DECIDUALIZATION INDUCES A SECRETOME SWITCH IN THE PERIVASCULAR NICHE CELLS OF THE HUMAN ENDOMETRIUM

The endometrial perivascular microenvironment is rich in mesenchymal stem-like cells that express type 1 integral membrane protein Sushi domain containing 2 (SUSD2) but the role of these cells in the decidual transformation of this tissue in pregnancy is unknown. We used an antibody directed against SUSD2 (W5C5) to isolate perivascular (W5C5+) and non-perivascular (W5C5-) fibroblasts from mid-luteal biopsies. We show that SUSD2 expression, and hence the ratio of W5C5+ to W5C5- cells, changes in culture depending on cell-cell contact and activation of the Notch signaling pathway. RNA sequencing revealed that cultures derived from W5C5+ progenitor cells remain phenotypically distinct by the enrichment of novel and established endometrial perivascular signature genes. In an undifferentiated state, W5C5+-derived cells produced lower levels of various chemokines and inflammatory modulators when compared to their W5C5- counterparts. This divergence in secretomes became more pronounced upon decidualization, which transformed perivascular W5C5+ cells into the dominant source of a range of trophic and immunomodulatory cytokines, including leukemia inhibitory factor (LIF). Our findings indicate that the decidual response is spatially organized with differentiating perivascular cells establishing distinct cytokine and chemokine gradients that could direct trophoblast towards maternal vessels and govern local immune responses in pregnancy. Overall design: Analysis of paired human endometrial stromal cultures, originating from either W5C5+ or W5C5- cells, from four biological replicates - a total of 8 samples - by Illumina RNAseq.

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Murakami K, Lee YH, Lucas ES, Chan YW, Durairaj RP, Takeda S, Moore JD, Tan BK, Quenby S, Chan JK, Gargett CE, Brosens JJ