Human  cells react to irradiation by UV-B light with a number of genetic changes, including the expression of distinct genes, which has been named the UV response. UV-B inducible genes comprise several proteinases, among the matrix metalloproteinase (MMPs), a superfamily of zinc dependent endopeptidases that is capable of degrading all extracellular matrix component, contributing to the breakdown of dermal interstitial collagen and other extracellular matrix components and thus apart from initiate and drive widespread atrophic scar in remodeling phase of wound healing.

This was in vitro studies of effects of UV-B irradiation o n the viability of confluent dermal fibroblasts, pro MMP -1, -3, levels and pro a1 (I) and (III) collagen, using monolayer cultu

res. The viability of confluent dermal fibrolasts was measured 24 h after incubation. 3-(4,5-dimetylthiazol-2-yl) -2,5- diphenyltetrazolium bromide (MTT-SIGMA) was used to quantify living metabolically active cells as described elsewhere (Fisher, 2001). Pro MMP-1 and pro MMP-3 ‘sandwich’ ELISA assays were performed according to the manufactures’s protocols (AMERSHAM Bioscience). Total cellular RNA was isolated from fibroblasts after dissolving in Trizol reagent (SIGMA Aldrich, Cat 15596-026) according to the manufactures’s instruction. Primers were derived from GeneBank sequences and where designed by Gene Works squence analysis software.

It was found that cells viability declined up to 55% by 10 Mj-uvb irradiation, 71,5% by 20 mJ and 75,40% by 40 mJ UV-B. There was decrease of cDNA pro a1 (I) colagen after irradiation 10 mJ and 20 mJ, but the level back to as higher as control after  40 mJ irradiation, but cDNA pro a1(III) collagen was increase, the level back to as higher as control after irradiation 40mJ. Pro MMPs-1, 24 h after UV-B irradiation at a dose 10 mJ (2,4 fold increase), in 20 mJ (8,69 fold increase) and 40 mJ (5,27 fold increase), regarding pro MMP-3 level, was an increase at a dose 10 mJ (1,52 fold increase), 20 mJ (2,27 fold increase) and 40 mJ (1,69) fold increase), compared with cells without irradiation.