Understanding The Phenomena And Mechanism Oflong-termsustained Extramedullary Hematopoiesis That Induced By Akkermansia Muciniphila

Bacterial infections can activate and mobilize hematoppoetic stem and progenitor cells(HSPCs)from the bone marrow(BM)to spleen,which is termed as extramedullary hematopoiesis(EMH).Recent studies suggest that commensal bacteria,particularly the microbiota,regulates not only the host immune system but also hemiatopoietic homeostasis.However,the impact of gut microbial species on hematopoietic pathology remains largely unknown.Here we found that injection of Akkermansia muciniphila(A.m.),a mucin degrading bacterium abundantly existing in the human gut rapidly activates BM myelopoiesis,and induce s a slow but long-lasting hepato-splenomegaly,characterized by the expansion and differentiation of functional HSPCs which we termed chronic EMH.Genetic deletion of Toll-like receptor-2 and-4(ILR2/4)partially diminished A m.-induced chronic EMH,while additional pharmacological inhibition of the interleukin-1 receptor(IL-1R)completely alleviated splenomegaly and EMH.Our results demonstete that cooperative IL-1R-and TLR-mediated innate immune signals regulate commensal bacteria-driven EMH,which might be relevant for certain autoimmune disorders.