HTK-N: Modified Histidine-Tryptophan-Ketoglutarate Solution-A Promising New Tool in Solid Organ Preservation

HTK vs. HTK-N for Coronary Endothelial Protection during Hypothermic, Oxygenated Perfusion of Hearts Donated after Circulatory Death

Protection of the coronary arteries during donor heart maintenance is pivotal to improve results and prevent the development of coronary allograft vasculopathy. The effect of hypothermic, oxygenated perfusion (HOP) with the traditional HTK and the novel HTK-N solution on the coronary microvasculature of donation-after-circulatory-death (DCD) hearts is known. However, the effect on the coronary macrovasculature is unknown. Thus, we maintained porcine DCD hearts by HOP with HTK or HTK-N for 4 h, followed by transplantation-equivalent reperfusion with blood for 2 h. Then, we removed the left anterior descending coronary artery (LAD) and compared the endothelial-dependent and -independent vasomotor function of both groups using bradykinin and sodium-nitroprusside (SNP). We also determined the transcriptome of LAD samples using microarrays. The endothelial-dependent relaxation was significantly better after HOP with HTK-N. The endothelial-independent relaxation was comparable between both groups. In total, 257 genes were expressed higher, and 668 genes were expressed lower in the HTK-N group. Upregulated genes/pathways were involved in endothelial and vascular smooth muscle cell preservation and heart development. Downregulated genes were related to ischemia/reperfusion injury, oxidative stress, mitochondrion organization, and immune reaction. The novel HTK-N solution preserves the endothelial function of DCD heart coronary arteries more effectively than traditional HTK.

Evaluation of a Novel Graft-Holding Solution in Hair Transplantation: A Randomized Controlled Clinical Study

BACKGROUND

Hair transplantation has become a popular choice for alopecia treatment; however, postsurgical hair shedding still annoys both patients and surgeons.

OBJECTIVE

To explore the impact of graft-holding solution on postsurgical hair shedding and testify the protective efficacy of histidine-tryptophan-ketoglutarate solution with adenosine triphosphate and deferoxamine (HTK-AD).

METHODS

There were 240 patients enrolled in the study, and the follicles were placed into either HTK-AD or Ringer solution (RS). Masson staining and live/dead staining were performed to evaluate graft morphology and apoptosis levels, respectively. The between-group comparison of postsurgical graft shedding, survival rate, complications, and patient satisfaction was performed.

RESULTS

Grafts in HTK-AD maintained organized dense collagen construction and higher cell viability, but those preserved in RS became soft, which hindered implantation. Histidine-tryptophan-ketoglutarate solution with adenosine triphosphate and deferoxamine significantly reduced the incidence of postsurgical hair shedding (73.81% vs 95%), delayed shedding onset, and diminished shedding amount versus RS ( p < .05) when ≥3,000 grafts were transplanted. The shedding duration was shortened, and hair regrowth started earlier in HTK-AD versus RS ( p < .05); thus, satisfaction was increased. The final survival rate showed no difference between 2 groups.

CONCLUSION

Histidine-tryptophan-ketoglutarate solution with adenosine triphosphate and deferoxamine is superior to RS for hair graft preservation because it improves graft viability and alleviates postsurgical shedding.

Abdominal Organ Preservation Solutions in the Age of Machine Perfusion

The past decade has been the foreground for a radical revolution in the field of preservation in abdominal organ transplantation. Perfusion has increasingly replaced static cold storage as the preferred and even gold standard preservation method for marginal-quality organs. Perfusion is dynamic and offers several advantages in comparison with static cold storage. These include the ability to provide a continuous supply of new metabolic substrates, clear metabolic waste products, and perform some degree of organ viability assessment before actual transplantation in the recipient. At the same time, the ongoing importance of static cold storage cannot be overlooked, in particular when it comes to logistical and technical convenience and cost, not to mention the fact that it continues to work well for the majority of transplant allografts. The present review article provides an overview of the fundamental concepts of organ preservation, providing a brief history of static cold preservation and description of the principles behind and basic components of cold preservation solutions. An evaluation of current evidence supporting the use of different preservation solutions in abdominal organ transplantation is provided. As well, the range of solutions used for machine perfusion of abdominal organs is described, as are variations in their compositions related to changing metabolic needs paralleling the raising of the temperature of the perfusate from hypothermic to normothermic range. Finally, appraisal of new preservation solutions that are on the horizon is provided.

Clinical Evaluation of an HTK Solution for Liver Transplantation: A Phase 3 Randomized Pilot Clinical Trial Study

BACKGROUND

Organ preservation solutions are not easily accessible in Iran, similar to many resource-limited countries. We aimed to evaluate the efficacy of a locally-produced HTK solution among adult liver transplantation candidates in a pilot clinical trial study.

METHODS

Adult patients undergoing liver transplantation were randomly allocated into two groups. One received the HTK solution (PharMedCina Inc., Shiraz, Iran), and the second received the commercially available HTK solution (Custodiol ®).

