Natural Resistance to Ovarian Hyperstimulation Syndrome in Estrildid Finches Reveals Macrophage GPR183 as a Potential Therapeutic Target.

Spontaneous ovarian hyperstimulation syndrome (OHSS) is closely associated with follicle stimulating hormone receptor (FSHR) functional mutations. We observed that estrildid finches naturally carry the gain-of-function FSHR p.Thr449Ala mutation found in humans, yet do not develop OHSS, thereby providing a novel and system to study aspects of OHSS prevention. Cross-species single-cell analysis revealed that macrophages, the most abundant immune cells in ovaries, play a pivotal role in OHSS progression. Macrophage depletion exacerbates the manifestations of OHSS in both birds and rats. Pharmacological activation of the G protein-coupled receptor 183 (GPR183) in ovarian macrophages, significantly alleviates OHSS symptoms. Mechanistically, GPR183 activation in macrophages maintains ovarian immune homeostasis by downregulating inflammatory factors (Interleukin 1 alpha: IL1A, Interleukin 6: IL6, Interleukin 1 beta: IL1B) and upregulating immune regulators responsive to external stimuli (sphingomyelin phosphodiesterase acid like 3A: Smpdl3a, Macrophage-expressed gene 1: Mpeg1, Epithelial stromal interaction 1: Epsti1, Unc-93 homolog B1: Unc93b1, Apolipoprotein B mRNA editing enzyme catalytic subunit 1: Apobec1). It markedly altered CD44 molecule (CD44)/Syndecan-4 (SDC4) -mediated intercellular communication between macrophages and endothelial/stromal cells, thereby modulating the ovarian microenvironment. This study identifies ovarian macrophages as a key therapeutic target for OHSS and proposes GPR183 as a novel receptor target for precision macrophage-based interventions.