Calcification resistance, biostability, and low immunogenic potential of porcine heart valves modified by dye-mediated photooxidation

The calcification potential, biostability, and immunogenic response of mate rials intended for long-term in vivo use, such as in heart-valve bioprosthe ses, are essential components of device performance. Here we explore these properties in photooxidized porcine heart valves. To study immunological se nsitization, we injected tissue extracts intradermally into guinea pigs. Te st and control animals received a challenge patch of the appropriate extrac t and were scored for dermal reactions. Neither cottonseed oil nor sodium c hloride extracts of photooxidized heart-valve tissues caused any dermal inf lammatory response. After implantation in the rat subcutaneous model for 90 days, the calcium content of 48-h-treated photooxidized cusp tissue [0.04 +/- 0.00 mg/g wet weight (gww)] was comparable to that of unimplanted contr ol tissues (usually <1 mg/gww) and much lower than that of glutaraldehyde-t reated controls (71 <plus/minus> 15 mg/,gww). The porcine aortic wall calci um content (49 +/- 31 mg/,gww) was comparable to that of glutaraldehyde-tre ated controls (59 +/- 8 mg/gww). Histologically, a time-dependent decrease in inflammation and vascularization with increasing photooxidation time was noted in the rat model along with an increase in the stability and organiz ation of collagen bundles. In summary, porcine valve tissues treated by dye -mediated photooxidation were resistant to calcification, were biostable, a nd demonstrated a low immunogenic response, indicating potential for use in heart-valve bioprostheses. (C) 2001 John Wiley & Sons, Inc.