Gonadotrope Remodeling in Sustained Low Estrogen States: Single-Cell Transcriptomic Analysis Reveals Gonadotrope Subtypes and Activation of Stem Cell Populations.

The 4-vinylcyclohexene diepoxide (VCD)-induced ovarian failure model provides a physiologically relevant alternative to ovariectomy to gradually reduce serum estradiol (E2) for studying tissue responses to a menopause-like state. This study utilized single-cell sequencing transcriptomics analyses (scRNA-seq) to determine how reduced E2 levels influence pituitary gonadotrope gene expression and cell state, with a focus on potential transcriptomic contributions from stem cells to gonadotrope population growth. VCD-treated mice were acyclic and exhibited 8–15-fold increases in serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) gonadotropin levels. E2 levels were 2X lower than those of normally cycling proestrous females. scRNA-seq identified two gonadotrope clusters based upon distinct gene expression signatures (designated GON1 and GON2). The GON1 population increased in number significantly in VCD-treated mice, expressing markers of progenitor cells. Both gonadotrope clusters showed upregulated genes for canonical pathways supporting mRNA translation and secretion, which correlated well with the high serum gonadotropin levels. However, the LH beta subunit (Lhb) transcript was unchanged and FSH beta subunit (Fshb) was significantly reduced, suggesting that the high gonadotropin secretion may be supported by post-transcriptional regulators. The pituitary Sox2-positive (Sox2) stem cell cluster exhibited increased expression of Sox9, a marker for more mature transitional progenitors, and showed upregulation of pathways involved in stem cell development, mitotic activity, and mRNA translation. This model provides insight into the cellular and molecular adaptations of the gonadotropes and their progenitor cells to the low estrogen/menopausal state, with potential relevance for understanding human perimenopausal and menopausal physiology.