Pelvic Organ Prolapse (POP) is the herniation of pelvic organs into the vagina, affecting 25% of all women. To overcome adverse events associated with transvaginal surgery using synthetic mesh for treating POP, we are developing a tissue engineering construct using endometrial mesenchymal stem cells (eMSC) and a novel polyamide/gelatin composite mesh (PA+G). Our aim was to assess the effects of eMSC on macrophage phenotype and response to PA+G implanted mesh using immunocompromised (NSG) and immunocompetent (C57BL6) mouse models to determine differences in eMSC persistence and changes in macrophage phenotype.
eMSC were obtained by magnetic-bead sorting SUSD2+ eMSC from single cell suspensions of 6 endometrial biopsies of reproductive aged women. The cells were cultured, transduced with mCherry lentiviral plasmid, and 250,000 were seeded onto to 1 cm2 PA+G mesh1 pieces and implanted subcutaneously into mice as a model of vaginal surgery. Harvested tissues were assessed by immunofluorescence and qPCR for macrophage M1 and M2 markers, and inflammatory cytokines by ELISA.
eMSC persisted longer in NSG mice (7 days), inducing longer term paracrine effects by decreasing production of TNF-α and IL-1β, although this response was lower than in C57Bl mice. eMSC reduced M1 macrophages around mesh filaments at day 3 in C57Bl6 mice. eMSC increased M2 macrophage marker mRNA expression at days 3 and 7 in C57BL6 mesh-implanted mice, but in NSG mice, greater effects were observed at days 14 and 30 in comparison with the controls implanted with mesh alone.
Our data suggest that eMSC are rapidly cleared from the implantation site in a xenogeneic immunocompetent model, suggesting autologous use may provide longer eMSC retention. eMSC dampen the macrophage-mediated inflammatory response to implanted mesh, exerting their modulatory effects via paracrine factor secretion influencing all types of innate immune cells in immunocompetent mice and only macrophages in immunocompromised mice.