Abstract
Hydrogen(H2), used as a treatment to counter adverse events associated with organ transplantation, is valued not only as an anti-oxidant, anti-inflammatory and anti-apoptotic agent, but also possibly as a mitochondrial protector. Although we previously demonstrated that administration of exogenous hydrogen using gas bubbling could potentially cause adverse events, including increased risk of bacterial contamination and possible mechanical injury due to bubbling, we have been investigating novel, feasible, and more secure hydrogen delivery methods for transplantation. Using a rat cardiac transplant model, we evaluated the efficacy of a hydrogen-rich water bath, a novel and portable graft preservation method that can provide H2 to stored organs during cold preservation safely, effectively, aseptically, and continuously. Elder cardiac grafts(60- to 70-week-old Lewis rats)or allografts(12-week-old Brown Norway rats)were harvested and packed with Celsior preservation solution. Packed grafts were stored at 4℃ in the cold water bath equipped with／without an electrolyzer to saturate the water with H2. Cold ischemia time was six hours for elder grafts or eight hours for allografts. Cardiac grafts then were heterotopically engrafted into Lewis rat recipients. The hydrogen level of cardiac tissue stored in the hydrogen-rich water bath significantly increased six hours after cold preservation(12.9±0.53 pmol／mg), whereas that in the control group stayed at basal level(0.87±0.26 pmol／mg). In both experimental settings, severe increases in serum injury markers for cardiac injury(CPK, troponinⅠ), neutrophil infiltration, and upregulation of mRNAs for pro-inflammatory cytokines／chemokines in grafts were observed three hours after reperfusion in the control group. Cold ischemic damage, including mitochondrial damage, myocardial fiber injury, and endothelial injury was ultrastructurally observed in the grafts without H2 treatment after preservation. Myocardial injury and inflammatory events were significantly attenuated by organ storage in the hydrogen-rich water bath. The grafts preserved in the hydrogen-rich water bath also exhibited higher hemeoxygenase (HO)-1 expression. Furthermore, tissue ATP content and mRNA levels of mitochondrial biogenesis-related factors increased in the grafts stored in the hydrogen-rich water bath. Continuous administration of H2 during cold preservation ameliorated myocardial injury in heart grafts pre- and post-transplantation. Hydrogen-rich water bath can be a useful method for cardiac preservation.
