Cell Biology

Stem Cells by a Whisker

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Science  21 Oct 2005:
Vol. 310, Issue 5747, pp. 407
DOI: 10.1126/science.310.5747.407d

During normal mammalian hair growth, hair follicles undergo phases of growth, regression, and rest throughout the life of the animal. At the onset of the growth phase, cells recruited from the hair bulge form a hair germ, from which a new hair bulb develops. The adult hair bulge harbors keratinocyte cells, some of which are capable of clonal growth in cell culture, which may represent progenitor cells that underlie the formation of different hair follicle cell lineages or may be multipotent stem cells that can sustain long-term hair follicle renewal.

Claudinot et al. now show that these follicular cells are bona fide mammalian stem cells. Single keratinocytes were isolated from the whisker follicles of adult rats, labeled and expanded in cell culture, and then injected into the skin of newborn mice when pelage hair was just being formed. Grafts were subsequently transplanted into nude mice. In some mouse hair follicles, all eight cell lineages present were constituted of entirely transplanted cells, including the root sheaths, hair shaft, sebaceous glands, and epidermis. Transplanted cells were still found after several hair cycles, which suggests that clonogenic keratinocytes are true multipotent stem cells. Furthermore, the transplanted rat cells retained the capacity to recognize and home to the mouse follicle hair bulge. In the future, stem cells from human hair follicles could be exploited to regenerate hair and reconstruct tissue in patients. — LDC

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.0507250102 (2005).

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