Abstract:

Objective To study the expression of matrix metalloproteinase（MMP）-1, -3 and -9 in sun-exposed and -unexposed skin as well as its significance in the mechanism of skin photoaging. Methods Skin samples were resected from the extensor 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 difference existed between sun-exposed and -unexposed skin in the three parameters （all P < 0.01）. A significant increase 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 difference in MMP-1 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 is an 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.