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/cm² for 24 hours. Main Outome 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.