Enhanced expression of caspase-3 in hypertrophic scars and keloid: Induction of caspase-3 and apoptosis in keloid fibroblasts in vitro

Recent studies have suggested that the regulation of apoptosis during wound healing is important in scar establishment and development of pathological scarring. To examine the phenomenon of apoptosis and its involvement in th e process of pathological scarring, we immunohistochemically quantified dif ferential levels of expression of caspase-3 and -2, which are activated dur ing apoptosis in vitro, in surgical resected scar tissues. We divided 33 ca ses of normally healed flat scars and 18 cases of pathological scars (15 ca ses of hypertrophic scars and 33 cases of keloid) into three groups (S1 = < 10 months' duration; S2 = 10 to 40 months' duration; and S3 = >40 months' d uration) according to the duration of scar. In all three groups examined, t he semiquantitative scores for caspase-3 staining were significantly higher for the combination of hypertrophic scars and keloid as a group compared w ith normally healed flat scars, suggesting reduced cell survival and increa sed apoptotic cell death in hypertrophic scars and keloid. Apoptosis and ca spase proteolytic activities were examined in vitro using two flat scar-der ived fibroblast lines (FSFB-1 and -2) and two keloid-derived fibroblast lin es (KFB-1 and -2). After 24 hours of serum deprivation, apoptotic cells wer e significantly increased in both KFB lines, whereas serum deprivation of F SFB-1 cells did not result in a significant increase in apoptotic cell numb er. After serum deprivation, significant increases in caspase-3 proteolytic activities were detected in both KFB lines compared with both FSFB lines. In contrast, no significant differences with caspase-8 activity were observ ed between similarly treated KFB and FSFB lines. Furthermore, serum depriva tion-induced apoptosis of KFB-2 cells was significantly inhibited by the ca spase-3 inhibitor Ac-Asp-Glu-Val-Asp-fluoromethyl ketone (DEVD-FMK), indica ting that caspase-3 is important for serum deprivation-induced apoptosis in KFB-2 cells. Considering the role of caspase-3 as a key effector molecule in the execution of apoptotic stimuli, our results suggested that enhanced expression of caspase-3 in hypertrophic scars and keloid induces apoptosis of fibroblasts, which may play a role in the process of pathological scarri ng.