Poster abstracts
Poster number 7 submitted by Arghavan Farzadi
Modulation of biomimetic mineralization of collagenous tissue by soluble ectodomain of discoidin domain receptor 2
Arghavan Farzadi (The Ohio State University, Department of Biomedical Engineering), Edward Calomeni (The Ohio State University, Department of Biomedical Engineering), Nicole M. Karn (The Ohio State University, Renal Pathology, Wexner Medical Center), John Lannutti (The Ohio State University, Department of Chemistry and Biochemistry), Lakshmi P Dasi (The Ohio State University, Department of Materials Science and Engineering), Gunjan Agarwal (The Ohio State University, Department of Biomedical Engineering)
Abstract:
Fibrils of collagen type I, serve as the major template for mineral deposits in both natural and bioprosthetic valves in cardiovascular diseases. In recent years, certain collagen binding or acidic proteins present in the peripheral blood are considered as a primary host factor modulating pathological mineralization. In this study, we examine how the ectodomain of the collagen receptor, discoidin domain receptor (DDR2), modulates mineralization of bioprosthetic material. For this purpose, we used glutaraldehyde-fixed porcine pericardium (GFPP), a collagenous tissue, which is commonly used for fabrication of bioprosthetic valves. GFPP was incubated in modified simulated body fluid (mSBF) and Polymer-induced liquid precursor (PILP) in the presence of recombinant DDR2 or a control protein to mediate extra or intrafibrillar mineralization of collagen. Thermogravimetric analysis showed increased mineral content in GFPP calcified in mSBF in the presence of DDR2 while no significant differences were observed in PILP mediated mineralization. Transmission and scanning electron microscopy confirmed the intra and extra fibrillar calcification of collagen fibrils. An increase in the size of mineral deposits was observed in the presence of DDR2 in mSBF. Stronger Von Kossa staining and Immunohistochemistry analysis of adjacent sections indicated that DDR2 co-localized with calcium phosphate deposits. Further DDR2 was found to mediate nucleation of hydroxyapatite independently of collagen. Taken together, our observations elucidate DDR2 as a novel player in the modulation of extrafibrillar mineralization of collagenous tissue.
References:
1.Flynn, L. A., Blissett, A. R., Calomeni, E. P. & Agarwal, G. Inhibition of Collagen Fibrillogenesisby Cells Expressing Soluble Extracellular Domains of DDR1 and DDR2. J. Mol. Biol. 395, (2010).
2. Bargal, R. et al. Mutations in DDR2 Gene Cause SMED with Short Limbs and Abnormal Calcifications. Am. J. Hum. Genet. 84, 80–84 (2009)
Keywords: Collagen, DDR2, Hydroxyapatite