Aj. Reynolds et al., A QUANTITATIVE STUDY OF THE DIFFERENTIAL EXPRESSION OF ALPHA-SMOOTH MUSCLE ACTIN IN CELL-POPULATIONS OF FOLLICULAR AND NON-FOLLICULAR ORIGIN, Journal of investigative dermatology, 101(4), 1993, pp. 577-583
Alpha-smooth muscle actin (ASMA) is an actin isoform present in the fi
laments of smooth muscle cells, myofibroblasts, and a specific region
of hair follicle dermal sheath in vivo. We employed double immunofluor
escence, two-dimensional electrophoresis, Western blots and DNA, prote
in, and actin isoform determinations to quantify the relative levels o
f ASMA in four populations of cultured hair follicle dermal cells, and
fibroblasts derived from three regions of adult and comparable areas
of 4-d rat skin. Although follicle sheath populations were morphologic
ally similar, they contained variable proportions of cells that expres
sed ASMA. Tissue from the most positive region in situ, the lower/mid
sheath, also gave rise to the most positive cells in culture (98%), fo
llowed by the end bulb (85%) and then upper sheath (50%). The follicle
dermal cells (including papilla 81%) displayed and maintained levels
of expression well above those obtained for adult (below 10%) or 4-d (
9-40%) fibroblasts, and even cultured smooth muscle cells. It was also
confirmed that levels of expression in adult fibroblasts could be pos
itively correlated with hair follicle density in the biopsies from whi
ch they were initiated. Differential expression of ASMA in follicle su
bpopulations provides an insight into how their behavior may be linked
to their specialized functions, for example, their likely involvement
in the mechanics of the hair cycle. Moreover, the proposition that ha
ir follicle dermal cells represent unappreciated constituents of gener
al skin fibroblast cultures has substantial implications.