Cross-linked hydrogel and polyester resorbable ventilation tubes in a Chinchilla model.

OBJECTIVES/HYPOTHESIS: To determine the resorption rate and biocompatibility characteristics of novel cross-linked hydrogel ventilation tubes and varied formulations of polyester ventilation tubes in a Chinchilla model. STUDY DESIGN: Animal Study. METHODS: Three cross-linked glycosaminoglycan hydrogel ventilation tubes fabricated by cross-linking thiol-modified chondroitin sulfate or thiol-modified carboxymethylated hyaluronic acid, four different polyester ventilation tubes (poly L-lactide [PLA], 50/50 poly D,L-lactide-co-glycolide [PLGA], and silver-impregnated versions of PLA and PLGA tubes) were placed into the tympanic membranes of chinchillas. Commercially available fluoroplastic ventilation tubes were placed in the contralateral ear of each animal to serve as a control. Integrity of the tubes was assessed by weekly otoscopy. Biocompatibility was assessed by auditory brainstem response, by otoscopic and histologic examination of the tympanic membrane at the tube site. RESULTS: The hydrogel tubes had very short resorption times that expanded and enlarged the myringotomy site. PLGA and silver-coated PLGA tubes maintained their integrity in the tympanic membrane for similar durations of 18.9 ± 6.4 days and 21.0 ± 6.0 days, respectively. The silver-coated PLGA tubes had lower neutrophil and fibrosis scores than PLGA tubes. PLA tubes demonstrated equivalent findings to commercially available nonresorbable tubes with respect to otoscopic findings, auditory brainstem response thresholds, and histologic inflammatory scores. CONCLUSIONS: Resorbable polyester pressure equalization tubes demonstrate predictable resorption behavior and similar biocompatibility characteristics when compared with nonresorbable tubes. Silver modification may confer some stability to PLGA tubes. Hydrogel tubes have very short resorption times, tend to enlarge the myringotomy site, and show greater inflammatory changes.

Development of cytomegalovirus-mediated sensorineural hearing loss in a Guinea pig model.

OBJECTIVE: To develop an animal model for cytomegalovirus (CMV)-induced sensorineural hearing loss. DESIGN: Guinea pig model. SETTING: University of Utah otolaryngology research labs. PARTICIPANTS: Thirty-one Hartley guinea pig pups were divided into 4 groups. Group 1 pups were delivered from pregnant dams inoculated with 1 x 10(5) plaque-forming units (PFU) of guinea pig CMV (gpCMV). Group 2 and group 3 pups were delivered from pregnant dams inoculated with higher doses of 2 and 4 x 10(5) PFU of gpCMV, respectively. Group 4 pups, the control group, were delivered from uninoculated dams. MAIN OUTCOME MEASURES: All groups underwent weekly auditory brainstem response studies. Six weeks after delivery, the brain, cochlea, salivary glands, lungs, liver, and kidneys were harvested. All tissue except the cochlea was analyzed for histologic evidence of the virus. All tissue underwent polymerase chain reaction (PCR) to detect gpCMV. RESULTS: Seven of the 19 (37%) inoculated pups developed a 30-dB hearing loss; none of the animals in the control group had a worse click threshold than 20 dB. Group 1 pups demonstrated statistically significant asymmetric hearing loss. All 3 inoculated groups showed evidence of progressive hearing loss over time. The control group did not demonstrate evidence of progressive threshold worsening. The PCR testing detected gpCMV in the cochleas of group 2 and group 3 animals. CONCLUSIONS: We have successfully demonstrated elevated auditory brainstem response click thresholds with characteristics of progressive and asymmetric loss that have been reported in clinical reports of congenital CMV infection. We also detected gpCMV via PCR testing in the cochleas of inoculated pups.