The wounded dermal equivalent offers a simplified model for studying wound repair in vitro

Dermal equivalents (DEs), fabricated by seeding fibroblasts into a collagen lattice, may be used as in vitro models for studying wounding and the remodelling processes observed in vivo. We investigated fibroblast responses to a wound stimulus in vitro by making small wounds in DEs. We found that, following wounding, fibroblasts appeared to migrate towards and into the wound defect and appeared to initiate the closure of the wound by bringing together the cut collagen surfaces over a period of 5-11 days. Fibroblast movement into the wound defects was significantly stimulated in the presence of EGF and PDGF (2.8- and 3.5-fold respectively) but not TGF-beta. Cell proliferation in wounded DEs was up to 21% greater than in non-wounded DEs and cell numbers were stimulated further by the addition of TGF-beta, EGF and PDGF (1.5-, 1.7- and 1.8-fold respectively). Wounded DEs also displayed a 2.1-fold increase in latent collagenase production followed by a 1.3-fold increase in active collagenase levels compared to non-wounded DEs. Staining actin fibers within fibroblasts using rhodamine-phalloidin showed that fibroblasts in DEs were under tension, but that this tension was lost upon wounding. Subsequently the stress fibers reappeared concomitantly with the observed "healing" process. Additionally a continuous cell-cell actin cable purse-string developed around the entire wound edge which may be involved in wound closure. The findings suggest that the wounded dermal equivalent offers a valuable model for studying wound healing in vitro.