Is single portal vein approach sufficient for hypothermic machine perfusion of DCD liver grafts?

Abstract

Reply to ‘Is single portal vein perfusion the best approach for machine preservation of liver grafts?’Journal of HepatologyVol. 64Issue 5PreviewWe appreciate the interest and comments expressed in the letter by Brüggenwirth et al. concerning our recent findings on single portal vein hypothermic liver graft perfusion prior to transplantation [1]. Full-Text PDF Is single portal vein perfusion the best approach for machine preservation of liver grafts?Journal of HepatologyVol. 64Issue 5PreviewWe have read with great interest the article by Schlegel et al., describing a single portal vein approach for hypothermic oxygenated machine perfusion (HOPE) of donation after circulatory death (DCD) liver grafts [1]. It is unquestionable that single portal vein perfusion adds simplicity to liver machine perfusion and may provide protection. However, the main question that needs to be addressed is whether this is the best perfusion technique. Full-Text PDF We recently published an article in the Journal of Hepatology demonstrating protection of the biliary tree by hypothermic oxygenated perfusion (HOPE) in a rodent donation after cardiac death (DCD) liver transplant model [[1]Schlegel A. Graf R. Clavien P.A. Dutkowski P. Hypothermic oxygenated perfusion (HOPE) protects from biliary injury in a rodent model of DCD liver transplantation.J Hepatol. 2013; 59: 984-991Abstract Full Text Full Text PDF PubMed Scopus (129) Google Scholar]. One-hour treatment by HOPE after initial warm ischemic injury followed by prolonged cold storage was effective against Kupffer-, endothelial-, and CD4+ T cell activation, leading to blunted downstream immunogenic responses [[1]Schlegel A. Graf R. Clavien P.A. Dutkowski P. Hypothermic oxygenated perfusion (HOPE) protects from biliary injury in a rodent model of DCD liver transplantation.J Hepatol. 2013; 59: 984-991Abstract Full Text Full Text PDF PubMed Scopus (129) Google Scholar]. Of note, the perfusion technique of HOPE was applied exclusively through the portal vein.We recently transferred the HOPE approach, well studied in rodent and pig models, to the clinical context [[2]Dutkowski P. Schlegel A. de Oliveira M. Mullhaupt B. Neff F. Clavien P.A. HOPE for human liver grafts obtained from donors after cardiac death.J Hepatol. 2014; 60: 765-772Abstract Full Text Full Text PDF PubMed Scopus (229) Google Scholar]. Up until the end of June, we perfused and implanted 30 human DCD liver grafts (Table 1). Despite prolonged donor warm ischemia times in all cases and the use of many older donors (Table 1), we did not observe intrahepatic cholangiopathy in our initial series with a median follow-up of 16 months. Each DCD liver was connected to an extracorporeal organ perfusion system (ECOPS) or Liver Assist device (Organ Assist®) and perfused through the portal vein only, with recirculated, cooled (10 °C) and oxygenated (60–80 kPa) UW gluconate solution (KPS-1®). To avoid shear stress in liver sinusoids during HOPE, the perfusion setting includes a low perfusion pressure with a threshold of 2.5–3 mmHg, resulting in low flow rates of 100 to 150 ml/min (0.13 ml/min/g liver). It has been questioned, however, whether perfusion solely through the portal vein is sufficient to confer protection to all liver cells including biliary epithelial cells. Some investigators claimed that an additional arterial perfusion is necessary [3Op den Dries S. Sutton M.E. Karimian N. de Boer M.T. Wiersema-Buist J. Gouw A.S. et al.Hypothermic oxygenated machine perfusion prevents arteriolonecrosis of the peribiliary plexus in pig livers donated after circulatory death.PLoS One. 2014; 9: e88521Crossref PubMed Scopus (93) Google Scholar, 4Guarrera J.V. Henry S.D. Samstein B. Reznik E. Musat C. Lukose T.I. et al.Hypothermic machine preservation facilitates successful transplantation of “orphan” extended criteria donor livers.Am J Transplant. 2015; 15: 161-169Crossref PubMed Scopus (222) Google Scholar, 5t Hart N.A. der van Plaats A. Leuvenink H.G. van Goor H. Wiersema-Buist J. Verkerke G.J. et al.Determination of an adequate perfusion pressure for continuous dual vessel hypothermic machine perfusion of the rat liver.Transpl Int. 2007; 20: 343-352Crossref PubMed Scopus (42) Google Scholar], although no studies are yet available addressing this issue.Table 1Parameters of 30 machine perfused human DCD liver grafts (n = 30, 1/2012–6/2015). Open table in a new tab Therefore, to assess perfusion quality during HOPE, we performed a set of experiments in different species including human (discarded livers) with quantification of perfusion by angiography or injection of a dye during perfusion, and subsequent microscopic evaluation of liver cells. In a first step, we injected fluorescein (n = 3) during HOPE, and documented the fluorescence under dark light after 10 min in rat, pig and discarded human DCD livers. All liver grafts were completely perfused macroscopically and histologically by single low flow portal vein perfusion (Fig. 1A).Next, we perfused pig DCD livers (n = 3, 60 min warm in situ ischemia) either through the portal vein or through the portal vein and the hepatic artery. Angiography showed no difference between both