2015 – STRUCTURAL AND FUNCTIONAL ANALYSIS OF BONE MARROW STROMAL NETWORKS DURING CHEMOTHERAPY

Cytoreductive treatments, such as 5-fluorouracil (5-FU), are often used as conditioning regimens in bone marrow (BM) transplantation and cancer therapy, eliminating highly proliferative hematopoietic progenitor cells and partially damaging the BM microenvironment. While the responses of the hematopoietic compartment to irradiation and chemotherapy have been studied in detail, the impact of these treatments on specific stromal components is less understood.

Here, we employ customized 3D microscopy and image-based analytical pipelines to investigate the dynamics and kinetics of injury and repair following treatment with 5-FU on sinusoidal endothelial and arterial cells (SECs and AECs), and CXCL12-abundant reticular cells (CARc) within the regenerated BM, as well as mapping the spatial distribution of HSCs. Finally, we integrate scRNA-seq data to reveal compositional changes in stromal networks and pathways involved in tissue regeneration.

We report that i) contrary to previous reports, CARc mostly survive 5-FU treatments and their numbers remain largely unaltered as determined by 3D-QM ii) myeloablation causes severe structural damage to CARc and vascular networks and fragmentation of CARc mesh iii) despite this, SECs and CARc demonstrate significant regenerative potential, restoring structural integrity and quantitative morphometric parameters iv) the regeneration of BM stroma coincides with HSC recovery and re-entry into quiescence v) while stromal networks regain their structure, the transcriptomic landscapes of both EC and MSC subsets remain strongly perturbed even after 16 weeks post 5-FU. These findings show that stromal networks possess self-organizing capabilities for rapid structural repair, but 5-FU treatment leads to long-term molecular changes in stromal cells, potentially affecting their functional regulation of hematopoiesis and HSC maintenance.