FIGURE 2. Periodic BMP signalling in the dermis and subcutaneous adipose tissue.

a, Different temporal stages are spatially laid across the skin strip. The dark-field illumination shows hair follicles (white) and Bmp2in situ hybridization (green). Note that the beginning and end of the hair cycle and the beginning and end of Bmp2in situ are out of phase. An, anagen; Comp, competent; Refr, refractory; Tel, telogen. Open arrow, the direction of the spreading waves; stop sign, boundary between anagen and refractory telogen. b, When the refractory telogen region becomes competent, anagen VI follicles still do not propagate. c, d, Bmp2 and Bmp4 expressions are detected by in situ and semi-quantitative PCR with reverse transcription. Both methods show that Bmp2 and Bmp4 are present in late anagen and refractory telogen, but absent in competent telogen. e, pSMAD immuno-staining is present in follicular epithelium, including in the bulge area (inset) and adjoining infundibulum (green arrow). f, Bmp2 expression (blue) co-localized within some Sudan-Red-positive adipocytes (red). g, Schematic summary of the hair-cycle rhythm (black) and the newly identified dermal rhythm (red). Together, they define four new functional stages. Catagen is omitted for simplification. Scale bars: a, 1 mm; b, 500 m; c, e, f, 200 m.