The arrector pili muscle, the bridge between the follicular stem cell niche and the interfollicular epidermis

Proximally, the arrector pili muscle (APM) attaches to the follicular stem cell niche in the bulge, but its distal properties are comparatively unclear. In this work, a novel method employing an F-actin probe, phalloidin, was employed to visualize the APM anatomy. Phalloidin staining of the APM was validated by comparison with conventional antibodies/stains and by generating three-dimensional reconstructions. The proximal attachment of the APM to the bulge in 8 patients with androgenic alopecia was studied using Masson's trichrome stain. Phalloidin visualized extensive branching of the APM. The distal end of the human APM exhibits a unique "C"-shaped structure connecting to the dermal-epidermal junction. The proximal APM attachment was observed to be lost or extremely miniaturized in androgenic alopecia. The unique shape, location, and attachment sites of the APM suggest a significant role for this muscle in maintaining follicular integrity. Proximally, the APM encircles the follicular unit and only attaches to the primary hair follicle in the bulge; this attachment is lost in irreversible hair loss. The APM exhibits an arborized morphology as it ascends toward the epidermis, and anchors to the basement membrane.

Decreased ATP synthesis and lower pH may lead to abnormal muscle contraction and skin sensitivity in human skin

BACKGROUND

Sensitive skin represents hyperactive sensory symptoms showing exaggerated reactions in response to internal stimulants or external irritants. Although sensitive skin is a very common condition affecting an estimated 50% of the population, its pathophysiology remains largely elusive, particularly with regard to its metabolic aspects.

OBJECTIVE

The objective of our study was to investigate the pathogenesis of sensitive skin.

METHODS

We recruited healthy participants with 'sensitive' or 'non-sensitive' skin based on standardized questionnaires and 10% lactic acid stinging test, and obtained skin samples for microarray analysis and subsequent experiments.

RESULTS

Microarray transcriptome profiling revealed that genes involved in muscle contraction, carbohydrate and lipid metabolism, and ion transport and balance were significantly decreased in sensitive skin. These altered genes could account for the abnormal muscle contraction, decreased ATP amount in sensitive skin. In addition, pain-related transcripts such as TRPV1, ASIC3 and CGRP were significantly up-regulated in sensitive skin, compared with non-sensitive skin.

CONCLUSIONS

Our findings suggest that sensitive skin is closely associated with the dysfunction of muscle contraction and metabolic homeostasis.

Improved penile histology by phalloidin stain: circular and longitudinal cavernous smooth muscles, dual-endothelium arteries, and erectile dysfunction-associated changes

OBJECTIVE

To investigate whether fluorochrome-conjugated phalloidin can delineate cavernous smooth muscle (CSM) cells and whether it can be combined with immunofluorescence (IF) staining to quantify erectile dysfunction (ED)-associated changes.

METHODS

ED was induced by cavernous nerve crush in rats. Penile tissues of control and ED rats were stained with Alexa-488-conjugated phalloidin and/or with antibodies against rat endothelial cell antigen (RECA), CD31, neuronal nitric oxide synthase (nNOS), and collagen-IV (Col-IV).

RESULTS

Phalloidin was able to delineate CSM as composed of a circular and a longitudinal compartment. When combined with IF stain for CD31 or RECA, it helped the identification of the helicine arteries as covered by endothelial cells on both sides of the smooth muscle layer. When combined with IF stain for nNOS, it helped the identification that nNOS-positive nerves were primarily localized within the dorsal nerves and in the adventitia of dorsal arteries. When combined with IF stain for Col-IV, it helped identify that Col-IV was localized around smooth muscles and beneath the endothelium. Phalloidin also facilitated the quantitative analysis of ED-related changes in the penis. In rats with cavernous nerve injury, RECA or Col-IV expression did not change significantly, but CSM and nNOS nerve contents decreased significantly.

CONCLUSION

Phalloidin stain improved penile histology, enabling the visualization of the circular and longitudinal compartments in the CSM. It also worked synergistically with IF stain, permitting the visualization of the dual endothelial covering in helicine arteries, and facilitating the quantification of ED-related histologic changes.