To dissect the role of the alarmins S100A8/S100A9 in bone marrow fibrosis and clonal evolution in myeloproliferative neoplasms
Final Report Abstract
The increasing availability of high throughput methods for single cell RNA sequencing allowed us to investigate the hematopoietic niche at a higher resolution than ever before. We were able to create a map of non-hematopoietic bone marrow cells in the context of myelofibrosis (MF) in myeloproliferative neoplasms on a single cell level. In this complex network of cells two subpopulations of mesenchymal stromal cells (MSCs) exhibited deep and stepwise transcriptional reprogramming: adipogenic MSCs (MSC-1) and osteogenic MSCs (MSC-2). These MSCs first lose their physiological signature and hematopoiesis supporting capacities in a model for pre-fibrotic MPN. In manifest fibrosis these MSCs acquire a pro-fibrotic and secretory phenotype with an especially strong induction of collageneous extracellular matrix (ECM). We were able to validate these findings in the disease relevant murine JAK2(V617F) model and also show that MSC-1 and MSC-2 show a strong overlap with Gli1+ MSCs, which have been described before to contribute to the deposition of ECM in myelofibrosis. An especially unexpected finding was that the differentiation trajectory analysis revealed a strong propensity of MSCs to differentiate not only into osteolineage cells (OLCs), but also Schwann cell progenitors (SCPs). This is particularly evident in the prefibrotic setting where SCPs show a significant expansion, whereas numbers subsequently decrease as fibrosis progresses. We hypothesize that this is indicative of a compensatory reaction in response to the sympathetic neuropathy induced by myeloproliferative neoplasms (MPN). A failure of this compensation is associated with progression to MF. We were able to successfully translate our findings to the human disease using minimal amounts of patient material. Single cell RNA sequencing of the healthy and fibrotic human bone marrow niche closely recapitulated the observations of our murine studies. In myelofibrosis MSC transcriptomes show a downregulation of MSC signature, hematopoiesis support as well as a distinct upregulation of matrix associated molecules and collagens. In both murine and human datasets, the alarmins S100A8 and S100A9 were increasingly and significantly induced in stromal cells, primarily MSCs, in the context of myelofibrosis. Quantification of S100A8 in the plasma and bone marrow of MPN and control patients revealed distinct dynamics over the course of MF progression. Our data suggest a strong relation between S100A8 and the phase transitions from pre-MF to overt MF as well as the progression to severe MF making it a valuable candidate in the search for clinical biomarkers. Additionally, we provide evidence that inhibition of S100A8 signaling in vivo ameliorates the clinical MPN phenotype and significantly reduces fibrosis severity. This identifies S100A8 as an important therapeutic target in the future.
Publications
- Dissecting the Functional Reprogramming of the Microenvironment in Bone Marrow Fibrosis at the Single Cell Level (November 26, 2019). CELL-STEM-CELL-D-19- 00795
Leimkühler, Nils B. and Ronghui, Li and Gleitz, Hélène F.E. and Snoeren, Inge A. M. and Fuchs, Stijn N.R. and Kuppe, Christoph and Stalmann, Ursula S. A. and Buesche, Guntram and Kreipe, Hans and Gütgemann, Ines and Krebs, Philippe and Banz, Yara and Boor, Peter and Tai, Evelyn Wing-Ying and Brümmendorf, Tim H. and Koschmieder, Steffen and Crysandt, Martina and Bindels, Eric and Kramann, Rafael and Costa, Ivan G. and Schneider, Rebekka K.
(See online at https://dx.doi.org/10.2139/ssrn.3493957) - Inflammatory bone marrow microenvironment. Hematology Am Soc Hematol Educ Program (2019) 2019 (1): 294–302
Nils B. Leimkühler, Rebekka K. Schneider
(See online at https://doi.org/10.1182/hematology.2019000045)
