Angiogenic changes in experimental periodontitis in rats. evidence for a possible role of pulp and dentin

ABSTRACT

During the progression of periodontal disease, the periodontal vasculature is profoundly affected. There has been little research on vascular changes in the untreated lesion of periodontitis. Angiogenesis is defined as the process of sprouting of new blood vessels from preexisting capillaries. Angiogenesis is regulated by many cytokines and growth factors. Vascular endothelial growth factor [VEGF] is a potent inducer of angiogenesis and vascular permeability and may be related to periodontal disease. Higher levels of VEGF were detected in whole saliva from periodontitis patients, in comparison to whole saliva from healthy controls. The present study aimed to his-tomorphometrically and immunohistochemically investigate the angiogenic changes in the inflamed periodontal tissues and to probe the possible effect on the pulp tissues of the adjoining tooth. Twenty adult male Albino rats were used in the study and were Subjected to experimental periodontitis by ligature placement around the mandibular 2nd molars of left side while those of the right side were left unligated to serve as a control. Tissue specimens of the pulp and periodontal ligament [PDL] of both sides were histologically examined. Immunostaining with anti VEGF antibody was also done to investigate its expression in these tissues and the number and diameter of BVs were morpho-metrically assayed. Results of the present work showed that experimental periodontitis resulted in remarkable histological, vascular and immunohistochemical changes in VEGF expression both in the periodontal ligament [PDL] as well as pulp tissues. The histological and histomorphometric results presented a statistically significant increase in the mean number of blood vessels [BVs] throughout the PDL and the connective tissue [CT] adjacent to the pocket epithelium in the periodontitis side. In contrast to the control side PDL, there was increased evidence of small BVs in the cementum related zone of the periodontitis side. Similarly, there was increased vessel density [number and diameter] in the coronal pulp of 2nd molars of this side as compared to the control without any obvious changes in the radicular pulp tissues. Immunohistochemically, experimental periodontitis was associated with increased expression of VEGF in alveolar bone, PDL and limited areas of the coronal pulp tissues. On the other hand, the histologically altered junctional and sulcular epithelia of this side presented decreased expression of the reaction. In view of these data, the present investigation proved that vascular and angiogenic changes takes place as a consequence of experimental periodontitis. Such changes were not limited to the PDL, but it also affected the coronal pulp tissue of the adjoining tooth. The evidence for involvement of dentin as .a possible source of the VEGF is also discussed. It was concluded that periodontitis is associated with increased angiogenesis in the PDL as well as the coronal pulp tissue of the adjoining tooth. Bone and dentin matrices may participate in these angiogenic changes