How reliable are sino-nasal cell lines for studying the pathophysiology of chronic rhinosinusitis?

Infection of primary nasal epithelial cells differentiates among lethal and seasonal human coronaviruses

The nasal epithelium is the initial entry portal and primary barrier to infection by all human coronaviruses (HCoVs). We utilize primary human nasal epithelial cells grown at air-liquid interface, which recapitulate the heterogeneous cellular population as well as mucociliary clearance functions of the in vivo nasal epithelium, to compare lethal [Severe acute respiratory syndrome (SARS)-CoV-2 and Middle East respiratory syndrome-CoV (MERS-CoV)] and seasonal (HCoV-NL63 and HCoV-229E) HCoVs. All four HCoVs replicate productively in nasal cultures, though replication is differentially modulated by temperature. Infections conducted at 33 °C vs. 37 °C (reflective of temperatures in the upper and lower airway, respectively) revealed that replication of both seasonal HCoVs (HCoV-NL63 and -229E) is significantly attenuated at 37 °C. In contrast, SARS-CoV-2 and MERS-CoV replicate at both temperatures, though SARS-CoV-2 replication is enhanced at 33 °C late in infection. These HCoVs also diverge significantly in terms of cytotoxicity induced following infection, as the seasonal HCoVs as well as SARS-CoV-2 cause cellular cytotoxicity as well as epithelial barrier disruption, while MERS-CoV does not. Treatment of nasal cultures with type 2 cytokine IL-13 to mimic asthmatic airways differentially impacts HCoV receptor availability as well as replication. MERS-CoV receptor DPP4 expression increases with IL-13 treatment, whereas ACE2, the receptor used by SARS-CoV-2 and HCoV-NL63, is down-regulated. IL-13 treatment enhances MERS-CoV and HCoV-229E replication but reduces that of SARS-CoV-2 and HCoV-NL63, reflecting the impact of IL-13 on HCoV receptor availability. This study highlights diversity among HCoVs during infection of the nasal epithelium, which is likely to influence downstream infection outcomes such as disease severity and transmissibility.

Infection of primary nasal epithelial cells differentiates among lethal and seasonal human coronaviruses

The nasal epithelium is the initial entry portal and primary barrier to infection by all human coronaviruses (HCoVs). We utilize primary nasal epithelial cells grown at air-liquid interface, which recapitulate the heterogeneous cellular population as well as mucociliary clearance functions of the in vivo nasal epithelium, to compare lethal (SARS-CoV-2 and MERS-CoV) and seasonal (HCoV-NL63 and HCoV-229E) HCoVs. All four HCoVs replicate productively in nasal cultures but diverge significantly in terms of cytotoxicity induced following infection, as the seasonal HCoVs as well as SARS-CoV-2 cause cellular cytotoxicity as well as epithelial barrier disruption, while MERS-CoV does not. Treatment of nasal cultures with type 2 cytokine IL-13 to mimic asthmatic airways differentially impacts HCoV replication, enhancing MERS-CoV replication but reducing that of SARS-CoV-2 and HCoV-NL63. This study highlights diversity among HCoVs during infection of the nasal epithelium, which is likely to influence downstream infection outcomes such as disease severity and transmissibility.

A thermoresponsive hydrogel system for long-acting corticosteroid delivery into the paranasal sinuses

Delivering localized treatment to the paranasal sinuses for diseases such as chronic rhinosinusitis (CRS) is particularly challenging because of the small natural openings leading from the sinuses that can be further obstructed by presence of inflammation. As such, oral steroids, topical nasal sprays or irrigation, and surgery can be utilized to treat persistent sinonasal inflammation, but there exists a need for post-operative options for long-term steroid delivery to prevent disease recurrence. In the present study, a Thermogel, Extended-release Microsphere-based-delivery to the Paranasal Sinuses (TEMPS) is developed with the corticosteroid mometasone furoate. Specifically, the bioactive steroid is released for 4 weeks from poly(lactic-co-glycolic acid) (PLGA) microspheres embedded in a poly(N-isopropylacrylamide) (p-NIPAAm)-based hydrogel. The temperature-responsive system undergoes a reversible sol-gel transition at 34-35 °C such that it can be applied as a liquid at ambient temperature, conforming to the sinonasal epithelium as it gels. In a rabbit model of CRS, TEMPS was maintained in rabbit sinuses and effectively reduced sinonasal inflammation as characterized by micro-computed tomography and histopathology analysis. Ultimately, the combination of controlled release microspheres with a thermoresponsive hydrogel provides flexibility for encapsulating therapeutics in a reversible and conforming system for localized delivery to the sinuses.

