RESUMO
Ciliary neurotrophic factor (CNTF) is a potent protective factor for striatal neurons in animal models of Huntington's disease (HD). Clinical application of this potential therapeutic still requires the design and optimization of delivery systems. In the case of HD, spatial spread in the vast volume occupied by the striatum and long-term delivery of the factor are particular challenges for these systems. We explored the potential of adenovirus-mediated gene transfer to fulfill these requirements by studying the functional and anatomical effects of single-site striatal delivery of CNTF recombinant vectors in a rat model of HD. In an initial series of experiments, unilateral injections of CNTF adenovirus were performed in rats 10, 30, or 90 d before a 5 d neurotoxic treatment with systemic 3-nitropropionic acid (3NP). Preservation of striatal neurons was observed at all time points, demonstrating temporally extended neuroprotective effects of the CNTF adenovirus. In a second series of experiments, bilateral injections of CNTF adenovirus were performed in the medial aspect of the striatum 10 d before starting 3NP intoxication. Despite placement of the CNTF-producing vector outside the lateral striatal area susceptible to lesion, massive protection of corticostriatopallidal circuits was observed, associated with significant behavioral benefits. This spatial spread of neuroprotection is discussed with reference to the retrograde transport of the adenovirus vector and the anterograde transport of the transgenic CNTF. Overall, adenovirus-mediated CNTF gene transfer appears to be a potentially useful delivery system for widespread, long-term circuit neuroprotection in HD patients.
Assuntos
Córtex Cerebral/efeitos dos fármacos , Fator Neurotrófico Ciliar/uso terapêutico , Corpo Estriado/efeitos dos fármacos , Globo Pálido/efeitos dos fármacos , Doença de Huntington/terapia , Adenoviridae/genética , Animais , Comportamento Animal/efeitos dos fármacos , Contagem de Células , Sobrevivência Celular/efeitos dos fármacos , Córtex Cerebral/patologia , Fator Neurotrófico Ciliar/genética , Fator Neurotrófico Ciliar/metabolismo , Corpo Estriado/metabolismo , Corpo Estriado/patologia , Modelos Animais de Doenças , Progressão da Doença , Expressão Gênica , Técnicas de Transferência de Genes , Terapia Genética/métodos , Vetores Genéticos/administração & dosagem , Vetores Genéticos/genética , Globo Pálido/patologia , Doença de Huntington/induzido quimicamente , Doença de Huntington/patologia , Masculino , Microinjeções , Fármacos Neuroprotetores/metabolismo , Fármacos Neuroprotetores/uso terapêutico , Nitrocompostos , Propionatos , RNA Mensageiro/biossíntese , Ratos , Ratos Endogâmicos LewRESUMO
We investigated the effects of endogenous neurotrophin signaling on the death-survival of immature retinal ganglion cells (RGCs) in vivo. Null mutation of brain-derived neurotrophic factor [(BDNF) alone or in combination with neurotrophin 4 (NT4)] increases the peak rate of developmental RGC death as compared with normal. Null mutation of NT4 alone is ineffective. Null mutation of the full-length trkB (trkBFL) receptor catalytic domain produces a dose-dependent increase in the peak RGC death rate that is negatively correlated with retinal levels of trkBFL protein and phosphorylated (activated) trkBFL. Depletion of target-derived trkB ligands by injection of trkB-Fc fusion protein into the superior colliculus increases the peak rate of RGC death compared with trkA-Fc-treated and normal animals. Adult trkBFL+/- mice have a normal number of RGCs, despite an elevated peak death rate of immature RGCs. Thus, target-derived BDNF modulates the dynamics of developmental RGC death through trkBFL activation, but BDNF/trkB-independent mechanisms determine the final number of RGCs.