Impact of aging on CD146+ mesenchymal stromal cells-mediated regulation of bone marrow CD34+ hematopoietic stem/progenitor cell mobilization

Background: The study of age-associated changes in the bone marrow (BM), a key organ for hematopoiesis and immune regulation, is crucial to understanding inflammatory processes linked to cardiovascular diseases. Notably, aging is associated with impaired mobilization of BM-derived cardioprotective CD34+ hematopoietic stem/progenitor cells (HSPCs), resulting in a lower frequency in the circulation and poorer cardiovascular outcomes. HSPCs pharmacological mobilizers (G-CSF, AMD3100) and sympathetic signaling stimulator (norepinephrine, NE) function mainly by acting on CD146+ Bone marrow stromal cells (BMSCs), key cellular players in this process. In this study, we developed a human in vitro BM simplified experimental model to assess the impact of aging on CD146+ BMSCs in this context. Methods: CD146+ BMSCs were isolated from 29 human subjects, stratified into middle-aged (middle-aged, ≤66 years; N = 13) and older adults (older adult, ≥75 years; N = 16). For functional assays, bone marrow HSPCs from a single donor (female, 64 years) were used. The in vitro BM simplified experimental model was developed by co-culturing CD146+ BMSC and CD34+ HSPCs in a transwell system. After treatment with mobilizing agents, CD146+ BMSCs’ viability, HSPC migration, transcriptome, metabolism, and paracrine activity were assessed. Results: AMD3100 enhanced HSPC migration in the model using MA-derived CD146+ BMSCs but not in OA-derived cells. RNA sequencing identified 9 ageassociated genes, with validated downregulation of NRK and upregulation of PDK4, AQP1, and LMO2 in OA CD146+ BMSC. Moreover, a differential gene expression response to mobilizing treatments was observed between groups. Cell-conditioned media from OA CD146+ BMSCs showed stronger chemoattractant effects on peripheral blood mononuclear cells and presented increased VCAM-1 levels. No age-related effects on oxidative respiration were observed. Conclusion: In this study, a BM in vitro co-culture system was developed to study CD146+ BMSC-dependent CD34+ mobilization in a subject-specific manner, and the complexity of the impact of aging on CD146+ BMSC and their response to mobilizing agents was highlighted.