Primary cilium expression in cells from normal and aberrant human skin.

Primary cultures of diploid fibroblasts from human skin have a high incidence of primary cilia associated with their centrosomal centrioles, particularly in stationary phase ("quiescent") cultures. Their progenitor cells in vivo have this same high incidence. Repeated subculturing to > 25 generations did not significantly alter the frequency of expression of cilia. The expression of ciliation remained largely unaffected in fibroblasts grown in culture from cases of hypertrophic scar and keloid, but generally run at a marginally lower level. In contrast, keratinocytes--which have an equally high incidence of primary cilium expression in vivo--seldom express primary cilia in vitro, a distinction most clearly seen when both cell types were present within the same culture. Fibroblasts grown in keratinocyte medium at low total Ca++ concentration ( < 2 x 10-5 M) possessed the same high incidence of ciliation as cells in high Ca++ medium (concentration 1-2.5 x 10-3 M). Increased Ca++ levels in the medium, which induced differentiation of keratinocytes from their low calcium proliferative state, were accompanied by a small increase in the expression of primary cilia over 23 h. The divergent abilities of different cell types in primary culture obtained from a common origin, i.e. skin biopsies, to develop primary cilia are demonstrated, opening up avenues for exploration of factors required for their expression in culture.