Rescue of the mucocutaneous manifestations in a mouse model of recessive dystrophic epidermolysis bullosa (RDEB) by human cord blood derived unrestricted somatic stem cells (USSCs)

RDEB is a severe inherited skin blistering disease caused by mutations in COL7A1 gene that encodes type VII collagen (C7), a major component in the anchoring fibrils at the basement membrane. Allogeneic hematopoietic stem cell transplantation in both experimental animals and human subjects with RDEB has resulted in an improvement but not cure of the RDEB symptoms. Therefore development of a more effective cell therapy is still in great demand. Our recent studies demonstrated that CB-derived non-hematopoietic stem cells, i.e., USSCs express C7 and promote epithelialization and wound closure in a murine wound healing model. We hypothesize that CB-derived USSCs may represent a novel stem cell source for the treatment of RDEB. In this study, we demonstrated that a single intra-hepatic injection of USSCs (0.2 x 10⁶) in newborn RDEB mice (col7a1^-/-) without immunosuppression arrested the blistering phenotype and significantly enhanced the median survival to 8 days, as compared to 2 days in PBS injected animals (P<0.0001) (Fig 1A and B). A second USSC intra- hepatic injection further elongated the median life span to 16 days (P<0.0001). Remarkably, two mice that received repeated injections survived more than 12 weeks (Fig 1B and C). Bioluminescent imaging and immunocytochemical analyses demonstrated specific migration of USSCs to the lesions and their engraftment in the dermis and hair follicles of the skin and gastrointestinal tract. The expression of C7 was detected and electron microscopy revealed a partial restoration of anchoring fibrils in skin biopsies from the USSC-treated RDEB mice. We also demonstrated that USSCs treatment induced an infiltration of macrophages with a regenerative “M2” phenotype. These data demonstrated that USSCs improved the RDEB mucocutaneous manifestations through multiple mechanisms. This study warrants future clinical investigation of USSCs as a novel allogeneic stem cell donor source in selected patients with RDEB.