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Stem Cell Markers and Alopecia
Researchers found different stem cell distribution in scarring and nonscarring alopecias.
Stem cells in the follicles may develop differently depending on location. Stem cells localized in the bulge are thought to be involved in the cyclical regeneration of hair follicles. Immunohistochemical markers can be used to identify stem cell types. To date, the best marker for bulge stem cells is CK15. Comparing the expression of CK15 and two antibody markers that target stem cells in other areas of the hair (CD34 and nestin), these authors examined the role of stem cells in the development of scarring and nonscarring alopecias.
The researchers examined 84 alopecia tissue samples (50 scarring and 34 nonscarring). The scarring group included patients with lupus erythematosus, lichen planopilaris, folliculitis decalvans, dissecting cellulitis, follicular degeneration syndrome, pseudopelade, traction alopecia, and end-stage scarring. The nonscarring group included patients with androgenetic alopecia, alopecia areata, telogen effluvium, and trichotillomania.
Immunohistochemical staining identified CK15 expression in the bulge and in the peripheral outer root sheath (ORS) above the arrector pili muscle. CD34 was detected in the peripheral ORS below the arrector pili muscle, and nestin was found in the inner ORS and in the infundibulum above the sebaceous gland.
In comparisons between alopecia types, only 53% of the scarring group showed CK15 at the bulge, compared with 100% of nonscarring samples. Nestin expression in the infundibular region was more common in scarring than in nonscarring alopecias (39% vs. 22%), but, in the inner ORS, nestin expression was present in all nonscarring samples and rarely found in scarring samples. Expression of CD34 in the peripheral ORS was seen in only 69% of scarring samples versus 100% of nonscarring samples.
Comment: Biopsy examination provides insight into the physiopathology of alopecia and may also predict the possibility of improvement or recuperation. The cellular heterogeneity of different hair follicle compartments might reflect different developmental pathways and functions. The enhanced expression of nestin in the infundibulum in scarring alopecias could point to a pool of stem cells identifiable by immunohistochemical staining and available for therapeutic intervention.
Published in Journal Watch Dermatology April 17, 2009
Citation(s):
Hoang MP et al. Stem cell markers (cytokeratin 15, CD34 and nestin) in primary scarring and nonscarring alopecia. Br J Dermatol 2009 Mar; 160:609.
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