KRasG12D expression in the bone marrow vascular niche affects hematopoiesis with inflammatory signals.
The bone marrow (BM) niche is an important milieu where hematopoietic stem and progenitor cells (HSPCs) are maintained. Previous studies have shown that genetic mutations in various components of the niche can affect hematopoiesis and promote hematologic abnormalities, but the impact of abnormal BM endothelial cells (BMECs), a crucial niche component, on hematopoiesis remains incompletely understood. To dissect how genetic alterations in BMECs could affect hematopoiesis, we have employed a novel inducible Tie2-CreERT2 mouse model, with a tdTomato fluorescent reporter, to introduce an oncogenic KRasG12D mutation specifically in the adult endothelial cells. Tie2-CreERT2;KRasG12D mice had significantly more leukocytes and myeloid cells in the blood with mostly normal BM HSPC populations and developed splenomegaly. Genotyping PCR found KRasG12D activation in BMECs but not hematopoietic cells, confirming that the phenotype is due to the aberrant BMECs. Competitive transplant assays revealed that BM cells from the KRasG12D mice contained significantly lower functional hematopoietic stem cells (HSCs) and immunofluorescence imaging showed that HSCs in the mutant mice were localized farther away from BM vasculature and closer to the endosteal area. RNA-seq analyses found an inflammatory gene network, especially TNFα, as a possible contributor. Together, our results implicate an abnormal endothelial niche in compromising normal hematopoiesis.
View details for DOI 10.1016/j.exphem.2019.10.003
View details for PubMedID 31669153