Fig 1.
Schematic illustration of the top view looking down on the cochlea depicting the approximate location where the SPs were implanted (grey circles).
The cochlear regions that were analysed for SGN density (region 1 to region 8; R1-R8) and tissue response to implantation (grey region on dotted lines–Ai-iii and Bi-iii) are shown. Tissue response data was averaged across region A and B. (B) A mid modiolar micrograph of an implanted cochlea showing the cochlear regions in which SGN density within Rosenthal’s canal was analysed (R1-R8).
Fig 2.
Example cochlear sections of the BDNF-SP and Control-SP treated cochleae for all six animals used in this study (GP_01 to 06).
Images show the upper basal turn (region 2) and sections are stained with a neuronal marker (neurofilament: green) and a nucleus marker (DAPI: blue). Rosenthal’s canal containing the SGN is depicted by the white dotted line in each image. It is clearly evident that there is greater SGN survival in the BDNF-SP treated cochleae compared to the contralateral cochleae that received Control-SP treatment. This is consistent across the entire cohort of animals used in the study.
Fig 3.
Representative examples of cochlear sections obtained from a cochlea treated with BDNF-SPs (left) and Control-SPs (right) for cochlear Regions 1–5 (A-F respectively).
(A) shows the lower basal region (Region 1) with Rosenthal’s canal outlined (dotted outline). There was a flattening of the sensory epithelium and complete loss of the organ of Corti (arrow) that was symmetrical between ears. There was a tissue response (*; Region Ai) to the presence of the SPs that was observed in the scala tympani with the osseous spiral lamina depicted with a dotted line. (B) Higher magnification image of SGNs (arrows) in Rosenthal’s canal in Region 1 from BDNF-SP treated cochlea (left) and from a Control-SP treated cochlea (right). There was a greater density of SGNs in the BDNF-SP treated cochlea compared to the control cochlea. (C) Cochlear section taken at Region 2 shows the Rosenthal’s canal (dotted line) and the fibrotic tissue response (*; Region Bi) for the BDNF-SP (left) and Control-SP (right) cochleae. (D–F) Cochlear section taken at Region 3–5 shows the Rosenthal’s canal (dotted line) for the BDNF-SP (left) and Control-SP (right) cochleae. There was no tissue response in these cochlear regions. Scale bar (A and C-F = 100 μm) and (B = 50 μm).
Fig 4.
(A) Average of the SGN density measured in each cochlear region after one month of treatment with BDNF-SP (black) and the Control-SPs (Grey). There was a significantly greater density of SGNs in cochleae treated with BDNF-SPs compared to the Control-SPs (two way ANOVA, p = 0.009) with post hoc analysis indicated (Holm-Sidak, **p<0.005, *p<0.05). Error bars ± 1 SEM. (B) Analysis of the cochlear tissue response measured in the scala tympani (ST) in cochlear Regions A and B showed a tissue response for Region A (near the site of the cochleostomy) that was significantly larger than the tissue response in Region B (Post Hoc Holm-Sidak; **p<0.001). The tissue response measured in Region A in the BDNF-SP treated cochleae was greater than that in the Control-SP treated cochlea (Post Hoc Holm-Sidak; *p = 0.003).