RESUMO
We have previously demonstrated that aTf (apotransferrin) accelerates maturation of OLs (oligodendrocytes) in vitro as well as in vivo. The purpose of this study is to determine whether aTf plays a functional role in a model of H/I (hypoxia/ischaemia) in the neonatal brain. Twenty-four hours after H/I insult, neonatal rats were intracranially injected with aTf and the effects of this treatment were evaluated in the CC (corpus callosum) as well as the SVZ (subventricular zone) at different time points. Similar to previous studies, the H/I event produced severe demyelination in the CC. Demyelination was accompanied by microglial activation, astrogliosis and iron deposition. Ferritin levels increased together with lipid peroxidation and apoptotic cell death. Histological examination after the H/I event in brain tissue of aTf-treated animals (H/I aTF) revealed a great number of mature OLs repopulating the CC compared with saline-treated animals (H/I S). ApoTf treatment induced a gradual increase in MBP (myelin basic protein) and myelin lipid staining in the CC reaching normal levels after 15 days. Furthermore, significant increase in the number of OPCs (oligodendroglial progenitor cells) was found in the SVZ of aTf-treated brains compared with H/I S. Specifically, there was a rise in cells positive for OPC markers, i.e. PDGFRα and SHH(+) cells, with a decrease in cleaved-caspase-3(+) cells compared with H/I S. Additionally, neurospheres from aTf-treated rats were bigger in size and produced more O4/MBP(+) cells. Our findings indicate a role for aTf as a potential inducer of OLs in neonatal rat brain in acute demyelination caused by H/I and a contribution to the differentiation/maturation of OLs and survival/migration of SVZ progenitors after demyelination in vivo.
Assuntos
Apoproteínas/fisiologia , Hipóxia-Isquemia Encefálica/patologia , Hipóxia-Isquemia Encefálica/prevenção & controle , Bainha de Mielina/metabolismo , Bainha de Mielina/patologia , Recuperação de Função Fisiológica/fisiologia , Transferrina/fisiologia , Animais , Animais Recém-Nascidos , Apoproteínas/uso terapêutico , Células Cultivadas , Corpo Caloso/patologia , Corpo Caloso/fisiologia , Feminino , Humanos , Hipóxia-Isquemia Encefálica/fisiopatologia , Masculino , Bainha de Mielina/fisiologia , Células-Tronco Neurais/patologia , Células-Tronco Neurais/fisiologia , Oligodendroglia/patologia , Oligodendroglia/fisiologia , Ratos , Ratos Wistar , Transferrina/uso terapêuticoRESUMO
In rats, iron deficiency produces an alteration in myelin formation. However, there is limited information on the effects of this condition on oligodendroglial cell (OLGc) proliferation and maturation. In the present study, we further analyzed the hypomyelination associated with iron deficiency by studying the dynamics of oligodendrogenesis. Rats were fed control (40 mg Fe/kg) or iron-deficient (4 mg Fe/kg) diets from gestation day 5 until postnatal day 3 (P3) or 11 (P11). OLGc proliferation, migration and differentiation were investigated before and after an intracranial injection of apotransferrin at 3 days of age (P3). The proliferating cell population was evaluated at P3. Iron-deficient (ID) animals showed an increase in the oligodendrocyte precursors cell (OPC) population in comparison with controls. The overall pattern of migration of cells labeled with BrdU was investigated at P11. Iron deficiency increased the amount of BrdU(+) cells in the corpus callosum (CC) and decreased OLGc maturation and myelin formation. Changes in nerve conduction were analyzed by measuring visual evoked potentials. Latency and amplitude were significantly disturbed in ID rats compared with controls. Both parameters were substantially normalized when animals were treated with a single intracranial injection of 350 ng apotransferrin (aTf). The current results give support to the idea that iron deficiency increases the number of proliferating and undifferentiated cells in the CC compared with the control. Treatment with aTf almost completely reverted the effects of iron deficiency, both changing the migration pattern and increasing the number of mature cells in the CC and myelin formation.
