| BackgroundThe hair follicle (HF) is a highly sensitive mini-organ whose cyclic transformations from phases of rapid growth (anagen), via regression (catagen) to relative quiescence (telegen) are profoundly influenced by numerous growth factors, cytokines, hormones, neuropeptides, and pharmaceutical products. Recent studies have provided insight into molecular control of HF induction and early morphogenesis. However, the mechanisms governing adult HF growth (anagen), regression (catagen) and quiescence (telogen) -that is, the hair cycle - remain a mystery.Hair follicle (HF) cycling is associated with substantial structural reorganization of the HF itself. The HF consists of a permanent (upper) portion and a cycling lower portion that undergoes cycles of complete destruction and restoration. HF transition from anagen to telogen is a physiological process of programmed organ involution, which is characterized by tightly coordinated apoptosis in the cyclic portion of the HF epithelium. During spontaneous HF regression, apoptosis first occurs in the HF matrix keratinocytes closely adjacent to the dermal papilla, and then, in more advanced catagen stages, is seen in the regressing outer and inner root sheaths and in the epithelial strand. This leads to the rapid shortening of cyclic portion of the HF associated with dermal papilla relocation from the subcutisto the dermis/subcutis border, where it contacts secondary hair germ and bulge.Apoptosis is a central feature of the developing and cycling hair follicle, and it may be expected that disruption of the exquisite intrafollicular controls of keratinocyte proliferation and apoptosis may lead to profound alterations of HF morphogenesis and cycling. The hair cycle stage is clinically soimportant because most cases of hair loss seen in clinical practice involve premature termination of hair follicle growth (anagen) and induction of catagen. Classically, this is seen in alopecia areata, chemotherapy-induced alopecia, and "telogen effluvium", but also in androgenetic alopecia, where progressive shortening of the anagen phase results in the vellus transformation of terminal follicles.Alopecia is one of the most distressing side-effects of many chemotherapeutic agents. In addition to the traumatizing stigma of hair loss there often is also a rather defective re-growth of abnormally structured and/or discolored hair. Although several animal studies have reported various drugs to be effective in preventing chemotherapy-induced alopecia or in promoting the re-growth of normal hair shafts, up to now there has been no effective and safe treatment available for this severe, psychologically devastating hair growth disorder in oncologic patients. It is now known that chemotherapeuic agents are potent inducers of apoptosis. Evidence from both electron microscopy and the terminal UTP nucleotide end labeling (TUNEL) method suggests that the massive induction of apoptosis in the hair follicle is one of the mechanisims by which cytostatic drugs damage growing (=anagen) hair follicles.It was shown previously that some Chinese herbal medicines could promote hair growth at an organ culture model of mouse vibrissa follicles in vitro. In this study, an animal model of C57BL/6 mice was used to investigate the effects and the possible mechanisms of several Chinese herbal medicines on hair cycles and apoptosis in normal catagen hair follicles. Furthermore, we also studied the effects of Chinese herbal medicine on hair growth in chemotherapy-induced alopecia mice. ObjectivesThe purposes of the present studies were: (1) to investigate the effects and the possible mechanisms of several Chinese herbal medicines on promoting murine hair follicles growth in vivo; (2) to study the effects ofChinese herbal medicines on hair growth in chemotherapy-induced alopeciamice.MethodsStudy one: normal C57BL/6 mice with hair in telogen as animal model, anagen was induced by depilation of hair shafts with wax/resin mixture, and the water fraction of herbal medicine (p.o. 0.2g/ml of... |
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