Disruption of periodontal integrity induces expression of apin by epithelial cell rests of Malassez

Nishio C, Wazen R, Kuroda S, Moffatt P, Nanci A. Disruption of periodontal integrity induces expression of apin by epithelial cell rests of Malassez. J Periodont Res 2010; 45: 709–713. © 2010 John Wiley & Sons A/S Background and Objective: It has been suggested that epithelial cell rests of Malassez (ERM) may express enamel matrix proteins and play an important role in periodontal regeneration. Two novel proteins, apin (APIN) and amelotin (AMTN), produced by maturation‐stage ameloblasts and junctional epithelium, have recently been identified. The objective of this study was to evaluate whether the ERM express APIN and AMTN under normal conditions and after periodontal challenge. Material and Methods: Gingivectomy and orthodontic tooth movement were carried out on the left side of the maxillae of rats. The control group included the untreated contralateral side of these animals and the maxillae of normal, untreated rats. Animals were sacrificed by intracardiac perfusion on days 3 and 5 after the experimental procedures and maxillary molars were decalcified and processed for paraffin embedding. Immunohistochemistry was used to evaluate the expression of various ameloblast products, including APIN, AMTN, ameloblastin (AMBN) and amelogenin (AMEL). Results: At 3 and 5 days after periodontal challenge, ERM were more evident in the periodontal ligament along the root surface and in the root furcations. Immunodetection of APIN, but not of the other three proteins, was observed in the ERM following the disruption of periodontal integrity. No immunolabeling for APIN, AMTN, AMBN and AMEL was detected in the ERM under normal conditions. Conclusion: The expression of APIN at an early time‐point following disruption of periodontal integrity suggests that this protein may be part of the cascade of events leading to the activation of ERM during periodontal healing and regeneration.