Fig. 3. De novo hair follicle formation in interfollicular epidermis. (A-F) Histology of the paw skin of (A,C,E) wild-type and (B,D,F) transgenic (line D4) mice treated daily with 4OHT for 1 week. A,B are montages reconstructed from images of sections covering the entire circumference of the paw. The boxed regions in A,B are shown at higher magnification in C,E and D,F respectively. Arrows in F indicate new follicles arising from interfollicular epidermis. (G-J) Visualisation of alkaline phosphatase activity (blue) as a dermal papilla marker in back skin (G) and paw (H-J) of transgenic (line D4) mice 8 days after a single application of 4OHT. Arrows in G show alkaline phosphatase-positive cells associated with the original dermal papilla (lowest arrow) and with new follicles arising from interfollicular epidermis (top arrow) and outer root sheath (middle arrow). The boxed regions in H are shown at higher magnification in I,J. (I) Original dermal papilla; (J) Two new rudimentary follicles. Scale bars: 500 µm (A,B) 100 µm (C-J).