Effect of in vitro mechanical compression on epylisin (matrix metalloproteinase-28) expression in hypertrophic scars

Epilysin, designated matrix metalloproteinase (MMP)-28, is the newest member of this family of proteases expressed by keratinocytes in response to an injury. MMP-28's physiological role and specific substrates are unknown, but its expression pattern suggests that it may serve a role in both tissue homeostasis and wound healing. The aim of this preliminary study was to observe the presence of MMP-28 protein in normotrophic and hypertrophic scars and to evaluate the effect of in vitro mechanical compression on its expression. Biopsies from normotrophic and hypertrophic scars resulting from burns were divided into two samples, one to be used as control (uncompressed) and the other to be compressed in an oxygenated organ chamber for 24 hours in the presence of a serum-free medium, using an electromechanical load transducer (stable pressure = 35 mmHg). Analysis of MMP-28 protein secretion, assessed by Western blot and beta-casein zymography in scar conditioned media, revealed that normotrophic scar did not release MMP-28 in any condition while hypertrophic scar released active MMP-28 both in control conditions and after compression. MMP-28 immunohistochemistry revealed a light protein presence in normotrophic scar keratinocytes and a strong MMP-28 positivity in hypertrophic scar keratinocytes in control conditions, while compression increased MMP-28 staining in normotrophic scar and induced a significant reduction of the protein presence in hypertrophic scar keratinocytes. As it has been suggested that MMP-28 may restructure the skin basal membrane (Saarialho-Kere et al., 2002), our data indicate that mechanical compression directly acts to modulate the remodeling phase of wound healing, altering release and activity of MMP-28 in hypertrophic scars.