Date of Award
Medical Doctor (MD)
Introduction: Uterine fibroids are a significant burden for reproductive aged women. Yet, effective medical treatments suitable for long-term use remain limited. There is an urgent need to better understand the signaling pathways involved in uterine fibroid pathogenesis, as well as how these pathways could be exploited for targeted therapeutics. Glucocorticoids are emerging transcriptional regulators in uterine fibroid cells and have been shown to promote fibroid cell proliferation. We hypothesize that glucocorticoid signaling in uterine fibroids regulates the expression of genes critical to fibroid pathogenesis.Methods: A bioinformatics analysis of COREMINE Medical, MetaCore, Ingenuity Pathway Analysis, and the Comparative Toxicogenomics Database was performed to identify novel glucocorticoid-associated genes that are linked to key uterine fibroid features, such as cell proliferation and extracellular matrix. Immortalized human uterine fibroid cells (UtLM) were treated with the endogenous or synthetic glucocorticoids cortisol and dexamethasone (10 or 100nM) for RNA and protein measurements, and key findings were validated in primary human uterine fibroid cells. In addition, parallel experiments were performed in immortalized uterine smooth muscle cells (UtSMC). The molecular mechanism of glucocorticoid regulation was explored via siRNA knockdown and actinomycin D treatment. For all experiments, biological replicates n>3. Results: We identified four genes that were associated with the search term “glucocorticoid receptor” and key uterine fibroid features. Glucocorticoid treatment significantly repressed the expression of all four genes in UtLM cells (p<0.05-0.0001). Notable among the repressed genes was the vitamin D receptor (VDR), which inhibits fibroid cell proliferation upon activation with vitamin D. Glucocorticoid-mediated repression of VDR expression was validated in primary human uterine fibroid cells. Repression of VDR mRNA was specific to fibroid cells. In fact, glucocorticoid exposure increased transcript levels of VDR in UtSMCs. We discovered that decreased transcript levels of VDR were not due to glucocorticoids enhancing the turnover of VDR mRNA. Instead, we found that repression of VDR occurs within hours, requires the presence of the glucocorticoid receptor (GR), and was significant for nascent VDR transcripts, supporting the potential for direct transcriptional regulation by GR. Interestingly, co-treatment of uterine fibroid cells with glucocorticoids and the active form of vitamin D, calcitriol, blunted expression of VDR- responsive genes, suggesting down-stream impacts of glucocorticoids on VDR action in uterine fibroids. Conclusions: These studies are the first to demonstrate that glucocorticoids may interfere with vitamin D signaling in uterine fibroid cells by repressing the expression of VDR. Thus, glucocorticoids may promote fibroid growth by inhibiting the protective actions of vitamin D.
Silva, Erin Jeannette, "Glucocorticoids Repress Vitamin D Receptor Expression In Human Uterine Fibroid Cells" (2022). Yale Medicine Thesis Digital Library. 4122.