Bone marrow stem cells represent a vital component of adult stem cell biology, playing essential roles in hematopoiesis, tissue regeneration, and immune regulation. Located within the specialized microenvironment of the bone marrow niche, these cells are primarily categorized into hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). Both populations exhibit multipotency, self-renewal capacity, and the ability to differentiate into multiple lineages, making them indispensable for maintaining physiological homeostasis and offering promising avenues for regenerative medicine. Recent advances in stem cell biology, epigenetics, and clinical applications have expanded our understanding of bone marrow stem cell heterogeneity, lineage commitment, and therapeutic potential.

Hematopoietic Stem Cells (HSCs)

Hematopoietic stem cells are responsible for the continuous generation of all blood cell types throughout an individual’s lifespan. These cells possess remarkable self-renewal ability and multilineage differentiation potential, giving rise to myeloid (e.g., erythrocytes, platelets, macrophages) and lymphoid (e.g., T cells, B cells, natural killer cells) lineages. Emerging evidence from recent studies indicates that HSCs exhibit intrinsic lineage biases—myeloid-biased, lymphoid-biased, or balanced—which are epigenetically programmed rather than representing stages of differentiation. This heterogeneity within the HSC compartment influences hematopoietic output and has important implications for aging, hematological diseases, and transplantation outcomes. Understanding the molecular regulation of HSC fate decisions continues to be a major focus in stem cell research, with advances in single-cell transcriptomics and epigenomics providing unprecedented resolution of HSC subpopulations.

Mesenchymal Stem Cells (MSCs)

Mesenchymal stem cells, also resident in the bone marrow stroma, are multipotent progenitors capable of differentiating into osteoblasts, chondrocytes, and adipocytes. Beyond their differentiation potential, MSCs exhibit potent immunomodulatory, anti-inflammatory, and proangiogenic functions, contributing to tissue repair and regeneration. These properties have propelled MSCs to the forefront of regenerative medicine and cell-based therapies for a variety of conditions including bone defects, autoimmune diseases, and cardiovascular disorders. Recent protocols for MSC isolation, expansion, and characterization have enhanced their clinical applicability, while ongoing research aims to elucidate the mechanisms underlying their therapeutic effects and optimize their efficacy in vivo.