In vitro differentiation of MSC into cells with a renal tubular epithelial-like phenotype.

Bone marrow mesenchymal stem (stromal) cells (MSCs) are shown to differentiate into different renal lineages in in vivo injury models. Nevertheless, the in vitro differentiation of MSCs into a renal tubular epithelial lineage has not been investigated. We hypothesize that the injured renal epithelial cells express renotypic factors that may influence the differentiation of MSCs into a renal tubular epithelial lineage. MSCs were cocultured for up to seven days with injured or uninjured murine cortical tubular renal epithelial cells (MCTs), which are separated by a physical barrier; following the coculture, MSCs were examined for the expression of two renal tubular epithelial-specific markers, kidney-specific cadherin (Ksp-cadherin) and aquaporin-1 (AQP1). MSCs differentiated into a tubular epithelial-like phenotype, as shown by the appearance of Ksp-cadherin and AQP1 by day 7 when cocultured with injured MCTs. Further, MSCs showed tubulogenic characteristics when cocultured in a three-dimensional matrix. Nonetheless, MSCs cultured with the conditioned medium from injured MCTs, cocultured with ureteric bud cells, or treated with nephrogenic factors did not differentiate into renal epithelial cells. Based on our findings, we conclude that MSCs can differentiate into a renal epithelial lineage independent of cell fusion when cocultured with injured renal cells.