Association Between Galactose-Deficient IgA1 Derived From the Tonsils and Recurrence of IgA Nephropathy in Patients Who Underwent Kidney Transplantation.

Background: Recurrence of IgA nephropathy (IgAN) in the transplanted kidney is associated with graft survival, but no specific treatment is available. Tonsillectomy (TE) reportedly arrests the progression of IgAN in the native kidney. Thus, we conducted a single-center retrospective cohort study to evaluate the effect of TE prior to IgAN recurrence. Methods: Of the 36 patients with biopsy-proven IgAN who underwent kidney transplantation, 27 were included in this study. Nine patients underwent TE at 1 year after kidney transplantation (group 1), and the remaining 18 did not undergo TE (group 2). Results: The rate of histological IgAN recurrence was significantly lower in group 1 than in group 2 (11.1 vs. 55.6%, log-rank p = 0.046). In addition, half of the recurrent patients in group 2 exhibited active lesions, compared to none in group 1. Serum Gd-IgA1 levels decreased after TE in group 1, whereas they remained stable or increased slightly in group 2. In the recurrent cases, IgA and Gd-IgA1 were found in the germinal center in addition to the mantle zone of tonsils. Finally, mesangial IgA and Gd-IgA1 immunoreactivity was reduced after TE in some cases. Conclusion: Our data suggest that TE at 1 year after kidney transplantation might be associated with the reduced rate of histological IgAN recurrence. TE arrested or reduced serum Gd-IgA1 and mesangial Gd-IgA1 immunoreactivity. Therefore, we generated a hypothesis that serum Gd-IgA1 derived from the tonsils may play a pivotal role in the pathogenesis of IgAN. Based on these findings, we need to conduct verification in a prospective randomized controlled trial.

Optimization of tenocyte lineage-related factors from tonsil-derived mesenchymal stem cells using response surface methodology.

BACKGROUND: In order to optimize the tenogenic differentiation of mesenchymal stem cells (MSCs), researchers should consider various factors. However, this requires testing numerous experimental settings, which is costly and time-consuming. We aimed to assess the differential effects of transforming growth factor beta-3 (TGF-ß3) on the tenogenesis of tonsil-derived MSCs (T-MSCs) and bone marrow-derived MSCs (BM-MSCs) using response surface methodology (RSM). METHODS: Bone marrow and tonsillar tissue were collected from four patients; mononuclear cells were separated and treated with 5 or 10 ng/mL of TGF-ß3. A full factorial experimental design with a categorical factor of 0 was employed to study the effect of tension based on T-MSCs. Eighty-four trials were fitted with RSM and then used to obtain mathematical prediction models. RESULTS: Exposure of T-MSCs and BM-MSCs to TGF-ß3 increased the expression of scleraxis (SCX), tenomodulin (TNMD), decorin, collagen I, and tenascin C. Expression of most of these factors reached a maximum after 2-3 days of treatment. The model predicted that the values of the tenocyte lineage-related factors assessed would be significantly increased at 2.5 days of culture with 2.7 ng/mL of TGF-ß3 for T-MSCs and at 2.3 days of culture regardless of TGF-ß3 concentration for BM-MSCs. CONCLUSIONS: This study demonstrated that the RSM prediction of the culture time necessary for the tenogenic differentiation of T-MSCs and BM-MSCs under TGF-ß3 stimulation was similar to the experimentally determined time of peak expression of tenocyte-related mRNAs, suggesting the potential of using the RSM approach for optimization of the culture protocol for tenogenesis of MSCs.

Can an otorhinolaryngological visit induce the suspect of allergic rhinitis in children?

Summary: Allergic rhinitis (AR) is very frequent in childhood. AR is commonly associated with some co-morbidities and typical clinical features. This study aimed to test the hypothesis whether an otorhinolaryngological (ORL) visit could induce the suspect of AR. Globally, 1,002 children (550 males, mean age 5.77 years) were consecutively visited at an ORL clinic. Clinical visit, nasal endoscopy, and skin prick test were performed in all patients. In particular, history investigated atopic familiarity, birth, feeding type, passive smoking, comorbidities, including asthma, respiratory infections, otitis media, respiratory sleep disorder. Endoscopy assessed the tonsil and adenoid volume, turbinate contacts, mucosal color, and nasal discharge. Univariate and multivariate analysis were performed. The study showed that 547 (54.6%) children had AR. Some parameters were predicting factor for suspecting AR: middle turbinate contact (OR = 9.27), familial atopy (OR = 6.24), pale nasal mucosa (OR = 4.95), large adenoid volume (OR = 3.02 for score 4), and asthma co-morbidity (OR = 2.95). In conclusion this real-life study showed that during an ORL visit it is possible to suspect AR in children with turbinate hypertrophy, familial atopy, nasal pale mucosa, adenoid enlargement, and asthma comorbidity.

