IADR Abstract Archives
Schwann cell activation and vascular changes during physiological root resorption
Objectives: The physiological root resorption (PRR) process in human primary teeth is mainly mediated by the dental follicle of the developing permanent tooth, a process that produces a progressive Wallerian-like axonal degeneration and inflammatory condition of the dental pulp. It has been established that Schwann cells dedifferentiate into repair phenotypes in damaged peripheral nerves, allowing axonal regeneration. The purpose of this study was to characterize changes in Schwann cell phenotypes and vascular components associated with axonal degeneration and inflammatory processes during physiological root resorption in human primary teeth.
Methods: Twenty one canine primary teeth were extracted under clinical indication, fixed in 4% PFA and decalcified with EDTA. Written parental consent and child agreement were requested. Teeth were classified in three different stages, according to root length remnants: early, middle, and advanced. Longitudinal cryosections were obtained and assayed with immunohistochemical procedures, using a panel of markers for nerve fibers (NF, TUBB3), Schwann cells (S100, c-Jun, p75NTR), vascular components (CD31, CD34, vWF, CD105), lymphatic vessels (PDPN) and immunocompetent cells (HLA-DR, CD68, CD15 and CD3). Quantitative analysis was performed on confocal image stacks at different magnifications.
Results: Dental pulp nerves at different PRR stages display axonal degeneration with a progressive degradation of myelin. At the same time, Schwann cells exhibit a significant over-expression of p75NTR and c-Jun. Vascular components were comparatively enlarged, with significant angiogenic activity in association with chronic immune cell infiltration.
Conclusions: Reprogrammation of Schwann cells into repair phenotypes constitutes a robust response to nerve injury during PRR. Vascular changes were prominent in connection with a conspicuous increase of immune-competent cell infiltration and the development of an extensive lymphatic network. These results validate the injury-activated plasticity condition of Schwann cells and increase our understanding of the physiological root resorption process.
Supported by Fondecyt 1141281(EC), CONICYT-PCHA/Magister Nacional/2016-22160217 (KS) and the CINV/Millenium Institute (P09-022-F).
Methods: Twenty one canine primary teeth were extracted under clinical indication, fixed in 4% PFA and decalcified with EDTA. Written parental consent and child agreement were requested. Teeth were classified in three different stages, according to root length remnants: early, middle, and advanced. Longitudinal cryosections were obtained and assayed with immunohistochemical procedures, using a panel of markers for nerve fibers (NF, TUBB3), Schwann cells (S100, c-Jun, p75NTR), vascular components (CD31, CD34, vWF, CD105), lymphatic vessels (PDPN) and immunocompetent cells (HLA-DR, CD68, CD15 and CD3). Quantitative analysis was performed on confocal image stacks at different magnifications.
Results: Dental pulp nerves at different PRR stages display axonal degeneration with a progressive degradation of myelin. At the same time, Schwann cells exhibit a significant over-expression of p75NTR and c-Jun. Vascular components were comparatively enlarged, with significant angiogenic activity in association with chronic immune cell infiltration.
Conclusions: Reprogrammation of Schwann cells into repair phenotypes constitutes a robust response to nerve injury during PRR. Vascular changes were prominent in connection with a conspicuous increase of immune-competent cell infiltration and the development of an extensive lymphatic network. These results validate the injury-activated plasticity condition of Schwann cells and increase our understanding of the physiological root resorption process.
Supported by Fondecyt 1141281(EC), CONICYT-PCHA/Magister Nacional/2016-22160217 (KS) and the CINV/Millenium Institute (P09-022-F).