Oncogenic Kras G12D activation in the non-hematopoietic bone marrow microenvironment causes myelodyplastic syndrom in mice. Oncogenic Kras G12D activation in the non-hematopoietic bone marrow microenvironment causes myelodyplastic syndrom in mice

The bone marrow microenvironment is key player in the regulation and maintenance of hematopoiesis and is also involved in the pathogenesis of hematologic malignancies. We investigated the effect of KrasG12D expression in the non-hematopoietic bone marrow microenvironment. Therefore, we generated chimeric mice which express oncogenic Kras only in the non-hematopoietic system. Within 6-8 weeks, these mice developed a myelodysplastic syndrome characterized by cytopenia, myeloid expansion and signs of disturbed differentiation and marked dysplasia within the myeloid lineage. Gene expression analysis of KrasG12D expressing non-hematopoietic cells of the bone marrow microenvironment revealed a significant upregulation of multiple genes and pathways including proinflammatory signaling such as upregulation of the NLRP3 inflammasome and related genes. Overall design: Rosa26Cre;LSL-KrasG12D mice were lethally irradiated and transplanted with bone marrow harvested from wild type mice. Single allele littermates were used as control. When the mice were fully engrafted, tamoxifen was administered to induce Cre-mediated KrasG12D expression in the non-hematopoietic tissues. Blood and bone marrow analyisis was performed 6-8 weeks after tamoxifen administration. In order to analyze gene expression changes in KrasG12D expressing bone marrow niche cells, Rosa26Cre;LSL-KrasG12D mice were treated with tamoxifen to ubiquitously induce KrasG12D expression. After 5.5 weeks, osteoblasts, mesenchymal stem and progenitor cells, endothelial cells as well as CXCL12 abundant reticular cells were isolated using fluorescence-activated cell sorting according to published cell surface marker characteristics. RNA was extracted for microarray based gene expression analysis.