Healing skin wounds with anatomic and functional integrity, especially under chronic pathological conditions, remain an enormous challenge. Due to their outstanding regenerative potential, mesenchymal stem cells (MSCs) have been explored in many studies to determine the healing ability for difficult-to-treat diseases. In this article, we review current animal studies and clinical trials of MSC-based therapy for chronic wounds, and discuss major challenges that confront future clinical applications. We found that a wealth of animal studies have revealed the versatile roles and the benefits of MSCs for chronic wound healing. MSC treatment results in enhanced angiogenesis, facilitated reepithelialization, improved granulation, and accelerated wound closure. There are some evidences of the transdifferentiation of MSCs into skin cells. However, the healing effect of MSCs depends primarily on their paracrine actions, which alleviate the harsh microenvironment of chronic wounds and regulate local cellular responses. Consistent with the findings of preclinical studies, some clinical trials have shown improved wound healing after transplantation of MSCs in chronic wounds, mainly lower extremity ulcers, pressure sores, and radiation burns. However, there are some limitations in these clinical trials, especially a small number of patients and imperfect methodology. Therefore, to better define the safety and efficiency of MSC-based wound therapy, large-scale controlled multicenter trials are needed in the future. In addition, to build a robust pool of clinical evidence, standardized protocols, especially the cultivation and quality control of MSCs, are recommended. Altogether, based on current data, MSC-based therapy represents a promising treatment option for chronic wounds.

Collagen membranes are widely used in guided bone regeneration (GBR) because of their good biocompatibility and low immunogenicity. As a bioderived collagen membrane, small intestinal submucosa (SIS) has good regenerative potential for soft tissue repair, but it lacks sufficient mechanical properties for GBR application unless properly modifided. Epigallocatechin-3-gallate (EGCG) is a natural cross-linking agent featuring osteoinductive activity. In this study, we modified SIS by EGCG cross-linking, and such modified materials were characterized both in vitro and in vivo. The results showed that EGCG cross-linking significantly improved the mechanical properties and hydrophilicity of SIS while maintaing good cytocompatibility. Compared to SIS, EGCG-cross-linked SIS (E-SIS) enhanced the adhesion of fibroblasts and preosteoblasts and promoted the osteogenic differentiation of MC3T3-E1 cells cultured on the materials. In a rat cranial defect model, E-SIS material showed better occlusion effect than SIS material. Most importantly, E-SIS material accelerated bone regeneration more than SIS material and even a commercially available GBR membrane. Taken together, we conclude that E-SIS is a promising material as a GBR membrane.