During epithelial differentiation of human adipose-derived stromal/stem cells, expression of zonula occludens protein-1 is induced by a combination of retinoic acid, activin-A and bone morphogenetic protein-7

Background aims. Adipose-derived stromal/stem cells (ASC) possess a multilineage differentiation potential, can be used from an autologous origin, and are, therefore, attractive candidates for clinical applications to repair or regenerate damaged tissues and organs. Beside their well-known differentiation into cells of mesodermal origin, ASC are able to differentiate into cells of ecto- and endodermal origin. Methods. Previous studies have shown that all trans retinoic acid (ATRA) induces the expression of cytokeratin 18 (CK18), indicating the beginning of differentiation into the epithelial lineage. Nevertheless, ATRA does not induce the expression of other epithelial markers. Therefore, we tested the additional influence of two growth factors on the onset of epithelial differentiation of ASC. The cells were cultured with ATRA, Activin A (ActA) and bone morphogenetic protein-7 (BMP-7), either alone or in combination. Differentiation into the epithelial lineage was assessed by the expression of the characteristic epithelial markers CK18 and zonula occludens protein 1 (ZO-1) using Western blot, immunofluorescence staining and polymerase chain reaction (PCR) analysis. Results. The mixture of all three factors induced epithelial differentiation of ASC without enhancing cell proliferation. Upon induction, the ASC showed phenotypic changes consistent with an epithelial phenotype. The addition of the growth factors ActA and BMP-7 enhanced the inductive effect of ATRA, as shown by the de novo expression of ZO-1 in addition to CK18 expression. Conclusions. Our study highlights the onset of the epithelial differentiation of ASC induced by culture with a combination of ATRA, ActA and BMP-7.