MICROVASCULAR LUMINAL VOLUME CHANGES IN AGED MOUSE PERIODONTAL-LIGAMENT

Data for the microvascular bed in the aged periodontal ligament have n ot been established. This investigation tested the hypothesis that the luminal microvascular volume decreased in the aged ligament. Mice 35 days old and one year old were vascular-perfused and the mandibular fi rst molar periodontal ligament processed for electron microscopy. Tiss ue quadrats from each circumferential third ligament region were recor ded at 150-mu m intervals from the alveolar crest to the apex for rand omized sampling of blood vessel lumina. The data were analyzed with a generalized linear model at the p < 0.01 level for the interaction of the aging effect with differences across regions. Stereological parame ters were established for vessel lumen volume, and for surface and len gth densities. Mean ligament width decreased from 119.9 +/- 16.94 (mu m +/- SE) in young mice to 60.0 +/- 10.58 (mu m +/- SE) in aged mice. The luminal volume of 8.63 +/- 1.37 (% +/- SE) in young ligament incre ased to 9.83 +/- 2.14 (% +/- SE) in aged ligament. Collecting venules and the combined group of arterio-venous anastomoses with terminal art erioles showed a two-fold increase in luminal volume density (p < 0.01 ). In aged ligament, regional shifts affected the microvascular bed di stribution, but these changes were not consistent across regions, or w ith depth. The average cross-sectional tissue area served per capillar y decreased from 2117 mu m(2) to 1451 mu m(2) for young and old. Avera ge ligament thickness served per capillary dropped from 52.5 mu m to 2 7.5 mu m. These reductions in average diffusion distances indicated a change in the quality of the diffusion barrier with age.