MMP1 and acne: The first comparative gene array expression profiling between inflammatory acne lesions and normal skin was carried out by Trivedi et al. in 2006 [79] and showed that many of the genes whose expression is increased in acne lesions are involved in inflammatory processes, the major genes including the matrix metalloproteinases MMP-1 and MMP-3, as well as the pro-inflammatory cytokine IL-8 and CXCL-2.