Differentiation and polypeptide expression in human papilla and dermal fibroblasts in vitro

Proliferation and differentiation of human scalp hair follicle papilla fibroblasts (PF) in the anagenic stage of development and of neighboring dermal fibroblasts (DF) of the same donor were studied with stem cell system-specific methods in primary and secondary populations in in vitro systems. Both populations differentiate along the sequence of mitotic fibroblasts (MF) MF I-MF II-MF III and postmitotic fibroblasts (PMF) PMF IV-PMF V-PMF VI-PMF VIIa/PMF VIIb, as described for fibroblast stem cell systems in general elsewhere (Bayreuther et al., Mutat. Res. 256, 233-242 (1991)). PF and DF populations are distinguished by a number of cell-biological parameters, like population dynamics, maximal cumulative population doublings (CPD), changes in cell type frequencies, changes in cloning efficiency as a function of the CPD level (CPDL) of mitotic mass population, in addition by distinct changes of cell type frequencies of postmitotic fibroblasts as a function of the duration of maintenance of postmitotic fibroblast population in stationary culture. Primary and secondary PFs express cell type-specific high molecular weight cellular polypeptides in the M(r) range of 190 to 270 x 10(3) and/or secrete cell type-specific low molecular weight polypeptides in the M(r) range of 27 to 28 x 10(3) as revealed by two-dimensional gel electrophoresis of [35S]methionine-labeled and [14C]proline-labeled polypeptides. These polypeptides are not expressed in the corresponding primary or secondary DF cell types. The expression of specific proteins in primary and secondary PF in vitro may correspond to specific functions of PF in vivo.