approaches and complete perfusion of livers within 30 s under low pressure cold perfusion conditions (Fig. 1B). Third, we investigated macroscopically and histologically the distal bile duct in perfused DCD livers (rat, human). The results demonstrated perfusion of the entire choledochus by portal branches within 5 min during HOPE (Fig. 1C, D).To our knowledge, this is the first attempt to quantify single portal vein machine perfusion under hypothermic conditions in DCD livers. This study established that portal vein branches contribute significantly to the intrahepatic and also extrahepatic biliary vascular supply (Fig. 1E), equal to earlier hypothesis [6Slieker J.C. Farid W.R. van Eijck C.H. Lange J.F. van Bommel J. Metselaar H.J. et al.Significant contribution of the portal vein to blood flow through the common bile duct.Ann Surg. 2012; 255: 523-527Crossref PubMed Scopus (32) Google Scholar, 7Ramesh Babu C.S. Sharma M. Biliary tract anatomy and its relationship with venous drainage.J Clin Exp Hepatol. 2014; 4: S18-S26Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar]. In addition, we observed complete perfusion of liver grafts already within the first five minutes, despite low portal perfusion pressure in the cold, and the lack of improvement of perfusate distribution to the liver periphery or to the extrahepatic bile duct by additional perfusion through the hepatic artery (Fig. 1A).Based on these studies, HOPE through the portal vein appears as an excellent method not only to target liver cells, but also delivering oxygen to biliary epithelial cells, which has been shown very recently to be of utmost importance for the regeneration and for the protection against later cholangiopathy [[8]Karimian N. Weeder P.D. Bomfati F. Gouw A.S. Porte R.J. Preservation injury of the distal extrahepatic bile duct of donor livers is representative for injury of the intrahepatic bile ducts.J Hepatol. 2015; 63: 284-287Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar]. The mechanism possibly involves changes in mitochondrial pathways, with subsequent cellular ATP load and prevention of released mitochondrial reactive oxygen species and danger associated molecular patterns [9Schlegel A. Rougemont O. Graf R. Clavien P.A. Dutkowski P. Protective mechanisms of end-ischemic cold machine perfusion in DCD liver grafts.J Hepatol. 2013; 58: 278-286Abstract Full Text Full Text PDF PubMed Scopus (181) Google Scholar, 10Schlegel A. Dutkowski P. Role of hypothermic machine perfusion in liver transplantation.Transpl Int. 2015; 28: 677-689Crossref PubMed Scopus (50) Google Scholar].In conclusion, HOPE through the portal vein provides oxygen and perfusate to the entire graft, including the extrahepatic biliary tree, and appears effective within a very short perfusion time. The technique is easily applicable after cold storage, cheap, and does not require transport of a complex perfusion device. A randomised controlled trial is underway to test HOPE in the general liver transplant population, and we would speculate a high practicability of this approach resulting in wide acceptance among centres.Conflict of interestThe authors report no conflict of interest in this study. We recently published an article in the Journal of Hepatology demonstrating protection of the biliary tree by hypothermic oxygenated perfusion (HOPE) in a rodent donation after cardiac death (DCD) liver transplant model [[1]Schlegel A. Graf R. Clavien P.A. Dutkowski P. Hypothermic oxygenated perfusion (HOPE) protects from biliary injury in a rodent model of DCD liver transplantation.J Hepatol. 2013; 59: 984-991Abstract Full Text Full Text PDF PubMed Scopus (129) Google Scholar]. One-hour treatment by HOPE after initial warm ischemic injury followed by prolonged cold storage was effective against Kupffer-, endothelial-, and CD4+ T cell activation, leading to blunted downstream immunogenic responses [[1]Schlegel A. Graf R. Clavien P.A. Dutkowski P. Hypothermic oxygenated perfusion (HOPE) protects from biliary injury in a rodent model of DCD liver transplantation.J Hepatol. 2013; 59: 984-991Abstract Full Text Full Text PDF PubMed Scopus (129) Google Scholar]. Of note, the perfusion technique of HOPE was applied exclusively through the portal vein. We recently transferred the HOPE approach, well studied in rodent and pig models, to the clinical context [[2]Dutkowski P. Schlegel A. de Oliveira M. Mullhaupt B. Neff F. Clavien P.A. HOPE for human liver grafts obtained from donors after cardiac death.J Hepatol. 