Multinucleated giant cells are hallmarks of ovarian aging with unique immune and degradation-associated molecular signatures

The ovary is one of the first organs to exhibit signs of aging, characterized by reduced tissue function, chronic inflammation, and fibrosis. Multinucleated giant cells (MNGCs), formed by macrophage fusion, typically occur in chronic immune pathologies, including infectious and non-infectious granulomas and the foreign body response, but are also observed in the aging ovary. The function and consequence of ovarian MNGCs remain unknown as their biological activity is highly context-dependent, and their large size has limited their isolation and analysis through technologies such as single-cell RNA sequencing. In this study, we define ovarian MNGCs through a deep analysis of their presence across age and species using advanced imaging technologies as well as their unique transcriptome using laser capture microdissection. MNGCs form complex interconnected networks that increase with age in both mouse and nonhuman primate ovaries. MNGCs are characterized by high Gpnmb expression, a putative marker of ovarian and non-ovarian MNGCs. Pathway analysis highlighted functions in apoptotic cell clearance, lipid metabolism, proteolysis, immune processes, and increased oxidative phosphorylation and antioxidant activity. Thus, MNGCs have signatures related to degradative processes, immune function, and high metabolic activity. These processes were enriched in MNGCs compared to primary ovarian macrophages, suggesting discrete functionality. MNGCs express CD4 and colocalize with T-cells, which were enriched in regions of MNGCs, indicative of a close interaction between these immune cell types. These findings implicate MNGCs in modulation of the ovarian immune landscape during aging given their high penetrance and unique molecular signature that supports degradative and immune functions. Transcriptomic profiling of ovarian multinucleated giant cells, stroma, and primary macrophages were compared

卵巢是最早出现衰老表征的器官之一，以组织功能衰退、慢性炎症及纤维化为典型特征。由巨噬细胞融合形成的多核巨细胞（Multinucleated Giant Cells, MNGCs）常出现于慢性免疫病理状态，包括感染性与非感染性肉芽肿、异物反应，但在衰老卵巢中亦有观测到。
卵巢MNGCs的功能与生物学效应迄今尚未明确：一方面其活性高度依赖具体情境，另一方面其庞大的体积限制了通过单细胞RNA测序（single-cell RNA sequencing）等技术进行分离与分析。
本研究通过先进成像技术，对不同年龄、不同物种的卵巢中MNGCs的分布情况开展深度分析，并借助激光捕获显微切割（laser capture microdissection）技术解析其独特的转录组特征，从而明确卵巢MNGCs的定义。MNGCs可形成复杂的相互连接网络，在小鼠与非人灵长类卵巢中，该网络的丰度均随年龄增长而升高。MNGCs以高表达Gpnmb为核心特征，该分子是卵巢及非卵巢来源MNGCs的潜在标志物。
通路富集分析显示，MNGCs具备凋亡细胞清除、脂质代谢、蛋白水解、免疫调控等功能，同时氧化磷酸化与抗氧化活性显著增强。综上，MNGCs具有与降解过程、免疫功能及高代谢活性相关的分子特征。与原代卵巢巨噬细胞相比，上述功能通路在MNGCs中显著富集，提示其具备独特的生物学功能。
MNGCs可表达CD4分子，并与T细胞发生共定位；而T细胞在MNGCs富集区域的丰度更高，表明这两类免疫细胞之间存在紧密的相互作用。鉴于衰老过程中卵巢MNGCs的高检出率，以及其兼具降解与免疫调控功能的独特分子特征，本研究结果提示MNGCs参与调控衰老过程中的卵巢免疫微环境。
本研究对卵巢多核巨细胞、卵巢间质细胞及原代卵巢巨噬细胞的转录组谱进行了比较分析。