RESULTS

Overall, 28 individuals entered the study, including 11 and 9 males (78.6% and 64.3%) in the Custodiol® and local HTK groups, respectively. Clinical characteristics, including postoperative biliary complications, reperfusion syndrome, infection and primary non-function (PNF) rates, amount of intraoperative bleeding, length of hospital and ICU stay, peak aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and duration of follow-up were similar between the two groups (P>0.05). One patient died in the locally-produced HTK group. The patient underwent re-transplantation 20 days after his first liver transplantation due to PNF. Two patients died in the Custodiol group, both due to PNF of the liver, which occurred five and three days after transplantation. The two groups did not show any difference regarding serum levels of AST, ALT, alkaline phosphatase (ALP), bilirubin, platelet count, prothrombin time and international normalized ratio, white blood cell count, blood urea nitrogen, and creatinine on the first postoperative day and on the day of discharge (P>0.05).

CONCLUSION

Based on the findings of this pilot study with the current sample size, no statistically significant difference was found between our locally-produced HTK solution and Custodiol® regarding clinical outcomes.

Addition of oh8dG to Cardioplegia Attenuated Myocardial Oxidative Injury through the Inhibition of Sodium Bicarbonate Cotransporter Activity

The biomarker 8-hydroxy-2′-deoxyguanosine (oh8dG) is derived from oxidized nucleic acids or products of oxidant-mediated DNA damage. Enhanced sodium bicarbonate cotransporter (NBC) activity is caused by reactive oxygen species (ROS) production in ventricular myocytes. Thus, we hypothesized that cardioplegia-solution-mediated ROS generation may be involved in the regulation of NBC activity in cardiomyocytes and that oh8dG treatment may modulate ROS and associated NBC activity. Langendorff-free cardioplegia-arrested cardiac strips and cardiomyocytes were isolated to determine the NBC activity and effects of oh8dG on oxidative-stress-mediated cardiac damage markers. We first determined the histidine-tryptophan-ketoglutarate (HTK) solution mediated NBC activity in cardiac strips and cells. The oh8dG treatment attenuated NBC activity in the electroneutral or electrogenic form of NBC. Additionally, exposure to HTK solution induced ROS, whereas co-administration of oh8dG attenuated ROS-mediated NBC activity, reduced ROS levels, and decreased the expression of apoptotic markers and fibrosis-associated proteins in cardiac cells. The oh8dG-administrated cardiac tissues were also protected from enhanced HTK-induced damage markers, heat shock protein 60 and polyADP-ribose. Our results show that oh8dG has a protective role against myocardial oxidative damage and provides a useful treatment strategy for restoring cardiac function.

Bryostatin-1 Attenuates Ischemia-Elicited Neutrophil Transmigration and Ameliorates Graft Injury after Kidney Transplantation

Ischemia reperfusion injury (IRI) is a form of sterile inflammation whose severity determines short- and long-term graft fates in kidney transplantation. Neutrophils are now recognized as a key cell type mediating early graft injury, which activates further innate immune responses and intensifies acquired immunity and alloimmunity. Since the macrolide Bryostatin-1 has been shown to block neutrophil transmigration, we aimed to determine whether these findings could be translated to the field of kidney transplantation. To study the effects of Bryostatin-1 on ischemia-elicited neutrophil transmigration, an in vitro model of hypoxia and normoxia was equipped with human endothelial cells and neutrophils. To translate these findings, a porcine renal autotransplantation model with eight hours of reperfusion was used to study neutrophil infiltration in vivo. Graft-specific treatment using Bryostatin-1 (100 nM) was applied during static cold storage. Bryostatin-1 dose-dependently blocked neutrophil activation and transmigration over ischemically challenged endothelial cell monolayers. When applied to porcine renal autografts, Bryostatin-1 reduced neutrophil graft infiltration, attenuated histological and ultrastructural damage, and improved renal function. Our novel findings demonstrate that Bryostatin-1 is a promising pharmacological candidate for graft-specific treatment in kidney transplantation, as it provides protection by blocking neutrophil infiltration and attenuating functional graft injury.

Ex-vivo Kidney Machine Perfusion: Therapeutic Potential

Kidney transplantation remains the gold standard treatment for patients suffering from end-stage kidney disease. To meet the constantly growing organ demands grafts donated after circulatory death (DCD) or retrieved from extended criteria donors (ECD) are increasingly utilized. Not surprisingly, usage of those organs is challenging due to their susceptibility to ischemia-reperfusion injury, high immunogenicity, and demanding immune regulation after implantation. Lately, a lot of effort has been put into improvement of kidney preservation strategies. After demonstrating a definite advantage over static cold storage in reduction of delayed graft function rates in randomized-controlled clinical trials, hypothermic machine perfusion has already found its place in clinical practice of kidney transplantation. Nevertheless, an active investigation of perfusion variables, such as temperature (normothermic or subnormothermic), oxygen supply and perfusate composition, is already bringing evidence that ex-vivo machine perfusion has a potential not only to maintain kidney viability, but also serve as a platform for organ conditioning, targeted treatment and even improve its quality. Many different therapies, including pharmacological agents, gene therapy, mesenchymal stromal cells, or nanoparticles (NPs), have been successfully delivered directly to the kidney during ex-vivo machine perfusion in experimental models, making a big step toward achievement of two main goals in transplant surgery: minimization of graft ischemia-reperfusion injury and reduction of immunogenicity (or even reaching tolerance). In this comprehensive review current state of evidence regarding ex-vivo kidney machine perfusion and its capacity in kidney graft treatment is presented. Moreover, challenges in application of these novel techniques in clinical practice are discussed.

