Temperature profiles of different cooling methods in porcine pancreas procurement

Porcine islet xenotransplantation is a promising alternative to human islet allotransplantation. Porcine pancreas cooling needs to be optimized to reduce the warm ischemia time (WIT) following donation after cardiac death, which is associated with poorer islet isolation outcomes. This study examines the effect of four different cooling Methods on core porcine pancreas temperature (n = 24) and histopathology (n = 16). All Methods involved surface cooling with crushed ice and chilled irrigation. Method A, which is the standard for porcine pancreas procurement, used only surface cooling. Method B involved an intravascular flush with cold solution through the pancreas arterial system. Method C involved an intraductal infusion with cold solution through the major pancreatic duct, and Method D combined all three cooling Methods. Surface cooling alone (Method A) gradually decreased core pancreas temperature to <10 °C after 30 min. Using an intravascular flush (Method B) improved cooling during the entire duration of procurement, but incorporating an intraductal infusion (Method C) rapidly reduced core temperature 15–20 °C within the first 2 min of cooling. Combining all methods (Method D) was the most effective at rapidly reducing temperature and providing sustained cooling throughout the duration of procurement, although the recorded WIT was not different between Methods (P = 0.36). Histological scores were different between the cooling Methods (P = 0.02) and the worst with Method A. There were differences in histological scores between Methods A and C (P = 0.02) and Methods A and D (P = 0.02), but not between Methods C and D (P = 0.95), which may highlight the importance of early cooling using an intraductal infusion. In conclusion, surface cooling alone cannot rapidly cool large (porcine or human) pancreata. Additional cooling with an intravascular flush and intraductal infusion results in improved core porcine pancreas temperature profiles during procurement and histopathology scores. These data may also have implications on human pancreas procurement as use of an intraductal infusion is not common practice.     

The attitude toward xenocorneal transplantation in wait‐listed subjects for corneal transplantation in Korea

Shortage of donor cornea is a significant problem in Asia, and xenocorneal transplantation is being actively studied to alleviate this problem. However, the attitudes of subjects who await corneal transplants toward xenocorneal transplantation are not known at all. Thus, this study aimed to investigate the attitudes of subjects on the waiting lists for corneal transplants, toward corneal xenotransplantation. A telephone questionnaire survey comprising six items was conducted in 132 subjects among the wait‐listed individuals (n = 590) who were awaiting corneal transplantation or had undergone corneal transplantation at Seoul National University Hospital from July, 2003 to August, 2012. Among six inquiries, four questions were used to analyze attitudes toward corneal xenotransplantation. Each question pertained to (1) the acceptance of xenocorneal transplantation, (2) willingness to participate in clinical trials, (3) worries in xenocorneal transplantation, and (4) the concern of self‐identity or social life after xenocorneal transplantation. To analyze demographic factors influencing the question, the subjects were arbitrarily divided into two groups: the young (age < 60 yr, n = 58) and the elderly (age ≥ 60 yr, n = 74) or the less‐educated (n = 53) and the well‐educated with high school diploma, college graduation, or higher education (n = 79). Collected demographic data were analyzed as influencing factors on each question using a chi‐square and logistic regression tests. In this study, 42.4% of the subjects (n = 56) expressed favorable views on xenocorneal transplantation using porcine corneas to cure visual loss from corneal blindness. Among those subjects expressing favorable views (n = 56), the willingness to participate in clinical trials, knowing they and their spouses must undergo long‐term surveillance, was 62.5% (n = 35). There were 76.5% of subjects (n = 101) expressing worries regarding xenocorneal transplantation, while 28.8% of subjects (n = 38) expressed their concerns about self‐identity or social life after xenotransplantation. Younger subjects expressed more worry about xenotransplantation than elderly subjects. The well‐educated expressed less concern over self‐identity and social life than the less‐educated. This survey among subjects who are wait‐listed for corneal transplant or who have received a corneal transplant demonstrates that there is an interest in xenocorneal transplantation as an alternate procedure, although there are worries about the procedure that should be further explored in educational campaigns and future studies of the general population.     

