Bioinformatic Analysis Of Epithelial Cell Gene Expression In Chronic Rhinosinusitis Identifies Constitutive Differences Between CRSwNP And CRSsNP

An Evaluation of SPARC Protein as a Serum Biomarker of Chronic Rhinosinusitis

OBJECTIVE

Precision medicine initiatives for chronic rhinosinusitis (CRS) management suggest tailoring treatment to the patient's individual disease profile; however, serum biomarkers for evaluation of disease activity or predicting response to therapy are lacking in CRS. Epithelial-to-mesenchymal transition (EMT) has been described as a component of barrier dysfunction in CRS. SPARC (secreted protein acidic and rich in cysteine) is a marker of EMT that has previously been identified in sinus epithelium by gene expression profiling. We wished to determine if SPARC could represent a serum biomarker for CRS by verifying (1) if SPARC could be detected in serum, (2) whether levels were sensitive to disease burden reduction following surgery, and (3) if it could predict response to therapy.

STUDY DESIGN

Prospective.

SETTING

Tertiary care center.

SUBJECTS

Patients with CRS undergoing endoscopic sinus surgery (ESS).

METHODS

Twenty-six patients undergoing ESS for CRS were prospectively recruited. Serum was collected at the time of surgery and 4 months following ESS and SPARC level measured using enzyme-linked immunosorbent assay. Postoperative outcome was characterized as "remission" or "unfavorable" based on symptomatology and endoscopy.

RESULTS

SPARC could be detected and measured in serum in all subjects. Following ESS, SPARC levels decreased by 33% ( P = .005) but did not predict evolution at 4 months postsurgery ( P = .94).

CONCLUSION

SPARC may be an interesting serum biomarker of disease activity in CRS, as it can be reliably measured and decreases following successful reduction of disease burden after surgery. However, it does not predict post-ESS evolution, suggesting that the link between EMT and outcome is not linear.

Expression of the extracellular matrix gene periostin is increased in chronic rhinosinusitis and decreases following successful endoscopic sinus surgery

BACKGROUND

The extracellular matrix (ECM) is a potentially important component of mucosal immunity. ECM dysregulation in chronic rhinosinusitis (CRS) is suggested by genomewide association studies identifying ECM genes as top candidates. Further support is afforded by the demonstration of increased expression of periostin (POSTN) in CRS biopsy samples compared to controls, and by reported roles in eosinophilic inflammation and steroid responsiveness. We wished to evaluate the potential utility of POSTN as a biomarker for disease activity by determining whether POSTN levels were modified in disease and whether they were modulated by endoscopic sinus surgery (ESS).

METHODS

Twelve patients undergoing ESS for CRS and 10 controls undergoing ESS for skull-base access were recruited. An epithelial sample from the frontal recess was collected using a cytology brush at time of and 3 months after surgery. Microarray analysis of gene expression was performed using the Illumina HumanHT-12 Beadchip v3. POSTN protein level in biopsy samples taken from the same place of brushings at surgery was analyzed by immunohistochemistry (IHC) staining.

RESULTS

All patients resolved CRS with ESS. At surgery, a higher expression of POSTN was seen in the CRS group compared to controls (fold change [FC] = 4.89, positive false discovery rate (pFDR) = 0.0006), which was also verified by IHC. After ESS, POSTN expression in CRS group decreased (FC = -3.074, pFDR = 0.0044), and was no longer different from controls (FC = 1.56, pFDR = 0.3).

CONCLUSION

Demonstration of reduced levels in the expression of POSTN, an ECM gene, following resolution of disease, implicates POSTN, a potential pathogenesis indicator or biomarker of CRS disease activity and responsiveness to treatment.

Genetics of rhinosinusitis

Suggestion for a potential genetic basis to chronic rhinosinusitis (CRS) is afforded by degree of inheritability suggested from family and twin studies, existence of CRS in simple mendelian diseases, and development of sinusitis as part of the phenotype of certain gene "knockout" murine models. Genetic association studies are expected to identify novel genes associated with CRS and suggest novel mechanisms implicated in disease development. Although these studies are subject to methodologic difficulties, associations of CRS and polymorphisms in more than 30 genes have been published, with single nucleotide polymorphisms in 3 (IL1A, TNFA, AOAH) replicated. While the individual risk conferred by these single nucleotide polymorphisms remains modest, taken as a group, they suggest an important implication of pathways of innate immune recognition and in regulation of downstream signaling in the development of CRS. In a demonstration of these techniques' potential to identify new targets for research, the authors present a functional investigation of LAMB1, the top-rated gene from a pooling-based genome-wide association study of CRS. Upregulation of gene expression in LAMB1 and associated laminin genes in primary epithelial cells from CRS patients implicates the extracellular matrix in development of CRS and offers a new avenue for further study.