Administration of Tonsil-Derived Mesenchymal Stem Cells Improves Glucose Tolerance in High Fat Diet-Induced Diabetic Mice via Insulin-Like Growth Factor-Binding Protein 5-Mediated Endoplasmic Reticulum Stress Modulation.

Type 2 diabetes mellitus (T2DM) is a prevalent chronic metabolic disorder accompanied by high blood glucose, insulin resistance, and relative insulin deficiency. Endoplasmic reticulum (ER) stress induced by high glucose and free fatty acids has been suggested as one of the main causes of ß-cell dysfunction and death in T2DM. Stem cell-derived insulin-secreting cells were recently suggested as a novel therapy for diabetes. In the present study, we demonstrate the therapeutic potential of tonsil-derived mesenchymal stem cells (TMSCs) to treat high-fat diet (HFD)-induced T2DM. To explore whether TMSC administration can alleviate T2DM, TMSCs were intraperitoneally injected in HFD-induced T2DM mice once every 2 weeks. TMSC injection markedly improved glucose tolerance and glucose-stimulated insulin secretion and prevented HFD-induced pancreatic ß-cell hypertrophy and cell death. In addition, TMSC injection relieved the ER-stress response and preserved gene expression related to glucose sensing and insulin secretion. Moreover, administration of TMSC-derived conditioned medium induced similar therapeutic outcomes, suggesting paracrine effects. Finally, proteomic analysis revealed high secretion of insulin-like growth factor-binding protein 5 by TMSCs, and its expression was critical for the protective effects of TMSCs against HFD-induced glucose intolerance and ER-stress response in pancreatic islets. TMSC administration can alleviate HFD-induced-T2DM via preserving pancreatic islets and their function. These results provide novel evidence of TMSCs as an ER-stress modulator that may be a novel, alternative cell therapy for T2DM.

Correlation between Brodsky Tonsil Scale and Tonsil Volume in Adult Patients.

PURPOSE: To evaluate the value of Brodsky tonsil scale in predicting the objective tonsil volume and to identify the potential factors that might interfere with the accuracy of prediction. METHODS: A total of 87 adult patients who underwent single tonsillectomy or uvulopalatopharyngoplasty (UPPP) procedure including tonsillectomy in our hospital between Jan 2015 and Dec 2016 were included. The data of Brodsky tonsil scale evaluated preoperatively and objective tonsil volume evaluated postoperatively were collected for analysis. RESULTS: Among the 87 adult patients included, 85 patients underwent bilateral tonsillectomy, while only 2 underwent unilateral procedure. Therefore, a total of 172 tonsils were included. Significant positive correlations were established between Brodsky scale and objective volume for either right (R = 0.647), left (R = 0.664), or overall tonsils (R = 0.654) (all p < 0.001). However, volume overlaps could be found between 2+ and 3+ tonsils. Age [odds ratio (OR) = 4.053, p = 0.003] and body mass index (BMI; OR=1.740, p = 0.044) were found to be independent factors that could influence the consistency between the Brodsky scale and objective volume. As a result, a formula "Index = -1.409+1.399×age+0.554×BMI" was constructed for the evaluation of the consistency. CONCLUSION: Tonsil grading was significantly correlated with tonsil volume; preoperative tonsil grading that reflected the real tonsil volume was regarded as the protocol for the evaluation of the tonsil size. Age and BMI were independent factors that could affect the consistency between tonsil grade and tonsil volume. A mathematical model was estimated to predict the consistency accurately.

Relationships between the obstructive character of the tonsils and the type of ventilation and lip posture.

