Expression of Midkine mRNA in Human Nasal Mucosa

Kim, Jeong Joon; Choi, Sung Bae; Lee, Chang Haeng; Lim, Ki Jung; Oh, Byung Hoon; Kim, Eun Joong; Lee, Heung Man; Lee, Sang hag

Abstract

BACKGROUND AND OBJECTIVES: A heparin-binding polypeptide called midkine is a family of secreted growth/differentiation cytokines and has a role in tumor growth by enhancing endothelial proliferation, vascular density and angiogenesis. In this respect, midkine may be involved in the pathogenesis of nasal polyposis. The aim of the present study is to evaluate the expression of midkine mRNA in the human nasal mucosa and polyps. MATERIALS AND METHOD: The total RNA was isolated from freshly disected inferior turbinate of patients who underwent rhinoplasty and from nasal polyps of chronic rhinosinusitis patients. The expression and distribution of midkine mRNA was investigated by reverse transcriptse- polymerase chain reaction (RT-PCR) and in situ hybridization. The midkine mRNA expression in nasal mucosa and polyps were semi-quantitatively evaluated by Southern blot hybridization.
RESULTS
The expression of midkine mRNA was identified in both normal inferior turbinate and nasal polyp. Histochemistry of in situ hybridization revealed that midkine mRNA in normal inferior turbinate was intensely expressed in the surface epithelium, submucosal glands, vascular endothelium, and inflammatory cells scattered in submucosal tissues. Midkine mRNA was expressed in the nasal polyps, many inflammatory cells and newly formed vascular endothelium, but not in the newly formed glandular epithelium. In semi-quantitative southern blot hybridization, midkine mRNAs did not have different expression levels between inferior turbinate and nasal polyps.
CONCLUSION
These results indicate that midkine mRNA is innately expressed in human nasal mucosa, playing a role in nasal physiology. Also, the results show that midkine may be involved in the pathogenesis of nasal polyps via angiogenesis, tissue growth, and inflammatory process.