Polycystic ovarian syndrome and premature ovarian failure are two of the most common causes of hormone imbalance and infertility in women, yet their underlying biological mechanisms have remained incompletely understood. A new study from researchers at the National Institute of Environmental Health Sciences, part of the National Institutes of Health, has now resolved a decades long mystery about the origin and function of a critical ovarian cell type, findings that could reshape how scientists approach the study and treatment of these reproductive disorders. The results were published in Nature Communications.
The Theca Cell Mystery at the Heart of Polycystic Ovarian Syndrome Research
The ovarian follicle is the basic functional unit of the ovary, consisting of a maturing egg surrounded by two distinct cell types: granulosa cells and theca cells. Scientists had previously established the cellular origins of the egg and the granulosa cells, but the origin of theca cells had remained unknown for decades. This gap in understanding was clinically significant because theca cells are essential to female hormone production, and their dysfunction is directly implicated in conditions including polycystic ovarian syndrome.
Using a technique called lineage tracing, NIEHS researcher Humphrey Yao and his colleagues determined that theca cells in mice originate from two separate sources, both inside and outside the ovary, from embryonic tissue known as mesenchyme. The finding that a single cell type can be assembled from two distinct cellular lineages was unexpected and suggests that theca cells may be more heterogeneous than previously recognized, a complexity that could be relevant to understanding why ovarian disorders like polycystic ovarian syndrome present so differently across patients.
How Theca Cells Drive Hormone Production and Follicle Growth
Without functional theca cells, women cannot produce the hormones necessary to sustain follicle growth and development. One of the primary hormones theca cells produce is androgen, a steroid commonly associated with male physiology but essential to female reproductive biology as well. In a precisely coordinated cellular collaboration, granulosa cells convert the androgen produced by theca cells into estrogen, the hormone that drives follicle maturation and the broader hormonal cycle.
The Yao research team also uncovered the molecular signaling pathway that enables theca cells to produce androgen. This communication system originates in granulosa cells and in the oocyte, the immature egg cell, and the crosstalk between all three cell types, the egg, the granulosa cells, and the theca cells, was an unexpected finding. For polycystic ovarian syndrome specifically, where androgen overproduction by theca cells is a defining feature, understanding this signaling pathway is directly relevant to identifying what goes wrong and where.
What This Means for Understanding Polycystic Ovarian Syndrome and Infertility
Chang Liu, first author on the paper and visiting fellow in Yao’s group, noted that the problem in ovarian disorders like polycystic ovarian syndrome starts within the theca cell compartment. Now that researchers know what drives theca cell growth and hormone production, they can begin searching for genetic mutations or environmental factors that disrupt that process, potentially identifying the upstream causes of conditions that have until now been managed primarily through their symptoms rather than their biological roots.
The study also opens new questions about why theca cells have two distinct cellular origins. The answer to that question may reveal additional layers of biological complexity relevant to understanding the range of presentations seen in polycystic ovarian syndrome and related disorders.
Next Steps in Ovarian Biology and Reproductive Disorder Research
Because this research was conducted in mice, Yao and his colleagues will need to verify that the same theca cell origins and signaling mechanisms apply in humans before the findings can be directly translated into clinical applications. That work is planned as a next step. If the human data confirms the mouse findings, the research could provide a biological foundation for new diagnostic markers and therapeutic targets in polycystic ovarian syndrome and premature ovarian failure.
FOMAT conducts clinical trials across multiple therapeutic areas including endocrinology and women’s health. To learn more about active studies, visit FOMAT’s patient studies page. To read more about reproductive and endocrine research, visit the FOMAT blog.
For the full source, see the original article at NIH.gov.