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Plasticity of Scarpa's Ganglion Neurons as a Possible Basis for Functional Restoration within Vestibular Endorgans.

Travo C, Gaboyard-Niay S, Chabbert C - Front Neurol (2012)

Bottom Line: When co-cultured with vestibular epithelia, primary vestibular neurons were able to establish de novo contacts with hair cells.Under the present paradigm, these contacts displayed morphological features of immature synaptic contacts.Preliminary observations using co-cultures of adult rodents suggest that this reparative capacity remained in older mice although to a lesser extent.

View Article: PubMed Central - PubMed

Affiliation: INSERM U1051, Institute for Neurosciences Montpellier, France.

ABSTRACT
In a previous study, we observed spontaneous restoration of vestibular function in young adult rodents following excitotoxic injury of the neuronal connections within vestibular endorgans. The functional restoration was supported by a repair of synaptic contacts between hair cells and primary vestibular neurons. This process was observed in 2/3 of the animals studied and occurred within 5 days following the synaptic damage. To assess whether repair capacity is a fundamental trait of vestibular endorgans and to decipher the cellular mechanisms supporting such a repair process, we studied the neuronal regeneration and synaptogenesis in co-cultures of vestibular epithelia and Scarpa's ganglion from young and adult rodents. We demonstrate that, under specific culture conditions, primary vestibular neurons from young mice or rats exhibit robust ability to regenerate nervous processes. When co-cultured with vestibular epithelia, primary vestibular neurons were able to establish de novo contacts with hair cells. Under the present paradigm, these contacts displayed morphological features of immature synaptic contacts. Preliminary observations using co-cultures of adult rodents suggest that this reparative capacity remained in older mice although to a lesser extent. Identifying the basic mechanisms underlying the repair process may provide a basis for novel therapeutic strategies to restore mature and functional vestibular synaptic contacts following damage or loss.

No MeSH data available.


Related in: MedlinePlus

Maturing synaptic contacts. In utricles (A) and cristae (B) of 11 DIV co-cultures of P4 rats, synaptic contacts were stained and observed between hair cells (blue) and neurites. Anti-CtBP2 antibodies used to label the ribeye protein, major molecular component of synaptic ribbons (green, small bright dots) and nuclei of hair cells, while anti-synaptophysin antibodies labeled small synaptic vesicles (red) contained in maturing synaptic afferents. Terminals of innervating fibers (arrows) entering sensory epithelia were observed. Co-labeling with ribeye shows close apposition of these synaptic terminals with ribbons in hair cells (arrow heads) in both cristae (A) and utricles (B). Scale bars 50 μm.
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Figure 4: Maturing synaptic contacts. In utricles (A) and cristae (B) of 11 DIV co-cultures of P4 rats, synaptic contacts were stained and observed between hair cells (blue) and neurites. Anti-CtBP2 antibodies used to label the ribeye protein, major molecular component of synaptic ribbons (green, small bright dots) and nuclei of hair cells, while anti-synaptophysin antibodies labeled small synaptic vesicles (red) contained in maturing synaptic afferents. Terminals of innervating fibers (arrows) entering sensory epithelia were observed. Co-labeling with ribeye shows close apposition of these synaptic terminals with ribbons in hair cells (arrow heads) in both cristae (A) and utricles (B). Scale bars 50 μm.

Mentions: To assess whether the de novo cell-to-cell contacts corresponded to synapses between afferent terminals and hair cells, we first used immunohistochemistry to label the pre- and post-synaptic elements. Hair cells were counterstained using calretinin, a calcium binding protein used as a specific marker (Dechesne et al., 1994; Zheng and Gao, 1997). The pre-synaptic ribbons, specific structures controlling the pool of releasable synaptic vesicles, were immuno-localized in the hair cell cytosol using antibodies against ribeye, the main component of the ribbon dense core element (Schmitz et al., 2000; Zanazzi and Matthews, 2009). The post-synaptic terminal element was identified and localized within the sensory epithelia using immunolabeling of synaptophysin. This small synaptic vesicle associated protein is characteristic of vestibular afferent terminals during synaptogenesis (Scarfone et al., 1991; Dechesne et al., 1997; Gaboyard et al., 2003). The juxtaposition of ribeye (Schmitz et al., 2000; Zanazzi and Matthews, 2009) and synaptophysin labeling indicated that the de novo cell-to-cell synaptic contacts were formed correctly at the site of pre-synaptic active zones. At 11 DIV (mice, n = 4), synaptophysin immunolabeling was observed in neuronal processes of both utricles (Figure 4A) and cristae (Figure 4B). In most cases, the synaptophysin immunoreactivity strongly correlated with the ribeye labeling (anti-CtBP2 antibodies; Figure 4B). Note that vesicles spread out along the fibers indicate an immature stage of synaptogenesis.


