Pb2604: the role of the gut microbiota in mediating bone marrow mesenchymal stem cells deficiency in patients with immune thrombocytopenia in pregnancy

Topic: 32. Platelet disorders Background: Immune thrombocytopenia (ITP) affects 1-10 in 10000 pregnancies, which significantly affecting the safety of ITP patients in pregnancy. However, the precise pathogenesis of ITP in pregnancy has not been fully studied. Aims: To explore the characteristics of mesenchymal stem cells (MSCs) in patients with immune thrombocytopenia (ITP) in pregnancy (PITP); to screen the differential metabolites in the bone marrow (BM) of patients with PITP and analyze the characteristics of the gut microbiota of patients with PITP; to explore the relationship among differential metabolites, the gut microbiota and PITP-MSCs to expand the understanding of the pathogenesis of PITP; and to discover new ideas and treatments for PITP. Methods: BM-derived MSCs were isolated from healthy controls (HCs), ITP patients and PITP patients. The proliferation, senescence, apoptosis and immunoregulatory function of these cells, as well as their ability to promote megakaryocyte (MK) maturation, were assessed by flow cytometry. Nontargeted metabolomic analysis of the BM was used to screen differential metabolites. A PITP mouse model and an ITP mouse model with specific metabolites were established. 16S rDNA sequencing technology was used to analyze the characteristics of the gut microbiota of mice and PITP patients. A mouse model of fecal microbiota transplantation (FMT) was established. RNA-seq technology was used to analyze the differentially expressed genes in the MSCs of the mice that received FMT. The serum levels of NOD1L were measured to explore the relationship among differential metabolites, the gut microbiota and PITP-MSC deficiency. Results: Both PITP-MSCs and ITP-MSCs exhibited significant senescence and apoptosis, impaired immunoregulatory functions and decreased ability to promote MK maturation, but the deficiency of PITP-MSCs was more significant. Based on the nontargeted metabolomics analysis of the BM, we found that progesterone was the metabolite that was most significant different in PITP. The mouse model experiments showed that progesterone mediates the deficiency of BM-derived MSCs in PITP mice. The results of the gut microbiota analysis showed that the α diversity of the mice with PITP was significantly lower than that of the mice with ITP, and the gut microbiota composition of the mice with PITP was different from that of the mice with ITP. The dominant bacteria in the mice with PITP were Helicobacter and unidentified_Lachnospiraceae and Candidatus_Arthromitus. Further analysis suggested that progesterone regulates the gut microbiota of mice with PITP. The FMT mouse model was established, and the results indicated that the MSCs of the mice in the PITP-FMT group showed increased senescence and apoptosis. RNA-seq analysis suggested abnormal expression of genes involved in cellular senescence and the NOD-like receptor signaling pathway, and decreased serum NOD1L levels were observed in the PITP-FMT group. Further analysis of the gut microbiota of patients with PITP also showed reduced α diversity, and the composition and dominant bacterial genera were significantly different from those of patients with ITP. There were differences in the gut microbiota of the two groups in various functional pathways. Summary/Conclusion: This study revealed a significant deficiency of PITP-MSCs, which may be related to the increased progesterone levels in the BM and the effect of progesterone on modulating the gut microbiota. This finding partially expands the understanding of the pathogenesis of PITP and the role of pregnancy in the pathophysiology of ITP. Targeting the gut microbiota may become a new approach for the treatment of PITP. Keywords: Mesenchymal stem cell, Pregnancy, ITP