Galectin-3 regulates erythropoiesis and enhances the immunoregulatory properties of CD71+ erythroid cells across developmental stages

Galectins are expressed by different immune and nonimmune cells with diverse immunomodulatory properties. However, their roles in erythropoiesis remain unknown. We investigated the expression of galectin genes in splenic CD71+ erythroid cells (CECs) from neonatal BALB/c mice at various developmental stages using bulk RNA sequencing. Our analysis revealed distinct gene expression profiles at different ages. Specifically, CECs from day-3 mice had a markedly different expression pattern compared to those from days 6, 12, and 28. Notably, Lgals1, Lgals3, Lgals4, Lgals8, and Lgals9 were constitutively expressed in CECs, with galectin-3 (Gal-3) showing predominant surface expression, unlike Gal-1 and Gal-9. Further analysis revealed that Gal-3+ CECs exhibited elevated levels of TGF-β, ROS, arginase I, VISTA, and PD-L1, correlating with enhanced immunosuppressive functions. These cells also demonstrated increased CD45, c-kit, Ki67, and p21 levels, indicating heightened proliferative activity despite showing increased apoptosis. Moreover, we found that Gal-3+ CECs displayed enhanced activation of signaling pathways, including STAT5, MAPK, and LCK. Additionally, Gal-3+ CECs co-expressed Fas and FasL, implicating these molecules in the regulation of early erythroblasts. Notably, Gal-3 interacted with CD71 and GARP, influencing CECs' immunoregulatory roles. In tissue-specific studies, we found varying frequencies of Gal-3+ CECs across the spleen, liver, and bone marrow (BM), with notable variations in the placenta and fetal liver. These results were paralleled in human BM-derived CECs, which also exhibited high Gal-3 levels. Our findings emphasize the critical role of Gal-3 in modulating erythropoiesis and suggest that Gal-3+ CECs possess enhanced immunoregulatory capacities.