Gelatinase activity in keloids and hypertrophic scars

Keloids and hypertrophic scars are characterized by excessive deposition of collagen, which may result from insufficient protein degradation. Little i s known about the levels of two gelatinases, matrix metalloproteinase-2 (72 kD type IV collagenase) and matrix metalloproteinase-9 (matrix metalloprot einase-9; 92 kD type IV collagenase) in these abnormal scars. The purpose o f this study was to determine levels of these proteinases in tissue from hy pertrophic scars, keloids, and donor skin. Ten hypertrophic scar samples, 9 keloid samples, and 10 donor skin samples were frozen, pulverized, homogen ized, clarified by centrifugation, and analyzed for matrix metalloproteinas es by quantitative zymography. Identity of matrix metalloproteinases was de termined using a conditioned media reference standard, molecular weight lad ders, and Western blotting. Levels of matrix metalloproteinase-9 activity w ere very low or undetectable in all samples. However, matrix metalloprotein ase-2 activity was significantly elevated in keloids and hypertrophic scars vs. donor samples: 2.6 and 3.9-fold increases for latent matrix metallopro teinase-2, 7.8 and 6.9-fold increases for active matrix metalloproteinase-2 , respectively. We conclude that little matrix metalloproteinase-9 activity (the gelatinase involved in early tissue repair) is present in keloids and hypertrophic scars, while matrix metalloproteinase-2 activity (the gelatin ase involved in prolonged tissue remodeling) is present in donor skin and i s significantly increased in hypertrophic scars and keloids.