Exception Policy Change Increased the Simultaneous Kidney-Liver Transplant Probability of Polycystic Disease in the Centers With High Median MELD at Transplantation.

BACKGROUND: In 2019, Organ Procurement and Transplantation Network/United Network for Organ Sharing changed the exception policy for liver allocation to the median model for end-stage liver disease at transplantation (MMaT). This study evaluated the effects of this change on-waitlist outcomes of simultaneous liver-kidney transplantation (SLKT) for patients with polycystic liver-kidney disease (PLKD). METHODS: Using the Organ Procurement and Transplantation Network/United Network for Organ Sharing registry, 317 patients with PLKD listed for SLKT between January 2016 and December 2021 were evaluated. Waitlist outcomes were compared between prepolicy (Era 1) and postpolicy (Era 2) eras. RESULTS: One-year transplant probability was significantly higher in Era 2 than in Era 1 (55.7% versus 37.9%; P  = 0.001), and the positive effect on transplant probability of Era 2 was significant after risk adjustment (adjusted hazard ratio, 1.76; 95% confidence interval, 1.22-2.54; P  = 0.002 [ref. Era 1]), whereas waitlist mortality was comparable. Transplant centers were separated into the high and low MMaT groups with a score of 29 (median MMaT) and transplant probability in each group between eras was compared. In the high MMaT transplant centers, the 1-y transplant probability was significantly higher in Era 2 (27.5% versus 52.4%; P  = 0.003). The positive effect remained significant in the high MMaT center group (adjusted hazard ratio, 2.79; 95% confidence interval, 1.43-5.46; P  = 0.003 [ref. Era 1]) but not in the low MMaT center group. Although there was a difference between center groups in Era 1 ( P  = 0.006), it became comparable in Era 2 ( P  = 0.54). CONCLUSIONS: The new policy increased 1-y SLKT probability in patients with PKLD and successfully reduced the disparities based on center location.

Improved Waitlist Outcomes in Liver Transplant Patients With Mid-MELD-Na Scores Listed in Centers Receptive to Use of Organs Donated After Circulatory Death.

BACKGROUND: Liver transplant (LT) using organs donated after circulatory death (DCD) has been increasing in the United States. We investigated whether transplant centers' receptiveness to use of DCD organs impacted patient outcomes. METHODS: Transplant centers were classified as very receptive (group 1), receptive (2), or less receptive (3) based on the DCD acceptance rate and DCD transplant percentage. Using organ procurement and transplantation network/UNOS registry data for 20 435 patients listed for LT from January 2020 to June 2022, we compared rates of 1-y transplant probability and waitlist mortality between groups, broken down by model for end-stage liver disease-sodium (MELD-Na) categories. RESULTS: In adjusted analyses, patients in group 1 centers with MELD-Na scores 6 to 29 were significantly more likely to undergo transplant than those in group 3 (aHR range 1.51-2.11, P < 0.001). Results were similar in comparisons between groups 1 and 2 (aHR range 1.41-1.81, P < 0.001) and between groups 2 and 3 with MELD-Na 15-24 (aHR 1.19-1.20, P < 0.007). Likewise, patients with MELD-Na score 20 to 29 in group 1 centers had lower waitlist mortality than those in group 3 (scores, 20-24: aHR, 0.71, P = 0.03; score, 25-29: aHR, 0.51, P < 0.001); those in group 1 also had lower waitlist mortality compared with group 2 (scores 20-24: aHR0.69, P = 0.02; scores 25-29: aHR 0.63, P = 0.03). One-year posttransplant survival of DCD LT patients did not vary significantly compared with donation after brain dead. CONCLUSIONS: We conclude that transplant centers' use of DCD livers can improve waitlist outcomes, particularly among mid-MELD-Na patients.

Effects of polyethylene glycol-20k IV solution on donor management in a canine model of donor brain death.

BACKGROUND: Traditionally, vasopressors and crystalloids have been used to stabilize brain dead donors; however, the use of crystalloid is fraught with complications. This study aimed to investigate the effectiveness of a newly developed impermeant solution, polyethylene glycol-20k IV solution (PEG-20k) for resuscitation and support of brain dead organ donors. METHODS: Brain death was induced in adult beagle dogs and a set volume of PEG-20k or crystalloid solution was given thereafter. The animals were then resuscitated over 16 h with vasopressors and crystalloid as necessary to maintain mean arterial pressure of 80-100 mmHg. The kidneys were procured and cold-stored for 24 h, after which they were analyzed using the isolated perfused kidney model. RESULTS: The study group required significantly less crystalloid volume and vasopressors while having less urine output and requiring less potassium supplementation than the control group. Though the two groups' mean arterial pressure and lactate levels were comparable, the study group's kidneys showed less preservation injury after short-term reperfusion indexed by decreased lactate dehydrogenase release and higher creatinine clearance than the control group. CONCLUSIONS: The use of polyethylene glycol-20k IV solution for resuscitating brain dead donors decreases cell swelling and improves intravascular volume, thereby improving end organ oxygen delivery before procurement and so preventing ischemia-reperfusion injury after transplantation.

