Mucociliary activity and histopathology of sinus mucosa in experimental maxillary sinusitis: a comparison of systemic administration of antibiotic and antibiotic delivery by polylactic acid polymer

Models for the study of nasal and sinus physiology in health and disease: A review of the literature

Objective

Chronic sinusitis is a very common yet poorly understood medical condition with significant morbidity. Hence, it remains an entity that is difficult to treat with unsatisfactory outcomes of current management options. This necessitates research into the etiology and pathophysiology of the condition to enhance our knowledge and the therapeutic options. Unfortunately, this kind of research is not always feasible on human subjects due to practical and ethical limitations. Therefore, an alternative model that simulates the disease had to be found in order to overcome these limitations. These models could either be in vivo or in vitro. The aim of our review is to summarize the research findings and key discoveries of both in vivo and in vitro models of chronic sinusitis that have enhanced our understanding of the condition today and have paved the way for the future research of tomorrow.

Data Sources: PubMed literature review.

Methods

A review of the literature was conducted to identify the main successful in vivo and in vitro models for chronic sinusitis.

Results

Creating a successful model for chronic sinusitis is no easy task. Over the years, both in vivo animal models and in vitro tissue culture models were proposed, with each model having its accolades and pitfalls, with the ideal model remaining elusive to this day. However, advancing three‐dimensional cell culturing techniques seems to be a promising new way to find a more accurate model.

Conclusion

None of the current models is perfect for a thorough study of chronic sinusitis. However, three‐dimensional cell cultures have the potential to bridge the gap between in vivo and in vitro studies.

Level of Evidence

NA

Osteitis and mucosal inflammation in a rabbit model of sinusitis

INTRODUCTION

Several experimental studies have shown osteitis after the onset of sinusitis, supporting the idea that bone involvement could participate in the dissemination and perpetuation of this inflammatory disease. However, procedures commonly performed for the induction of sinusitis, such as antrostomies, can trigger sinusitis by themselves.

OBJECTIVE

To evaluate osteitis in an animal model of sinusitis that does not violate the sinus directly and verify whether this is limited to the induction side, or if it affects the contralateral side.

METHODS

Experimental study in which sinusitis was produced by inserting an obstructing sponge into the nasal cavity of 20 rabbits. After defined intervals, the animals were euthanized and maxillary sinus samples were removed for semi-quantitative histological analysis of mucosa and bone.

RESULTS

Signs of bone and mucosal inflammation were observed, affecting both the induction and contralateral sides. Statistical analysis showed correlation between the intensity of osteitis on both sides, but not between mucosal and bone inflammation on the same side, supporting the theory that inflammation can spread through bone structures, regardless of mucosal inflammation.

CONCLUSION

This study demonstrated that in an animal model of sinusitis that does not disturb the sinus directly osteitis occurs in the affected sinus and that it also affects the contralateral side.

Evaluation of the ability of an experimental model to induce bacterial rhinosinusitis in rabbits

INTRODUCTION

For decades, animals have been used in sinonasal experimental models, and the practice has increased substantially in the last few years. This study aimed to assess the pathogenesis of infectious process and medication efficiency to treat rhinosinusitis.

OBJECTIVE

To evaluate the efficiency of the proposed experimental model to induce an acute bacterial sinonasal infectious process through histological analysis and sinus secretion cultures.

METHODS

This was an experimental study with 22 New Zealand rabbits, divided into: group A (six rabbits), group B (seven rabbits), group C (seven rabbits), and group D (control group with two rabbits). Rhinosinusitis was induced by the insertion of a synthetic sponge into the right nasal cavity of 20 animals (study groups), followed by the instillation of bacterial strains (50% Staphylococcus sp. and 50% Streptococcus sp.). The groups were euthanized within 10 days (group A), 17 days (group B), and 30 days (groups C and D).

RESULTS

All the rabbits of the study group developed acute bacterial rhinosinusitis, which was diagnosed through macroscopic evaluation, histological analysis, and sinus secretion culture.

CONCLUSION

The proposed model is technically simple to perform, it is similar to the rhinogenic model in human beings, and it is highly efficient to reproduce an acute bacterial sinus infection.

