The wound environment as a regulator of fibroblast phenotype

Fibroblasts are fundamental to successful wound healing. We hypothesized that the induction and regulation of various fibroblast functions (proliferation, collagen synthesis, and remodeling) are determined by the wound environment. We examined the effect of wound fluid (WF), as a reflection of the wound environment, on the phenotypic expression of normal dermal (NF) and wound-harvested fibroblasts (WHF). WF and WHF were obtained from implanted polyvinyl alcohol sponges in 10-day-old wounds. NF and WHF were used between one and three passages. Proliferative function was assayed in a microculture system using serum stimulation ( n = 12). The proliferative response of both NF and WHF to serum was significantly reduced by the addition of 20% WF (17,261 ± 1231 cpm vs 2704 ± 1215 cpm for NF, P < 0.05; and 15,391 ± 3735 cpm vs 1701 ± 816 cpm for WHF, P < 0.05 in serum and WF, respectively). Total protein synthesis (measured by [ 3H]proline incorporation) was equal in both fibroblast types; however, the relative collagen synthesis (collagenase-digestible fraction) was markedly different (2.2 ± 0.9% for NF vs 11.4 ± 2% for WHF, P < 0.05). Addition of WF markedly enhanced NF collagen synthesis to 9.4 ± 2%, but had no effect on WHF. Mechanical and remodeling functions were assayed using fibroblast-populated collagen lattices. In serum, WHF contracted the lattices faster than NF (499 ± 14 mm 2 vs 770 ± 30 mm 2 at 24 hr, P < 0.05, and 301 ± 18 mm 2 vs 540 ± 21 mm 2 at 72 hr, P < 0.05). Addition of WF further increased lattice contraction by WHF and induced enhanced contractile activity in NF. Thus, WHF demonstrate reduced proliferation and enhanced collagen synthesis and remodeling in comparison to NF. The phenotype of NF can be altered to resemble WHF by the addition of 10-day-old WF. Thus, the wound environment alters fibroblast phenotype to facilitate wound repair by maximizing collagen synthesis and remodeling, while down-regulating proliferation.