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DOI: 10.1055/s-2007-967425
Bradykinin and NONOate reduce apoptosis in cryopreserved human allografts during the thawing process
Objective: Early calcification of cryopreserved allograft heart valves has been observed to a variable extent and apoptosis has been suggested as one contributing factor. Recent research demonstrated significant levels of apoptosis accompanied by NOS-III expression during the thawing process. The current study investigated the impact of an NO-donor and NOS-III stimulator on apoptosis in human cryopreserved allografts during the thawing process.
Methods: Five human allografts, unsuitable for implantation due to structural defects, were harvested and cryopreserved according to standard clinical protocol. Myocardial tissue samples from each valve were either thawed according to standard clinical protocol (control), or thawed with addition of the NO-donor NONOate, or the NOS-III stimulator bradykinin. The following assays were conducted by immunohistostaining: activated NOS-III, cGMP, and as markers of apoptosis, activated caspase 3 and PARP. Quantitative analysis was performed by television densitometry.
Results: In comparison to control, valves treated with NONOate and bradykinin showed significantly higher gray values of NOS-III and cGMP (p<0.001). PARP and caspase 3 gray values were substantially lower in the NONOate and bradykinin group, however the difference was only significant in control vs. bradykinin (p<0.03).
Conclusions: NOS-III expression during thawing of cryopreserved allografts is significantly increased by addition of NONOate and bradykinin. Increased NOS-III expression seems to have a protective effect on myocardial tissue during thawing, as apoptosis activity was reduced. Addition of NO-donors or NOS-stimulators may be a future approach for improved allograft preservation.