Effect of poly-hydroxy aliphatic ester polymer type on amoxycillin release from cylindrical compacts

The objective of the work was to investigate the effects of a range of poly-hydroxy aliphatic esters (poly-lactide (PLA) and poly-lactide-co-glycolide (PLGA)) of different molecular weight and composition on the release and stability of the amphoteric drug amoxycillin. The effect of this amphoteric drug on the extent and kinetics of polymer degradation was also investigated. The polymers were used to prepare drug-free and drug-loaded cylindrical discs. Drug release profiles were determined while changes in polymer composition were monitored by weight loss and molecular weight change. The extent of drug release was highly dependent on polymer molecular weight and composition, with earlier complete release occurring with the lower molecular weight and lower lactide containing polymers. A larger proportion of drug was released by polymer degradation control with the higher lactide containing polymer. The proportion of drug released intact was influenced by the polymer molecular weight, with a greater proportion of intact drug being released from the higher molecular weight systems. The inclusion of amoxycillin influenced polymer degradation and resulted in slower polymer hydrolysis. Model parameters obtained for polymer degradation indicated that this retardation effect increased with increasing lactide content of the polymer. The results suggest that small amounts of amoxycillin or its degradation products may bind or cross link with the polymers, thus retarding their degradation.

An investigation of the mechanism of release of the amphoteric drug amoxycillin from poly(D,L-lactide-co-glycolide) matrices

Amoxycillin-poly (D,L-lactide-co-glycolide) (PLGA) compacts were prepared by direct compression of both powder mixtures or films in a pre-heated press. Release profiles generally showed two phases separated by an induction period. Thus, both diffusion and polymer degradation mechanisms were involved in drug release, the relative importance of each depending on processing type and drug loading. Drug release parameters for each phase were determined. The fraction of total drug released, in the initial release phase, increased with drug loading and was much larger for compressed physical mixtures than for compressed composites prepared from co-evaporate films. Comparison of the polymer mass loss profiles of drug-loaded and drug-free discs indicated that the presence of the amphoteric drug amoxycillin had little impact on the polymer degradation rate, in contrast to the marked acceleration previously reported for basic drugs. Significant drug degradation occurred and was associated with release at later times. Release data was fitted to an equation accounting for degradation of the drug on release and suggested accelerated amoxycillin degradation during the polymer degradation controlled release phase, consistent with changes in pH in the microenvironment of the eroding compact.

Acute sinusitis in the rabbit: a new rhinogenic model

The objective of this study was to create a rhinogenic model of sinusitis using an implanted foreign body in the nasal cavity of the rabbit. The study design was a prospective controlled trial of the experimental design. In this model an obstructing foreign body was placed into the nasal cavity and then impregnated with pathogenic bacteria. This model was studied histologically using whole-mount techniques. Quantitative assessment of the degree of inflammation was made for the maxillary and ethmoid sinus and for overall effect for each animal. Bacteriologic study was performed in a limited number of animals. The results indicated that a significant infection develops in about half of animals. This peaks in intensity between 1 and 2 weeks after implantation and subsequently subsides with some evidence of long-term changes present after 4 weeks. It is concluded that this is a viable and perhaps preferable animal model to study sinusitis. Further investigation is necessary to completely characterize this model.

Possible value of nasal smear in acute maxillary sinusitis: an experimental study

The aim of this study is to determine the role of nasal smear in evaluating diagnosis and response to the treatment by the patient of acute maxillary sinusitis. We compared nasal smear and histopathological findings obtained from rabbits experimentally induced acute maxillary sinusitis. The animals were divided into two groups; one with blocked ostium and treated with antibiotic and the other applied natural ostiotomy, during a 4-week period. There was no statistically significant difference between the two groups in respect of recovery period. This conclusion was derived from nasal smear and biopsy findings. It was observed that nasal smear and biopsy findings were consistent with each other and with clinical findings. The results of this study revealed that nasal smear may be used in the diagnosis and treatment follow-up of acute maxillary sinusitis.