OR08-02 In Situ Reconstruction Of Distinct Normal And Pathological Cell Populations Within The Human Adrenal Gland Using Spatial Transcriptomics
Authors: Rui Fu , Walters Kathryn , Koc Katrina , Baldwin Amber , Kiseljak-Vassiliades Katja , Fishbein Lauren Michelle , Mukherjee Neelanjan 
Published: October 2023

Abstract
Disclosure: F. Rui: None. K. Walters: None. K. Koc: None. A. Baldwin: Stock Owner; Self; Tempus Labs. K. Kiseljak-Vassiliades: Advisory Board Member; Self; HRA Pharma. L.M. Fishbein: Consulting Fee; Self; Lantheus/Progenics Azedra. N. Mukherjee: None.
The human adrenal gland is a vital endocrine organ controlling a multitude of functions through the secretion of cortical steroid and medullary catecholamine hormones. Several outstanding questions remain about the adrenal spatial organization and related differential developmental signaling pathways which have functional consequences within and between the cortex and medulla. The current model of the functional zonation of the cortex posits a centripetal differentiation process in which the cortical cells arise in the capsule and migrate inwards changing their gene expression patterns as they progress to the three different functional layers of the cortex. The evidence for this model is based on mouse lineage tracing experiments, and it is unclear to what extent it applies to human adrenal glands. To address this, we performed spatially resolved transcriptomics on four adult adrenal sections from two different human specimens to identify cell populations and their spatial relationship in this highly organized and functionally diverse organ. We identified 14 distinct cell populations; 79% of these spots represented the cortex or medulla and exhibited the concentric expression pattern reflecting the known spatial organization of the human adrenal gland. Trajectory inference analysis of the cortical cells showed continuous expression transitions from cells of the capsule to zona glomerulosa to zona fasciculata to zona reticularis. These data demonstrate for the first time that the centripetal differentiation model for functional zonation in mice is consistent for adult human adrenal tissue. We also validated the spatial expression pattern of a subset of WNT-related genes specifically expressed with distinct patterns in the capsule and zona glomerulosa cells. These genes represent novel regulatory factors that may be crucial in the differentiation of adult human adrenal cortex. Finally, we observed two CYP11B2 positive aldosterone producing cell clusters (APCC) in the adrenal tissue section from a 72-year-old woman. APCCs are thought to play a role in the pathological progression of primary aldosteronism; however, it is unclear if there are unifying expression signatures other than CYP11B2 protein expression. Our analysis found both similarities and differences to previously published data sets of APCC signatures. It is unclear to what extent these expression differences are technical (i.e. different platforms) or due to biological heterogeneity (between individuals or APCCs). The subgroup of similar gene expression in APCCs across all studies thus far may represent a core APCC signature which should be validated on a larger cohort. Altogether, our study uses spatial transcriptomics of the normal human adrenal and the results have important implications for the differentiation and functional zonation,as well as, for the early dysregulation leading to primary aldosteronism.
Presentation: Friday, June 16, 2023