Cav-1-/- mice exhibit a net change in collagen synthesis. (A and B) Prolyl-4-hydroxylase (P4HB) expression in the skin from wild-type (A) and Cav-1-/- (B) mice. P4HB is a key enzyme in collagen biosynthesis that catalyzes the 4-hydroxylation of prolyl residues. Immuno-staining indicates positive labeling of the cells expressing P4HB. Representative images are shown from three animals per group. Note that the dermis of Cav-1-/- mice contains an increased number of P4HB positive cells. In addition, the P4HB positive cells in Cav-1-/- mice exhibited a marked increased expression of this enzyme. (C and D) In situ collagenase activity was determined using DQ-collagen type I, as substrate in skin from wild-type (B) and Cav-1-/- mice (C). Multiple cryostat sections of the skin from these animals were incubated overnight with DQ-Collagen type I, dissolved in LGT-agarose. Fluorescence due to collagenase activity (green) was found in the epidermis (e), stromal cells of the dermis (s) and in hair follicles (h). Note that we observed similar collagenase activity in the skin from both wild-type and Cav-1-/- mice. Take together, this data suggest that the skin from Cav-1-/- mice may displays a net increase in collagen synthesis and/or accumulation. Scale bar = 50 microns.