Peritoneal cavity-derived GATA6⁺ macrophages inhibit fibrosis through IL33 in endometrium

Macrophages exhibit a high degree of plasticity and play pivotal roles both in the normal physiological cycle of the endometrium and in its regeneration following injury. Although some new subsets of endometrial macrophages have been identified, their origins and functions remain to be further explored. In this study, we employed single-cell sequencing to analyze the endometrium of patients with normal endometrium and intrauterine adhesion (IUA) caused by injury. We identified a unique subset of macrophages distinguished by the expression of GATA6, a marker indicative of cavity macrophages. We verified that these GATA6⁺ macrophages were large peritoneal macrophages (LPMs) that migrated from the peritoneal cavity to the injured endometrium. Upon activation by injured endometrium, these LPMs demonstrated increased expression of Interleukin-33 (IL33), mediated by the Lars-Fos signaling axis, which interacts with the IL33 enhancer. Moreover, our studies revealed that IL33 derived from LPMs inhibited the differentiation of endometrial stromal cells (ESCs) into myofibroblasts, a critical step in the development of endometrial fibrosis. Furthermore, we confirmed the inhibitory effect occurred through the binding of IL33 to the ST2 receptor on ESCs, leading to the upregulation of JMJD3 and subsequent suppression of myofibroblast differentiation. Our findings highlight the essential role of LPMs in promoting endometrial repair and inhibiting fibrosis in IUA.