RESUMO
The epigenetic manipulation of precursors may provide data to elucidate the potential interactions among these cells in different brain regions. However, the response to epigenetic signals is modulated by the environment in which the cells are manipulated. Therefore, data regarding the action of a particular factor must be considered in the light of a specific system. To compare septal and striatal precursors, we have tested the effect of nerve growth factor (NGF) on the proliferation and neuronal differentiation of epidermal growth factor (EGF)-responsive cells from these brain regions. Precursors were cultivated as 'neuropheres' in serum free medium (SFM) to which NGF was added. NGF did not support the proliferation of EGF-generated precursors so that no differences in the cell magnitude with respect to control cultures were observed. Differentiation of precursors in SFM plus 1% fetal bovine serum (FBS) on poly-D-lysine showed that the neuron number was increased two-fold in septal cultures treated with NGF but not in those from striatum. A quantitative evaluation of the soma surface and the number of primary neurites showed differences between both populations of precursor-generated neurons. In addition, we also observed no influence of NGF on these parameters of cellular morphology. Thus, taken together these results seem to indicate that at this developmental stage in which these populations of precursors were isolated, heterogeneities exist between them, which is probably related to their origin and/or functional roles in vivo.
Assuntos
Corpo Estriado/metabolismo , Fator de Crescimento Epidérmico/metabolismo , Fator de Crescimento Neural/metabolismo , Neurônios/metabolismo , Septo do Cérebro/metabolismo , Células-Tronco/metabolismo , Animais , Agregação Celular/efeitos dos fármacos , Agregação Celular/fisiologia , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Divisão Celular/efeitos dos fármacos , Divisão Celular/fisiologia , Células Cultivadas , Corpo Estriado/citologia , Corpo Estriado/embriologia , Meios de Cultura Livres de Soro , Fator de Crescimento Neural/administração & dosagem , Neurônios/classificação , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Ratos , Ratos Wistar , Valores de Referência , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Septo do Cérebro/citologia , Septo do Cérebro/embriologia , Células-Tronco/classificação , Células-Tronco/efeitos dos fármacos , Células-Tronco/fisiologiaRESUMO
Subcultured astroglial cells from striatum, cerebral cortex and ventral mesencephalon obtained from primary cultures of fetal (E14, E17 and E21) or postnatal (days 5-6) rats showed different regional, age-dependent morphological response (stellation) to cyclic AMP. While most of the cerebral cortex and ventral mesencephalic astroglial cell population was responsive at all ages tested, striatal cells at E14 and E17 were not. At age E21 striatal astroglia showed a significant shift toward a mature-like type of response to cyclic AMP. Postnatal striatal astroglia responded to cyclic AMP as the cortical and ventral mesencephalic astroglia did, with generalized stellation. Prenatal striatal astroglia was characterized immunocytochemically as A2B5+, fibronectin+, vimentin+, S-100+ and GFAP-. Failure of early prenatal (E14, E17) striatal astroglia to differentiate in response to cyclic AMP, was overcome by previous (5-7 days) co-culture with primary cell dissociates from postnatal-, but not from prenatal donors, from all brain regions tested including a non-target region for striatal cells, such as septum. This effect was duplicated when striatal astroglia was co-cultured with cell populations enriched in neurons through Percoll gradients. Only cell-to-cell contact co-cultures were able to induce a change in the studied response. Dead neuron-enriched populations obtained following various types of physical treatments were also able to change significantly striatal cell response toward cyclic AMP. Enriched astroglial populations from postnatal donors did not change striatal astroglial response toward cyclic AMP, except for ventral mesencephalic astroglia which induced a comparatively reduced but significant increase in striatal cell responsiveness. It is concluded that astroglial maturation and potential for phenotype expression during brain development proceeds with regional heterochrony. Also, that maturation of prenatal striatal astroglia responsiveness toward cyclic AMP is inducible by non-diffusible factors, probably of neuronal origin, expressed in live or dead primary cultures from various, homotopic and heterotopic, postnatal brain regions. It is further suggested that striatal afferents and/or mature local striatal neurons express membrane associated molecules that regulate responsiveness for phenotype expression of striatal glial cells, thus reinforcing the concept of a highly interactive, continuous neuron-glial developmental process that takes place during brain organization.