Progenitor cell kinetics during guided tissue regeneration in experimental periodontal wounds

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Abstract
The present investigation compared the premitotic labelling of cells in the bone and periodontal ligament (PDL) compartments apical to a surgically created fenestration wound containing a “periodontal space.” Buccal fenestration wounds (3x3 mm) were made at midroot level in 4 Macaca fascicularis monkeys. The exposed root surfaces were planed and a piece of millipore filter was placed over each fenestration prior to flap replacement. Wounding in the different dentition segments and sacrifice of monkeys were scheduled to provide observation periods of I h I, 2, 3, 7 and 21 d in each monkey. One hour prior to sacrifice, tritiated thymidine (1 μCi/gm body weight) was administered intravenously. Autoradiographs were used to determine the labeling index (L.I.) of fibroblast‐like cells in each of the three following histologic compartments: PDL, alveolar bone adjacent to the apical border of the fenestration, and the wound proper. No significant differences in the L.I. between the bone and PDL tissue compartments were noted for nearly all of the observation periods. L.I. in the PDL peaked at 2 d while the alveolar bone demonstrated two peaks of activity, one at 2 d and the other at 7 d. Labeled cells first appeared at the edge of the wound proper at 3 d. At 7 d, labeled cells were noted throughout the wound compartment indicating continued activity of migrated cells. The 21‐d specimens demonstrated a few labeled cells in the wound compartment and a reduction of mitotic activity in the adjacent PDL and bone compartments to almost normal levels. The results of the present investigation suggest that both the bone and PDL tissue compartments supply cells to a periodontal wound containing a surgically created periodontal space. Moreover, some of the cells which migrate into the potential space formed by the physical barrier continue to prepare for mitosis as they migrate.