Rapid Disease Progression of Myelodysplastic Syndrome is Reflected in Transcriptomic and Functional Abnormalities of Bone Marrow MSCs.

Bone marrow (BM) mesenchymal stromal cells (MSCs) are important regulators of hematopoietic stem and progenitor cells (HSPCs). When transformed to a dysplastic phenotype, MSCs contribute to hematopoietic diseases such as myelodysplastic syndromes (MDS), but it remains unclear if there are specific properties in MDS-MSCs that contribute to the disease course. To understand this, we investigated MDS-MSCs from fast (MDSfast) vs slow (MDSslow) progressing disease groups and discovered differences between these groups. MDSfast-MSCs secrete more inflammatory factors, support myeloid-skewed differentiation of HSPCs, and importantly, show poorer response to hypomethylation as a key differentiator in GSEA analysis. When exposed to long-term in vivo stimulation with primary MDSfast-MSCs-based scaffolds, healthy donor (HD) HSPCs show elevated NF-κB expression, similar to leukemic HSPCs in MDS. Those "MDSfast-MSCs-primed" HD-HSPCs continue to show enhanced engraftment rates in secondary MDS-MSC-based scaffolds, providing evidence for the microenvironmental selection pressures in MDS towards leukemic HSPCs. Together, our data point towards a degree of co-development between MSCs and HSPCs during the progression of MDS, where changes in MDS-MSCs take place mainly at the transcriptomic and functional levels. These unique differences in MDS-MSCs can be utilized to improve disease prognostication and implement targeted therapy for unmet clinical needs.