Synapses on human spiral ganglion cells: a transmission electron microscopy and immunohistochemical study

Rask‐Andersen, Helge; Tylstedt, Sven; Kinnefors, Anders; Illing, Robert‐Benjamin

doi:10.1016/s0378-5955(99)00179-3

Cited by 37 publications

(36 citation statements)

References 15 publications

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“…The fi ne structure of the human spiral ganglion differs from that of other mammalian species studied so far [Kimura et al, 1979;Ota and Kimura, 1980;Arnold, 1987;Tylstedt et al, 1997;Rask-Andersen et al, 2000b]. Unlike in most animals the perikarya of the human spiral ganglion are unmyelinated.…”

Section: Ultrastructure Of Human Sgcsmentioning

confidence: 84%

“…Neurons showed deep impressions and microvillilike structures at contact regions with nerve fi bers on their cell surface that might improve attachment. Neural interactions were found between nerve fi bers and large cells as well as axosomatic connections between efferent and small ganglion cells [Rask-Andersen et al, 2000b;Tylstedt and Rask-Andersen, 2001]. Interactions between nerve fi bers and ganglion cells are frequently found in TEM preparations but were generally diffi cult to observe using SEM, due to its 'hiding' behind the covering Schwann cells.…”

Section: Ultrastructure Of Human Sgcsmentioning

confidence: 99%

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The Human Spiral Ganglion: New Insights into Ultrastructure, Survival Rate and Implications for Cochlear Implants

Glueckert¹,

Pfaller

Kinnefors

et al. 2005

Audiol Neurotol

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This study was based on high-resolution SEM assessment of freshly fixed, normal-hearing, human inner ear tissue. In addition, semiquantitative observations were made in long-term deafened temporal bone material, focusing on the spiral ganglia and nerve projections, and a detailed study of the fine bone structure in macerated tissues was performed. Our main findings detail the presence of extensive bony fenestrae surrounding the nerve elements, permitting a relatively free flow of perilymph to modiolar structures. The clustering of the spiral ganglion cells in Rosenthal’s canal and the detailed and intricate course of postganglionic axons are described. The close proximity of fibers to cell soma is demonstrated by impression in cell surfaces, and presence of small microvilli-like structures at the contact regions, anchoring nerve fibers to the cell wall. Extensive fenestrae and the presence of a fragile network of endosteal bony structures at the surfaces guiding nerve fibers are described in detail for the first time. This unique freshly prepared human material offers the opportunity for a detailed ultrastructural study not previously possible on postmortem fixed material and more accurate information to model electrostimulation of the human auditory nerve through a cochlear implant. On the basis of this study, we suggest that the concentration and high density of spiral ganglion cells, and the close physical interaction between neural elements, may explain the slow retrograde degeneration found in humans after loss of peripheral receptors. Moreover, the fragile bony columns connecting the spiral canal with the osseous spiral lamina may be a potential site for trauma in (perimodiolar) electrode positioning.

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Section: Ultrastructure Of Human Sgcsmentioning

confidence: 84%

Section: Ultrastructure Of Human Sgcsmentioning

confidence: 99%

The Human Spiral Ganglion: New Insights into Ultrastructure, Survival Rate and Implications for Cochlear Implants

Glueckert¹,

Pfaller

Kinnefors

et al. 2005

Audiol Neurotol

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“…Synaptophysin is a well known marker for synaptic vesicles and is present in auditory nerve terminals in the organ of Corti. It can also act as a calcium-binding protein and is expressed in SGNs of the mammalian cochlea (Anniko et al, 1995;Rask-Andersen et al, 2000;Khalifa et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

Nuclear Factor κB Deficiency Is Associated with Auditory Nerve Degeneration and Increased Noise-Induced Hearing Loss

