title: Repair process of fetal brain after 5-azacytidine-induced damage.
abstract: The fetal brain is susceptible to many extrinsic stresses. Some of these stresses induce excessive cell death in the prenatal stage, leading to anomalies in the neonatal brain. However, it is unclear how the developing brain responds to and repairs the prenatal tissue damage. We treated pregnant rats on day 13 of gestation with 5-azacytidine, one of the compounds that induces excessive cell death and inhibits proliferation in neural progenitor cells, to damage the fetal brain, and investigated the repair process up to 60 h after treatment. Histological analysis showed that 5-azacytidine induced strong apoptosis of neural cells. By 60 h, apoptotic cells disappeared and the tissue was repaired, although the telencephalic wall remained thinner than in controls. Flow cytometry analysis showed that the cell cycle distribution also returned to control levels at 60 h, suggesting that the repair process was completed around 60 h. During the repair period, amoeboid microglia infiltrated the brain and ingested the apoptotic cells. These microglial cells were positive for the multiple microglial markers, and mRNAs for the microglia-related cytokines tumor necrosis factor alpha, interleukin 1beta and macrophage colony stimulating factor (M-CSF) were up-regulated. DNA microarray analysis showed the up-regulation of genes relevant to glial cells, inflammation, the extracellular matrix, glycolysis, proliferation and neural development. We show here that the developing brain has the capacity to respond to the damage induced by extrinsic chemical stresses, including changing the expression of numerous genes and the induction of microglia to aid the repair process.
authors.affiliation: Department of Veterinary Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. ms-ueno@umin.ac.jp
authors.forename: Masaki
authors.initials: M
authors.lastname: Ueno
authors.forename: Kei-Ichi
authors.initials: K
authors.lastname: Katayama
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yamauchi
authors.forename: Akira
authors.initials: A
authors.lastname: Yasoshima
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakayama
authors.forename: Kunio
authors.initials: K
authors.lastname: Doi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001374:Azacitidine; D001921:Brain / Q000187:drug effects* / Q000196:embryology / Q000648:ultrastructure; D001930:Brain Injuries / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D053331:Ectodysplasins / Q000378:metabolism; D004622:Embryo, Mammalian; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D007150:Immunohistochemistry / Q000379:methods; D020287:In Situ Nick-End Labeling / Q000379:methods; D046228:Microarray Analysis / Q000379:methods; D008840:Microfilament Proteins; D046529:Microscopy, Electron, Transmission / Q000379:methods; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013997:Time Factors; D014945:Wound Healing / Q000502:physiology*
chemical_list: C100745:Aif1 protein, rat; D002135:Calcium-Binding Proteins; D016207:Cytokines; D053331:Ectodysplasins; D008840:Microfilament Proteins; D012333:RNA, Messenger; D001374:Azacitidine