2014; 60: 765-772Abstract Full Text Full Text PDF PubMed Scopus (229) Google Scholar]. Up until the end of June, we perfused and implanted 30 human DCD liver grafts (Table 1). Despite prolonged donor warm ischemia times in all cases and the use of many older donors (Table 1), we did not observe intrahepatic cholangiopathy in our initial series with a median follow-up of 16 months. Each DCD liver was connected to an extracorporeal organ perfusion system (ECOPS) or Liver Assist device (Organ Assist®) and perfused through the portal vein only, with recirculated, cooled (10 °C) and oxygenated (60–80 kPa) UW gluconate solution (KPS-1®). To avoid shear stress in liver sinusoids during HOPE, the perfusion setting includes a low perfusion pressure with a threshold of 2.5–3 mmHg, resulting in low flow rates of 100 to 150 ml/min (0.13 ml/min/g liver). It has been questioned, however, whether perfusion solely through the portal vein is sufficient to confer protection to all liver cells including biliary epithelial cells. Some investigators claimed that an additional arterial perfusion is necessary [3Op den Dries S. Sutton M.E. Karimian N. de Boer M.T. Wiersema-Buist J. Gouw A.S. et al.Hypothermic oxygenated machine perfusion prevents arteriolonecrosis of the peribiliary plexus in pig livers donated after circulatory death.PLoS One. 2014; 9: e88521Crossref PubMed Scopus (93) Google Scholar, 4Guarrera J.V. Henry S.D. Samstein B. Reznik E. Musat C. Lukose T.I. et al.Hypothermic machine preservation facilitates successful transplantation of “orphan” extended criteria donor livers.Am J Transplant. 2015; 15: 161-169Crossref PubMed Scopus (222) Google Scholar, 5t Hart N.A. der van Plaats A. Leuvenink H.G. van Goor H. Wiersema-Buist J. Verkerke G.J. et al.Determination of an adequate perfusion pressure for continuous dual vessel hypothermic machine perfusion of the rat liver.Transpl Int. 2007; 20: 343-352Crossref PubMed Scopus (42) Google Scholar], although no studies are yet available addressing this issue. Therefore, to assess perfusion quality during HOPE, we performed a set of experiments in different species including human (discarded livers) with quantification of perfusion by angiography or injection of a dye during perfusion, and subsequent microscopic evaluation of liver cells. In a first step, we injected fluorescein (n = 3) during HOPE, and documented the fluorescence under dark light after 10 min in rat, pig and discarded human DCD livers. All liver grafts were completely perfused macroscopically and histologically by single low flow portal vein perfusion (Fig. 1A). Next, we perfused pig DCD livers (n = 3, 60 min warm in situ ischemia) either through the portal vein or through the portal vein and the hepatic artery. Angiography showed no difference between both approaches and complete perfusion of livers within 30 s under low pressure cold perfusion conditions (Fig. 1B). Third, we investigated macroscopically and histologically the distal bile duct in perfused DCD livers (rat, human). The results demonstrated perfusion of the entire choledochus by portal branches within 5 min during HOPE (Fig. 1C, D). To our knowledge, this is the first attempt to quantify single portal vein machine perfusion under hypothermic conditions in DCD livers. This study established that portal vein branches contribute significantly to the intrahepatic and also extrahepatic biliary vascular supply (Fig. 1E), equal to earlier hypothesis [6Slieker J.C. Farid W.R. van Eijck C.H. Lange J.F. van Bommel J. Metselaar H.J. et al.Significant contribution of the portal vein to blood flow through the common bile duct.Ann Surg. 2012; 255: 523-527Crossref PubMed Scopus (32) Google Scholar, 7Ramesh Babu C.S. Sharma M. Biliary tract anatomy and its relationship with venous drainage.J Clin Exp Hepatol. 2014; 4: S18-S26Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar]. In addition, we observed complete perfusion of liver grafts already within the first five minutes, despite low portal perfusion pressure in the cold, and the lack of improvement of perfusate distribution to the liver periphery or to the extrahepatic bile duct by additional perfusion through the hepatic artery (Fig. 1A). Based on these studies, HOPE through the portal vein appears as an excellent method not only to target liver cells, but also delivering oxygen to biliary epithelial cells, which has been shown very recently to be of utmost importance for the regeneration and for the protection against later cholangiopathy [[8]Karimian N. Weeder P.D. Bomfati F. Gouw A.S. Porte R.J. Preservation injury of the distal extrahepatic bile duct of donor livers is representative for injury of the intrahepatic bile ducts.J Hepatol. 2015; 63: 284-287Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar]. The mechanism possibly involves changes in mitochondrial pathways, with subsequent cellular ATP load and prevention of released mitochondrial reactive oxygen species and danger associated molecular patterns [9Schlegel A. Rougemont O. Graf R. Clavien P.A. Dutkowski P. Protective mechanisms of end-ischemic cold machine perfusion in DCD liver grafts.J Hepatol. 2013; 58: 278-286Abstract Full Text Full Text PDF PubMed Scopus (181) Google Scholar, 10Schlegel A. Dutkowski P. Role of hypothermic machine perfusion in liver transplantation.Transpl Int. 2015; 28: 677-689Crossref PubMed Scopus (50) Google Scholar]. In conclusion, HOPE through the portal vein provides oxygen and perfusate to the entire graft, including the extrahepatic biliary tree, and appears effective within a very short perfusion time. The technique is easily applicable after cold storage, cheap, and does not require transport of a complex perfusion device. A randomised controlled trial is underway to test HOPE in the general liver transplant population, and we would speculate a high practicability of this approach resulting in wide acceptance among centres. Conflict of interestThe authors report no conflict of interest in this study. The authors report no conflict of interest in this study.