Induction of mRNA for matrix metalloproteinase 1 and tissue inhibitor of metalloproteinases 1 in human skin in vivo by solar simulated radiation

Repeated exposure to solar ultraviolet radiation results in premature skin aging due, in part, to the degradation of dermal collagen by fibroblast col lagenase (matrix metalloproteinase 1 [MMP-1]). We have established TaqMan(T M) reverse transcription (RT) polymerase chain reaction (PCR) systems to qu antify the messenger RNA (mRNA) expression of MMP-1 and its specific inhibi tor TIMP-1 in human buttock skin exposed in vivo to solar simulated radiati on (SSR). A time-course study (n = 6) with two minimal erythema doses (MED) of SSR showed maximal induction of MMP-1 and TIMP-1 at 24 h. A dose-respon se study (n = 6) sampled at 24 h revealed that doses of about 1 MED were ne cessary to induce expression of MMP-1 mRNA, and our data suggest that the r esponse is saturated at about 2 MED. We also investigated SSR-induced gene expression in the dermis and epidermis separately (n = 5). MMP-1 was presen t in both tissues, but TIMP-1 was only detected in the dermis, In general, we could only measure MMP-1 mRNA in the nonirradiated control skin of volun teers who were smokers. We hypothesize very large interpersonal variation w ith MMP-1 induction compared with TIMP-1 which was detected in all the cont rol sites. This suggests a lack of relationship between MMP-1 and TIMP-1 mR NA expression. The large donor variability for MMP-1 in all the studies dem onstrates that it is important to analyze gene expression individually.