INTRODUCTION: The role of obstructive tonsils in ventilatory disorders and abnormal lip posture is widely discussed in the literature but remains controversial. The data reported on the probable relationship between obstructive tonsils and an existing breathing disorder or lip incompetence were subjective. The purpose of this study was to evaluate the relationship between the obstructive character of the tonsils and the type of ventilation and lip posture. MATERIALS AND METHODS: This is a cross-sectional study performed in children aged from 6 to 12 years old. The subjects were divided into two groups (A and B) according to the obstructive or non-obstructive character of the palatal tonsils. Type of ventilation and lip posture at rest were recorded for each child. The collected data were analysed using the SPSS 20.0 software (for Windows). A Student's t-test and a Chi2 test were respectively used to compare quantitative and qualitative variables according to the obstructive character of the tonsils for each group. The level of significance is fixed at P=0.05. RESULTS: The subjects in group B with obstructive palatal tonsils were significantly more likely to oral breathing and lip incompetence than the subjects with non-obstructive tonsils (group A). CONCLUSION: The clinical examination of children with ventilatory and postural disorders with lip incompetence must be directed towards the search for associated obstructive palatal tonsils in order to plan an early etiological treatment. This would allow to avoid subsequent problems in the dentofacial structures.

Therapeutic potential of tonsil-derived mesenchymal stem cells in dextran sulfate sodium-induced experimental murine colitis.

The therapeutic potential of tonsil-derived mesenchymal stem cells (TMSC) prepared from human tonsillar tissue has been studied in animal models for several diseases such as hepatic injury, hypoparathyroidism, diabetes and muscle dystrophy. In this study, we examined the therapeutic effects of TMSC in a dextran sulfate sodium (DSS)-induced colitis model. TMSC were injected in DSS-induced colitis mice via intraperitoneal injection twice (TMSC[x2]) or four times (TMSC[x4]). Control mice were injected with either phosphate-buffered saline or human embryonic kidney 293 cells. Body weight, stool condition and disease activity index (DAI) were examined daily. Colon length, histologic grading, and mRNA expression of pro-inflammatory cytokines, interleukin 1ß (IL-1ß), IL-6, IL-17 and tumor necrosis factor α, and anti-inflammatory cytokines, IL-10, IL-11 and IL-13, were also measured. Our results showed a significant improvement in survival rates and body weight gain in colitis mice injected with TMSC[x2] or TMSC[x4]. Injection with TMSC also significantly decreased DAI scores throughout the experimental period; at the end of experiment, almost complete reversal of DAI scores to normal was found in colitis mice treated with TMSC[x4]. Colon length was also significantly recovered in colitis mice treated with TMSC[x4]. However, histopathological alterations induced by DSS treatment were not apparently improved by injection with TMSC. Finally, treatment with TMSC[x4] significantly reversed the mRNA levels of IL-1ß and IL-6, although expression of all pro-inflammatory cytokines tested was induced in colitis mice. Under our experimental conditions, however, no apparent alterations in the mRNA levels of all the anti-inflammatory cytokines tested were found. In conclusion, our findings demonstrate that multiple injections with TMSC produced a therapeutic effect in a mouse model of DSS-induced colitis.

Pulsating Tonsil Due to Medial Displacement of the Internal Carotid Artery.

BACKGROUND The internal carotid artery (ICA) is about 2.5 cm away from the tonsils. It has no branches in the cervical portion. ICA anomalies of the neck zone may result in a massive arterial bleeding during pharynx and neck surgery. Due to these anomalies, the surgeon must be aware of this risk during tonsillectomy, adenoidectomy, and pharyngeal operations.  CASE REPORT A 23-year-old woman who was discovered to have an acute S curling-type anomaly of the ICA in contact with the lateral border of the right tonsil during a work-up for a tonsillectomy. This anomaly was incidentally discovered via computed tomography (CT) with contrast. In re-evaluating the course of treatment, we found a severe S-shape kink on the right side, bringing it close to the right tonsil by approximately 2 mm, and putting it at severe risk of injury during a simple tonsillectomy, possibly exposing the patient to serious bleeding. Partial tonsillectomy was performed for this patient with the aim to preserve and not expose the internal carotid artery. Pulsation of right tonsil was recorded. The patient made an uneventful postoperative recovery. CONCLUSIONS Undetected ICA anomaly variation can lead to fatal bleeding during a simple procedure, like tonsillectomy. We recommend vigilance during tonsillectomy if one is using a hot dissection method versus a cold dissection method, which may allow for detection of a perioperative ICA anomaly. Tonsillectomy performed by a junior resident should be under direct supervision, particularly if the hot dissection method is used.

Predicting the effect of treatment in paediatric OSA by clinical examination and functional respiratory imaging.

