Deciphering molecular mechanisms controlling age-associated uterine adaptabilityto pregnancy

PROJECT SUMMARY
Advanced maternal age (i.e., ≥35 years old) is considered a major risk factor for birth defects. In women over 40
years of age, the incidence of spontaneous abortion can increase to >30%. Much attention has been focused on
ovarian function and oocyte quality, but we provide evidence that uterine decidualization defects could be a
major cause of age-related reproductive decline. This problem is likely due to a blunted progesterone (P4)
responsiveness of the aging uterus, via its cognate nuclear receptor PGR. PGR is the master regulator for the
establishment and maintenance of pregnancy; however, a significant diminution in PGR results in a blunted
hormonal response as the uterus ages. The underlying molecular mechanisms that diminish expression of PGR
and deregulate PGR target genes likely account for uterine aging, a mechanism that has remained elusive. Our
recent discovery of uterine Sirtuin 1 (SIRT1) as a critical driver of age-related PGR action by which endometrial
stromal cells decidualize impacts our knowledge of uterine biology and reproductive aging. By deleting uterine
SIRT1 in mice, we generated a genetic model (PgrCre/+Sirt1f/f, i.e. Sirt1d/d) for research on premature uterine aging
due to blunted PGR response that are similar to those associated with physiologic aging. Thus, this study will be
the first attempt to use physiological (46-54 weeks of age) and genetic (Sirt1-deficient) aging mouse models
to discover a novel uterine perspective of mammalian reproductive aging. This proposal will provide the first
molecular characterization of implantation and decidualization in the context of premature uterine aging (genetic
aging; Sirt1d/d) by all-in-one multimodal single-cell ATAC-seq/RNA-seq and comparative analyses with
physiologic aging, identifying common gene signatures, cis-regulatory elements and transcriptional co-factors in
endometrial cells required for establishment and maintenance of pregnancy but susceptible to reproductive aging.
We will also translate the findings in mice to human biology using hTERT-immortalized human endometrial
stromal cells (T-HESCs) as decidualization of stromal cells are major defects during physiological and genetic
aging. Combined with multimodal single cell datasets between human and mouse models, as well as functional
validation of candidate cis-regulatory elements and transcriptional co-factors by CRISPR deletion and activation
systems, respectively, this proposal will delineate SIRT1-responsive regulatory network required for PGR actions
that deregulate as uterus ages. We strongly believe that our study will give a deeper and more comprehensive
insight into progesterone-resistant endometrium during reproductive aging. With that new knowledge, research
can pursue strategies to counteract adverse effects of aging on outcomes of pregnancy.