Effect of Aging on the Human Myometrium at Single-Cell Resolution

Abstract

The myometrial dysfunction associated with aging can prompt complications during pregnancy and labor, causing a 7.8-fold increase in maternal mortality in women over 40. Using single-cell/single-nucleus RNA sequencing and spatial transcriptomics, we constructed a cellular atlas of the aging myometrium from 186,120 cells across twenty peri- and post-menopausal women. We identified 23 myometrial cell subpopulations, including novel contractile capillary, venous capillary, immune-modulated fibroblasts, and nervous system regulatory fibroblasts. Myometrial aging leads to fewer contractile capillary cells, a reduced level of ion channel expression in smooth muscle cells, and impaired gene expression in endothelial, smooth muscle, fibroblast, perivascular, and immune cells. We observed altered myometrial cell-to-cell communication as an aging hallmark associated with the loss of 25/229 signaling pathways, including those related to angiogenesis, tissue repair, contractility, immunity, and nervous system regulation. These insights may contribute to a better understanding of the complications faced by older women during pregnancy and labor.

A high-resolution view of the heterogeneous aging endothelium

“…While temporal changes remain unclear due to lack of young or pre-menopausal samples [ 98 ], TFs of the SOX family have been shown to be strongly dysregulated in the aging endothelium of various mouse tissues [ 56 ]. Healthy-aging analyses of the ovary and myometrium at single-cell resolution revealed a loss of lymphatic EC density and an overall decrease of blood vascular ECs in aged samples [ 99 , 100 ]. Furthermore, EC clusters revealed a decrease in genes related to the proteasome, DNA repair, and metabolism, as well as an increased expression of genes linked to apoptosis, senescence, cell-cycle, and immunoregulation in aged donors.…”

“…Furthermore, EC clusters revealed a decrease in genes related to the proteasome, DNA repair, and metabolism, as well as an increased expression of genes linked to apoptosis, senescence, cell-cycle, and immunoregulation in aged donors. Angiogenesis-related findings were conflicting, as signatures related to VEGF signaling were found increased in aged donors in one study [ 99 ], while findings of decreased EC abundance in myometrial aging, and decreased HGF, ANGPTL, and EDN pathway signaling between stromal cells and ECs would suggest impairment of angiogenesis in the aging myometrium [ 100 ]. In line with findings in the aging muscle, the number of interactions between ECs and other cell types in aged samples decreased [ 99 ].…”

“…In line with findings in the aging muscle, the number of interactions between ECs and other cell types in aged samples decreased [ 99 ]. Finally, a tissue-specific contractile capillary EC population was found in a comparative myometrium atlas of healthy human donors pre- and post-menopause [ 100 ]. Upon aging, a decrease in function and size of this population could be observed on a spatial level, as well as a decrease in their marker genes FLNA and ACTG2 .…”

“…Upon aging, a decrease in function and size of this population could be observed on a spatial level, as well as a decrease in their marker genes FLNA and ACTG2 . In addition, the angiopoietin-like pathway was dysregulated in ECs of the aged myometrium, all suggestive of alterations to regulation of blood flow and hampered vascularization [ 100 ]. Unfortunately, while additional in-depth single-cell studies are available in context of the aging FRS, an analysis of the endothelium is typically lacking [ 97 , 101 ].…”