Applications of Mesenchymal Stromal Cells in Hematologic Disease: Advances, Challenges, and Bioengineering Strategies

Mesenchymal stromal cells (MSCs) are multipotent cells of mesodermal origin capable of self-renewal and multilineage differentiation. Characterized by low immunogenicity and tropism toward injury sites, MSCs exhibit critical properties including hematopoietic support, immunomodulation, and tissue regeneration. These unique attributes position MSCs as promising therapeutic tools for hematologic diseases, where disruption of the bone marrow niche impairs normal hematopoiesis. Co-transplantation of MSCs with hematopoietic stem cells (HSCs) facilitates HSC homing to the bone marrow niche and significantly improves post-transplant hematopoietic reconstitution. Furthermore, MSCs show considerable therapeutic potential in both prophylaxis and management of graftversus- host disease (GVHD), a major complication of allogeneic transplantation. The therapeutic mechanisms of MSCs have evolved from an initial focus on engraftment to a broader understanding of their paracrine actions via the "hit-and-run" mechanism, wherein MSCs exert functions through secreted factors and extracellular vesicles before host clearance. Despite these advances, clinical translation faces significant challenges, including poor homing efficiency, cellular heterogeneity, culture-induced senescence, and vulnerability to inflammatory and oxidative stress. This review summarizes clinical applications of MSCs in aplastic anemia, leukemia, and co-transplantation with HSCs, while critically evaluating the balance between therapeutic efficacy and potential risks. Additionally, we discuss emerging bioengineering strategies designed to overcome current limitations and enhance MSC therapeutic potency for next-generation cell therapies in hematologic diseases.