Microstructure and Osteogenic Gene Profile Variation Between Alveolar/Basal Bone

Objective: Alveolar bone loss after tooth extraction leads to bone insufficiency and often compromises denture functions and implants integration. Most resorption occurs in the alveolar process, whereas basal bone remains intact. We hypothesize, therefore, that gene expression is different in these two areas.  To complement this biological assessment, we also are interested in the microarchitecture of alveolar versus basal bone.  This study aimed to correlate these morphological differences with regional distinctions in osteocyte phenotype.

Method: Mandibles were harvested from six Sprague Dawley rats. Half were scanned using skyscan 1174 micro CT, later decalcified and prepared for H&E sections staining to count osteocytes. Other halves were used for RNA preparation and real time PCR study for selected osteogenic and other regulatory genes.  Changes in bone structural properties, cell count and gene expression were analyzed using ANOVA and T-test (alpha =0.05).

Result: Osteocyte area density, bone surface/volume ratio and closed porosity were significantly higher in alveolar bone than basal bone, while trabecular thickness and diameter were significantly lower in alveolar bone.  Gene expression of MEPE, E11, DMP-1 and SPP1 were all significantly higher in basal bone than alveolar bone, suggesting a higher rate of bone turnover.

Conclusion: Baseline differences in morphology and gene expression exist between alveolar and basal bone.  Future studies will compare characteristics of osteocytes isolated from these bone regions and how mechanical stress alters these responses.