Conclusions
Our results suggest that ESC-CM contains a number of factors, including BMP4, which are capable of reprogramming mouse skin keratinocytes to make them more developmentally potent, as evidenced by their ability to be re-differentiated into cells of the neuronal lineage. Our findings also imply a continuum of differentiation within the basal keratinocyte population. An increase in developmental potential combined with directed differentiation could increase the therapeutic relevancy of somatic cells.
Methods
Contact and non-contact co-cultures of skin keratinocytes and murine ESCs were used initially to confirm any reprogramming ability of ESC-conditioned medium (CM). Immunofluoresence was used to assess nuclear expression of octamer-4 (Oct-4), as well as to confirm neuronal protein expression in neuroectodermally directed keratinocytes. Transcript expression changes were evaluated using semiquantitative reverse transcription-polymerase chain reaction. Western blotting, accompanied by densitometry analysis, was used to evaluate protein expression following morphology changes.
Results
We found that keratinocytes treated with ESC-CM changed their morphology and were stimulated to express the pluripotency regulator, Oct-4, and its target transcripts, Sox-2, Nanog, Utf1 and Rex-1. We demonstrate that at least one of the reprogramming factors is bone morphogenetic factor-4 (BMP4). Pre-treated keratinocytes could be specifically directed to differentiate into cells of the neuronal lineage. The majority of responsive keratinocytes were the epidermal stem cell population, with a small percentage of transit-amplifying cells also being affected. Conclusions: Our results suggest that ESC-CM contains a number of factors, including BMP4, which are capable of reprogramming mouse skin keratinocytes to make them more developmentally potent, as evidenced by their ability to be re-differentiated into cells of the neuronal lineage. Our findings also imply a continuum of differentiation within the basal keratinocyte population. An increase in developmental potential combined with directed differentiation could increase the therapeutic relevancy of somatic cells.