Immunomodulatory properties of mesenchymal stromal cells and their therapeutic consequences for immune-mediated disorders.

Bone marrow-derived mesenchymal stromal cells (MSCs) represent a population of nonhematopoietic cells, which play a crucial role in supporting hematopoiesis and can differentiate into various cell types such as osteocytes, chondrocytes, adipocytes, and myocytes. Due to their differentiation capability, MSCs emerge as promising candidates for therapeutic applications in tissue engineering. In addition, they display immunomodulatory properties that have prompted consideration of their potential use for treatment modalities aimed at the inhibition of immune responses. In this context, MSCs efficiently inhibit maturation, cytokine production, and T-cell stimulatory capacity of dendritic cells (DCs). They also markedly impair proliferation, cytokine secretion, and cytotoxic potential of natural killer cells and T lymphocytes. Furthermore, MSCs are able to inhibit the proliferation of B cells and their capacity to produce antibodies. Various animal models confirm the immunomodulatory properties of MSCs. Thus, administered MSCs prolong the survival of skin and cardiac allografts and ameliorate acute graft-versus-host disease (GVHD) as well as experimental autoimmune encephalomyelitis. Clinical studies enrolling patients with severe acute GVHD reveal that the administration of MSCs results in significant clinical responses. Due to their immunomodulatory capability and their low immunogenicity, MSCs represent promising candidates for the prevention and treatment of immune-mediated diseases.