OBJECTIVE: The aim of this study was to investigate whether functional respiratory imaging (FRI) or clinical examination could predict treatment outcome for obstructive sleep apnea (OSA) in normal-weight, non-syndromic children. METHODS: Normal weight children diagnosed with OSA by polysomnography were prospectively included. All children got a thorough evaluation and an ultra-low dose computed tomography scan of the upper airway (UA). A 3-D reconstruction was built combined with computational fluid dynamics for FRI. Decisions on the need and type of surgery were based upon findings during drug-induced sleep endoscopy. A second polysomnography was performed 3-12 months after surgery. RESULTS: Ninety-one children were included: 62 boys, 5.0 ± 2.7 years, and BMI z-score of -0.1 ± 1.2. Children with more severe OSA had a smaller volume of the overlap region between the adenoids and tonsils. Nineteen out of 60 patients had persistent OSA (oAHI >2/h). A lower conductance in the UA and a higher tonsil score predicted successful treatment. CONCLUSIONS: A less constricted airway, as characterized by both FRI and a lower tonsil score, was associated with a less favorable response to (adeno) tonsillectomy. Further studies after treatment using FRI and DISE are warranted to further characterize the UA of these subjects.

Ultrastructure of the human palatine tonsil and its functional significance.

The human palatine tonsils represent a mucosa-associated lymphoid tissue with a significant function in mucosal protection against alimentary and airborne pathogens. The ultrastructure of different morphological compartments in the human palatine tonsil was studied in eighteen tonsils obtained from the patients who had undergone elective tonsillectomy due to chronic tonsillitis. The tonsillar specimens were analyzed by scanning and transmission electron microscopy. The results showed the presence of tight junctions between superficial epithelial cells of the oropharyngeal tonsillar surface. The crypt epithelium is a sponge-like structure infiltrated by non-epithelial cells, mostly lymphocytes, and is characterized by the presence of small pores - microcrypts occupied by large microvillus cells and/or lymphocytes. Antigen-presenting Langerhans cells with typical intracytoplasmic Birbeck granules were also found in the crypt epithelium. The lymphoid follicles are composed of lymphocytes and two types of non-lymphoid follicular cells: small fibroblast-like cells and large cells, morphologically consistent with antigen-bearing follicular dendritic cells or macrophages. The interfollicular areas consisted of a dense network of reticular cells and reticular fibers; many lymphocytes were interspersed between the reticular fibers. In addition to arterioles and high endothelial venules in the interfollicular lymphoid tissue, some fenestrated capillaries were seen intraepithelially and subepithelially. The complex ultrastructure of the human palatine tonsil provides a microenvironment necessary for antigen uptake, antigen processing and immune response.

3D culture of tonsil-derived mesenchymal stem cells in poly(ethylene glycol)-poly(L-alanine-co-L-phenyl alanine) thermogel.

Poly(ethylene glycol)-poly(L-alanine-co-L-phenyl alanine) (PEG-PAF) aqueous solutions undergo sol-to-gel transition as the temperature increases. The transition is driven by the micelle aggregation involving the partial dehydration of the PEG block and the partial increase in ß-sheet content of the PAF block. Tonsil-tissue-derived mesenchymal stem cells (TMSCs), a new stem cell resource, are encapsulated through the sol-to-gel transition of the TMSC-suspended PEG-PAF aqueous solutions. The encapsulated TMSCs are in vitro 3D cultured by using induction media supplemented with adipogenic, osteogenic, or chondrogenic factors, where the TMSCs preferentially undergo chondrogenesis with high expressions of type II collagen and sulfated glycosaminoglycan. As a feasibility study of the PEG-PAF thermogel for injectable tissue engineering, the TMSCs encapsulated in hydrogels are implanted in the subcutaneous layer of mice by injecting the TMSC suspended PEG-PAF aqueous solution. The in vivo studies also prove that TMSCs undergo chondrogenesis with high expression of the chondrogenic biomarkers. This study suggests that the TMSCs can be an excellent resource of MSCs, and the thermogelling PEG-PAF is a promising injectable tissue engineering scaffold, particularly for chondrogenic differentiation of the stem cells.

Differentiation of tonsil-tissue-derived mesenchymal stem cells controlled by surface-functionalized microspheres in PEG-polypeptide thermogels.

