What controls hair follicle cycling?

Despite more than a hundred years of professional hair research, and substa ntial recent progress in unravelling the molecular controls of hair follicl e morphogenesis, the chronobiological control system that cyclically drives the hair follicle through dramatic remodelling processes between phases of growth (anagen), regression (catagen), and relative resting (telogen) have remained disappointingly obscure. In view of the vast literature that has become available over the past decades on numerous genetic, biochemical, ce llular and pharmacological aspects of hair growth control under physiologic al and pathological conditions, it is astounding how comparatively few rese archers in the field have published theoretical concepts that explore how h air follicle cycling might be controlled. Since this question is at the ver y heart of basic and clinically applied hair biology, it deserves a much mo re systematic and serious public exploration, which the following contribut ions are designed to stimulate.