“…Increased vascularity of the dermis may be an important aspect of tretinoin treatment of photoaging and intrinsic aging of skin218; indeed, many of the clinical and histologie changes in the skin due to treti¬ noin treatment may require the increased blood flow that accompanies the increased vascularity. 19 As previously observed," tretinoin treatment increased intracellular (ie, fibroblast) staining for pN collagen I, indicating procollagen I formation and pre¬ sumably subsequent formation of collagen I. pN Colla¬ gen I was increased in fibroblasts of skin treated with both doses of tretinoin, although it reached statistical significance compared with vehicle treatment only in the 0.025% tretinoin group, presumably due to few samples in the 0.1% tretinoin group. Unlike our previ¬ ous study of photoaged forearms, we did not observe significant restoration of papillary dermal extracellular pN collagen I staining in tretinoin-treated facial skin, perhaps due to the relatively small number of biopsy specimens that were assessed.…”