Immunolocalization of macrophages and transforming growth factor-beta(1) in induced rat periapical lesions

Apical periodontitis was induced in Wistar rats by exposing the pulp chambe r of right mandibular first molars to the oral environment. Animals were ki lled 0, 5, 10, 15, 20, 30, 60, and 80 days after lesion induction. Microrad iographic and automated image analysis showed that the lesions expanded sig nificantly in a time-dependent manner from day 0 to day 20 (0.039 mm(2)/day , p < 0.05, active phase) and stabilized thereafter (chronic phase). A line ar regression test revealed a positive correlation between the numbers of E D-1 positive macrophage per microscopic high power field and the periapical lesion size during the active phase (r = 0.98, p < 0.01). Immunohistochemi cal studies showed that transforming growth factor-beta(1) positive macroph ages distributed around the root apex and areas showing bone resorption dur ing active lesion phase, whereas TGF-beta(1)-positive osteoblasts were dete cted during the chronic stage (days 30, 60, and 80 after pulp exposure). Hi stologically TGF-beta(1) positive osteoblasts possessed a large, round nucl eus as well as an abundant cytoplasm and located in close vicinity to areas exhibiting reparative bone formation. These results suggest that macrophag es may play important role(s) in the initiation and development of periapic al lesions and TGF-beta(1) may play dual roles in both bone resorption and deposition in induced rat periapical lesions.