Inherent physical characteristics and gene expression differences between alveolar and basal bones

Abstract

Objectives: The objective of this study was to evaluate the baseline differences between alveolar and basal areas of the rat mandible.

Study design: Rat mandibular alveolar and basal bones were evaluated using histology and micro-computed tomography to compare osteocyte number as well as bone density and architecture and polymerase chain reaction to measure gene expression levels.

Results: Micro-computed tomography data indicated that basal bone is denser and less porous than alveolar bone. Histologic analysis showed that alveolar bone has more osteocytes per unit area compared with basal bone. Real-time polymerase chain reaction results showed higher levels of expression of the following genes in basal bone than in alveolar bone: SOST, E-11, DMP-1, and MEPE.

Conclusions: Three of these gene products are associated with mature osteocytes, and this suggests that basal bone has more mature osteocyte phenotypes compared with alveolar bone. These findings are suggestive of fewer bone mineralization units and therefore a slower remodeling rate.

Fig. 1

Representative micrographs of alveolar and basal bone from rats (×10 magnification). A, Alveolar bone—negative control (no anti-podoplanin antibody). B, Basal bone—negative control (no anti-podoplanin antibody). C, Alvolar bone—immunohistochemical stained with anti-podoplanin. D, Basal bone—immunohistochemical stained with anti-podoplanin. Black arrows indicate examples of cells stained positively for podoplanin. White arrows indicate examples of cells not stained positively for podoplanin.

Fig. 2

Micro-computed tomography (CT) results of bone surface/bone volume (BS/BV; measured in mm² mm⁻³), trabecular thickness (TbTh; measured in mm), and closed porosity (Po; measured as a percentage)–normalized basal/alveolar bone. *Denotes significant difference of α = 0.05.

Fig. 3

Micro-computed tomography (CT) image of bone showing alveolar bone surrounding molar and basal bones below the central incisor (left) and alveolar and basal areas indicated (right).

Fig. 4

Real-time polymerase chain reaction (PCR) results—average fold change values with respect to alveolar bone. *Denotes significant difference of α < 0.05.