The Phenolic Antioxidant 3,5-dihydroxy-4-methoxybenzyl Alcohol (DHMBA) Prevents Enterocyte Cell Death under Oxygen-Dissolving Cold Conditions through Polyphyletic Antioxidant Actions

Cold preservation in University of Wisconsin (UW) solution is not enough to maintain the viability of the small intestine, due to the oxidative stress. The novel phenolic antioxidant 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA) has dual properties to reduce oxidative stress, radical scavenging, and antioxidant protein induction, in other cells. This study was designed to determine whether DHMBA reduces cold preservation injury of enterocytes, and to identify the effector site. Enterocytes were subjected to 48-h cold preservation under atmosphere in UW solution (±DHMBA), and then returned to normal culture to replicate reperfusion of the small intestine after cold preservation. At the end of cold preservation (ECP) and at 1, 3, 6, and 72 h after rewarming (R1h, R3h, R6h, and R72h), we evaluated cell function and the injury mechanism. The results showed that DHMBA protected mitochondrial function mainly during cold preservation, and suppressed cell death after rewarming, as shown by the MTT, ATP, mitochondrial membrane potential, LDH, and lipid peroxidation assays, together with enhanced survival signals (PI3K, Akt, p70S6K) and induction of antioxidant proteins (HO-1, NQO-1, TRX-1). We found that DHMBA mitigates the cold-induced injury of enterocytes by protecting the mitochondria through direct and indirect antioxidative activities.

Tryptophan Metabolism via Kynurenine Pathway: Role in Solid Organ Transplantation

Solid organ transplantation is a gold standard treatment for patients suffering from an end-stage organ disease. Patient and graft survival have vastly improved during the last couple of decades; however, the field of transplantation still encounters several unique challenges, such as a shortage of transplantable organs and increasing pool of extended criteria donor (ECD) organs, which are extremely prone to ischemia-reperfusion injury (IRI), risk of graft rejection and challenges in immune regulation. Moreover, accurate and specific biomarkers, which can timely predict allograft dysfunction and/or rejection, are lacking. The essential amino acid tryptophan and, especially, its metabolites via the kynurenine pathway has been widely studied as a contributor and a therapeutic target in various diseases, such as neuropsychiatric, autoimmune disorders, allergies, infections and malignancies. The tryptophan-kynurenine pathway has also gained interest in solid organ transplantation and a variety of experimental studies investigating its role both in IRI and immune regulation after allograft implantation was first published. In this review, the current evidence regarding the role of tryptophan and its metabolites in solid organ transplantation is presented, giving insights into molecular mechanisms and into therapeutic and diagnostic/prognostic possibilities.

The relevance between graft preservation solutions and QTc interval during living donor kidney transplantation and rat cardiomyocytes sampling

BACKGROUND

The purpose of the retrospective study was to identify the impacts of different solutions on the electrocardiogram and cardiovascular changes. Moreover, the differences between these solutions were analyzed by examining their impacts on rat ventricular cardiomyocytes.

METHODS

Eighty renal transplant patients were evaluated retrospectively. The patients were divided into two groups: Group UW (n =40) used the University of Wisconsin solution, and Group HTK (n =40) used the Histidine-Tryptophan-Ketoglutarate solution. Electrocardiograms of the subjects were obtained three times at different periods; during the pre-perfusion, intraoperative kidney reperfusion, and postperfusion phase at the end of the surgery. Any Electrocardiogram or cardiovascular alterations were noted and analyzed. Adult male Wistar rats were used for in vitro experiments. Myocyte contractility, action potentials, and membrane current were recorded in enzymatically isolated ventricular myocytes.

RESULTS

Sinus bradycardia was detected in 19 patients of Group UW, while there was short-term asystole in eight patients. However, no cardiac changes were observed in Group HTK patients. In both Groups, reperfusion and postperfusion corrected QT (QTc) intervals were different from pre-perfusion QTc intervals. Group UW patients' reperfusion and postperfusion QTc's values were higher than those of the Group HTK patients. In rat myocytes, prominent asystole episodes were observed at specific concentrations of the UW solution compared to the HTK solution. The UW solution depolarized the resting membrane potential significantly and decreased the peak value of action potential, whereas the HTK solution did not elicit a significant change in those parameters. Accordingly, the UW solution elicited a significant inward current at -70 mV, while the HTK solution activated only a modest current, which may not change the membrane potential.

CONCLUSION

Prolongation of QTc intervals was detected with reperfusion in both groups according to electrocardiography analysis. However, the QTc interval was observed to be longer in cases using the UW solution and required intervention intraoperatively. HIPPOKRATIA 2021, 25 (1):22-30.