Localized proliferative effect of preadipocytes on cultured human epidermal keratinocytes

The effect of preadipocytes (ST 13) on cultured normal human epidermal keratinocytes (NHEK) was investigated. The growth of NHEK was accelerated with co-cultured ST 13 cells. This stimulative effect must have been localized around viable ST 13 cells, because neither the medium nor the surface conditioned by ST 13 or the ST 13 cell fragments showed any promotion of NHEK growth, and NHEK showed a compact, paving-like arrangement only when they were attached directly to ST 13 cells. It became clear that these compactly arranged keratinocytes have an active proliferative ability, since their nuclei showed a marked uptake of 5-bromodeoxyuridine (BrdU) and they were positively stained with anticytokeratin 37, a monoclonal antibody against the basal epidermis. Under electron microscopy, ST 13 preadipocytes were closely connected with NHEK. These results, together with those of previous reports, suggest that the localized proliferative effect of ST 13 cells on NHEK is due to cell-to-cell contact.