Hu, Z, Ulfendahl, M and Olivius, NP. NGF stimulates extensive neurite outgrowth from implanted dorsal root ganglion neurons following transplantation into the adult rat inner ear. Neurobiol Dis 18: 184-192
ABSTRACT Neuronal tissue transplantation is a potential way to replace degenerated spiral ganglion neurons (SGNs) since these cells cannot regenerate in adult mammals. To investigate whether nerve growth factor (NGF) can stimulate neurite outgrowth from implanted neurons, mouse embryonic dorsal root ganglion (DRG) cells expressing enhanced green fluorescent protein (EGFP) were transplanted into the scala tympani of adult rats with a supplement of NGF or artificial perilymph. DRG neurons were observed in the cochlea for up to 6 weeks postoperatively. A significant difference was identified in the number of DRG neurons between the NGF and non-NGF groups. In the NGF group, extensive neurite projections from DRGs were found penetrating the osseous modiolus towards the spiral ganglion. These results suggest the possibility that embryonic neuronal implants may become integrated within the adult auditory nervous system. In combination with a cochlear prosthesis, a neuronal implantation strategy may provide a possibility for further treatment of profoundly deaf patients.
- SourceAvailable from: Peter J Little
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- "NGF possesses neurotrophic effects and is critical for the neurite outgrowth and survival and maintenance of neurons. Studies, in vitro and in vivo, have shown that NGF stimulates neurite outgrowth and axonal branching and extension   . Most importantly, NGF has strong antiapoptotic effect and, with deprivation of NGF, neurons exhibit a series of morphological changes and eventually undergo apoptosis . "
ABSTRACT: Neuroprotective therapies which focus on factors leading to retinal ganglion cells (RGCs) degeneration have been drawing more and more attention. The beneficial effects of nerve growth factor (NGF) on the glaucoma have been recently suggested, but its effects on eye tissue are complex and controversial in various studies. Recent clinical trials of systemically and topically administrated NGF demonstrate that NGF is effective in treating several ocular diseases, including glaucoma. NGF has two receptors named high affinity NGF tyrosine kinase receptor TrkA and low affinity receptor p75NTR. Both receptors exist in cells in retina like RGC (expressing TrkA) and glia cells (expressing p75NTR). NGF functions by binding to TrkA or p75NTR alone or both together. The binding of NGF to TrkA alone in RGC promotes RGC's survival and proliferation through activation of TrkA and several prosurvival pathways. In contrast, the binding of NGF to p75NTR leads to apoptosis although it also promotes survival in some cases. Binding of NGF to both TrkA and p75NTR at the same time leads to survival in which p75NTR functions as a TrkA helping receptor. This review discusses the current understanding of the NGF signaling in retina and the therapeutic implications in the treatment of glaucoma.BioMed Research International 08/2014; 2014:759473. DOI:10.1155/2014/759473 · 2.71 Impact Factor
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- "Their ability to integrate into the ear and respond to the denervated cochlear environment suggests that the neural progenitors that we used were at a developmental stage that retained the plasticity to respond to these potential signals from the immediate environment. These cells are more likely to be responsive to cues in the host ear than differentiated neurons (Hu et al., 2005a) that did not grow neurites toward hair cells when transplanted into the inner ear and neural stem cells that did not show evidence of neurite outgrowth toward the hair cells in the inner ear of guinea pigs (Hu et al., 2005b). The cues guiding axon growth might also be interpreted best by progenitor cells rather than mature neurons since molecules that guide axon growth by binding to receptors on growth cones are expressed in the embryo (Brors et al., 2003;Tessarollo et al., 2004). "
ABSTRACT: Hearing loss in mammals is irreversible because cochlear neurons and hair cells do not regenerate. To determine whether we could replace neurons lost to primary neuronal degeneration, we injected EYFP-expressing embryonic stem cell-derived mouse neural progenitor cells into the cochlear nerve trunk in immunosuppressed animals 1 week after destroying the cochlear nerve (spiral ganglion) cells while leaving hair cells intact by ouabain application to the round window at the base of the cochlea in gerbils. At 3 days post transplantation, small grafts were seen that expressed endogenous EYFP and could be immunolabeled for neuron-specific markers. Twelve days after transplantation, the grafts had neurons that extended processes from the nerve core toward the denervated organ of Corti. By 64-98 days, the grafts had sent out abundant processes that occupied a significant portion of the space formerly occupied by the cochlear nerve. The neurites grew in fasciculating bundles projecting through Rosenthal's canal, the former site of spiral ganglion cells, into the osseous spiral lamina and ultimately into the organ of Corti, where they contacted hair cells. Neuronal counts showed a significant increase in neuronal processes near the sensory epithelium, compared to animals that were denervated without subsequent stem cell transplantation. The regeneration of these neurons shows that neurons differentiated from stem cells have the capacity to grow to a specific target in an animal model of neuronal degeneration.Journal of Neurobiology 11/2006; 66(13):1489-500. DOI:10.1002/neu.20310 · 3.84 Impact Factor
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- "However, the possibility that transplanted neurons could regenerate new connections to hair cells has not been explored. Transplantation of dorsal root ganglion neurons and neuronal stem cells demonstrated survival of neurons in the cochlea (Hu et al., 2005a, 2005b), but the processes from these cells extended to other neurons not to hair cells (Hu et al., 2005a). "
ABSTRACT: Hearing loss can be caused by primary degeneration of spiral ganglion neurons or by secondary degeneration of these neurons after hair cell loss. The replacement of auditory neurons would be an important step in any attempt to restore auditory function in patients with damaged inner ear neurons or hair cells. Application of beta-bungarotoxin, a toxin derived from snake venom, to an explant of the cochlea eradicates spiral ganglion neurons while sparing the other cochlear cell types. The toxin was found to bind to the neurons and to cause apoptotic cell death without affecting hair cells or other inner ear cell types as indicated by TUNEL staining, and, thus, the toxin provides a highly specific means of deafferentation of hair cells. We therefore used the denervated organ of Corti for the study of neuronal regeneration and synaptogenesis with hair cells and found that spiral ganglion neurons obtained from the cochlea of an untreated newborn mouse reinnervated hair cells in the toxin-treated organ of Corti and expressed synaptic vesicle markers at points of contact with hair cells. These findings suggest that it may be possible to replace degenerated neurons by grafting new cells into the organ of Corti.Journal of Neurobiology 04/2006; 66(4):319-31. DOI:10.1002/neu.20232 · 3.84 Impact Factor