Identification of bone morphogenetic protein (BMP)-7 as a key instructive factor for human epidermal Langerhans cell differentiation and proliferation

Langerhans dendritic cells represent abundantly occuring and evolutionary highly conserved DCs specifically located in the stratified epithelial tissues. LCs are unique among DC family members in that they express epithelial-type adhesion molecules, allowing them to form a tight three-dimensional network in basal and suprabasal epidermal keratinocyte layers and developmentally dependent on the cytokine TGF-β1. In the present study, we identified BMP-7 as another key factor inducing LC differnetiation. Here we have performed comparative analysis of highly purified CD207+/CD1a+ in vitro generated Langerhans cells in the presence of BMP-7 and TGF-β1. We have identified that both BMP-7-LCs and TGF-β1-LCs are closely related to each other. CD34+ hematopoietic stem cells were isolated from freshly obtained cord blood and cultured in the presence of GM-CSF, SCF, Flt3L, TNFa and either TGF-β1 or BMP-7 for 7 days to get immature LCs. RNA was isolated from these in vitro genetared LCs.