Cold non‐ischemic heart preservation with continuous perfusion prevents early graft failure in orthotopic pig‐to‐baboon xenotransplantation

Abstract

Background Successful preclinical transplantations of porcine hearts into baboon recipients are required before commencing clinical trials. Despite years of research, over half of the orthotopic cardiac xenografts were lost during the first 48 hours after transplantation, primarily caused by perioperative cardiac xenograft dysfunction (PCXD). To decrease the rate of PCXD, we adopted a preservation technique of cold non‐ischemic perfusion for our ongoing pig‐to‐baboon cardiac xenotransplantation project. Methods Fourteen orthotopic cardiac xenotransplantation experiments were carried out with genetically modified juvenile pigs (GGTA1‐ KO/hCD46/hTBM) as donors and captive‐bred baboons as recipients. Organ preservation was compared according to the two techniques applied: cold static ischemic cardioplegia (IC; n = 5) and cold non‐ischemic continuous perfusion (CP; n = 9) with an oxygenated albumin‐containing hyperoncotic cardioplegic solution containing nutrients, erythrocytes and hormones. Prior to surgery, we measured serum levels of preformed anti‐non‐Gal‐antibodies. During surgery, hemodynamic parameters were monitored with transpulmonary thermodilution. Central venous blood gas analyses were taken at regular intervals to estimate oxygen extraction, as well as lactate production. After surgery, we measured troponine T and serum parameters of the recipient’s kidney, liver and coagulation functions. Results In porcine grafts preserved with IC, we found significantly depressed systolic cardiac function after transplantation which did not recover despite increasing inotropic support. Postoperative oxygen extraction and lactate production were significantly increased. Troponin T, creatinine, aspartate aminotransferase levels were pathologically high, whereas prothrombin ratios were abnormally low. In three of five IC experiments, PCXD developed within 24 hours. By contrast, all nine hearts preserved with CP retained fully preserved systolic function, none showed any signs of PCXD. Oxygen extraction was within normal ranges; serum lactate as well as parameters of organ functions were only mildly elevated. Preformed anti‐non‐Gal‐antibodies were similar in recipients receiving grafts from either IC or CP preservation. Conclusions While standard ischemic cardioplegia solutions have been used with great success in human allotransplantation over many years, our data indicate that they are insufficient for preservation of porcine hearts transplanted into baboons: Ischemic storage caused severe impairment of cardiac function and decreased tissue oxygen supply, leading to multi‐organ failure in more than half of the xenotransplantation experiments. In contrast, cold non‐ischemic heart preservation with continuous perfusion reliably prevented early graft failure. Consistent survival in the perioperative phase is a prerequisite for preclinical long‐term results after cardiac xenotransplantation.

Blood Cardioplegia Induction, Perfusion Storage and Graft Dysfunction in Cardiac Xenotransplantation

“…The issue may lie in cardiac xenografts’ increased response to ischemia-reperfusion injury, as demonstrated by improved outcomes in this study by employing progressive levels of cardiac preservation with oxygenated blood. Notably, Längin, et al has demonstrated significantly depressed systolic function leading to early graft failure when traditional cardioplegia was employed, compared to NICP ( 6 ). In this study, the potential merit of blood cardioplegia for induction and preservation of cardiac xenografts to overcome PCXD as a less costly and cumbersome alternative to NICP is discussed.…”

“…PCXD is characterized as graft failure within 24-48 hours of transplantation that is independent of immune organ rejection. It has been considered to be associated with ischemia-reperfusion (I/R) injury a nd a s ystemic inflammatory response to xenotransplantation (3)(4)(5)(6). Mitigating PCXD and inflammation has resulted in up to 6 months of survival in pig-to-baboon cardiac xenotransplants, using a non-ischemic continuous perfusion preservation technique (NICP) and anti-inflammatory agents, among other adjuncts (7).…”

Minimizing Ischemia Reperfusion Injury in Xenotransplantation

“…Only with XIRI minimization were Langin et al. able to achieve consistent xenograft survival more than one day ( 25 , 327 , 328 ).…”

“…XIRI is a critical barrier to clinical xenotransplantation, but it affects xeno-organs to different degrees ( 25 , 153 , 329 , 330 ). The xeno-heart seems to require robust XIRI minimization technique to avoid perioperative cardiac xenograft dysfunction (PCXD) ( 25 , 153 , 328 ). Additionally, Shah et al.…”

Clinical trials in cardiac xenotransplantation: Are we ready to overcome barriers?

“…Iwase et al 13 demonstrated that XTx recipients had a rapid decline of free triiodothyronine after the procedure and this information was then used to improve the graft perfusate 14 by adding hormones to the solution used to protect the graft. Besides improving the myocardial protection, a recent strategy also involved a cold nonischemic continuous perfusion which guaranteed optimal xenograft function in the early postoperative period 15 …”