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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

Repair capacity is conserved in mature tissue. In 17 DIV co-cultures from 4 week old (A,B) and 19 DIV co-cultures from 3 months old (C,D) animals, re-innervation of vestibular epithelia by primary afferents was still observed. At low magnification (A,C), we observed nerve fibers (green) preferentially growing toward the sensory epithelia. At higher magnification (B,D), contacts between hair cells (red) and neurites were observed. Even calyceal terminals were observed (arrows) at both ages in the presence of PMA. Nuclei were stained with ToPro3, blue in (A,C). Scale bars 100 μm in (A,C) and, 10 μm in (B,D).
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Figure 6: Repair capacity is conserved in mature tissue. In 17 DIV co-cultures from 4 week old (A,B) and 19 DIV co-cultures from 3 months old (C,D) animals, re-innervation of vestibular epithelia by primary afferents was still observed. At low magnification (A,C), we observed nerve fibers (green) preferentially growing toward the sensory epithelia. At higher magnification (B,D), contacts between hair cells (red) and neurites were observed. Even calyceal terminals were observed (arrows) at both ages in the presence of PMA. Nuclei were stained with ToPro3, blue in (A,C). Scale bars 100 μm in (A,C) and, 10 μm in (B,D).

Mentions: Since the previously described co-culture experiments were performed using tissue explanted from neonatal rodents with ongoing synaptogenesis, we undertook preliminary experiments to test whether re-innervation capacity remained in mature tissue. Scarpa’s ganglia and vestibular epithelia from young adult (Figures 6A,B; 4 weeks old; n = 4) and mature adult (Figures 6C,D; 3 months old; n = 3) rats were co-cultured with PMA added to potentiate the re-innervation and re-connection process. With both young adult and mature adult tissue (Table 1), we observed oriented neurite re-growth toward sensory epithelia, utricles, and crista (Figures 6A,C). At higher magnification, nerve terminals were seen penetrating the sensory cell layer, weaving between hair cells and eventually establishing bouton- and calyx-type contacts (Figures 6B,D). Note that the lack of calretinin labeling at the calyx-type connection supports the hypothesis that this typical synaptic connection was properly formed with mature type I hair cells, as expression of this calcium binding protein is lost after synapse formation. These preliminary experiments suggest that the re-innervation and re-connection capacity was still present in mature tissue following de-afferentation.


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)

Repair capacity is conserved in mature tissue. In 17 DIV co-cultures from 4 week old (A,B) and 19 DIV co-cultures from 3 months old (C,D) animals, re-innervation of vestibular epithelia by primary afferents was still observed. At low magnification (A,C), we observed nerve fibers (green) preferentially growing toward the sensory epithelia. At higher magnification (B,D), contacts between hair cells (red) and neurites were observed. Even calyceal terminals were observed (arrows) at both ages in the presence of PMA. Nuclei were stained with ToPro3, blue in (A,C). Scale bars 100 μm in (A,C) and, 10 μm in (B,D).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Repair capacity is conserved in mature tissue. In 17 DIV co-cultures from 4 week old (A,B) and 19 DIV co-cultures from 3 months old (C,D) animals, re-innervation of vestibular epithelia by primary afferents was still observed. At low magnification (A,C), we observed nerve fibers (green) preferentially growing toward the sensory epithelia. At higher magnification (B,D), contacts between hair cells (red) and neurites were observed. Even calyceal terminals were observed (arrows) at both ages in the presence of PMA. Nuclei were stained with ToPro3, blue in (A,C). Scale bars 100 μm in (A,C) and, 10 μm in (B,D).
Mentions: Since the previously described co-culture experiments were performed using tissue explanted from neonatal rodents with ongoing synaptogenesis, we undertook preliminary experiments to test whether re-innervation capacity remained in mature tissue. Scarpa’s ganglia and vestibular epithelia from young adult (Figures 6A,B; 4 weeks old; n = 4) and mature adult (Figures 6C,D; 3 months old; n = 3) rats were co-cultured with PMA added to potentiate the re-innervation and re-connection process. With both young adult and mature adult tissue (Table 1), we observed oriented neurite re-growth toward sensory epithelia, utricles, and crista (Figures 6A,C). At higher magnification, nerve terminals were seen penetrating the sensory cell layer, weaving between hair cells and eventually establishing bouton- and calyx-type contacts (Figures 6B,D). Note that the lack of calretinin labeling at the calyx-type connection supports the hypothesis that this typical synaptic connection was properly formed with mature type I hair cells, as expression of this calcium binding protein is lost after synapse formation. These preliminary experiments suggest that the re-innervation and re-connection capacity was still present in mature tissue following de-afferentation.

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