Fig. 3.

Loss of label-retaining cells and increased epidermal turnover in Itga3 eKO mice. (A) The number of BrdU-LRCs is significantly reduced in back skin HFs of 8- and 14-wk-old Itga3 eKO mice compared with that in HFs of WT mice. LRCs occur almost twice less frequently in the IFE of Itga3 eKO mice (*P < 0.05). (B) LRCs are present in the IFE of Itga3 eKO mice and can proliferate (arrowheads) [nonspecific staining in the sebaceous glands (SGs)]. (Scale bar, 50 μm.) (C) Whole mounts of tail epidermis 24 h after a single application of TPA. Whereas a large number of LRCs are still present in the HF bulge of a WT mouse, very few LRCs remain in the HF of an Itga3 eKO littermate (nonspecific staining in SG). (Scale bars, 50 μm.) (D and E) Increased epidermal turnover and desquamation in Itga3 eKO mice is shown by fewer BrdU⁺ cells in the Itga3-null IFE 14 d after pulse and the accelerated loss of dansyl chloride from the epidermis of Itga3 eKO mice, respectively (*P < 0.05, **P < 0.01, ***P < 0.001). (Scale bar, 20 μm.) (F) Short-term treatment of mouse back skin with TPA induces hyperproliferation, which does not significantly differ between Itga3 eKO mice and WT littermates. DMBA treatment causes apoptosis in very few cells of the IFE of WT and Itga3 eKO mice. Treatments were a single dose of TPA, effect analyzed 24 h later; a single dose of DMBA followed by four doses of TPA spread evenly over 14 d, effect analyzed 24 h later; the respective vehicle controls (acetone); treated and analyzed in parallel; a single dose of DMBA, number of apoptotic cells (active caspase-3 IHC) analyzed 24 h later. (G) Increased proliferation in HFs of Itga3 eKO compared with that in HFs of WT mice (*P < 0.05). (Scale bar, 50 μm.)