Bone Marrow-Derived Stem Cells Migrate into Intraepidermal Skin Defects of a Desmoglein-3 Knockout Mouse Model but Preserve their Mesodermal Differentiation

Inherited forms of epidermolysis bullosa are blistering diseases of the skin and mucosa resulting from various gene mutations. Transplantation of bone marrow-derived stem cells might be a promising systemic treatment for severe dystrophic or junctional epidermolysis bullosa, but many key questions remain unresolved. Two open questions of clinical interest are whether systemically transplanted bone marrow-derived stem cells of mesodermal origin might be able to transdifferentiate into keratinocytes with an ectodermal phenotype and whether these cells are also capable of repairing a specific intraepidermal gene defect. To address these questions, we transplanted bone marrow-derived stem cells into mice with a blistering disease exclusively localized to the epidermis resulting from a functional knockout of desmoglein-3 (Dsg3). We found that Dsg3⁺ donor-derived cells migrate into the recipient epidermis. However, these cells failed to restore the missing Dsg3 mRNA and DSG3 protein expression in the transplanted Dsg3^-/- mice. The donor-derived cells found in the epidermis preserved their CD45⁺ hematopoietic origin, and no transdifferentiation into integrin α6⁺ keratinocytes or integrin α6⁺/CD34⁺ epidermal stem cells occurred. Our results indicate that bone marrow-derived stem cells preserve their mesodermal fate after systemic transplantation and are not capable of treating patients with epidermolysis bullosa with an intraepidermal skin defect.