Bilayer Silk Fibroin/Sodium Alginate Scaffold Delivered hUC-MSCs to Enhance Skin Scarless Healing and Hair Follicle Regeneration with the IRE1/XBP1 Pathway Inhibition

Efficient local delivery of mesenchymal stem cells (MSCs)is adecisive factor for their application in regeneration processes. Here,we prepared a biomimetic bilayer silk fibroin/sodium alginate (SF/SA)scaffold to deliver human umbilical mesenchymal stem cells (hUC-MSCs)for wound healing. An SA membrane was prepared by the casting methodon the upper layer of the scaffold to simulate the dense epidermalstructure. On the lower layer, porous materials simulating the loosestructure of the dermis were formed by the freeze-drying method. In vitro, the scaffold was proven to have a high-densitypore structure, good swelling property, and suitable degradation rate.The hUC-MSCs could survive on the scaffold for up to 14 days and maintaincell stemness for at least 7 days. In vivo, SF/SAscaffolds loaded with hUC-MSCs (M-SF/SA) were applied to full-thicknessdefect wounds and compared with the local injection of hUC-MSCs. TheM-SF/SA group showed excellent therapeutic efficacy, characterizedby induction of macrophage polarization, regulation of TGF-beta expression and collagen components, and enhancement of vascular regeneration,thereby preventing scar formation and promoting hair follicle regeneration.Furthermore, the expression of endoplasmic reticulum stress markersIRE1, XBP1, and CHOP was inhibited significantly in M-SF/SA treatment.In conclusion, the bilayer SF/SA scaffold is an ideal delivery platformfor hUC-MSCs, and the M-SF/SA system could locally promote scarlessskin healing and hair follicle regeneration by alleviating the IRE1/XBP1signal pathway.