Assaying Candidate Human Skin Keratinocyte Stem Cells by Determining Their Long-Term Serial Proliferative Output in...

Stem cells are found in niches around the body, including the epidermis of the skin, and can be distinguished from their more committed progeny by their high long-term proliferative capacity in vitro. Here we describe a technique used to isolate three main epidermal cell fractions from human neonatal foreskin termed early differentiating (ED), transient amplifying (TA) and keratinocyte stem cells (KSC) based on their differential expression of two cell surface markers: CD49f and CD71. These three fractions were cultivated in parallel in a serial proliferation assay to determine their long-term proliferative output. This assay demonstrates that the KSC fraction had the highest proliferative output (total cell yield) over a long experimental timeframe of 2-3 months, as well as a higher proliferative rate compared to the other two fractions (P > 0.05). This assay can be utilized under similar conditions to determine the proliferative capacity of other putative stem cells using novel stem cell markers for epidermal or other stem cell populations.