Inflammasome-resistant IPSC-derived myeloid-derived suppressor cells (iMDSCs) ameliorate xenogeneic GVHD

Acute graft versus host disease (aGVHD) is considered a major complication of allogeneic hematopoietic stem cell transplant (aHSCT). Front-line pharmaceutical treatment is not uniformly effective and has toxic side effects. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells with potent immunosuppressive functions. Their potential to control GVHD has been proven in different rodent models. However, a high MDSC to T cell ratio and multiple doses of MDSCs are needed to achieve maximum effectiveness. Clinical translation of in vitro MDSC generation limits its clinical usage by a relatively low yield and need for personalized patient products, especially challenging for multiple treatment courses. Therefore, we developed an in vitro method to generate MDSCs on a large scale from a human induced pluripotent stem cell (iPSC)-derived CD34+ cells. iMDSCs shared a similar morphology, phenotype, and suppressive function with peripheral blood (PB)-MDSCs. In striking contrast to PB-MDSCs, iMDSCs retained 95% of suppressor function when exposed to the damage-associated molecular pattern stimuli, LPS + ATP, released during GVHD. RNAseq analysis and gene knockdown studies revealed that inflammasome-resistant iMDSCs maintained expression of phosphoglycerate dehydrogenase, an enzyme involved in purine metabolism. Consistent with the retention of suppressor function during lethal xenogeneic GVHD-induced tissue injury, recipients of human iMDSCs and peripheral blood mononuclear cells (PBMC) experienced therapeutic benefits. Together, these data provide a platform for translating in vitro generated, off-the-shelf iMDSCs into the clinic for suppressing GVHD and other adverse immune responses. Human myeloid derived suppressor cells were differentiated from PBMC and iPSC. For inflammasome study, PBMC derived MDSCs (PB MDSC) and iPSC derived MDSCs (iMDSC) were treated with/without LPS and ATP to induce the inflammasome and then frozen down with lysis buffer for RNAseq. For iMDSCs subtypes(CD14- vs CD14+) comparison, cells were flow sorted by the CD14 expression and frozen down with lysis buffer for RNAseq.