title: Analysis of low affinity nerve growth factor receptor during pulpal healing and regeneration of myelinated and unmyelinated axons in replanted teeth.
abstract: Nerve regeneration was examined in rat molars that were briefly extracted and then replanted in the socket for 1-90 days. Immunocytochemistry was used to evaluate neural and nonneural immunoreactivity (IR) for low affinity nerve growth factor receptor (p75-NGFR) and for laminin and calcitonin gene-related peptide (CGRP). Three different types of pulpal response to replantation were found. Type I: Some replanted teeth had mild injury and still contained coronal odontoblasts and associated fibroblasts that retained p75-NGFR-IR; they continued regular dentin formation and had excellent reinnervation. Type II: Teeth with intermediate injury lost most or all of the coronal pulp tissue, but they regenerated odontoblast-like cells that formed irregular dentin, they had numerous dispersed p75-NGFR-IR fibroblasts in crown pulp during early regeneration, and they had excellent reinnervation. Type III: Severely injured teeth lost their original pulp; they filled with dense connective tissue and bone and had poor reinnervation. After Type I or II injury the Schwann cells around degenerating myelinated and unmyelinated axons had increased expression of p75-NGFR by 1-3 days. By 7-10 days those Schwann cells had formed hollow tubes (bands of Bungner) along the degenerating axon tracks. They maintained their increased p75-NGFR-IR during and after regeneration of unmyelinated axons, whereas Schwann cells involved in remyelination lost p75-NGFR-IR at that stage. The number of CGRP-IR axons in the regenerating pulp increased from 7 to 90 days. Laminin-IR increased in all replanted teeth at 3-10 days and only returned to normal patterns in teeth with Type I or Type II response at 20-90 days. The special p75-NGFR-IR of pulpal fibroblasts of adult rat molars did not usually persist in regenerated, reinnervated pulp. The extensive depletion of fibroblast p75-NGFR-IR and the continuing enhanced p75-NGFR-IR in unmyelinated nerve fibers at 90 days show that altered growth factor conditions characterize regenerated pulp of replanted teeth.
authors: Department of Anesthesiology, University of Washington, Seattle 98195.
authors: M R
authors: MR
authors: Byers
authors: I
authors: I
authors: Kvinnsland
authors: M
authors: M
authors: Bothwell
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology*; D003782:Dental Pulp / Q000294:innervation / Q000502:physiology; D003789:Dental Pulp Exposure / Q000378:metabolism*; D005260:Female; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D009416:Nerve Regeneration / Q000502:physiology*; D051381:Rats; D017475:Receptors, Nerve Growth Factor / Q000032:analysis*; D012038:Regeneration / Q000502:physiology; D014090:Tooth Replantation; D014945:Wound Healing / Q000502:physiology
chemical_list: D017475:Receptors, Nerve Growth Factor