Microvascular Luminal Volume Changes in Aged Mouse Periodontal Ligament

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Abstract
Data for the microvascular bed in the aged periodontal ligament have not 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 first molar periodontal ligament processed for electron microscopy. Tissue quadrats from each circumferential third ligament region were recorded at 150-μm intervals from the alveolar crest to the apex for randomized 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 parameters were established for vessel lumen volume, and for surface and length densities. Mean ligament width decreased from 119.9 ± 16.94 (μm ± SE) in young mice to 60.0 ± 10.58 (μm ± SE) in aged mice. The luminal volume of 8.63 ± 1.37 (% ± SE) in young ligament increased to 9.83 ± 2.14 (% ± SE) in aged ligament. Collecting venules and the combined group of arterio-venous anastomoses with terminal arterioles showed a two-fold increase in luminal volume density (p < 0.01). In aged ligament, regional shifts affected the microvascular bed distribution, but these changes were not consistent across regions, or with depth. The average cross-sectional tissue area served per capillary decreased from 2117 μm2 to 1451 μm 2 for young and old. Average ligament thickness served per capillary dropped from 52.5 μm to 27.5 μm. These reductions in average diffusion distances indicated a change in the quality of the diffusion barrier with age.