Retinal pigment epithelial phenotype induced in human adipose tissue-derived mesenchymal stromal cells

The non-exudative form of age-related macular degeneration (ARMD) is characterized by a progressive decay of retinal pigment epithelium cells at the posterior pole of the eye. As mesenchymal stromal cells (MSC) have been shown to differentiate into various cell types from the mesodermal and ectodermal lineages, we investigated whether we can induce a phenotype displaying retinal pigment epithelium (RPE) characteristics.

The differentiation of human lipo-aspirate-derived MSC toward the RPE lineage was triggered by exposure to conditioned medium from either human or porcine RPE cells. In a second approach we tested whether adding vasoactive intestinal peptide (VIP) is capable of further modifying differentiation processes. Resulting cell populations were assessed for expression of RPE-specific markers by immunofluorescence, quantitative real time (RT)-polymerase chain reaction (PCR) and Western blotting. The potential for pigment synthesis was assessed by the response to melanocyte-stimulating hormone (MSH).

Following culture of undifferentiated MSC with RPE-conditioned medium and/or VIP, expression of typical RPE markers bestrophin, cytokeratins 8 and 18 and RPE 65 was induced. MSH induced the formation of pigmented granula in differentiated MSC.

MSC are shown to express RPE markers upon induction with either RPE-conditioned medium and/or VIP. The gain of basic functional features of RPE cells was indicated by melanin synthesis. This alludes to a differentiation potential of MSC into the neuroectodermal lineage, yielding cells with phenotypic characteristics of RPE cells.