Mesenchymal stem cells for bone repair and metabolic bone diseases

Abstract

Human mesenchymal stem cells offer a potential alternative to embryonic stem cells in clinical applications. The ability of these cells to self-renew and differentiate into multiple tissues, including bone, cartilage, fat, and other tissues of mesenchymal origin, makes them an attractive candidate for clinical applications. Patients who experience fracture nonunion and metabolic bone diseases, such as osteogenesis imperfecta and hypophosphatasia, have benefited from human mesenchymal stem cell therapy. Because of their ability to modulate immune responses, allogeneic transplant of these cells may be feasible without a substantial risk of immune rejection. The field of regenerative medicine is still facing considerable challenges; however, with the progress achieved thus far, the promise of stem cell therapy as a viable option for fracture nonunion and metabolic bone diseases is closer to reality. In this review, we update the biology and clinical applicability of human mesenchymal stem cells for bone repair and metabolic bone diseases.

FIGURE.

Developmental hierarchy of stem cells (SCs) and therapeutic potential of human mesenchymal stem cells (MSCs). On fertilization of an egg, a blastocyst forms. The inner cell mass of the blastocyst consists of the most primitive SC or totipotent SC. This totipotent SC can give rise to cells of embryonic and extraembryonic origin. Pluripotent SCs are multipotent SCs that can self-renew and differentiate into hematopoietic SCs, endothelial SCs, and MSCs. Hematopoietic SCs differentiate into blood cells, whereas endothelial progenitors give rise to mature endothelial cells. However, MSCs are characterized by their multilineage differentiation potential, including for bone, cartilage, and adipose tissue. Human MSCs have been tested in several clinical applications to repair bone in different types of bone disease, including fracture nonunion, osteogenesis imperfecta, and hypophosphatasia.