Contribution of Epithelial Cells to Defense Mechanisms in the Human Vagina
Purpose of Review
The vaginal milieu in women differs from that of other mammals, including non-human primates, in composition of secretions, the endogenous microbiota, and level of acidity. These changes apparently reflect evolutionary variations that maximized productive responses to a uniquely human vaginal environment. This review will highlight recent findings on properties of human vaginal epithelial cells that contribute to maintenance of a healthy vaginal environment.
Vaginal epithelial cells are responsive to the composition of the vaginal microbiome even in women who are in apparently good health and do not exhibit any adverse physical symptoms. This is especially important during pregnancy when immune defenses are modified and an effective epithelial cell-derived anti-microbial activity is essential to prevent the migration to the uterus of bacteria potentially harmful to pregnancy progression. When Lactobacillus crispatus numerically predominates in the vagina, epithelial cell activity is low. Conversely, predominance of Lactobacillus iners, Gardnerella vaginalis, or other non-Lactobacilli evokes production and release of a large variety of compounds to minimize the potentially negative consequences of an altered microbiome. The extent of autophagy in vaginal epithelial cells, a basic process that functions to maintain intracellular homeostasis and engulf microbial invaders, is also sensitive to the external microbial environment Vaginal epithelial cells bind and release norepinephrine and upregulate their anti-microbial activity in response to external stress.
Vaginal epithelial cells in women are responsive to local conditions that are unique to humans and, thereby, contribute to maintenance of a healthy milieu.
KeywordsAutophagy Stress Vaginal epithelial cells Vaginal microbiome
Compliance with Ethical Standards
Conflict of Interest
Iara M. Linhares, Giovanni Sisti, Evelyn Minis, Gabriela B. de Freitas, Antonio F. Moron, and Steven S. Witkin declare they have no conflict of interest.
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
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