Human Mesenchymal Stromal Cells Engineered To Express Collagen Vii Can Restore Anchoring Fibrils In Recessive Dystrophic Epidermolysis Bullosa Skin Graft Chimeras

Recessive dystrophic epidermolysis bullosa (RDEB) is a debilitating genodermatosis caused by loss-of-function mutations in COL7A1 encoding type VII collagen (C7), the main component of anchoring fibrils (AFs) at the dermal-epidermal junction (DEJ). With no curative treatments presently available, retrovirally-transduced autologous epidermal grafts and intradermal lentivirally-engineered fibroblast injections are being investigated. Alternative approaches aim to infuse allogeneic mesenchymal stromal cells (MSCs) to provide a more generalised treatment for RDEB. We investigated whether healthy human MSCs could be engineered to overexpress C7 and correct RDEB in a human:murine chimeric model. Initially, engineered MSCs incorporated ex-vivo into RDEB grafts, their presence confirmed by FISH, revealed recovery of DEJ function with no signs of blister formation. Importantly, detection of AFs by transmission electron microscopy corroborated structural recovery. Next, MSCs co-transduced to express C7 and luciferase were delivered intradermally into grafted RDEB skin, resulting in localised MSC persistence with deposition of de novo C7 at the site. Notably, C7 expression was sufficient to restore AF density to normal levels. In contrast, intravenously injected engineered MSCs were undetectable within grafts and lacked AF reconstitution. Our data suggest that while localised correction may be achievable using engineered MSCs, strategies for systemic administration require further modelling.