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A quantitative study of membrane coating granules in follicles undergoing experimental comedo formation.

The British journal of dermatology·1978
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Cohesion of horny cells during comedo formation. An electron microscope study.

The British journal of dermatology·1977
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The effect of vitamin A acid on experimentally induced comedones: an electron microscope study.

P C Woo-Sam

    The British Journal of Dermatology
    |March 1, 1979
    PubMed
    Summary

    Vitamin A acid effectively treats comedones by promoting non-cohesive hyperkeratinization, loosening and expelling blockages from hair follicles within seven days. Higher concentrations accelerate this process and alter cell structures within the follicle.

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    Area of Science:

    • Dermatology
    • Cell Biology
    • Histology

    Background:

    • Comedones are a primary feature of acne vulgaris, resulting from follicular hyperkeratinization and obstruction.
    • Oleic acid is known to induce a cohesive horny mass within hair follicles, mimicking comedone formation.
    • Understanding the follicular response to therapeutic agents is crucial for developing effective acne treatments.

    Purpose of the Study:

    • To investigate the effects of various concentrations of vitamin A acid on experimentally induced comedones.
    • To elucidate the cellular mechanisms by which vitamin A acid influences follicular keratinization and desquamation.
    • To determine the optimal concentration and timeframe for vitamin A acid's efficacy in resolving comedones.

    Main Methods:

    • Experimental induction of comedones using oleic acid in a model system.
    • Topical application of varying concentrations of vitamin A acid (retinoic acid) to induced comedones.
    • Histological and electron microscopic examination of follicular structures post-treatment.
    • Quantification of cellular changes, including hyperkeratinization, desmosome integrity, and membrane coating granules.

    Main Results:

    • All tested concentrations of vitamin A acid induced non-cohesive hyperkeratinization, leading to the expulsion of follicular contents within 7 days.
    • The highest concentration (0.1%) demonstrated the most rapid and pronounced non-cohesive desquamation.
    • Electron microscopy revealed thinning and easy rupture of horny cell membranes, scarcity of desmosomes, and absence of tight junctions in treated follicles.
    • Vitamin A acid also caused epithelial hyperplasia, increased mitotic activity, and a significant increase (approx. 70%) in membrane coating granules at a 0.025% concentration.

    Conclusions:

    • Vitamin A acid effectively resolves experimentally induced comedones by disrupting follicular hyperkeratinization and promoting desquamation.
    • The mechanism involves altering cell membrane integrity, reducing cell-to-cell adhesion, and potentially enhancing follicular epithelial turnover.
    • These findings support the therapeutic use of vitamin A acid in managing conditions characterized by follicular obstruction, such as acne vulgaris.