Behavior of transplanted bone marrow-derived mesenchymal stem cells in periodontal defects

Background: Recently, there have been an increased number of basic and clinical reports indicating the superior potential of bone marrow-derived mesenchymal stem cells (MSCs) for tissue regeneration. In periodontal treatment, previous animal studies indicated that autotransplantation of bone marrow MSCs into experimental periodontal defects enhanced periodontal tissue regeneration. However, mechanisms for periodontal tissue regeneration with MSCs are still unclear. The purpose of this study was to elucidate the behavior of transplanted MSCs in periodontal defects. Methods: Bone marrow MSCs were isolated from beagle dogs, labeled with green fluorescent protein (GFP), and expanded in vitro. The expanded MSCs were mixed with atelo-collagen (2% type I collagen) at final concentrations of 2 x 107 cells/ml and transplanted into experimental Class III periodontal defects. Localizations of GFP and proliferating cell nuclear antigen (PCNA)-positive cells were evaluated by immunohistochemical analysis. Results: Four weeks after transplantation, the periodontal defects were almost regenerated with periodontal tissue. Cementoblasts, osteoblasts, osteocytes, and fibroblasts of the regenerated periodontal tissue were positive with GFP. PCNA-positive cells were present in regenerating connective tissue. Conclusion: These findings suggest that transplanted mesenchymal stem cells could survive and differentiate into periodontal tissue cells, resulting in enhancement of periodontal tissue regeneration.