Mechanisms of Endometrial Repair

The uterus in women is a unique organ in its ability to undergo repeated physiological damage and repair during the monthly menstrual cycle. The endometrium, in particular, is extensively regenerated following menstrual shedding. Our long-term research goal is to understand the normal mechanisms of endometrial regeneration and repair and how these processes, when mis-regulated, contribute to diseases/dysfunction such as endometrial cancer, endometriosis, thin endometrium, Asherman’s Syndrome and infertility. In this project, experiments are designed to investigate mesenchymal-epithelial transition (MET) as a mechanism of endometrial epithelial regeneration. Research shows that MET is one mechanism by which the endometrial epithelium is regenerated postpartum and in a menses-like model in mice and has been proposed as a mechanism in women. During MET, which is a type of cellular transdifferentiation, a mesenchymal cell is reprogrammed and converted into an epithelial cell. To our knowledge, the endometrium is the only tissue that uses cellular transdifferentiation under normal physiological conditions (e.g. postpartum and menses-like repair) in the adult. Unfortunately, our understanding of this unique repair mechanism is very incomplete. Two specific aims will further investigate MET in epithelial regeneration: (1) Test the function of MET-derived endometrial epithelial cells; and (2) Compare MET by endometrial-derived and bone marrow (BM)-derived mesenchymal cells. A combination of mouse models including lineage tracing, menses-like endometrial breakdown and repair and a novel orthotopic transplantation technique along with scRNA-seq will be employed to address fundamental questions about the function, characteristics, and origin of MET-derived epithelial cells. Particularly, whether they are bona fide endometrial epithelial cells and whether they originate from endometrial stromal cells and/or bone marrow cells, will be investigated. Importantly, orthotopic transplantation will be used to assess MET by human stromal cells as in vivo studies cannot be performed in women. Proper endometrial regeneration, including replacement of lost or damaged epithelial cells, is necessary for preparation of the uterus for subsequent reproductive cycles and pregnancy. No other organ is subject to such extreme tissue regeneration as that seen in the uterus during the menstrual cycle. It is perhaps because of the extent of damage and repair that the uterus undergoes that it is subject to development of diseases. Increased understanding of endometrial repair mechanisms will provide greater insight into how these processes, when gone awry, contribute to endometrial diseases and impact fertility ultimately leading to better therapeutics.

Uterine Fibroid Pathogenesis

Uterine fibroids are the most common tumor observed in reproductive age women, occurring in 25-89% of women in the United States, and are the leading indication for hysterectomies due to associated morbidities. Approximately 25% of women present with clinically significant fibroids, the symptoms for which include, pelvic discomfort/pain, excessive menstruation, anemia, and recurrent pregnancy loss and infertility. A substantially greater proportion of African American women have fibroids, and are more symptomatic compared to Caucasian women, indicating a racial disparity. Short term therapies (Lupron, SERMs) are available and can provide some relief, but their long-term use is proscribed because of associated side-effects; the only definitive treatment for the disease is hysterectomy resulting in sterility. Therefore, there is a clear need for better therapeutic options. We performed RNA-seq on matched normal myometria and fibroids from women in order to better understand the disease at the transcriptomic level; our goal was to identify targets for novel therapeutic options that do not leave women sterile. Our results indicate that Periostin was over-expressed in the majority of fibroids analyzed. Periostin is an extracellular matrix protein that is a critical regulator and well-established biomarker for fibrosis in tissues such as lung, skin, and kidney. It has been further implicated in TGFb signaling and collagen deposition which are hallmarks of uterine fibroids but, Periostin’s direct association with uterine fibroids has not been previously documented. As a component of the extracellular matrix, Periostin may serve as an easily accessible target for potential drugs. Importantly, Periostin has recently been investigated as a druggable target for several diseases including breast, ovarian and colorectal cancer, kidney fibrosis, scar formation in traumatic spinal cord injury, and intestinal inflammation. It is the hope that the results from our research will provide evidence for the role of Periostin in uterine fibroid formation and give justification to further investigate its potential as a therapeutic target, thereby mitigating the need for fertility-robbing hysterectomy.

Ovarian Cancer Stem Cells and Metastasis

Ovarian cancer (OvCa) is the 5th leading cause of cancer deaths for women and ranks as the most lethal gynecological cancer in the United States. In 2021, it was estimated that 21,410 new cases were diagnosed and over 13,000 women’s lives will be taken by this disease. Epithelial OvCa, which encompasses 90% of OvCa types, can be subdivided into distinct histotypes including serous, endometroid, mucinous and clear cell. The serous histotype accounts for 52% of epithelial OvCa and high-grade serous OvCa (HGSOC), specifically, is responsible for the most fatalities. Eighty percent of OvCa patients with the serous histotype are diagnosed at stage III or IV with local and/or distant metastases and have only a 42% and 26% chance at 5-year survival, respectively. Since serous OvCa, particularly HGSOC, is so often caught in the late stages, the mechanisms of development and growth are largely unknown. Cancer stem cells (CSCs) are rare cells found within a tumor that, like normal tissue stem cells, can both self-renew and give rise to the different cell types that constitute the tumor. Putative OvCa CSCs have been identified and are thought to play a major role in metastatic spread, chemoresistance, and recurrence. A widely accepted mechanism of metastatic spread is epithelial-mesenchymal transition (EMT) whereby epithelial OvCa cells acquire a mesenchymal phenotype allowing them to become migratory and invasive. EMT is suggested to be a feature of CSCs due to their plasticity making them more capable of acquiring a mesenchymal phenotype. SUSD2 is a marker of putative mesenchymal stem cells in the uterus, bone marrow, and tonsil and has been implicated in various cancers and metastasis. Contradictory reports using OvCa cell lines have suggested that SUSD2 is either a tumor suppressor or oncogene and either represses or facilitates EMT and metastasis. This discrepancy has left a gap in our current understanding of the role of SUSD2 in HGSOC, specifically as it relates to CSCs and EMT. Our central hypothesis is that SUSD2 plays an oncogenic role in HGSOC development metastasis. In collaboration with Dr. Mark Hunter (ObGyn Dept.) we are beginning to test this by characterizing SUSD2-expressing (SUSD2+) cells in HGSOC tumors and determining the in vitro tumorigenic activity of SUSD2+ cells.