A 3D "In Vitro" Model to Study Hyaluronan Effect in Nasal Epithelial Cell Line Exposed to Double-Stranded RNA Poly(I:C)

Environmental agents, including viral and bacterial infectious agents, are involved in the alteration of physicochemical and biological parameters in the nasal epithelium. Hyaluronan (HA) has an important role in the regulation of tissue healing properties. High molecular weight HA (HMW-HA) shows greater anti-inflammatory responses than medium molecular weight HA (MMW-HA) and low molecular weight HA (LMW-HA). We investigated the effect of HMW-HA, MMW-HA and LMW-HA on the regulation of physicochemical and biological parameters in an “in vitro” model that might mimic viral infections of the nasal epithelium. Human nasal epithelial cell line RPMI2650 was stimulated with double-stranded RNA (dsRNA) Poly(I:C) for 5 days in air-liquid-interface (ALI) culture (3D model of airway tissue). dsRNA Poly(I:C) treatment significantly decreased transepithelial electrical resistance (TEER) in the stratified nasal epithelium of RPMI2650 and increased pH values, rheological parameters (elastic G’ and viscous G’’), and Muc5AC and Muc5B production in the apical wash of ALI culture of RPMI2650 in comparison to untreated cells. RPMI2650 treated with dsRNA Poly(I:C) in the presence of HMW-HA showed lower pH values, Muc5AC and Muc5B production, and rheological parameters, as well as increased TEER values in ALI culture, compared to cells treated with Poly(I:C) alone or pretreated with LMW-HA and MMW-HA. Our 3D “in vitro” model of epithelium suggests that HMW-HA might be a coadjuvant in the pharmacological treatment of viral infections, allowing for the control of some physicochemical and biological properties affecting the epithelial barrier of the nose during infection.

Expression analysis of human solute carrier (SLC) family transporters in nasal mucosa and RPMI 2650 cells

With nearly 400 members, the solute-linked carrier (SLC) superfamily is one of the most important gene classes concerning the disposition of drugs and the transport of physiological substrates in the human body. The mapping of related transport proteins is already well advanced for the intestines, kidneys and liver, but it has recently been brought into focus for various respiratory epithelia. The aim of this study was to evaluate the expression of several SLC transporters in differently cultured RPMI 2650 cells, as well as in specimens of the human nasal mucosa. The expression profiles of PEPT2, OATP1A2, OATP4C1, OCT2, OCTN1 and OCTN2 were investigated at the gene and protein levels by performing RT-PCR, western blot analysis and immunohistological staining. Uptake assays using appropriate substrates and inhibitory substances were performed to compare the activity of peptide, organic anion and organic cation transporters, respectively, among the three models. Expression of the six SLC transporters under investigation was confirmed at the mRNA and protein levels in human nasal mucosa ex vivo as well as in RPMI 2650 cells grown under different culture conditions. The functionality was almost equal among all of the models for the PEPT and OCT(N) transporters, while the functional activity of the OATP transporters was more pronounced for both in vitro models than for excised nasal tissue. Despite negligible variations in transporter capacities, the RPMI 2650 cell cultures and freshly isolated human nasal epithelium showed nearly comparable expression patterns for the examined SLC proteins. Therefore, in vitro models based on the RPMI 2650 cell line could provide helpful data during the preclinical investigation of intranasally administered drug formulations and in the development of strategies to target nasal drug transporters for either local or systemic drug delivery.

Challenges in nasal drug absorption: how far have we come?

The nasal route is commonly used for local delivery of drugs to treat inflammatory conditions. It is also an attractive route for systemic delivery of some drugs. Irrespective of intended use, administered drugs must permeate the epithelial or olfactory membrane to be effective. The enthusiasm for potential use of the nasal route for systemic drug delivery has not been met by comparable success. In this paper, the anatomical and physiological attributes of the nasal cavity and paranasal sinuses important for drug delivery and challenges limiting drug absorption are discussed. Efforts made so far in improving nasal drug absorption such as overcoming restrictive nasal geometry and paranasal sinuses accessibility, mucociliary clearance, absorption barriers, metabolism and drug physicochemical challenges are discussed. Highlights on future prospects of nasal drug delivery/absorption were discussed.

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