 mice aged 8 weeks were randomly divided into four groups: control group (n = 9); hydrogel-alone group (n = 9); hUC-MSC-alone group (n = 9); and hydrogel-hUC-MSC combination group (n = 9). PBS, fibrin hydrogel, hUC-MSCs or fibrin hydrogel loaded with hUC-MSCs were injected into wounds, respectively. The wound of each mice was recorded with a digital camera to calculate the wound healing rate. On days 3, 7 and 14, serial sections of the wound and surrounding tissues were prepared. Hematoxylin and eosin staining, immunofluorescent staining for green fluorescent protein, keratin 10, and keratin 14 were performed. Meanwhile, the expressions of vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and transforming growth factor-β1 (TGF-β1) were detected using RT-PCR. Results: We found that the fibrin hydrogel owned three-dimensional mesh structure and low cytotoxicity, and could prolong the cell survival time around the wound. The combination therapy of hydrogel and hUC-MSCs sped up wound closure. The combination therapy of hydrogel and hUC-MSCs upregulated the relative gene expressions of EGF, TGF-β1, VEGF, and VEGFA, which promoting epithelial regeneration and angiogenesis.Conclusions: The fibrin hydrogel scaffold provides a relatively stable sterile environment for cell adhesion, proliferation, and migration and prolongs cell survival at the wound site. The hydrogel-hUC-MSC combination therapy can promote wound closure, re-epithelialization, and neovascularization. It exhibits a remarkable therapeutic effect than hUC-MSCs or the hydrogel alone.