Expression of matrix metalloproteinases in sun-exposed and-unexposed skin

Abstract

Objective To study the expression of matrix metalloproteinase(MMP)-1,-3 and-9 in sun-exposed and-unexposed skin as weil as its significance in the mechanism of skin photoaging.Methods Skin samples were resected from the exmnsor side of forearm(sun-exposed area)and flexor side of upper arm(sun-unexposed area)of 23 healthy female volunteers.The expression of MMP-1,-3 and-9 was detected by immunohistochemical staining in 46 skin samples.Immunoreactive intensity distribution index (IRIDI)was calculated to assess the expression of MMP-1,-3 and-9.Wilcoxon signed ranks test,Mann-Whitney U-test and Spearman rank correlation analysis were performed.Results MMP-1,-3 and-9 were expressed in both sun-exposed and -unexposed skin.The average IRIDI value for MMP-1,-3 and-9 was 7.70(range,3 to 12).9.22(range,6 to 12),8.30(range,6 to 12)in sun-exposed skin,and 4.26 (range,2 to 6),5.39(range,2 to 9),4.04(range,1 to 6)in sun-unexposed skin,respectively;significant difierence existed between sun.exposed and-unexposed skin in the three parameters(all P＜0.01).A significant inerease was observed in the average IRIDI value for MMP-1,-3 and-9 in sun-exposed skin vs.sun-unexposed skin in women above 50 years of age (9.17 vs 4.75,10.58 vs 6.42,8.92 vs 4.33,respectively,all P＜0.05).In women younger than 50 years,the average IRIDI value for MMP-1,-3 and-9 was 6.09(range,3 to 8),7.73(range,6 to 9),7.64(range,6 to 12)in sun-exposed skin,significantly higher than that in sun-unexposed skin[3.73(range,2 to 6),4.27(range,2 to 8),3.73(range,1 to 6),all P＜0.05].Increased IRIDI scores of MMP-1,-3 and -9 were noticed in sun-exposed skin in women above 50 years of age vs.those younger than 50 years.but there was no statistical difrerence in MMP-I or MMP-9 between the two aged groups in sun-unexposed skin(all P＞0.05).The IRIDI scores of MMP-1,MMP-3 and MMP-9 were positively correlated with age(r=0.66,0.69,0.74,all P＜0.01)in sun-exposed skin,but the IRIDI scores of MMP-1 and MMP-9 uncorrelated with age in sun-unexposed skin.Conclusions There isan elevated expression of MMP-1,-3 and.9 in sun-exposed skin VS.SUn.unexposed skin.hinting that these three MMPs play a role in the occurrence and development of photoaging,but their biological mechanism may be different. Key words: Skin aging; Matrix metalloproteinase 1; Matrix metalloproteinase 3; Matrix metalloproteinase 9