KSCs and their progeny exhibit equivalent epidermal tissue-regenerative capability when cocultured with early-passage dermal cells. (a–h) Epithelial tissue regeneration in organotypic cultures obtained from 4.5 × 10⁴ UF cells (a and b), KSCs (c and d), TA cells (e and f), and differentiating cells (g and h) on dermal equivalents populated with p1 foreskin dermal cells (p1 DEs) analyzed at day 4 (prior to lifting to the air-liquid interface; see a, c, e, and g) and at day 14 after airlift (b, d, f, and h). Note that the actively cycling TA cells had regenerated a thicker epithelium compared with the other fractions of keratinocytes by day 4 (e). By day 14, however, all fractions, including differentiating cells, had regenerated an epithelium of similar thickness and cellularity. Scale bar: 50 μm. (i–l) Coculture with minimally passaged dermal cells enhances the epidermal regenerative capacity of low numbers of differentiating α₆^dim basal keratinocytes. Here, 4.5 × 10⁴ (i and j) or 10⁴ α₆^dim cells (k and l) collected from a single FACS experiment were placed simultaneously in organotypic cultures consisting of either p7 DEs (i and k) or p1 DEs (j and l) and were harvested at day 14 after airlift. H&E-stained sections of these cultures show that while the tissue regeneration obtained from α₆^dim cells on the p7 DEs (i) can be compromised by decreasing the number of keratinocytes plated to 10⁴ (k), this can be compensated for by coculture with p1 DEs (l). Inset: higher magnification of regenerated epidermis from differentiating cells shown in k. Scale bar: 50 μm.