title: Effect of methotrexate-induced neutropenia on pulpal inflammation in rats.
abstract: The purpose of this study was to determine the role of neutropenia in pulpal inflammation. We investigated the effect of methotrexate-induced neutropenia on pulpal inflammation in rats. Pulpal inflammation was produced by pulpal exposure. Thirty-six rats were divided equally into control and experimental groups. The control animals received no injection, whereas the experimental animals were injected with 7.5 mg/kg of methotrexate once a day for 3 days before the pulpal exposure. The pulp was exposed in the mandibular first molar of all animals, and the exposed areas were left open. Animals were killed at 2, 4, and 7 days thereafter. Before they were killed, peripheral blood was taken. The number of total leukocytes and neutrophils in the peripheral blood of experimental animals was significantly decreased compared with those of control animals. The methotrexate-induced neutropenia resulted in the initiation of a bacterial invasion into the pulpal tissue and an increase in pulpal necrosis, as well as lessened abscess formation. Histometrically, the area of pulpal necrosis in experimental animals was significantly greater than that in the control animals. Immunohistochemically, the neutropenia resulted in inhibition of the infiltration by neutrophils. These results suggest that the neutrophil plays an important role in the defense against bacteria in pulpal tissue.
authors.affiliation: Department of Endodontics, School of Dentistry, Aichi-Gakuin University, Nagoya, Japan.
authors.forename: Koki
authors.initials: K
authors.lastname: Nakamura
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamasaki
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nishigaki
authors.forename: Akihiro
authors.initials: A
authors.lastname: Iwama
authors.forename: Ichro
authors.initials: I
authors.lastname: Imaizumi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakamura
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Kameyama
mesh_terms: D000818:Animals; D003782:Dental Pulp / Q000382:microbiology / Q000473:pathology; D003789:Dental Pulp Exposure / Q000150:complications; D003790:Dental Pulp Necrosis / Q000382:microbiology / Q000503:physiopathology; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000009:adverse effects*; D007958:Leukocyte Count; D018655:Lymphocyte Count; D008297:Male; D008727:Methotrexate / Q000009:adverse effects*; D008963:Molar; D009503:Neutropenia / Q000139:chemically induced* / Q000503:physiopathology; D020556:Neutrophil Infiltration / Q000502:physiology; D009504:Neutrophils / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D010482:Periapical Abscess / Q000382:microbiology / Q000503:physiopathology; D010486:Periapical Tissue / Q000382:microbiology / Q000473:pathology; D011671:Pulpitis / Q000209:etiology / Q000382:microbiology / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D007166:Immunosuppressive Agents; D008727:Methotrexate