Epidermal Cells Expressing Putative Cell Markers in Nonglabrous Skin Near the Distal End of the Arrector Pili Muscle

This review examines current knowledge on human epithelial hair follicle stem cells, their markers, and outlines challenges in translating findings from murine studies to human research, but does not report new experimental results.

This study found that in androgenic alopecia, the arrector pili muscle degenerates and is replaced by fat, unlike in normal skin or telogen effluvium.

This study found that loss of contact between the arrector pili muscle and the hair follicle bulge may explain why hair loss in male and female pattern baldness is largely irreversible, unlike in alopecia areata.

This study found that in neonatal mice, the absence of the NG2 proteoglycan leads to reduced epidermal thickness and delayed subcutis thickening due to impaired proliferation and adipocyte deficiencies.

This study found that coculturing human hair follicle keratinocyte stem cells with dermal papilla cells increased expression of the hair-specific keratin 6hf gene, which requires β-catenin/lef-1 signaling for hair differentiation.

MCSP may help identify and regulate skin stem cells, affecting hair growth and regeneration.

The K15 promoter effectively targets stem cells in the hair follicle bulge.

This study demonstrated that multipotent stem cells in adult mice whisker follicles migrate to produce whisker growth, and that this process requires precise control of stem cell trafficking.

In this study, researchers found that hair follicle stem cells in mice can generate both hair follicle and epidermis cells, highlighting their potential bipotency.

This study found that keratin 15 expression is downregulated in hyperproliferative conditions like psoriasis and hypertrophic scars, suggesting it is not compatible with keratinocyte activation.

This study found that K15 is variably expressed in sheep and mouse hair follicles, with specific patterns suggesting a role in the early stages of keratinocyte differentiation.

In this study, researchers found that bulge cells in mouse hair follicles undergo transient proliferation during early anagen, indicating their role as follicular stem cells. However, another factor beyond dermal papilla proximity may be required to initiate a new anagen phase.