Mechanical Cues Regulate Estrogen and Progesterone-Induced Nascent ECM Deposition by Human Endometrial Stromal Cells

The endometrium, the mucosal lining of the uterus, is a highly regenerative tissue that undergoes cyclic remodeling guided by tightly regulated levels of estrogen and progesterone. Stromal cells are embedded within the connective tissue of the endometrium and contribute to the rapidly changing extracellular matrix (ECM). With hormone exposure, endometrial stromal cells undergo decidualization, which alters their morphology and protein secretion. While an increase in tissue modulus is associated with gynecological diseases, the relationship between mechanical properties, hormone exposure, and ECM deposition remains poorly understood. Here, we investigated how both stiffness and hormones regulate ECM deposition by human endometrial stromal cells during decidualization. Using metabolic labeling with sugar analogs and click chemistry, we measure newly secreted ECM proteins deposited by endometrial stromal cells during decidualization. Additionally, we study the nascent ECM in response to different mechanical properties using hyaluronic acid hydrogels. To increase throughput and reproducibility, we designed an automated ImageJ-based workflow for unbiased quantification of nascent ECM deposition. Our results demonstrate that hormones induce decidualization, characterized by F-actin stress fiber formation and prolactin secretion. In addition, we show that decidualization on hydrogels is characterized by an increase in nascent ECM deposition which depends on the initial hydrogel modulus. In contrast, endometrial stromal cells on glass show little change in nascent ECM deposition during hormone exposure. Collectively, these findings demonstrate that both mechanical and biochemical cues regulate ECM deposition during endometrial remodeling. These observations may provide new insights towards future studies addressing the mechanisms of ECM remodeling in gynecological diseases.