Increased expression and role of thymic stromal lymphopoietin in nasal polyposis

Abstract

Purpose: Nasal polyposis is a chronic inflammatory disease of the upper airways often associated with asthma and characterized by markedly increased numbers of eosinophils, Th2 type lymphocytes, fibroblasts, goblet cells and mast cells. Previous studies have shown elevated levels of thymic stromal lymphopoietin (TSLP) in atopic diseases like asthma, atopic dermatitis and mainly in animal models of allergic rhinitis (AR). Here, we investigated the expression of TSLP in nasal polyps from atopics and non-atopics in comparison with the nasal mucosa and its potential role in nasal polyposis.

Methods: Messenger RNA expression for TSLP, thymus and activation-regulated chemokine (TARC) and macrophage derived chemokine (MDC) in nasal polyps and nasal mucosa of atopics and non-atopics was analyzed by real time PCR. Immunoreactivity for TSLP in nasal polyps and in the nasal mucosa of patients with AR and non-allergic rhinitis (NAR) was analyzed by immunohistochemistry. Eosinophil counts was analyzed by Wright-Giemsa staining and nasal polyp tissue IgE, by ELISA.

Results: Messenger RNA expression for TSLP,TARC and MDC was markedly higher in nasal polyps as compared to the allergic nasal mucosa. Immunoreactivity for TSLP was detected in epithelial cells, endothelial cells, fibroblasts and inflammatory cells of the nasal mucosa and nasal polyps. The number of TSLP+ cells was significantly greater in the nasal mucosa of AR than NAR patients. The number of TSLP+ cells in nasal polyps from atopics was significantly greater than that of non-atopics and that in the allergic nasal mucosa. The number of TSLP+ cells correlated well with the number of eosinophils and the levels of IgE in nasal polyps.

Conclusions: The high expression of TSLP in nasal polyps and its strong correlation to eosinophils and IgE suggest a potential role for TSLP in the pathogenesis of nasal polyps by regulating the Th2 type and eosinophilic inflammation.

Keywords: IgE; Nasal polyps; TSLP; Th2 cytokines; eosinophils.

Fig. 1

Relative messenger RNA expression of thymic stromal lymphopoietin (TSLP), thymus and activation-regulated chemokine (TARC) and macrophage derived chemokine (MDC) in nasal polyps (atopic and non-atopic) and allergic nasal mucosa. The mRNA expression was analyzed by real time PCR as described in the text. The quantitative real-time PCR assay was based on primers that specifically amplify TSLP, TARC and MDC. The mRNA expression of TSLP as well as TARC and MDC was markedly higher in nasal polyps from atopics as compared to the allergic nasal mucosa and relatively higher than in nasal polyps from non-atopics. A+ Po, nasal polyps from atopics (n=4); A-Po, nasal polyps from non-atopics (n=3); A+NM, nasal mucosa from allergic rhinitis patients (n=3).

Fig. 2

Immunoreactivity and localization of thymic stromal lymphopoietin (TSLP) in the nasal mucosa. The immunoreactivity for TSLP was analyzed by immunohistochemistry using the peroxidase-based Avidin-Biotin Complex (ABC) method as described in the text. TSLP immunoreactivity is shown as in (A) in the nasal mucosa of patients with non-allergic rhinitis (NAR). TSLP was expressed strongly especially in epithelial cells. (B) Negative control in NAR shows no immunoreactivity for TSLP. (C) In allergic rhinitis nasal mucosa. TSLP was strongly expressed in epithelial cells, and inflammatory cells. (D) Negative control shows no immunoreactivity for TSLP (magnification ×400 HPF).

Fig. 3

Immunoreactivity and localization of thymic stromal lymphopoietin (TSLP) in nasal polyps. The immunoreactivity for TSLP was analyzed by immunohistochemistry using the using the peroxidase-based Avidin-Biotin Complex (ABC) method as described in the text. TSLP immunoreactivity is as shown in (A). In nasal polyps from non-atopics, TSLP was expressed strongly especially in epithelial cells. (B) Negative control shows no immunoreactivity for TSLP. (C) In nasal polyps from atopics. TSLP expression was detected in the epithelial cells, endothelial cells, fibroblasts and in inflammatory cells in nasal polyps from both atopics and non-atopics. Stronger immunoreactivity for TSLP was detected in the nasal polyps from atopics. (D) Negative control shows no immunoreactivity for TSLP (magnification ×400 HPF).

Fig. 4

The number of thymic stromal lymphopoietin (TSLP) positive cells in the nasal mucosa and nasal polyps. Immunohistochemistry for TSLP was performed as described in the text. Positively stained cells were counted as described in the text in an area on 0.202 mm²×400 HPF. (A) The number of TSLP positive cells in the nasal mucosa of patients with allergic rhinitis (AR) was significantly greater than that in the nasal mucosa of patients with non-allergic rhinitis (NAR) (^*P<0.01). (B) The number of TSLP positive cells in nasal polyps from atopics was significantly greater than that of non-atopics (^*P<0.01). (C) The number of TSLP positive cells was greater in the nasal polyps of atopics as compared to that of AR nasal mucosa (^*P<0.01). (D) No significant difference was found in the number of TSLP+ cells between non-atopic nasal polyps and nasal mucosa of NAR patients. A+ Po, nasal polyps from atopics; A-Po, nasal polyps from non-atopics; A+NM, nasal mucosa from AR patients; A-NM, nasal mucosa from NAR patients.

Fig. 5

Epithelial cell expression of thymic stromal lymphopoietin (TSLP) in the nasal mucosa and nasal polyps. TSLP expression in nasal epithelial cells was scored using an Image J analysis system as described in the text. (A) The expression of TSLP in nasal epithelial cells of patients with allergic rhinitis (AR) was significantly greater than that in the nasal mucosa of patients with non-allergic rhinitis (NAR) (^*P<0.05). (B) TSLP expression in the nasal polyp epithelial cells of atopic patients was slightly higher than that of non-atopics but no significant difference was detected. (C) No difference was detected in the expression of TSLP in epithelial cells of nasal polyps from atopics and nasal mucosa of AR patients. (D) No difference was detected between nasal polyp epithelial cells of non-atopics and nasal epithelial cells of NAR patients. A+ Po, nasal polyps from atopics; A-Po, nasal polyps from non-atopics; A+NM, nasal mucosa from AR patients; A-NM, nasal mucosa from NAR patients.

Fig. 6

Correlation between thymic stromal lymphopoietin (TSLP) and eosinophils in nasal polyps. There was a statistically significant correlation between the number of TSLP+ cells (A) and the number of eosinophils in nasal polyps (B) (r =0.78, P<0.05).