The effect of macrophage secretome on equine endometrial fibroblast transcriptomic and functional characteristics

Endometrial fibrosis is a main hallmark of endometrosis, a degenerative condition of the equine endometrium. Fibrosis, is characterized by the excessive accumulation of extracellular matrix (ECM) components. Current research highlights the crucial role of MΦ in activating fibroblasts in the development of fibrotic processes. However, the specific actions of distinct MΦ subpopulations on equine endometrial fibroblasts remain to be elucidated. Thus, this study aimed to investigate the long-term effect of the secretome of equine in vitro-generated monocyte-derived (eqMD)-MΦ^IFNγ/LPS (pro-inflammatory MΦ1) and eqMD-MΦ^IL-4/IL-13 (anti-inflammatory MΦ2a) on the transcriptomic profiles, expression of ECM-related components, inflammatory markers, and functional characteristics of equine endometrial fibroblasts cultured in vitro. Analysis of all 404 differentially expressed genes (DEGs) identified in fibroblasts following treatment with MΦ1 secretome revealed annotations associated with cell movement of neutrophils, lymphocyte migration, proliferation of connective tissue cells, and growth of connective tissue. Analysis of all 282 DEGs identified in fibroblasts following treatment with MΦ2a secretome was annotated to assembly of intercellular junctions, formation of the plasma membrane, and development of gap junctions. MΦ1 and MΦ2a affected the expression of ECM-associated components and inflammatory markers as well as increased the proliferation and migration of endometrial fibroblasts. Our data suggest that MΦ1 subpopulation influences the expression of genes associated with the inflammatory response in fibroblasts, while MΦ2 subpopulation appears to affect the expression of genes linked to tissue organization processes. These findings suggest that the sequential or balanced activation of MΦ1-and MΦ2-like signaling may be crucial for effective endometrial repair in the mare.