Plasticity of Scarpa's Ganglion Neurons as a Possible Basis for Functional Restoration within Vestibular Endorgans.

Travo C, Gaboyard-Niay S, Chabbert C - Front Neurol (2012)

Maturing synaptic contacts. In utricles (A) and cristae (B) of 11 DIV co-cultures of P4 rats, synaptic contacts were stained and observed between hair cells (blue) and neurites. Anti-CtBP2 antibodies used to label the ribeye protein, major molecular component of synaptic ribbons (green, small bright dots) and nuclei of hair cells, while anti-synaptophysin antibodies labeled small synaptic vesicles (red) contained in maturing synaptic afferents. Terminals of innervating fibers (arrows) entering sensory epithelia were observed. Co-labeling with ribeye shows close apposition of these synaptic terminals with ribbons in hair cells (arrow heads) in both cristae (A) and utricles (B). Scale bars 50 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368229&req=5

Figure 4: Maturing synaptic contacts. In utricles (A) and cristae (B) of 11 DIV co-cultures of P4 rats, synaptic contacts were stained and observed between hair cells (blue) and neurites. Anti-CtBP2 antibodies used to label the ribeye protein, major molecular component of synaptic ribbons (green, small bright dots) and nuclei of hair cells, while anti-synaptophysin antibodies labeled small synaptic vesicles (red) contained in maturing synaptic afferents. Terminals of innervating fibers (arrows) entering sensory epithelia were observed. Co-labeling with ribeye shows close apposition of these synaptic terminals with ribbons in hair cells (arrow heads) in both cristae (A) and utricles (B). Scale bars 50 μm.
Mentions: To assess whether the de novo cell-to-cell contacts corresponded to synapses between afferent terminals and hair cells, we first used immunohistochemistry to label the pre- and post-synaptic elements. Hair cells were counterstained using calretinin, a calcium binding protein used as a specific marker (Dechesne et al., 1994; Zheng and Gao, 1997). The pre-synaptic ribbons, specific structures controlling the pool of releasable synaptic vesicles, were immuno-localized in the hair cell cytosol using antibodies against ribeye, the main component of the ribbon dense core element (Schmitz et al., 2000; Zanazzi and Matthews, 2009). The post-synaptic terminal element was identified and localized within the sensory epithelia using immunolabeling of synaptophysin. This small synaptic vesicle associated protein is characteristic of vestibular afferent terminals during synaptogenesis (Scarfone et al., 1991; Dechesne et al., 1997; Gaboyard et al., 2003). The juxtaposition of ribeye (Schmitz et al., 2000; Zanazzi and Matthews, 2009) and synaptophysin labeling indicated that the de novo cell-to-cell synaptic contacts were formed correctly at the site of pre-synaptic active zones. At 11 DIV (mice, n = 4), synaptophysin immunolabeling was observed in neuronal processes of both utricles (Figure 4A) and cristae (Figure 4B). In most cases, the synaptophysin immunoreactivity strongly correlated with the ribeye labeling (anti-CtBP2 antibodies; Figure 4B). Note that vesicles spread out along the fibers indicate an immature stage of synaptogenesis.

Bottom Line: When co-cultured with vestibular epithelia, primary vestibular neurons were able to establish de novo contacts with hair cells.Under the present paradigm, these contacts displayed morphological features of immature synaptic contacts.Preliminary observations using co-cultures of adult rodents suggest that this reparative capacity remained in older mice although to a lesser extent.

View Article: PubMed Central - PubMed

Affiliation: INSERM U1051, Institute for Neurosciences Montpellier, France.

ABSTRACT
In a previous study, we observed spontaneous restoration of vestibular function in young adult rodents following excitotoxic injury of the neuronal connections within vestibular endorgans. The functional restoration was supported by a repair of synaptic contacts between hair cells and primary vestibular neurons. This process was observed in 2/3 of the animals studied and occurred within 5 days following the synaptic damage. To assess whether repair capacity is a fundamental trait of vestibular endorgans and to decipher the cellular mechanisms supporting such a repair process, we studied the neuronal regeneration and synaptogenesis in co-cultures of vestibular epithelia and Scarpa's ganglion from young and adult rodents. We demonstrate that, under specific culture conditions, primary vestibular neurons from young mice or rats exhibit robust ability to regenerate nervous processes. When co-cultured with vestibular epithelia, primary vestibular neurons were able to establish de novo contacts with hair cells. Under the present paradigm, these contacts displayed morphological features of immature synaptic contacts. Preliminary observations using co-cultures of adult rodents suggest that this reparative capacity remained in older mice although to a lesser extent. Identifying the basic mechanisms underlying the repair process may provide a basis for novel therapeutic strategies to restore mature and functional vestibular synaptic contacts following damage or loss.

No MeSH data available.


Related in: MedlinePlus