Periodontal Regeneration Using Engineered Rat Bone Marrow Mesenchymal Stromal Cells

Objectives: Periodontal regeneration presumes simultaneous reconstitution of both hard (alveolar bone, cementum) and soft (periodontal ligament) connective tissues. To date bone marrow mesenchymal stromal cells (BM-MSCs) have demonstrated connective tissue regenerative potential. We hypothesized that rat BM-MSCs expanded ex vivo on a resorbable scaffold will support regeneration of lost periodontal tissues.

Methods: BM-MSCs isolated from transgenic green fluorescent protein (GFP)⁺ Sprague Dawley rats were expanded ex vivo on gelatin microcarrier beads prior to transplantation into surgically created rat periodontal defects. Control groups included control defect alone and defects treated with microcarrier beads alone. At three weeks all animals were sacrificed, jaws removed, decalcified and processed for histological examination.

Results: At 3 weeks healing in all groups was uneventful. The percentage of new bone (50.6±18.5%) and number of perpendicular periodontal ligament fibers (5.2±1.8/100µM) were statistically greater in the beads plus cells group when compared to beads alone (26.4±4.6% new bone and 2.4±2.2/100 µM new ligament) or defect alone (23.5±8% new bone and 1.1±0.6/100µM new ligament) groups. The cell group and beads alone group regenerated significantly more cementum than the defect alone group. Within all three-tissue compartments, we successfully tracked GFP⁺ positive cells within new bone, cementum and periodontal ligament.

Conclusions: A novel rat bone marrow stromal cell expansion approach utilizing gelatin micro beads was applied to a rat jaw periodontal defect model. Significantly more alveolar bone, and functionally orientiated periodontal ligament were regenerated in the beads plus cells group. New cementum was deposited and anchored the new periodontal ligament fibers. The significant increase in cementum formation in both beads group may reflect that the beads served as a functional barrier to support regeneration of cementum. We have demonstrated that both the newly formed periodontal hard and soft connective tissues may originate at least in part from the transplanted GFP⁺ BM-MSCs.