Negative Evidence of Direct Differentiation from Bone-Marrow Cells to Keratinocytes in Normal and Wounded Skin Using Keratin 5-Specific Reporter Mice

The Conundrum of Allogeneic Bone Marrow Transplantation for Epidermolysis Bullosa

Epidermolysis bullosa is a heterogeneous group of heritable blistering disorders with considerable morbidity and mortality. Currently, there is no effective treatment or cure for epidermolysis bullosa, but bone marrow transplantation has been suggested to improve the clinical presentation and quality of life of some patients with the recessive dystrophic subtype of epidermolysis bullosa. In this issue, two studies (Hünefeld et al., and Egawa and Kabashima) address the issue whether bone marrow transplantation could be applied to patients with epidermolysis bullosa simplex with intraepidermal blistering. Utilizing a desmoglein-3 mouse model (Dsg3^-/-) or keratin 5-specific reporter mice, the investigators show that transplanted bone marrow-derived cells migrate to the skin of bone marrow transplantation recipient mice, but these cells fail to transdifferentiate into epidermal keratinocytes, and there was no improvement in the clinical manifestations of the Dsg3^-/- mice. Thus, further preclinical experimentation, possibly using mouse models that more faithfully recapitulate the epidermolysis bullosa simplex phenotype, is advisable before commencing clinical trials of bone marrow transplantation for epidermolysis bullosa simplex.