Fig 1.
A schematic the rationale and approach.
This approach would allow for delivery to the tympanic cavity with diffusion through the round window to the inner ear, bypassing the blood-labyrinth barrier (BLB)..
Fig 2.
Parts of the implant as provided by Instech Laboratories.
A. The entire set: injection port unit, magnetic cap (red), and catheter. B. Close-up of the injection port and the embedded magnet (arrowhead). C. Side-view of the injection port unit showing smaller epidermal base (arrow), a larger subdermal wheel-shaped flange (arrowhead), and a metal tubing (double arrow) to connect the injection port to the catheter.
Fig 3.
Visualization of the surgery process.
A. the initial incisions (arrow), B. exposing the PSCC and bulla, C. fenestration in the bulla, D. attaching the catheter to the bulla, E. attaching the injection port, F. suturing the area around the button, G. suturing the remaining incision, H. and I. close-up on completion of surgery. Anatomical orientation noted in panels A, D, and G represents the anatomical orientation of the other panels in the same row.
Fig 4.
The position of TCAP and post-implantation posture and mobility.
Panels A – C illustrate the following points A. A picture taken immediately after the implantation surgery shows the injection port mounted dorsally between the shoulder blades. B and C. Still frames from associated video (supplemental material) recorded several days after implantation, showing a mouse displaying normal posture and the ability to reach for food standing on two legs.
Table 1.
Raw ABR thresholds from an individual mouse at 8, 16, and 32 kHz. Hearing test time points were pre-implantation, 2- and 4-week post-implantation, designated ‘Pre’, ‘Post 2’ and ‘Post 4’, respectively. The TCAP left ear (LE) was implanted; the right ear (RE) served as the control ear. The table shows data from four wild-type (numbers 1-4) and two USH3A (numbers 4 & 5) mice. Column 2 indicates age of individual mouse days postnatal (P) at various time points during the experiment.
Table 2.
Combined analysis of ABR thresholds of mice in this study across the study period. Mean ABR threshold across the study period for the left ear (TCAP implanted) and right ear (un-implanted control) (column 2); pre-implantation (Pre) time point (column 3); two weeks post- implantation (Post 2) (column 4); four weeks post-implantation (Post 4) (column 5).
Fig 5.
ABR recordings from mouse # 2 (Table 1).
Waveforms from pre-surgery, post-surgery 2 weeks, and post-surgery 4 weeks, shown here. TCIP implanted in the left (LE); right ear (RE) served as the control ear. It should be noted that at 8 kHz, the ABR waveform in the un-implanted right ear (RE) 2 weeks post implantation (post 2 weeks) suggest possible hearing loss, but it is likely an artifact of displaced tube placed in the ear to deliver sound stimuli, because the RE from the same mouse at 4 weeks post implantation (post 4 weeks) showed ABR waveforms and thresholds comparable to pre-ABR (pre-implantation).
Fig 6.
ABR recordings from an USH3A mouse #6 (Table 1).
Waveforms from pre-surgery, post-surgery 2 weeks, and post-surgery 4 weeks, shown here. Surgery performed in the left ear (LE); the right ear (RE) served as the control ear.
Table 3.
Statistical approach. Linear mixed effects model evaluating the relationship between hearing threshold, and the main and interactive effects of time (Week) and ear tested (L, left; R, right), and the random effect of mouse.
Fig 7.
Graphical representation of trends between hearing threshold and time at various pure tone frequencies tested.
Trends between hearing threshold (y-axis) and study week (x-axis) at 8 kHz (blue), 16 kHz (red), and 32 kHz (green). Implanted left ear (circle); un-implanted right ear (triangle). N = 6 (4 wildtype, 2 USH3A).
Fig 8.
Post-mortem dissection of TCAP implanted mice at 6 weeks post implantation.
A. Post-auricular incision showing catheter integrated into surrounding tissue, B. Expanded view of post-auricular incision with integrated catheter, C. Catheter removed from bulla hole showing tissue having grown around it, D. Removed injection port showing tissue grown through and around it, having fully integrated it.