Superior Survival Outcomes of a Polyethylene Glycol-20k Based Resuscitation Solution in a Preclinical Porcine Model of Lethal Hemorrhagic Shock.

OBJECTIVE: To compare early outcomes and 24-hour survival after LVR with the novel polyethylene glycol-20k-based crystalloid (PEG-20k), WB, or hextend in a preclinical model of lethal HS. BACKGROUND: Posttraumatic HS is a major cause of preventable death. current resuscitation strategies focus on restoring oxygen-carrying capacity (OCC) and coagulation with blood products. Our lab shows that PEG-20k is an effective non-sanguineous, LVR solution in acute models of HS through mechanisms targeting cell swelling-induced microcirculatory failure. METHODS: Male pigs underwent splenectomy followed by controlled hemorrhage until lactate reached 7.5-8.5 mmol/L. They were randomized to receive LVR with PEG-20k, WB, or Hextend. Surviving animals were recovered 4 hours post-LVR. Outcomes included 24-hour survival rates, mean arterial pressure, lactate, hemoglobin, and estimated intravascular volume changes. RESULTS: Twenty-four-hour survival rates were 100%, 16.7%, and 0% in the PEG-20k, WB, and Hextend groups, respectively (P= 0.001). PEG-20k significantly restored mean arterial press, intravascular volume, and capillary perfusion to baseline, compared to other groups. This caused complete lactate clearance despite decreased OCC. Neurological function was normal after next-day recovery in PEG-20k resuscitated pigs. CONCLUSION: Superior early and 24-hour outcomes were observed with PEG-20k LVR compared to WB and Hextend in a preclinical porcine model of lethal HS, despite decreased OCC from substantial volume-expansion. These findings demonstrate the importance of enhancing microcirculatory perfusion in early resuscitation strategies.

Refining murine heterotopic heart transplantation: A model to study ischemia and reperfusion injury in donation after circulatory death hearts.

Heart transplantation is a lifesaving procedure, which is limited by the availability of donor hearts. Using hearts from donors after circulatory death, which have sustained global ischemia, requires thorough studies on reliable and reproducible models that developing researchers may not have mastered. By combining the most recent literature and our recommendations based on observations and trials and errors, the methods here detail a sound in vivo heterotopic heart transplantation model for rats in which protective interventions on the ischemic heart can be studied, and thus allowing the scientific community to advance organ preservation research. Knowledge gathered from reproducible animal models allow for successful translation to clinical studies.

Cholangiocyte Epithelial to Mesenchymal Transition (EMT) is a potential molecular mechanism driving ischemic cholangiopathy in liver transplantation.

Donation after circulatory death (DCD) has expanded the donor pool for liver transplantation. However, ischemic cholangiopathy (IC) after DCD liver transplantation causes inferior outcomes. The molecular mechanisms of IC are currently unknown but may depend on ischemia-induced genetic reprograming of the biliary epithelium to mesenchymal-like cells. The main objective of this study was to determine if cholangiocytes undergo epithelial to mesenchymal transition (EMT) after exposure to DCD conditions and if this causally contributes to the phenotype of IC. Human cholangiocyte cultures were exposed to periods of warm and cold ischemia to mimic DCD liver donation. EMT was tested by assays of cell migration, cell morphology, and differential gene expression. Transplantation of syngeneic rat livers recovered under DCD conditions were evaluated for EMT changes by immunohistochemistry. Human cholangiocytes exposed to DCD conditions displayed migratory behavior and gene expression patterns consistent with EMT. E-cadherin and CK-7 expressions fell while N-cadherin, vimentin, TGFß, and SNAIL rose, starting 24 hours and peaking 1-3 weeks after exposure. Cholangiocyte morphology changed from cuboidal (epithelial) before to spindle shaped (mesenchymal) a week after ischemia. These changes were blocked by pretreating cells with the Transforming Growth Factor beta (TGFß) receptor antagonist Galunisertib (1 µM). Finally, rats with liver isografts cold stored for 20 hours in UW solution and exposed to warm ischemia (30 minutes) at recovery had elevated plasma bilirubin 1 week after transplantation and the liver tissue showed immunohistochemical evidence of early cholangiocyte EMT. Our findings show EMT occurs after exposure of human cholangiocytes to DCD conditions, which may be initiated by upstream signaling from autocrine derived TGFß to cause mesenchymal specific morphological and migratory changes.

Effects of a novel low volume resuscitation solutions on coagulation and platelet function.