The role of platelets in coagulation dysfunction in xenotransplantation,and therapeutic options

Xenotransplantation could resolve the increasing discrepancy between the availability of deceased human donor organs and the demand for transplantation. Most advances in this field have resulted from the introduction of genetically engineered pigs, e.g., α1,3‐galactosyltransferase gene‐knockout (GTKO) pigs transgenic for one or more human complement‐regulatory proteins (e.g., CD55, CD46, CD59). Failure of these grafts has not been associated with the classical features of acute humoral xenograft rejection, but with the development of thrombotic microangiopathy in the graft and/or consumptive coagulopathy in the recipient. Although the precise mechanisms of coagulation dysregulation remain unclear, molecular incompatibilities between primate coagulation factors and pig natural anticoagulants exacerbate the thrombotic state within the xenograft vasculature. Platelets play a crucial role in thrombosis and contribute to the coagulation disorder in xenotransplantation. They are therefore important targets if this barrier is to be overcome. Further genetic manipulation of the organ‐source pigs, such as pigs that express one or more coagulation‐regulatory genes (e.g., thrombomodulin, endothelial protein C receptor, tissue factor pathway inhibitor, CD39), is anticipated to inhibit platelet activation and the generation of thrombus. In addition, adjunctive pharmacologic anti‐platelet therapy may be required. The genetic manipulations that are currently being tested are reviewed, as are the potential pharmacologic agents that may prove beneficial.     

Protective Effects of Transgenic Human Endothelial Protein C Receptor Expression in Murine Models of Transplantation

Thrombosis and inflammation are major obstacles to successful pig‐to‐human solid organ xenotransplantation. A potential solution is genetic modification of the donor pig to overexpress molecules such as the endothelial protein C receptor (EPCR), which has anticoagulant, anti‐inflammatory and cytoprotective signaling properties. Transgenic mice expressing human EPCR (hEPCR) were generated and characterized to test this approach. hEPCR was expressed widely and its compatibility with the mouse protein C pathway was evident from the anticoagulant phenotype of the transgenic mice, which exhibited a prolonged tail bleeding time and resistance to collagen‐induced thrombosis. hEPCR mice were protected in a model of warm renal ischemia reperfusion injury compared to wild type (WT) littermates (mean serum creatinine 39.0 ± 2.3 μmol/L vs. 78.5 ± 10.0 μmol/L, p < 0.05; mean injury score 31 ± 7% vs. 56 ± 5%, p < 0.05). Heterotopic cardiac xenografts from hEPCR mice showed a small but significant prolongation of survival in C6‐deficient PVG rat recipients compared to WT grafts (median graft survival 6 vs. 5 days, p < 0.05), with less hemorrhage and edema in rejected transgenic grafts. These data indicate that it is possible to overexpress EPCR at a sufficient level to provide protection against transplant‐related thrombotic and inflammatory injury, without detrimental effects in the donor animal.     

胎儿卵巢组织玻璃化冻存效果的研究

目的探讨玻璃化冻存法对胎儿卵巢组织形态和功能的保存效果。方法采用改良EG5.5/30玻璃化液冻存胎儿卵巢皮质片,解冻后观察卵巢组织学变化,卵巢皮质片异种异位移植后,观察受体鼠动情周期恢复率、恢复时间、卵泡发育状况。结果实验组与新鲜培养后移植组、添加抗氧化剂培养后移植组相比动情周期恢复率差异无统计学意义(P>0.05),但高于新鲜移植组(P<0.005);动情周期恢复需要的天数接近于新鲜移植组,明显短于两种培养组(P<0.05);在卵泡计数上,实验组每高倍视野的卵泡计数明显高于新鲜移植组(P<0.005),与培养后移植组间的差异无统计学意义(P>0.05)。移植后18周,组织学观察见大量窦卵泡,而培养组仅偶见窦卵泡。结论玻璃化冻存法可有效冻存胎儿卵巢组织,且不影响卵泡继续发育的潜能。