Differentiation of the endometrial macrophage during pregnancy in the cow

The presence of conceptus alloantigens necessitates changes in maternal immune function. One player in this process may be the macrophage. In the cow, there is large-scale recruitment of macrophages expressing CD68 and CD14 to the uterine endometrium during pregnancy. In the present study, the function of endometrial macrophages during pregnancy was inferred by comparison of the transcriptome of endometrial CD14(+) cells isolated from pregnant cows as compared to that of blood CD14(+) cells. The pattern of gene expression was largely similar for CD14(+) cells from both sources, suggesting that cells from both tissues are from the monocyte/macrophage lineage. A total of 1,364 unique genes were differentially expressed, with 680 genes upregulated in endometrial CD14(+) cells as compared to blood CD14(+) cells and with 674 genes downregulated in endometrial CD14(+) cells as compared to blood CD14(+) cells. Twelve genes characteristic of M2 activated macrophages (SLCO2B1, GATM, MRC1, ALDH1A1, PTGS1, RNASE6, CLEC7A, DPEP2, CD163, CCL22, CCL24, and CDH1) were upregulated in endometrial CD14(+) cells. M2 macrophages play roles in immune regulation, tissue remodeling, angiogenesis and apoptosis. Consistent with a role in tissue remodeling, there was over-representation of differentially expressed genes in endometrium for three ontologies related to proteolysis. A role in apoptosis is suggested by the observation that the most overrepresented gene in endometrial CD14(+) cells was GZMA. Results indicate that at least a subpopulation of endometrial macrophages cells differentiates along an M2 activation pathway during pregnancy and that the cells are likely to play roles in immune regulation, tissue remodeling, angiogenesis, and apoptosis.