Identification of a cell layer containing ?-smooth muscle actin in the connective tissue sheath of human anagen hair

Abstract

Immunohistochemical and immunoelectron microscopy studies revealed the presence of alpha-smooth muscle (alpha-SM) actin in fibroblasts located in the connective tissue sheath (CTS) of human anagen hair follicles. Immunostaining was positive from the base of the bulb to the upper part of the lower portion of the mature anagen hair follicles. The late catagen hair follicles did not stain. Ultrastructurally, alpha-SM actin was detected only in the fibroblasts located in the innermost layer of the transverse collagenous fibres. Since alpha-SM actin is located in cells with contractile potential, this newly identified layer may play an important role in the morphological changes of the lower portion of the hair follicle during the hair growth cycle.

Age-Related Changes in Female Scalp Dermal Sheath and Dermal Fibroblasts: How the Hair Follicle Environment Impacts Hair Aging

“…Little αSMA expression was seen in the sheath, which may reflect the predominance of anagen follicles, raising the question whether αSMA is upregulated during follicle contraction. In murine catagen HFs, DS contraction pulls the DP upwards (Martino et al, 2020, Heitman et al, 2020; while this has not been observed in humans, higher αSMA DS expression in proximal anagen HF (Urabe et al, 1992) suggests the same mechanism occurs. In culture, DS expression of αSMA J o u r n a l P r e -p r o o f significantly reduced with age (Figure 3j), suggesting loss of DS traits.…”

Human hair shape is programmed from the bulb

“…Immunohistochemical and immunoelectron microscopic studies of human anagen follicles revealed the presence of α‐SMA in fibroblasts located in the innermost layer of the transverse collagenous fibres of the connective tissue sheath. These cells are thought to play an important role in the hair growth cycle 19 . Changes in α‐SMA expression in the dermal sheath during the hair cycle indeed suggested that α‐SMA, usually characteristic of dermal sheath cells (or myofibroblasts), could be related to contractile processes that might control hair follicle shortening.…”

“…These cells are thought to play an important role in the hair growth cycle. 19 Changes in a-SMA expression in the dermal sheath during the hair cycle indeed suggested that a-SMA, usually characteristic of dermal sheath cells (or myofibroblasts), could be related to contractile processes that might control hair follicle shortening. In nonmuscle cells, bundles of a-SMA filaments, associated with other proteins, perform specific functions such as contraction, mechanical support and cell adhesion.…”

Human dermal pericytes express 3G5 ganglioside – A new approach for microvessel histology in the skin

“…Two more novel findings from our study should be discussed. The first is the demonstration that myoepithelial cells (of the sweat glands) and myofibroblasts (of the hair follicle) 23,24 were negative with 3G5 mAB. In respect to the debate over whether pericytes give rise to myofibroblasts, 6 our results indicate that the PC is (at least by these criteria) a different cell type.…”