The Bone marrow stroma in human myelodysplastic syndrome reveals alterations that regulate disease progression [Human and Mouse]

Myelodysplastic syndromes (MDS) are a heterogenous group of diseases affecting the hematopoietic stem cell that are curable only by stem cell transplantation. Both hematopoietic cell intrinsic changes and extrinsic signals from the bone marrow niche seem to ultimately lead to MDS. Animal models of MDS indicate that alterations in specific mesenchymal progenitor subsets in the bone marrow microenvironment can induce or select for abnormal hematopoietic cells. Here we identify a subset of human bone marrow (BM) mesenchymal cells marked by the expression of CD271, CD146 and CD106. This subset of human mesenchymal cells is equivalent to those in mice that, when perturbed, results in an MDS-like syndrome. Transcriptional analysis identified epithelial to mesenchymal transition as the most enriched gene set and Osteopontin (SPP1) as the most overexpressed gene. The loss of expression of Spp1 in the microenvironment resulted in an accelerated progression of the transplanted Vav-driven Nup98-HoxD13 MDS model as demonstrated by increased chimerism, increased contribution of mutant cells to the myeloid lineage and a more pronounced anemia when compared to animals with a wild type microenvironment. These data indicate that molecular perturbations can occur in specific bone marrow mesenchymal subsets of MDS patients. However, the niche adaptations to dysplastic clones include Spp1 overexpression that can constrain disease progression. Therefore, niche changes with malignant disease can also serve to protect the host. Overall design: Human: Sorted mesenchymal subsets from bone marrow and digested spicules from filter bags of transplant procedure. Dead, hematopoieitc, erythroid and endothelaial cells were removed by gating on 7AAD-, CD45-, CD235ab-, CD31- and CD34- cells. Five subsets were sorted as follows: DP (CD271+CD146+CD106+), DN (CD271+, CD146+, CD106-), SP (CD271+, CD146-, CD106+), SN (CD271+CD146-, CD106-), N (CD271-, CD146-). In addition, non-hematopoietic non-endothelial CD51+ cells and CD45+ cells were sorted as controls Mouse: Sorted GFP+ osteoblasts and osteoprogenitors from digested bones of Ocn-GFP and Osx-GFP:Cre reporter mice respectively. Dead, hematopoietic, erythroid and endothelial cells were removed by gating on 7AAD-, CD45-, Ter119-, CD31- cells. In addition, non-hematopoietic non endothelial CD51+ and CD45+ cells (from bone marrow) were sorted as controls