DECIDUALIZATION PROGRAM CONDITIONS MATERNAL MONOCYTES TO A DC-10 PROFILE INDUCING REGULATORY T CELL RESPONSE.

GORI S, SCHAFIR A, SOCZEWSKI E, FERNÁNDEZ L, BESTACH Y, CASTAGNOLA L, MARTÍNEZ G, IRIGOYEN M, SALAMONE G, PÉREZ LEIRÓS C, AND RAMHORST R

Congreso; Amereican Socitety of Reproductive Immunology meeting; 2021

Problem: The decidualization program allows the secretion of immunoregulatory factors by endometrial stromal cells which may condition maternal leukocytes to a regulatory profile. In this context, we recently showed that decidualized cells conditions maternal monocytes to a tolerogenic profile with characteristics of Myeloid Regulatory Cells, particularly DC-10. This novel and distinctive subset of dendritic cell is characterized to be a potent IL-10 producer and type 1 regulatory T (Tr1) cells-inducer through HLA-G pathway. Considering that DC-10 was found increased in decidua, here we focus on the impact of decidualization in conditioning monocytes to this subset and its ability to induce Foxp3neg regulatory T cells. Moreover, taking into account that decidualized cells have been proposed as biosensors of blastocyst quality, we also evaluated whether this conditioning would be altered by the presence of soluble factors secreted by normal and impaired developing blastocysts. Method of Study: Human Endometrial Stromal Cells line (HESC) was decidualized for 8 days with MPA+dbcAMP (Dec) or not (Non-Dec). Then, they were cultured for 48 h with fresh medium and conditioned media (CM) were collected. In parallel, decidualized HESC cells were stimulated with pooled human blastocysts-conditioned media (BCM) obtained from normal developing blastocysts or impaired ones for 48 h. Finally, isolated monocytes from peripheral blood mononuclear cells of healthy donors were cultured with rhGM-CSF+rhIL-4 for 5 days in the absence/presence of CM and we tested the expression of DC-10-tolerogenic markers by flow cytometry and ELISA. After allogeneic stimulation, the production of IL-10, IFN- and regulatory T cells profile were evaluated by flow cytometry and ELISA.Results: First, monocytes-derived cells were stimulated with CM from decidualized and non-decidualized HESC cells and interestingly, only those cultures stimulated with CM from decidualized cells induced a higher expression of the characteristic DC-10 tolerogenic marker, HLA-G (p