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Ann Thorac Surg 2005;79:905-910
© 2005 The Society of Thoracic Surgeons

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Original article: Cardiovascular

Carbodiimide Treatment Dramatically Potentiates the Anticalcific Effect of Alpha-Amino Oleic Acid on Glutaraldehyde-Fixed Aortic Wall Tissue

^a Chris Barnard Division of Cardiothoracic Surgery, Cape Heart Center, University of Cape Town, Cape Town, South Africa

Accepted for publication December 10, 2003.

^* Address reprint requests to Dr Zilla, Cape Heart Center, Faculty of Health Sciences, University of Cape Town, Anzio Rd, Observatory 7925, Cape Town, South Africa
peter.zilla{at}uct.ac.za

BACKGROUND: Bifunctional amines were previously found to act as bridging molecules between the terminal ends of incomplete glutaraldehyde (GA) cross-links. The additional cross-links thus formed between -NH₂ groups of tissue were seen to significantly inhibit bioprosthetic calcification. In the current study, the potential ability of -amino oleic acid (AOA) to act as a bridging molecule between -NH₂- and COOH-dependent cross-links was hypothesized to similarly augment the anticalcification effect of the AOA molecule.

METHODS: Porcine aortic wall tissue from Medtronic Freestyle valve bioprostheses incorporating the AOA anticalcification process additionally underwent carboxyl-group cross-linking with Jeffamine (poly[propylene glyco]-bis-[aminopropyl ether]) using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Tissue was subdermally implanted into 5-week-old Long-Evans rats for 60 days. Standard 0.2% GA-fixed tissue served as a control. To further assess the impact of storage solution on AOA tissue, samples were either stored in GA (0.2%GA) or EDC (25 mmol/L carbodiimide) before implantation. Tissue calcification was assessed by atomic absorption spectroscopy and histochemical staining.

RESULTS: Aldehyde end-capping with AOA achieved only a modest reduction of calcification in GA-treated aortic wall tissue (–20.0%; p < 0.05). Replacing GA with EDC as a storage solution led to a further 32.4% (p < 0.01) mitigation of calcification in Freestyle tissue. Incorporating an intermediate EDC/Jeffamine cross-linking step achieved a distinct additional reduction of calcification by 40.4% (p < 0.05). Overall, aortic wall calcification was 59.7% (p < 0.0001) lower if commercial Freestyle tissue underwent an additional EDC/Jeffamine cross-linking step and subsequent storage in EDC. Relative to control GA-fixed tissue, this represented a 67.8% (p < 0.0001) reduction. Incorporation of AOA was essential for the beneficial effect of the additional EDC/Jeffamine cross-linking step.

CONCLUSIONS: Potentially utilizing both the amino- and the carboxyl moieties of AOA for tissue binding dramatically reduces aortic wall calcification of GA-fixed tissue.

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