The effects of growth factors on the survival and differentiation of cultured dentate gyrus neurons

Abstract

Dentate granule cells (DGCs) are the principal cell population of the hippocampal dentate gyrus, and granule cells provide the main excitation to the hippocampus proper via their mossy fibers axons. Although it is well established that granule cells express various growth factors and growth factor receptors, the functional effects of growth factors on the normal development and response to injury of granule cells are relatively unknown. To address this question, primary cultures enriched in DGCs were prepared by microdissecting hippocampal slices from neonatal rats and growing dissociated cells in defined media with added nerve growth factor, brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), neurotrophin-4/5 (NT4/5), ciliary neurotrophic factor, basic fibroblast growth factor (bFGF), or vehicle. The effects on cell survival and morphology were quantified by studying neuron-specific enolase-immunostained cells at various time points, plating densities, host ages, and growth factor concentrations. BDNF or bFGF significantly increased both neuronal survival and differentiation by 30-80% compared with control cultures. Maximal effects were observed at relatively longer time points (5-12 d), with younger cells (postnatal day 3-5) and at lowest plating densities. Addition of a trkB-IgG fusion protein that blocks the activity of BDNF or NT4/5 inhibited the effects of BDNF and attenuated the differentiation of cells cultured at high plating densities. Furthermore, treatment of cultures with the kinase inhibitor K252b specifically blocked the effects of BDNF, suggesting involvement of trkB (the high-affinity BDNF receptor) in BDNF-induced differentiation. These results show that growth properties of cultured neonatal DGCs are influenced by exogenously applied BDNF or bFGF in a time-, age-, and density-dependent manner. The effect of plating density suggests an endogenous expression of growth factors in these culture conditions, and this is mediated in part by endogenous BDNF acting via a tyrosine kinase receptor. Combined with previous work showing that various growth factors and their receptors are expressed by DGCs, these findings provide strong support for the hypothesis that BDNF and bFGF influence both the growth and development of DGCs in vivo.

TrkB and TrkC neurotrophin receptors cooperate in promoting survival of hippocampal and cerebellar granule neurons.

“…In trkB/trkC double mutants, no significant apoptosis was detected in the Ammon's horn, where hippocampal pyramidal neuron cell bodies are located. In contrast, the survival of dentate gyrus neurons was enhanced by BDNF and NT3 in vitro (Lowenstein and Arsenault 1996), consistent with the observed selective vulnerability of dentate gyms neurons in trkB-/-; trkC + / -and trkB + / -;trkC-/ -mutant mice.…”

Brain-derived neurotrophic factor Val66met polymorphism and volume of the hippocampal formation

“…Additionally, growth properties of cultured neonatal dentate granule cells are influenced by exogenously applied BDNF. 47 Lastly, Suzuki et al 48 have demonstrated that injection of kainate into the hippocampus is associated with a long-lasting global trophic response of granule cells involving somatic and dendritic growth, which is correlated with a specific overexpression of BDNF. A potential limitation of this study is that casecontrol association studies can be influenced by undetected population stratification.…”

Actions of Brain-Derived Neurotrophic Factor in Slices from Rats with Spontaneous Seizures and Mossy Fiber Sprouting in the Dentate Gyrus

“…Moreover, the results suggest that activation of trkB receptors could contribute to the hyperexcitability observed in animals with sprouting. Because human granule cells also express increased BDNF mRNA after seizures, and sprouting can occur in temporal lobe epileptics, the results may have implications for understanding temporal lobe epilepsy.Key words: neurotrophin; growth factor; hippocampus; epilepsy; glutamate; tyrosine kinase BDNF is widely recognized as a neurotrophin with an important role in normal development that has both trophic and protective effects (Hofer and Barde, 1988;Alderson et al, 1990;Knüsel et al, 1991;Spina et al, 1992;Yan et al, 1992;Lindholm et al, 1993;Morse et al, 1993;Beck et al, 1994;Cheng and Mattson et al, 1994;Ghosh et al, 1994;Kokaia et al, 1994;Acheson et al, 1995;McAllister et al, 1995;L owenstein and Arsenault, 1996). More recently it has become clear that BDN F also has acute, neuromodulatory effects on synaptic transmission.…”