INCREASED PROLIFERATION IN KELOID FIBROBLASTS WOUNDED IN-VITRO

A keloid is a pathological overgrowth of scar expanding beyond the bou ndaries of the initiating skin wound. Ultimately, this expansive scar is a result of excess collagen synthesized by fibroblasts within the w ound, The processes that lead to this collagen excess remain unknown. An in vitro wound model was developed to test the hypothesis that fibr oblasts isolated from keloid tissue and wounded in vitro might prolife rate more rapidly than similarly wounded normal dermal fibroblasts, Ke loid fibroblasts (KF) and normal human dermal fibroblasts (NDF) were g rown to confluence and quiescence in flexible-bottomed culture plates, Wounds were created in a standardized fashion using a specially desig ned jig, The jig utilized a 25 gauge needle to reproducibly ablate 16- 20% of cells from confluent cell sheets. Wounded and nonwounded cells were labeled with H-3-thymidine at 24, 48, 72, and 96 hr postwounding to measure DNA synthesis. Wounded KF and NDF demonstrated increased H- 3-thymidine incorporation compared to nonwounded control cultures, and wounded KF demonstrated significantly higher levels of H-3-thymidine incorporation than wounded NDF both 24 and 48 hr after wounding. A sim ilar trend was seen in cell counts. The wounded KF also showed a stati stically greater labeling index quantitated by autoradiography than di d wounded NDF, The increased commitment to DNA synthesis in response t o wounding in vitro in keloid fibroblasts correlates with pathology se en in vivo. Keloid fibroblasts may have a lower inherent threshold for S phase entry than do normal fibroblasts contributing to the increase d proliferation of keloid fibroblasts in response to wounding in vitro . (C) 1996 Academic Press, Inc.