Lang¹,

Schulte²,

Zhou³

et al. 2006

J. Neurosci.

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Degeneration of the spiral ganglion neurons (SGNs) of the auditory nerve occurs with age and in response to acoustic injury. Histopathological observations suggest that the neural degeneration often begins with an excitotoxic process affecting the afferent dendrites under the inner hair cells (IHCs), however, little is known about the sequence of cellular or molecular events mediating this excitotoxicity. Nuclear factor B (NFB) is a transcription factor involved in regulating inflammatory responses and apoptosis in many cell types. NFB is also associated with intracellular calcium regulation, an important factor in neuronal excitotoxicity. Here, we provide evidence that NFB can play a central role in the degeneration of SGNs. Mice lacking the p50 subunit of NFB (p50 Ϫ/Ϫ mice) showed an accelerated hearing loss with age that was highly associated with an exacerbated excitotoxic-like damage in afferent dendrites under IHCs and an accelerated loss of SGNs. Also, as evidenced by immunostaining intensity, calcium-buffering proteins were significantly elevated in SGNs of the p50 Ϫ/Ϫ mice. Finally, the knock-out mice exhibited an increased sensitivity to low-level noise exposure. The accelerated hearing loss and neural degeneration with age in the p50 Ϫ/Ϫ mice occurred in the absence of concomitant hair cell loss and decline of the endocochlear potential. These results indicate that NFB activity plays an important role in protecting the primary auditory neurons from excitotoxic damage and age-related degeneration. A possible mechanism underlying this protection is that the NFB activity may help to maintain calcium homeostasis in SGNs.

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“…Moreover, the regrowing neurites seemed to find other SGNs as their targets and generate various types of synapse-like contacts. Direct contacts between SGNs have been reported in mature primate SGNs (Spoendlin and Schrott, 1988;Nadol, 1990) and in human SGNs (Rask-Andersen et al, 2000;Thiers et al, 2000). The functional implication of the newly established contacts among SGNs, if occurring also in situ, is unknown.…”

Section: Sgns Form Contacts With Other Sgns After Loss Of Their Normamentioning

confidence: 99%

Survival, synaptogenesis, and regeneration of adult mouse spiral ganglion neurons in vitro

Wei

Jin

Järlebark

et al. 2006

Developmental Neurobiology

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ABSTRACT:The inner ear spiral ganglion is populated by bipolar neurons connecting the peripheral sensory receptors, the hair cells, with central neurons in auditory brain stem nuclei. Hearing impairment is often a consequence of hair cell death, e.g., from acoustic trauma. When deprived of their peripheral targets, the spiral ganglion neurons (SGNs) progressively degenerate. For effective clinical treatment using cochlear prostheses, it is essential to maintain the SGN population. To investigate their survival dependence, synaptogenesis, and regenerative capacity, adult mouse SGNs were separated from hair cells and studied in vitro in the presence of various neurotrophins and growth factors. Coadministration of fibroblast growth factor 2 (FGF-2) and glial cell line-derived neurotrophic factor (GDNF) provided support for long-term survival, while FGF-2 alone could strongly promote neurite regeneration.Fibroblast growth factor receptor FGFR-3-IIIc was found to upregulate and translocate to the nucleus in surviving SGNs. Surviving SGNs formed contacts with other SGNs after they were deprived of the signals from the hair cells. In coculture experiments, neurites extending from SGNs projected toward hair cells. Interestingly, adult mouse spiral ganglion cells could carry out both symmetric and asymmetric cell division and give rise to new neurons. The authors propose that a combination of FGF-2 and GDNF could be an efficient route for clinical intervention of secondary degeneration of SGNs. The authors also demonstrate that the adult mammalian inner ear retains progenitor cells, which could commit neurogenesis. '

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Synapses on human spiral ganglion cells: a transmission electron microscopy and immunohistochemical study

Cited by 37 publications

References 15 publications

The Human Spiral Ganglion: New Insights into Ultrastructure, Survival Rate and Implications for Cochlear Implants

The Human Spiral Ganglion: New Insights into Ultrastructure, Survival Rate and Implications for Cochlear Implants

Nuclear Factor κB Deficiency Is Associated with Auditory Nerve Degeneration and Increased Noise-Induced Hearing Loss

Survival, synaptogenesis, and regeneration of adult mouse spiral ganglion neurons in vitro

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