ADO-RGS pathway components show dynamic, cell-type-specific expression in mouse and human kidneys under hypoxic and fibrotic stress.

Cellular adaptation to oxygen deprivation is critical for organ function and survival, particularly in the kidneys, which are highly vulnerable to hypoxia—a major driver of chronic kidney disease (CKD). While the hypoxia-inducible factor (HIF) signaling pathway is well-established as the primary mediator of hypoxic responses, the oxygen-dependent 2-Aminoethanethiol-Dioxygenase-Regulator of G-Protein Signaling (ADO-RGS) pathway has recently emerged as an alternative mechanism for oxygen-sensitive regulation of G-protein signaling. A systematic characterization of ADO and its RGS substrates across specific renal cell types under various physiological and pathological conditions has been lacking, representing a critical knowledge gap this study addresses.

This study systematically mapped the spatial expression of Ado and its associated Rgs4, Rgs5, and Rgs16 genes in mouse and human kidneys. Researchers used RNAscope™ in situ hybridization to visualize gene expression patterns in mouse kidney sections under normoxic, hypoxic (induced by anemia), and fibrotic conditions. These findings were further quantified using RT-qPCR. To provide translational context, the mouse data were compared with ADO-RGS expression patterns observed in human kidney biopsies from patients with various kidney diseases. The study focused on identifying cell-type-specific localization and changes in expression under different stress conditions.

The study revealed distinct and dynamic expression patterns for ADO-RGS pathway components in the kidney. Ado expression remained largely uniform across all renal regions, cell types, and conditions, suggesting its consistent presence. In contrast, RGS genes displayed significant plasticity: > Rgs4 showed strong induction in cortical and outer medullary fibroblasts during anemia-induced hypoxia, and was also upregulated in fibroblasts and proximal tubules within fibrotic lesions. Beyond its baseline presence in vascular cells, Rgs5 was highly expressed in vascular structures and demonstrated hypoxia-induced upregulation in medullary fibroblasts and vasa recta, with moderate induction under fibrotic conditions. Tubular epithelial expression of Rgs5 also occurred during fibrosis. Rgs16 was predominantly expressed in Pdgfrb⁺ interstitial cells specifically within fibrotic kidneys. Importantly, human kidney-disease biopsies corroborated these findings, displaying distinct RGS4 and RGS5 expression patterns that mirrored the mouse observations. These results highlight that while ADO is consistently available, the functional impact of ADO-RGS signaling is likely dictated by the dynamic, cell-type-specific regulation of its RGS effector genes during both acute and chronic hypoxic stress.