Exploring the vaginal ecosystem: insights into host-microbe interactions and microbial community dynamics

The vaginal tract is a complex environment that changes throughout various life stages. Recent advances have improved our understanding of the vaginal microbiota and the influence of host factors on microbial colonization. The vaginal niche is characterized by unique qualities such as high abundances of glycogen and mucin, low pH, active cellular immunity, and fluctuations in hormone signaling that support a complex microbiota. While traditionally thought to be dominated by Lactobacillus species, emerging research highlights a more diverse microbiota, including both commensal and potentially pathogenic microbes. Given the interconnectedness of the microbial and host factors in this environment, minor shifts can lead to significant downstream effects on health. This review takes an ecosystems approach to explore the multifaceted relationship between the vaginal mucosa, the microbiota, and influences of environmental factors on shaping the two. We discuss the contribution of hormone signaling in shaping microbial communities, concepts of vaginal community stability and dysbiosis, and the emerging understanding of microbial metabolism and cross-feeding dynamics within the vaginal tract. Additionally, we will examine the interactions between microbes and immune cells in the vaginal mucosa, including mechanisms by which the immune system modulates the local environment. By considering the feedback loops between the host and the resident microbiota, we propose key knowledge gaps and suggest interdisciplinary avenues for future research aimed at improving our understanding of vaginal health and disease. Understanding these complex interactions is important for advancing vaginal healthcare across all individuals.