Changes of Bone Matrix Proteins during Healing Process of Periapical Lesion

Abstract

The healing of periapical infections is achieved by physiologically sterilizing the root canal up to the apical foramen. However, for intractable periapical infections that are treated in the usual manner but do not manage to heal properly, surgical endodontic treatment may be chosen. In previous studies, we found that, for intractable periapical infections, by cleaning the periapical lesion through the root canal with 5% sodium hypochlorite solution, necrosed tissue and bacteria of the periapical lesion could be resolved and removed, thus resulting in early healing. Meanwhile, in studies on lesion cleaning using sodium hypochlorite solution, none of the research either focused on the bone matrix proteins or analyzed their prevalence through biochemical investigation. Therefore, in this study, a periapical lesion was produced in rats, sodium hypochlorite solution was used for cleaning the lesion, the bone matrix proteins around the lesion were extracted, collagenous proteins and non-collagenous proteins were fractionated according to their extraction properties into an EDTA soluble fraction and a guanidine soluble fraction, and their respective quantitative and qualitative changes were observed. In this study, by the treatment, quantitative changes in the collagenous proteins were thus found to increase in the short term. In addition, in a search for collagen molecular species using the electrophoretic method, types I, III and V collagens were detected but the rate of type III collagen substantially decreased in comparison to normal tissue. As for non-collagenous proteins, in an electrophoretic search, differences in the component ratio at the peak of the specific molecular weight were found in both the EDTA fraction and guanidine fraction. In a search for glycoproteins using a lectin blot analysis, differences were found in the protein component ratio, at around 50kD for the EDTA fraction, but such differences were hardly observed for the guanidine fraction. Based on the above findings, it was found that, by cleaning sodium periapical lesions with hypochlorite solution, the quantity of collagenous proteins, the EDTA fraction, namely the quantity of mineral-associated proteins, and the electrophoretic behavior changed during the healing process. Further analyses on the molecular weight of the proteins that were observed to have especially and substantially changed in this experiment are now underway in order to help elucidate the process of periapical lesion healing.