Poly(ethylene glycol)-poly(l-alanine) diblock copolymer (PEG-L-PA; molecular weight of each block of 1000-1080 Da) aqueous solutions undergo sol-to-gel transition in a 3.0-8.0 wt % concentration range as the temperature increases. By incorporating the polystyrene microspheres with different functional groups with a size of 100-800 µm in in situ formed PEG-L-PA thermogels, the differentiation of tonsil-tissue-derived mesenchymal stem cells (TMSCs) was investigated. The mRNA expression and immunohistochemical assays suggested that the TMSCs preferentially undergo adipogenesis in the ammonium (-NH3(+))- or thiol (-SH)-functionalized microsphere incorporated thermogels; chondrogenesis in the thiol-, phosphate (PO3(2-))-, or carboxylate (-COO(-))-functionalized microsphere incorporated thermogels; and osteogenesis in the phosphate-, carboxylate-functionalized, or neat polystyrene microsphere incorporated thermogels. This paper provides a new TMSC 3D culture system of a sol-gel reversible matrix and suggests that the surface-functional groups of microspheres in the thermogel can control the preferential differentiation of stem cells into specific cell types during the 3D culture.

Long term outcome of tonsillar regrowth after partial tonsillectomy in children with obstructive sleep apnea.

OBJECTIVE: We investigated the long-term effects of partial tonsillectomy, and potential risk factors for tonsillar regrowth in children with obstructive sleep apnea hypopnea syndrome (OSAHS). METHODS: Children affected by OSAHS with obstructive hypertrophic tonsils underwent partial tonsillectomy or total tonsillectomy with radiofrequency coblation. Polysomnography was performed prior to and 5 years following surgery. Blood samples from all participants were taken prior to and 1 month following surgery to assess immune function. All participants were interviewed 5 years following surgery to ascertain effects of the surgery, rate of tonsillar regrowth, and potential risk factors. RESULTS: All parents reported alleviation of breathing obstruction. Postoperative hemorrhage did not occur in the partial tonsillectomy group compared to 3.76% in the total tonsillectomy group. Tonsillar regrowth occurred in 6.1% (5/82) in children following partial tonsillectomy. Palatine tonsil regrowth occurred a mean of 30.2 months following surgery, and 80% of children with tonsillar regrowth were younger than 5 years of age. All five patients had a recurrence of acute tonsillitis prior to enlargement of the tonsils. Four of the five had an upper respiratory tract allergy prior to regrowth of palatine tonsils. There were no differences in IgG, IgM, IgA, C3, or C4 levels following partial tonsillectomy or total tonsillectomy. CONCLUSION: Partial tonsillectomy is sufficient to relieve obstruction while maintaining immunological function. This procedure has several post-operative advantages. Palatine tonsils infrequently regrow. Risk factors include young age, upper respiratory tract infections, history of allergy, and history of acute tonsillitis prior to regrowth.

A pro-inflammatory role for nuclear factor kappa B in childhood obstructive sleep apnea syndrome.

STUDY OBJECTIVES: Childhood obstructive sleep apnea syndrome (OSAS) is associated with an elevation of inflammatory markers such as C-reactive protein (CRP) that correlates with specific morbidities and subsides following intervention. In adults, OSAS is associated with activation of the transcription factor nuclear factor kappa B (NF-kB). We explored the mechanisms underlying NF-kB activation, based on the hypothesis that specific NF-kB signaling is activated in children with OSAS. DESIGN: Adenoid and tonsillar tissues from children with OSAS and matched controls were immunostained against NF-kB classical (p65 and p50) and alternative (RelB and p52) pathway subunits, and NF-kB-dependent cytokines: interleukin (IL)- 1α, IL-1ß, tumor necrosis factor-α, and IL-8). Serum CRP levels were measured in all subjects. NF-kB induction was evaluated by a luciferase-NF-kB reporter assay in L428 cells constitutively expressing NF-kB and in Jurkat cells with inducible NF-kB expression. p65 translocation to the nucleus, reflecting NF-kB activation, was measured in cells expressing fluorescent NF-kB-p65-GFP (green fluorescent protein). SETTING: Sleep research laboratory. PATIENTS OR PARTICIPANTS: Twenty-five children with OSAS and 24 without OSAS. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Higher expression of IL-1α and classical NF-kB subunits p65 and p50 was observed in adenoids and tonsils of children with OSAS. Patient serum induced NF-kB activity, as measured by a luciferase-NF-kB reporter assay and by induction of p65 nuclear translocation in cells permanently transfected with GFP-p65 plasmid. IL-1ß showed increased epithelial expression in OSAS tissues. CONCLUSIONS: Nuclear factor kappa B is locally and systemically activated in children with obstructive sleep apnea syndrome. This observation may motivate the search for new anti-inflammatory strategies for controlling nuclear factor kappa B activation in obstructive sleep apnea syndrome.

