TGFBR2 Coordinates the Endometrial Response to Estrogen, Preventing Endometrial Hyperplasia and Associated Infertility

Sydney E. Parks,^1,2,3 Suni Tang,^1,3 Anna Catherine Unser,^1,3 Vanessa J. Joseph,^1,3 Ananya L. Bhonsley,^1,3Eunbi M. Chung,^1,3 Dominique I. Cope,^1,3 and Diana Monsivais^1,2,3,4

1Department of Pathology & Immunology, ²Cancer and Cell Biology Program, ³Center for Drug Discovery, ⁴Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX 77030, USA.


Abstract Text:

Approximately 25% of pregnancies experience complications or result in pregnancy loss, and women seeking fertility care are 10x as likely to have endometrial hyperplasia. Thus, defining the signals that coordinate endometrial receptivity and maintain healthy pregnancies are critical for improving both pregnancy outcomes and women’s overall health. To identify the mechanisms controlling the dialog between TGFβ/estrogen (E2)/progesterone (P4) signaling during early pregnancy, we generated a new mouse model with conditional inactivation of the TGFβ type 2 receptor, TGFBR2, using progesterone receptor cre (PRcre) (“Tgfbr2 cKO”). 6-month fertility trials demonstrated that Tgfbr2 cKO females were infertile (controls, 584 pups, n=6; Tgfbr2 cKO, 1 pup, n=6), and had a significantly reduced overall survival compared to their control counterparts. Tgfbr2cKO females that survived the 6-month trial all had reproductive tract masses (6/6), with one also presenting with metastases to the lungs. Analysis of female virgins demonstrated that even by 14 weeks of age, Tgfbr2 cKO females exhibit endometrial epithelial hyperplasia and a near total loss of glandular FOXA2 – a known tumor suppressor in the endometrium. Timed mating analyses demonstrated that defects in pregnancy occurred during the peri- and post- implantation stages, where compared to controls, Tgfbr2 cKO mice displayed fewer implantation sites at 4.5 days post coitum (dpc), 5.5 dpc, 6.5 dpc, and 8.5 dpc. Almost no implantation sites were recovered at 12.5 dpc in the Tgfbr2 cKO mice, indicating that embryo resorption was likely completed by this point. Molecular analyses of control and Tgfbr2 cKO implantation sites indicate a dysregulation of early pregnancy starting at implantation, that worsens throughout pregnancy and results in abnormalities in decidualization, uterine natural killer cell (uNK) invasion, and angiogenesis. At 4.5 dpc, implantation sites of Tgfbr2 cKO mice demonstrate an increase in E2-response genes such as Lifr, Lif, Lcn2, and Muc1, suggesting unopposed E2 response during early pregnancy. At 5.5 dpc, implantation sites of cKO females demonstrate a significant decrease in progesterone receptor (PR) expression. When treated with E2 and P4, endometrial epithelial organoids from Tgfbr2 cKO mice displayed increased Esr1 and E2-response genes, further suggesting a connection between SMAD4 and estrogen receptor (ER) in the mouse uterus. Analysis of published genome-wide ER and SMAD4 binding datasets revealed overlapping ER and SMAD4 binding peak within the PR promoter. Thus, we propose that TGFBR2, through its downstream transcription factor, SMAD4, modulate PR expression by co-binding its promoter with ER, ultimately controlling epithelial hyperplasia and pregnancy processes such as implantation, decidualization, and uNK recruitment.

Studies were supported by Eunice Kennedy Shriver National Institute of Child Health and Human Development grants R00-HD096057, R01-HD105800. Sydney Parks receives support from NIH T32 Training Grant Diversity Supplement (3T32HD098068-05S1; PI: Dr. Stephanie Pangas). Diana Monsivais, Ph.D. holds a Next Gen Pregnancy Award (NGP10125) from the Burroughs Wellcome Fund.