Selective enrichment and biochemical characterization of seven human skin fibroblasts cell types in vitro

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The mitotic and postmitotic populations of the human skin fibroblast cell line HH-8 are heterogeneous when studied in vitro. There are reproducible changes in the frequencies of the mitotic fibroblasts (MF), MF I, MF II, MF III, and the postmitotic fibroblasts (PMF), PMF IV, PMF V, PMF VI, and PMF VII. For biochemical characterization, methods for selective enrichment of homogeneous populations of these seven fibroblast cell types have been established. Clonal populations with 95% purity for the mitotic fibroblasts MF I, MF II, and MF III can be raised in uniform clone types of fibroblasts (CTF) CTF I, CTF II, and CTF III. Pure clonal subpopulations of MF I type cells are present in mass populations in the range of 1–20 cumulative population doublings (CPD). Populations of mitotic fibroblasts represent nearly homogeneous populations of MF II (75–85 % purity) in the range of 28–34 CPD and MF III (73–86% purity) in the range of 48–53 CPD. These populations can be easily expanded to up to 10 7–10 8 cells. The spontaneous transition of MF III to PMF VI takes 140–180 days. In order to shorten this period and increase the proportion of distinct postmitotic types, mitotic fibroblast mass populations (CPD 30–32, MF II: 75–85 % purity) have been induced by uv-irradiation to differentiate to nearly homogeneous populations of PMF IV, PMF V, PMF VI, and PMF VII within 4 to 36 days of culture. Using this method, 10 7 cells of one differentiation stage can be obtained. Spontaneously arising and experimentally selected or induced homogeneous clonal and mass populations of MF I, MF II, MF III, PMF IV, PMF V, PMF VI, and PMF VII express an identical differentiation-dependent and cell-type-specific [ 35S]methionine-labeled polypeptide pattern.