OHTA Yasuhiko Kanazawa University, School of Medicine, Professor, 医学系研究科, 助教授 (00272964)
WATANABE Go Kanazawa University, School of Medicine, Assistant Professor, 医学系研究科, 教授 (60242492)
OBATA Hitoshi Kansai University, Faculty of Engineering, Professor, 工学部, 教授 (00067646)
KAWAHARA Hidehisa Kansai University, Faculty of Engineering, Assistant Professor, 工学部, 助教授 (10234105)
小田 誠 金沢大学, 医学系研究科, 講師 (50224241)
[Purpose] Several factors affect preservation of the lung : one is the temperature to which the organ is exposed. Preserving it at a low temperature reduces the metabolic rate of the organ to be transplanted, thus reducing energy demand and suppressing the development of ischemic disturbances. If the preservation temperature approaches 0℃, however, the interior of the organ freezes, cellular structures and eventually the entire organ may be destroyed, an effect contrary to the purpose of preservation.
It has been noted recently that there are various cryoprotective substances in the body of organisms that are capable of surviving subfreezing temperatures. Furthermore the result of a preclinical study indicated that a lung can be preserved for an extended period at a low temperature if a cryoprotective agent (such as ethanol) has been added to the preservative fluid. Thus a hypothesis is proposed that the antifreeze product added to a preserving fluid keeps the organ to be transplanted f
rom freezing and prolongs the preservation period by keeping the organ at a temperature even lower than what has been applied (freezing temperature). In the current study, anti-freeze polysaccharides that stabilize cells and preserve them at a low temperature were added to the preservation fluid. An animal experiment was conducted using rats and the effects of preserving a lung at a low temperature (freezing temperature) using such additives were observed on the preservation of the cells and prevention of post-transplantation reperfusion disorders.
[Subjects and method] Euro-Collins (EC) solution containing no sugar was used as a preservative fluid. The following were prepared from this EC solution : ECG solution with the addition of glucose (3.5 g/100 ml) ; ECT solution, an EC solution to which trehalose (6,84 g/100 ml), a highly effective preservative, was added ; and AFP solution, an ECG solution to which an AFP derived from Bacillus thuringiensis (200 μg/ml) was added. Cardiac arrest was induced in Wistar rats weighing 250 to 300 g and their hearts and lungs were removed and preserved for 1 and 24 hours according to one of the following 8 methods of preservation (n=4 for each group) : group 1, -1℃ EC solution ; group 2, 4℃ EC solution ; group 3, -1℃ ECG solution ; group 4, 4℃ ECG solution ; group 5, -1℃ ECT solution ; group 6, 4℃ ECT solution ; group 7, -1℃ AFP solution ; and group 8, 4℃ AFP solution.
Tissue activities of the preserved lungs-such as trypan blue excretion, cellular activities expressed by ATP and LDH, and pulmonary destruction recognized in pathological examinations-were evaluated (n=4 in each group).
The left lungs collected from groups 3,5, and 7 were used for allotransplantation to Wister rats weighing 250 to 300g. Within 2 hours of transplantation, the transplanted lungs were removed for pathological evaluation and determination of the dry and wet weight ratio (n=2 for each group).
[Results] Evaluation of organ preservation : cellular ATP and LDH ratios in the lungs preserved for one hour vs.24 hours were listed for groups 1 to 8 : (ATP %), 69.5, 34.5, 84.1, 73.5, 91.4, 76.7, 86.1, and 76.5 ; (LDH %), 112.0, 151.0, 104, 0, 93.7, 92.5, 92.4, 83.8, and 98.0. The pulmonary ATP activity was significantly reduced in the 4℃ groups in comparison with the -1℃ groups. Successful preservation of ATP was noted in the following order : ECT【greater than or equal】AFP【greater than or equal】ECG>EC at 4℃ and ECT>AFP【greater than or equal】ECG>EC at -1℃. The extent of the escape of pulmonary LDH was eminent in the following sequence, EC>AFP【greater than or equal】ECG【greater than or equal】ECT at 4℃ and EC>ECG>ECT>AFP at -1℃. Similarly, cytological disruptions, expressed by trypan blue excretion and cellular edema, were more pronounced in the -1℃ group in comparison with the 4℃ group. Cytological deviations were more exaggerated in the EC group than in the other 3 groups, whereas there was no significant differences among these 3 groups.
Evaluation of the excised left lungs after allotransplantation : a pathological examination detected pulmonary edema in groups 3, 5 and 7 but no outstanding difference was found among these groups. The ratio of wet and dry organ weights were 0.45, 0.41 and 0.43 for groups 3, 5 and 7, respectively, with few intergroup differences.
[Conclusion] The lung preserving effect of AFP is inferior to that of trehalose but the former may be effective for organ preservation, in particular at low temperatures. Less