Colchicine prolongs patency of myringotomy in an animal model

Improved postauricular surgical approach to the round window of rats

OBJECTIVES

Research using rat as an in-vivo model has played an important role in otological research. The rat ear anatomy has been described; however, detailed surgical procedures to access the temporal bone are limited. The authors present a technique to approach the inner ear of rat that was standardized by cadaveric dissections and later replicated in living animals.

METHODS

Adult Wistar albino rats were dissected via the post-auricular approach. The emphasis was on early identification of the facial nerve that formed a reliable landmark for the tympanic bulla, which in turn houses the round window and stapedial artery. The point of identification of facial nerve was postero-inferior to the external auditory meatus. The procedure was then repeated in living animals.

RESULTS

Seventeen cadaveric rats were dissected. Initially, the investigators attempted to identify the facial nerve at its crossing over the external auditory meatus. However, that method was found to be unsatisfactory. The facial nerve was then attempted to be identified in its course postero-inferior to the external auditory meatus. The technique improved drastically, and the facial nerve was identified promptly and reliably. The procedure was then repeated in seven living rats under general anaesthesia. The major issues encountered were bleeding from the stapedial artery, hematoma of the pinna in one rat.

CONCLUSION

This study suggests that the post-auricular approach is a feasible and less time consuming route for round window drug delivery experiments in Wistar albino rats. Recognition of anatomical landmarks, particularly the facial nerve is the key to surgery.

The evaluation of cochlear functions in Familial Mediterranean Fever

Familial Mediterranean Fever (FMF) is a progressive disease characterized by chronic inflammation, which also has negative effects on cochlear functions and hearing levels. We investigated whether the cochlear functions and hearing levels of FMF patients were different than healthy controls and also evaluated the relationship of hearing levels with the age at diagnosis, duration without treatment, and inflammation and lipid parameters in this study. A total of 60 patients diagnosed with FMF and 48 age, gender and body mass index (BMI)-matched healthy controls were included in the study. The hemogram, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and lipid parameters of the subjects were studied and they all underwent pure tone audiometry and Transient evoked otoacoustic emission tests after an otologic examination. The hearing levels of the FMF group were significantly higher than those of the control group. The TEOAE signal/noise (S/N) ratios were similar in both groups. A positive relationship was present between the audiometric test results and the age, BMI, low-density lipoprotein and triglyceride levels and a negative relationship with the high-density lipoprotein levels. A negative relationship was present between the TEOAE S/N ratios and the age of the patients, duration without treatment, lipid parameters, inflammation markers and the creatinine level. FMF patients are exposed to chronic inflammation and this can influence their hearing levels. The age at diagnosis, duration without treatment, chronic inflammation, unfavorable lipid parameters, and obesity can affect hearing tests negatively.

Animal models of chronic tympanic membrane perforation: a 'time-out' to review evidence and standardize design

OBJECTIVE

To review the literature on techniques for creation of chronic tympanic membrane perforations (TMP) in animal models. Establishing such models in a laboratory setting will have value if they replicate many of the properties of the human clinical condition and can thus be used for investigation of novel grafting materials or other interventions.

METHODS

A literature search of the PubMed database (1950-August 2014) was performed. The search included all English-language literature published attempts on chronic or delayed TMP in animal models. Studies of non English-language or acute TMP were excluded.

RESULTS

Thirty-seven studies were identified. Various methods to create TMP in animals have been used including infolding technique, thermal injury, re-myringotomy, and topical agents including chemicals and growth factor receptor inhibitors. The most common type of animal utilized was chinchilla, followed by rat and guinea pig. Twenty three of the 37 studies reported success in achieving chronic TMP animal model while 14 studies solely delayed the healing of TMP. Numerous experimental limitations were identified including TMP patency duration of <8 weeks, lack of documentation of total number of animals attempted and absence of proof for chronicity with otoscopic and histologic evidence.

CONCLUSION

The existing literature demonstrates the need for an ideal chronic TMP animal model to allow the development of new treatments and evaluate the risk of their clinical application. Various identified techniques seem promising, however, a need was identified for standardization of experimental design and evidence to address multiple limitations.

Reduction of intraarticular adhesion by topical application of colchicine following knee surgery in rabbits

The aim of this study was to investigate the efficacy of topical application of colchicine in reducing intraarticular adhesion in rabbits. Thirty-six rabbits were randomly and equally divided into three groups. An approximately 10 × 10 mm² area of cortical bone was removed from both sides of the left femoral condyle, and the cancellous bone underneath was exposed. Cotton pads soaked with different concentrations of colchicine or saline were applied to the decorticated areas for 10 minutes. The surgical limb was fixed in a flexed position for 4 weeks postoperatively. To evaluate knee intraarticular adhesion, we performed macroscopic evaluation, histological and collagen density analyses, hydroxyproline content determination, fibroblast counting and densitometric analyses. The results showed that loose collagen tissues with little or no adhesion were present around the decorticated areas in the group treated with 0.5 mg/ml colchicine. The intraarticular adhesion score, hydroxyproline content, number of fibroblasts and densitometric value in this group were also significantly lower than those in the other groups. There was moderate intraarticular adhesion in the group treated with 0.1 mg/ml colchicine. However, dense scar tissue with dense adhesions was found in the control group. In conclusion, topical application of 0.5 mg/ml colchicine may reduce knee intraarticular adhesion.

Systematic review of animal models of middle ear surgery

Animal models of middle ear surgery help us to explore disease processes and intervention outcomes in a manner not possible in patients. This review begins with an overview of animal models of middle ear surgery which outlines the advantages and limitations of such models. Procedures of interest include myringoplasty/tympanoplasty, mastoidectomy, ossiculoplasty, stapedectomy, and active middle ear implants. The most important issue is how well the model reflects the human response to surgery. Primates are most similar to humans with respect to anatomy; however, such studies are uncommon now due to expense and ethical issues. Conversely, small animals are easily obtained and housed, but experimental findings may not accurately represent what happens in humans. We then present a systematic review of animal models of middle ear surgery. Particular attention is paid to any distinctive anatomical features of the middle ear, the method of accessing the middle ear and the chosen outcomes. These outcomes are classified as either physiological in live animals, (e.g., behavioural or electrophysiological responses), or anatomical in cadaveric animals, (e.g., light or electron microscopy). Evoked physiological measures are limited by the disruption of the evoking air-conducted sound across the manipulated middle ear. The eleven identified species suitable as animal models are mouse, rat, gerbil, chinchilla, guinea pig, rabbit, cat, dog, sheep, pig and primate. Advantages and disadvantages of each species as a middle ear surgical model are outlined, and a suggested framework to aid in choosing a particular model is presented.