Assuntos
Apoproteínas/uso terapêutico , Proliferação de Células/efeitos dos fármacos , Doenças Desmielinizantes/tratamento farmacológico , Doenças Desmielinizantes/patologia , Deficiências de Ferro , Oligodendroglia/efeitos dos fármacos , Efeitos Tardios da Exposição Pré-Natal , Transferrina/uso terapêutico , Fatores Etários , Análise de Variância , Animais , Animais Recém-Nascidos , Apoproteínas/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Peso Corporal/fisiologia , Encéfalo , Bromodesoxiuridina/metabolismo , Contagem de Células , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Corpo Caloso/metabolismo , Corpo Caloso/patologia , Doenças Desmielinizantes/etiologia , Doenças Desmielinizantes/fisiopatologia , Eletroencefalografia/métodos , Potenciais Evocados Visuais/efeitos dos fármacos , Potenciais Evocados Visuais/fisiologia , Feminino , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Hematócrito/métodos , Proteína Básica da Mielina/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Molécula L1 de Adesão de Célula Nervosa/metabolismo , Oligodendroglia/fisiologia , Estimulação Luminosa/métodos , Gravidez , Antígeno Nuclear de Célula em Proliferação/metabolismo , Ratos , Ácidos Siálicos/metabolismo , Transferrina/metabolismoRESUMO
We have used a model of iron deficiency in the rat to analyze the effects of a disruption in iron availability on oligodendroglial cell (OLGc) maturation and myelinogenesis and to explore the possible beneficial influence of an intracranial injection (ICI) of apotransferrin (aTf) at 3 days of age on this process. Studies carried out on postnatal days 17 and 24 showed that iron deficiency produced a decrease in myelin proteins and lipids at 24 days of age. Immunohistochemistry showed that in untreated iron-deficient (ID) rats, the immunoreactivity of anti-adenomatous polyposis coli (APC) and anti-MBP antibodies decreased markedly with reference to normal controls, whereas in ID rats treated with an ICI of aTf, the immunoreactivity of these markers increased. A similar situation occurred with the immunoreactivity of H-ferritin. In primary OLGc cultures from ID rats, there was a high number of cells positive to the antibody against the polysialylated form of the cell surface glycoprotein NCAM (PSA-NCAM) compared with in OLGc cultures prepared from normal controls or from ID animals treated with aTf. The number of MBP+ cells in cultures from ID rats increased after treatment with aTf. The presence of lipid rafts evaluated with a specific anti-protein prion cellular (PrPc) antibody showed a smaller number of PrPc-positive structures in ID rat cultures. Treatment of the ID animals with a single ICI of aTf stimulated myelination, producing a significant correction in the different biochemical parameters affected by ID.
Assuntos
Anemia Ferropriva/tratamento farmacológico , Anemia Ferropriva/patologia , Apoproteínas/uso terapêutico , Doenças Desmielinizantes/tratamento farmacológico , Doenças Desmielinizantes/patologia , Fibras Nervosas Mielinizadas/patologia , Transferrina/uso terapêutico , Anemia Ferropriva/sangue , Animais , Animais Recém-Nascidos , Apoproteínas/farmacologia , Células Cultivadas , Doenças Desmielinizantes/sangue , Modelos Animais de Doenças , Feminino , Bainha de Mielina/efeitos dos fármacos , Bainha de Mielina/patologia , Fibras Nervosas Mielinizadas/efeitos dos fármacos , Gravidez , Ratos , Ratos Wistar , Transferrina/farmacologiaRESUMO
Twenty-one-day-old Wistar rats were fed a diet containing 0.6% cuprizone for 2 weeks. Studies carried out after withdrawal of cuprizone showed histological evidences of marked demyelination in the corpus callosum. Biochemical studies of isolated myelin showed a marked decrease in myelin proteins, phospholipids, and galactocerebrosides as well as a marked decrease in myelin yield. Treatment of these animals with a single intracranial injection of 350 ng of apotransferrin at the time of withdrawal of cuprizone induced a marked increase in myelin deposition resulting in a significantly improved remyelination, evaluated by histological, immunocytochemical, and biochemical parameters, in comparison to what was observed in spontaneous recovery. Immunocytochemical studies of cryotome sections to analyze developmental parameters of the oligodendroglial cell population at the time of termination of cuprizone and at different times thereafter showed that in the untreated animals, there was a marked increase in the number of NG2-BrdU-positive precursor cells together with a marked decrease in MBP expression at the peak of cuprizone-induced demyelination. As expected, the amount of precursor cells decreased markedly during spontaneous remyelination and was accompanied by an increase in MBP reactivity. In the apotransferrin-treated animals, these phenomena occurred much faster, and remyelination was much more efficient than in the untreated controls. The results of this study suggest that apotransferrin is a very active promyelinating agent which could be important for the treatment of certain demyelinating conditions.