Co-expression of Midkine and Chemokine in Human Periapical Granulomas

Objectives: Objects:Midkine(MK) is a heparin binding growth factor expressed by endothelial cells, and it is known that midkine is abundantly expressed in the tumors such as meningiomas to promote differentiation or growth of the cells. Recent studies indicated that midkine was deeply concerned with mechanism of pathogenesis in the chronic inflammation with bone resorption by cell migration as well as chemokines. The purpose of this study was to examine the localization and the gene expression of midkine and chemokines (CXCL12, CXCL13 and CX₃CL₁) in periapical granulomas.
Methods: Methods: Periapical lesions were removed from 60 patients during endodontic surgery or tooth extraction. Those samples were embedded in OCT compound, followed by freezing in a mixture of dry ice and acetone. Then, cryostat sections were prepared in 7μm-thick. After 54 samples were diagnosed as periapical granulomas based on histological evaluation, cryostat sections were examined by two-color immunofluorescent staining with anti-human midkine and anti-human chemokines antibodies to search the expression of midkine and chemokines in endothelial cell. In addition, a quantitative analysis of midkine and chemokines mRNA expression was performed by real-time PCR, using total RNA extracted from cryostat sections of periapical granulomas and gingival tissue. The assays were performed using Smart Cycler, and gene expression levels were normalized by dividing the calculated values for the mRNA samples by those of GAPDH mRNA. Healthy gingival tissues were used as a negative control. Real time PCR dates were statistically analyzed using Mann-Whitney U test. Defference were considered at p＜0.05.
Results: Results:Midkine positive endothelial cells in periapical granulomas were stained with chemokines Abs. Midkine and chemokines mRNA were expressed in human periapical granulomas, and those expression levels in periapical granulomas were significantly higher than negative control.
Conclusions: Conclusion:Results indicated the possibility that midkine and chemokines expression could be concerned with pathogenesis and growth of human periapical granulomas.