An aged human bone marrow mesenchymal niche causes impaired function of human hematopoietic stem cells under regeneration-induced stress

Hematopoietic stem cells (HSCs) reside in the bone marrow (BM) and are responsible for blood formation throughout life. With advancing age, HSCs show reduced functional capacity. While clear intrinsic cellular changes in human HSCs (hHSCs) occur during aging, it remains unclear how the human bone marrow (hBM) niche contributes to hHSC dysfunction. This research gap is largely due to a lack of suitable experimental models capable of replicating the organization and function of the aged hBM environment. This study demonstrates that aged hBM mesenchymal stromal cells (hBMSCs) act as important niche regulators of hHSC function by contributing to the myeloid-biased differentiation of young hHSCs. Furthermore, hBMSCs play a crucial role in protecting hHSCs during regeneration-induced stress while this protective function of hBMSCs is impaired with age.