Release and Activation of Matrix Metalloproteinase-9 During In Vitro Mechanical Compression in Hypertrophic Scars

Objective To investigate induction of matrix metalloproteinases (MMPs) during mechanical compression of hypertrophic scars. Mechanical pressure blocks hypertrophy inducted on extracellular matrix in scars by a mechanism that involves MMP-2 (gelatinase A) and MMP-9 (gelatinase B). Design We assayed conditioned media obtained from normotrophic and hypertrophic scars during 24 hours of in vitro mechanical compression using gelatin zymography. Setting Scars from various areas of the bodies of hospitalized patients. Patients We obtained 3 normotrophic and 7 hypertrophic biopsy specimens from 10 patients (5 men and 5 women). Intervention In vitro compression at a pressure of 35 mm Hg/cm 2 for 24 hours. Main Outcome Measures Vitality of scars was analyzed by means of lactic dehydrogenase test; medium samples were collected for zymographic analysis of MMP activity. Results We found MMP-2 in basal (uncompressed) samples from normotrophic and hypertrophic scars. Mechanical compression induced MMP-9 release and activation (range, 86.7%-78.7%) in hypertrophic scars after 4 hours. Conclusion Production, release, and activation of MMP-9 in hypertrophic scars could be an effector mechanism responsible for hypertrophy regression induced by mechanical compression.