Nickel, Regina;
(2004)
An exploration of the role of gap junctions in the avian inner ear.
Doctoral thesis (Ph.D.), University College London (United Kingdom).
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Abstract
Gap junctions in the normal and regenerating inner ear of chick hatchlings have been immunohistochemically and functionally examined. Additionally, the effect of blocked gap junction channels on the proliferation of supporting cells in response to hair cell death has been assessed. Studies have been conducted primarily in organotypic cultures of the auditory and vestibular sensory epithelium of chicken hatchlings. For regeneration studies, explants of basilar papilla and utricle were exposed to gentamicin, an ototoxic antibiotic, to induce hair cell loss. Following hair cell death, proliferation of supporting cells was upregulated and after 5 days immature, new hair cells were apparent. Blocking of gap junctions by carbenoxolone led to a significant reduction in the proliferation of supporting cells, suggesting an involvement of intercellular communication in the regeneration of hair cells. Expression of connexin 43 (Cx43) and the chicken-specific connexin 31 (cCx31) was examined by immunohistochemistry and confocal microscopy. cCx31 was strongly expressed in the normal basilar papilla and utricle. Cx43 was confined to the supporting cells of the auditory sensory epithelium, where its immunolabelling co-localised with cCx31. In response to hair cell loss, Cx43 was transiently downregulated. This finding, together with the absence of Cx43 in the sensory epithelium of the utricle, which has a constant turnover of hair cells, might point to an inhibitory effect of Cx43 on supporting cell proliferation. A dye-coupling assay, based on fluorescence recovery after photobleaching (FRAP), has been developed to examine the diffusion of the fluorescent tracer, calcein, between supporting cells in the intact tissue. Recovery of fluorescence occurred in supporting cells, but not in hair cells and was inhibited by the presence of carbenoxolone. Most notably, an asymmetric dye transfer across the basilar papilla was observed. The absence of directional permeability in the utricular macula, and in the drug-damaged basilar papilla, strongly suggests that the co-expression of cCx31 and Cx43 results in chemically rectifying gap junctions.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D. |
| Title: | An exploration of the role of gap junctions in the avian inner ear |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| Keywords: | (UMI)AAI10014335; Biological sciences; Gap junctions |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10103380 |
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