New approaches to the diagnosis of sleep-disordered breathing in children.

Sleep-disordered breathing in general and particularly, obstructive sleep apnea syndrome (OSAS) are highly prevalent conditions in children. Current diagnostic approaches range from exclusively using clinical presentation and physical examination to the current "Gold Standard" of overnight polysomnography (NPSG). But while it is clear that the former is fraught with major limitations, the latter is also associated with significant obstacles, such as relative unavailability of appropriately equipped sleep laboratories and trained personnel, the labor intensive nature of NPSG and its inconvenience, and, of course, the high cost of the procedure. These limitations are detrimental to timely diagnosis and treatment. Novel approaches to the evaluation of community-based and clinically referred pediatric populations are discussed and should stimulate the field in the search for improved diagnostic technologies and delineation of a more pragmatic and reliable diagnostic approach for pediatric SDB.

Ultramicroscopic examination of the ovine tonsillar epithelia.

As solid morphological knowledge of ovine tonsillar epithelia might contribute to a better understanding of the pathogenesis of several diseases including prion diseases, the epithelia of all tonsils of 7 one-year-old Texel sheep were examined using scanning and transmission electron microscopy. Major parts of the pharyngeal and tubal tonsils were covered by pseudostratified columnar ciliated epithelia that were interrupted by patches of epithelium containing cells with densely packed microfolds or microvilli, and cells with both microvilli and cilia. Smaller parts were covered by either flattened polygonal cells with densely packed microvilli or microfolds, squamous epithelial cells, or patches of reticular epithelium. The palatine and paraepiglottic tonsils were mainly lined by squamous epithelial cells with apical microplicae or short knobs. Additionally, regions of reticular epithelium containing epithelial cells with apical microvilli were seen. The lingual tonsil was uniformly covered by a keratinized squamous epithelium and devoid of microvillous cells and patches of reticular epithelium. The rostral half of the tonsil of the soft palate was lined by a pseudostratified columnar ciliated epithelium with characteristics of the pharyngeal and tubal tonsils. The epithelium of the caudal part resembled the epithelia of the palatine and paraepiglottic tonsils. Putative M cells, mainly characterized by apical microvilli or microfolds and a close association with lymphoid cells, seem manifestly present on the nasopharyngeal tonsils. The reticular epithelium of the palatine and paraepiglottic tonsils also harbor cells with small apical microvilli. The exact nature of these presumptive M cells should, however, be elucidated in functional studies.

Interleukin-22-producing innate immune cells: new players in mucosal immunity and tissue repair?

Mucosal tissues, lying at the interface with the external environment, are constantly challenged by microbial, physical and chemical assaults. To provide the necessary immune defence to such challenges, lymph nodes and Peyer's patches are formed in utero in response to inductive signals from lymphoid-tissue inducer (LTi) cells. As discussed in this Progress article, a series of recent reports has identified a population of interleukin-22-producing mucosal cells in the gut and tonsils that share features with both LTi cells (by expressing RORgammat) and natural killer cells (by expressing NKp46) and that might be involved in immunity and homeostasis in mucosal tissues.

In vitro culture of equine respiratory mucosa explants.

An in vitro model of the upper respiratory tract of the horse was developed to investigate mechanisms of respiratory diseases. Four tissues of the upper respiratory tract of three horses were collected. Explants were maintained in culture at an air-liquid interface for 96h. At 0, 24, 48, 72 and 96h of cultivation, a morphometric analysis was performed using light microscopy, scanning electron microscopy and transmission electron microscopy. The explants were judged on morphometric changes of epithelium, basement membrane and connective tissue. Viability was evaluated using a fluorescent Terminal deoxynucleotidyl transferase-mediated dUTP Nick End Labelling (TUNEL) staining. No significant changes in morphometry and viability of any of the explants were observed during cultivation. Hence, the in vitro model may be useful to study infectious and non-infectious diseases at the level of the equine respiratory tract, with potential application to the development of vaccines and treatments for diseases of the respiratory tract.