Patients with type 1 diabetes are 3 times more likely to be hospitalized due to long-term vascular complications.1 Furthermore, the lifespan of young individuals can be reduced by up to 13 years.1 Beta cell therapy using allogeneic islet transplantation is an alternative treatment to exogenous insulin for patients with problematic glycemic control. Despite improvements in achieving longer stabilization against hypoglycemic events with the implementation of the Edmonton protocol,2 a series of factors and events influence the success of islet cell transplant programs. The technique used for pancreas preservation is one factor that significantly influences the yield and quality of islet preparations.
The study reported by Papas et al in Transplantation uses RNA sequencing (RNAseq) to provide an in depth view of the transcriptomic changes associated with different modes of preservation.3 Indeed, this is the first study to characterize the transcriptional changes. A series of human islet preparations from deceased donors isolated after preservation by static sold storage (SCS) (n = 11) were compared with preparations of pancreata preserved by SCS followed by a period of oxygen persufflation (SCS + PSF) (n = 13). PSF was carried out by bubbling 40% humidified oxygen into the superior mesenteric and splenic arterial supply of the pancreas whilst submerged in University of Wisconsin (UW) solution. Previous studies have demonstrated this to provide a more even distribution of the gas leading to improved islet cell viability, increased ATP levels and reduced metabolic stress compared to other techniques of preservation.4,5
Using RNA seq analyses, the authors describe reduced expression of proinflammatory genes (IL 1ß, IL6, CXCL1, and CCL20) and enhanced transcription of adaptive metabolic response genes (HIF 3 alpha and pyruvate dehydrogenase kinase) in islets from a cohort of matched SCS + PSF pancreata (n = 5) compared with those preserved by SCS (n = 4). To confirm the transcriptional changes, RTqPCR was performed in a subcohort of SCS and SCS + PSF pancreata matched for the duration of cold ischemia. The fold changes of 42 genes correlated with the fold changes generated by RNAseq. Seventy-seven genes were altered by SCS + PSF compared with SCS. The reduced expression of proinflammatory cytokines and upregulation of metabolic processes are likely to improve ß-cell function.6 IL-1ß is one of the main mediators in the inhibition of insulin secretion and also causes islet cell death.5 McCall et al7 reported the combination of an IL-1 receptor antagonists (Anakinra) and anti-TNFα (Etanercept) agent post islet cell transplantation to reduce the inflammatory response and improve insulin secretion and viability.
The duration of cold ischemia is a limiting factor in islet cell transplantation with prolonged duration >12 hours reducing yield, viability, and insulin secretion.2 This study also demonstrated in a further subcohort of SCS and SCS + PSF preparations, matched for the total preservation time, that the preservation time can be extended by up to 52% without loss of viability or function by introducing PSF. Persufflation is a simple and low-cost technique that appears to protect against the detrimental effects of cold ischemia and enable longer preservation periods.
The study has several limitations. It is an analysis of a small cohort of islet cell preparations from different centers with the subanalyses of subcohorts to quantify and support the noted differences in transcriptional changes. Importantly, age and BMI were matched in the overall and subcohorts, and the population represented both male and female donors. Although islet cell purity and viability were not different between the groups, the study does not report on islet yield/quantity from each pancreas. A sufficient yield is essential for insulin independence and to reduce the likelihood of retransplantation. Further studies are required to establish whether PSF could increase the yield. Furthermore, the outcome measures are restricted to the assessment of the islets in vitro rather than the outcome after transplant.
Added to the simplicity of PSF is that its application after SCS is logistically straightforward. Experimental evidence supports its use compared with SCS or the 2-layer method which used perfluorocarbon as an oxygen carrier.4,5 Nonetheless, there are other up-and-coming technologies that may rival PSF. There have been attempts at normothermic perfusion of pancreas although studies to date have not been promising.8 Hypothermic machine perfusion technologies have been unsuccessful in the past for pancreas preservation, causing edema and loss of viability.9 However, an article by Branchereau and Renaudin10 recently presented a series of 9 human deceased donor pancreata perfused on a new hypothermic machine perfusion system developed by Waters Medical Systems. The WAVE perfusion machine operates at a pressure of 25 mm Hg. Tissue biopsies at 6, 12, and 24 hours of perfusion showed no evidence of edema. The application of oxygen during mechanical perfusion may be even more advantageous.
This study is the first to examine changes in the inflammatory and metabolic profile of islet cell preparations after preservation of the pancreas using a combination of SCS and PSF. The results are highly informative and provide insight into the beneficial actions of the addition of oxygen under hypothermic conditions. This will aid in the development of future preservation technologies and help to tailor the treatment of the recipient to improve the outcome of islet cell transplantation.
1. Miller RG, Secrest AM, Sharma RK, et al. Improvements in the life expectancy of type 1 diabetes: the Pittsburgh epidemiology of diabetes complications study cohort. Diabetes
2. Shapiro AM, Lakey JR, Ryan EA, et al. Islet transplantation in seven patients with type 1 diabetes mellitus using a glucocorticoid-free immunosuppressive regimen. N Engl J Med
3. Papas KK, Kelly AC, Smith KE, et al. Oxygen perfusion (Persufflation) of human Pancreata enhances insulin secretion and attenuates islet Proinflammatory Signaling. Transplantation
4. Suszynski TM, Rizzari MD, Scott WE 3rd, et al. Persufflation (or gaseous oxygen perfusion) as a method of organ preservation. Cryobiology
5. Scott WE 3rd, Weegman BP, Ferrer-Fabrega J, et al. Pancreas oxygen persufflation increases ATP levels as shown by nuclear magnetic resonance. Transplant Proc
6. Böni-Schnetzler M, Häuselmann SP, Dalmas E, et al. Β cell-specific deletion of the IL-1 receptor antagonist impairs β cell proliferation and insulin secretion. Cell Rep
7. McCall M, Pawlick R, Kin T, et al. Anakinra potentiates the protective effects of etanercept in transplantation of marginal mass human islets in immunodeficient mice. Am J Transplant
8. Barlow AD, Hamed MO, Mallon DH, et al. Use of ex vivo Normothermic perfusion for quality assessment of discarded human donor pancreases. Am J Transplant
9. Taylor MJ, Baicu SC. Current state of hypothermic machine perfusion preservation of organs: the clinical perspective. Cryobiology
. 2010;60(Suppl 3):S20–S35.
10. Branchereau K, Renaudin D. Cantarovich. Hypothermic Pulsatile machine perfusion for human pancreas preservation. Abstract. American Transplant Congress