TGF-β1 stimulates cultured human fibroblasts to proliferate and produce tissue-like fibroplasia: A fibronectin matrix-dependent event

TLDR

During wound repair and fibrotic disorders, fibroblasts accumulate and form fibroplasia, a process promoted by TGF‑β, yet normal fibroblasts cease proliferating once confluent in culture. The study aimed to define TGF‑β1‑based culture conditions that enable human fibroblasts to proliferate and stratify into tissue‑like fibroplasia in vitro. TGF‑β1, together with serum, ascorbate, and proline, stimulated post‑confluent human dermal fibroblasts to proliferate, stratify into up to 16 layers, and form a tissue‑like fibroplasia that depended on fibronectin matrix assembly but not on collagen matrix. © 1997 Wiley‑Liss, Inc., J Cell Physiol 170:69–80.

Abstract

During wound repair, fibroblasts accumulate in the injured area until any defect is filled with stratified layers of cells and matrix. Such fibroplasia also occurs in many fibrotic disorders. Transforming growth factor-β (TGF-β), a promotor of granulation tissue in vivo and extracellular matrix production in vitro, is expressed during the active fibroplasia of wound healing and fibroproliferative diseases. Under usual tissue culture conditions, normal fibroblasts grow to confluence and then cease proliferation. In this study, culture conditions with TGF-β1 have been delineated that promote human fibroblasts to grow in stratified layers mimicking in vivo fibroplasia. When medium supplemented with serum, ascorbate, proline, and TGF-β was added thrice weekly to normal human dermal fibroblasts, the cells proliferated and stratified up to 16 cell layers thick within the culture dish, producing a tissue-like fibroplasia. TGF-β stimulated both DNA synthesis as measured by 1H-thymidine uptake and cell proliferation as measured by a Hoechst dye DNA assay in these postconfluent cultures. The stratification was dependent on fibronectin assembly, as demonstrated by anti-fibronectin antibodies which inhibited both basal and TGF-β-stimulated cell proliferation and stratification. Suppression of collagen matrix assembly in cell layers with β-amino-proprionitrile (BAPN) did not inhibit basal or TGF-β stimulated in vitro fibroplasia. BAPN did not interfere with fibronectin matrix assembly as judged by immunofluorescence microscopy. Thus, in concert with serum factors, TGF-β stimulates postconfluent, fibronectin matrix-dependent, fibroblast growth creating a fibroplasia-like tissue in vitro. J Cell Physiol 170:69–80, 1997 © 1997 Wiley-Liss, Inc.