12311 Identification Of Oxytocin Receptors In The Human Anterior Pituitary Gland

Abstract Disclosure: M. Muhammed: None. S. Freeman: None. M. Mahamdeh: None. M. Martinez-Lage Alvarez: None. K.K. Miller: Other; Self; Dr. Miller has received study medication and investigator-initiated research grants from Amgen and has equity in Bristol-Myers Squibb (BMS), General Electric, Boston Scientific, and Becton Dickinson.. R.J. Soberman: None. E.A. Lawson: Other; Self; Funding and study drug (intranasal oxytocin/placebo) from Tonix Pharmaceuticals;, U.S. provisional patent application no. 63/467,980 Oxytocin-Based Therapeutics to Improve Cognitive Control in Individuals with Attention Deficit Hyperactivity Disorder. Objectives: Oxytocin (OXT) is a hypothalamic-posterior pituitary hormone that induces pleotropic effects by binding to a G-protein-coupled receptor (OXTR) that is present across multiple organ systems. There is evidence that signaling by OXTRs modulates anterior pituitary function, increasing the release of prolactin, growth hormone, and gonadotroph hormone, while reducing the release of thyroid stimulating hormone and adrenocorticotropin hormone. However, it is not known whether OXTRs are present in the human pituitary gland. Studying OXTR distribution is challenging due to homology and cross reactivity between OXTRs and vasopressin receptors, and reliable OXTR-specific antibodies are not available. RNAscope technology is a reliable and validated in situ hybridization method that can detect gene expression with high specificity. Therefore, we aimed to determine whether OXTRs are present in the human anterior pituitary gland using OXTR-specific probes that are complimentary to OXTR mRNA and do not cross react with mRNA for vasopressin receptors. We hypothesized that OXTR mRNA would be co-expressed in cells also expressing prolactin, growth hormone, thyroid-stimulating hormone, pro-opiomelanocortin, or follicle stimulating hormone subunit genes, consistent with OXTR presence across anterior pituitary cell types. Methods: De-identified nonclinical human pituitary tissue was used. Pituitary tissue was obtained at autopsy (postmortem). Formalin-fixed paraffin embedded tissue blocks were sectioned at 5 μm and mounted on microscope slides. RNA in situhybridization experiments were performed using RNAscope Multiplex Fluorescent v2 assays (Advanced Cell Diagnostics, Newark, CA) according to the manufacturer’s instructions. The samples were stained with Opal570 (OXTR) and Opal690 (others) and imaged using a Yokogawa spinning disc confocal on a Nikon Ti2 inverted microscope, and acquired images were evaluated for co-expression using Fiji, an open source image processing software. Results: Using RNAscope in situ hybridization, we confirmed that anterior pituitary cell populations that expressed prolactin, growth hormone, thyroid-stimulating hormone, pro-opiomelanocortin, or follicle stimulating hormone subunit also co-expressed OXTR mRNA. Conclusions: These data support our hypothesis that OXTR is present on human anterior pituitary lactotroph, somatotroph, thyrotroph, corticotroph, and gonadotroph cells. Our results provide a rationale to elucidate the function and clinical relevance of OXTRs in the anterior pituitary gland. Presentation: 6/3/2024