Single-cell atlas of the aging human myometrium reveals impaired contractility

Normal myometrium is essential to produce orchestrated uterine contractions, which are critical for a number of reproductive and obstetric processes such as embryo implantation or parturition. This study aimed to map at single-cell level the human myometrium and to characterize substantial age-related changes that could be linked to infertility and/or obstetric complications. Single-cell and nuclei RNA-seq analysis was performed on 186,120 single cells from 20 perimenopausal (<55 years old) and post-menopausal (≥55 years old) donors through the 10X Chromium system and Illumina NovaSeq 6000. Eight of these samples were preserved in paraffin for spatial transcriptomics analyses using the Visium Gene Expression Slide (10X Genomics) and Illumina HiSeqX sequencing. FASTQ files from sc/snRNA-seq and spatial transcriptomics were aligned to GRCh38-2020-A human reference transcriptome with Cell Ranger and Space Ranger, respectively. Downstream analyses for differential cell abundance (DA), differential gene expression (DGE), data integration, and overrepresentation analysis were performed using R tools. Single cells/nuclei revealed the cellular heterogeneity of the aging myometrium, composed of endothelium, fibroblast, smooth muscle, perivascular, and immune system as major cell types. DA and DGE analyses depicted loss of contractile capillary cells along with collagen regulation (COL3A1, COL1A1, COL1A2...) and contractility (ACTG2, FLNA, DES...) markers in aging myometrium. Fibrosis and senescence markers (JUN, FOS) were also increased with aging. Spatial transcriptomics validated these findings, while also systematically mapping these features onto the tissue. Furthermore, cell to cell communication patterns uncovered altered pathways in the postmenopausal state, with a shift to a less contractile and more inflammatory and fibrotic profile of the aging myometrium, driven by an interplay between different cells and transcriptional factors. Our findings provide the cellular heterogeneity of aging myometrium at single-cell resolution, which reveal striking differences in cell composition and cell interactions linked with aging, setting the basis for the diagnosis and treatment of defective contractility through novel biomarkers.