Sinus Microanatomy and Microbiota in a Rabbit Model of Rhinosinusitis

Abstract

Background: Rabbits are useful for preclinical studies of sinusitis because of similar physiologic features to humans. The objective of this study is to develop a rabbit model of sinusitis that permits assessment of microanatomy and sampling for evaluating shifts in the sinus microbiota during the development of sinusitis and to test how the mucociliary clearance (MCC) defect might lead to dysbiosis and chronic rhinosinusitis (CRS).Methods: Generation of CRS was accomplished with an insertion of a sterile sponge into the left middle meatus of New Zealand white rabbits (n = 9) for 2 weeks. After sponge removal, 4 rabbits were observed for another 10 weeks and evaluated for CRS using endoscopy, microCT, visualization of the functional micro-anatomy by micro-optical coherence tomography (μOCT), and histopathological analysis of the sinus mucosa. Samples were taken from the left middle meatus and submitted for microbiome analysis.Results: CT demonstrated opacification of all left sinuses at 2 weeks in all rabbits (n = 9), which persisted in animals followed for another 12 weeks (n = 4). Histology at week 2 showed mostly neutrophils. On week 14, significant infiltration of plasma cells and lymphocytes was noted with increased submucosal glands compared to controls (p = 0.02). Functional microanatomy at 2 weeks showed diminished periciliary layer (PCL) depth (p < 0.0001) and mucus transport (p = 0.0044) compared to controls despite a thick mucus layer. By 12 weeks, the thickened mucus layer was resolved but PCL depletion persisted in addition to decreased ciliary beat frequency (CBF; p < 0.0001). The mucin fermenting microbes (Lactobacillales, Bacteroidales) dominated on week 2 and there was a significant shift to potential pathogens (e.g., Pseudomonas, Burkholderia) by week 14 compared to both controls and the acute phase (p < 0.05).Conclusion: We anticipate this reproducible model will provide a means for identifying underlying mechanisms of airway-surface liquid (ASL) depletion and fundamental changes in sinus microbial communities that contribute to the development of CRS. The rabbit model of sinusitis exhibited diminished PCL depth with delayed mucus transport and significant alterations and shift in the sinus microbiome during the development of chronic inflammation.

Animal models for inflammatory mucosal disease and their potential for studying the microbiome in chronic rhinosinusitis

“…Differences could emerge when looking at an increased level of taxonomic resolution. Besides describing the baseline microbiome in rabbits, Cho et al found the genus Corynebacterium as a potential CRS-associated biomarker which is in accordance with results from human studies (13,89) . This shows that despite potential differences in basic microbial composition, putative disease-associated organisms remain similar.…”

“…Despite the large variety of different rhinosinusitis models and their applications, only two studies to date have employed a model to study the sinonasal microbiota (10,89) . Microbial dysbiosis has been recently hypothesised to play a crucial role in the process of chronic mucosal inflammation (14) and a recent meta-analysis found that the bacterial community of CRS patients is significantly less diverse than that of healthy controls (13) .…”

“…An improved Merocel® obstructing method has recently been described (89) . In contrast to Liang et al (2008), rabbit sinuses were occluded by the exact placement of Merocel® into the opening of the middle meatus, the natural drainage pathway of the maxillary sinus, under endoscopic guidance.…”

“…In contrast to Liang et al (2008), rabbit sinuses were occluded by the exact placement of Merocel® into the opening of the middle meatus, the natural drainage pathway of the maxillary sinus, under endoscopic guidance. No bacterial inoculum or inflammatory reagents were added, but the success rate for CRS development was increased from 50 % to 100 % of animals (51,89) . Cho Cho et al also reported a higher bacterial diversity associated with CRS in rabbits compared to healthy controls (the same animal before intervention) in contrast with some previous human studies (12,13,90) .…”

“…Cho Cho et al also reported a higher bacterial diversity associated with CRS in rabbits compared to healthy controls (the same animal before intervention) in contrast with some previous human studies (12,13,90) . A plausible explanation for this discrepancy is that the reduced bacterial diversity in CRS patients could be due to multiple courses of antibiotics prior to recruitment, whereas antibiotics were not administered to the animal model (89) . The endoscopically guided nasal obstruction model provides an opportunity for further investigation of microbial communities in CRS and aetiology of inflammatory mucosal disease.…”