BACKGROUND: Novel crystalloid solutions containing polyethylene glycol polymers (PEG-20k) produce dramatic resuscitation effects but dose-dependently produce a hypocoagulative state. The objective of this study was to examine possible mechanisms of this effect. Based on previous thromboelastography data, we hypothesize the effect is largely due to platelet interactions with the polymers. METHODS: Whole citrated blood from healthy volunteers was diluted ex-vivo 10% with crystalloids and tested for coagulation and platelet function. The specific tests included prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen and von Willebrand factor (vWf) activity, thrombin generation, thromboelastography with and without platelet mapping, platelet flow cytometry, and erythrocyte sedimentation rate. FINDINGS: Fibrinogen and vWF activities, PT, and aPTT were not affected by PEG-20k dilutions. Thrombin activity was mildly suppressed with PEG-20k (TTP- 20%). Platelet mapping demonstrated significantly greater % inhibition of both ADP and arachidonic acid-induced platelet aggregation with PEG-20k, but direct ADP-activated gpIIa/IIIb (PAC1) and P-selectin (CD62P) binding site expression was not altered. Mild dose-dependent suppression of TEG-MA was seen with PEG-20k using platelet poor plasma. Erythrocyte Sedimentation Rates (ESR) were dramatically accelerated after dilution with 10% PEG-20k, which was competitively blocked by smaller PEG polymers, suggesting nonspecific PEG-20k cell binding effects. CONCLUSIONS: PEG-20k creates a mild hypocoagulative state in whole blood at concentrations ≥10%, which may be due to platelet-PEG interactions at the IIb/IIIa interface with lesser effects on fibrin polymerization. This interaction may cause a functional thrombasthenia induced by nonspecific platelet surface passivation by the PEG polymer.

Acute resuscitation with polyethylene glycol-20k: A thromboelastographic analysis.

BACKGROUND: Previous ex vivo studies have shown that polyethylene glycol-20,000 Da (PEG-20k), a novel synthetic polymer that is highly effective for resuscitation, has a hypocoagulable effect on human blood. This study's objective was to determine the in vivo effects of PEG-20k-based resuscitation solutions on coagulation and platelet function in a porcine model of hemorrhagic shock. METHODS: Anesthetized pigs underwent controlled hemorrhage until the lactate reached 7 mmol/L or 50% to 55% of their estimated blood volume was removed. A laparotomy was performed to simulate tissue injury. Low volume resuscitation (LVR) was given with fluorescein isothiocyanate-labeled 10% PEG-20k solution (100 mg/mL) or Lactated Ringers, both delivered at volumes equal to 10% of the estimated blood volume (n = 5). Thromboelastography was performed after surgery (baseline), after hemorrhage, and 15 minutes, 120 minutes, and 240 minutes postresuscitation. Hemoglobin was measured to determine changes in plasma volume. Plasma PEG-20k concentration was measured by indicator dilution. RESULTS: Pigs given PEG-20k survived 2.6-fold longer than controls (p < 0.001) and had a significant increase in plasma volume demonstrated by the sustained drop in hemoglobin, relative to controls. Pigs resuscitated with LR died from hypotension an average of 90 minutes after resuscitation compared to the PEG-20k pigs, which all survived 240 minutes and were then euthanized with normal blood pressure and lactate. Administration of PEG-20k primarily decreased the thromboelastograph maximum amplitude, however this began to return toward baseline by 240 minutes. Peak plasma concentration of PEG-20k after LVR were 40% lower than predicted, based on simple dilution (5.7 mg/mL vs. 10 mg/mL) and the half-life was 59.6 minutes. CONCLUSION: These data demonstrate that acute resuscitation with PEG-20k significantly improves tolerance to hypovolemia but also decreases platelet function in the coagulation cascade, which was due, in part, to its volume expanding effects.

Assessment of trochanteric osteotomy fragment union after acetabular fracture surgery.

BACKGROUND: Trochanteric osteotomies are performed in conjunction with standard approaches to improve surgical exposure during open reduction and internal fixation (ORIF) of acetabular fractures. The literature on total hip arthroplasty reports nonunion rates as high as 30% associated with trochanteric osteotomies; however, few data exist regarding the outcomes of trochanteric osteotomies for acetabular fracture surgery. Our hypotheses were 1) patients receiving trochanteric osteotomies during ORIF of acetabular fractures have a low rate of nonunion of the osteotomy fragment, and 2) hip abduction precautions are not necessary with digastric type osteotomies. PATIENTS AND METHODS: A retrospective review was conducted to identify patients with acetabular fractures between July 2002 and June 2010 (n=734 fractures) who required trochanteric osteotomies (n=64, 9% of fractures). Forty-seven met inclusion criteria of adequate follow-up (>56days). No excluded patient experienced a complication. Fractures were classified using the Letournel-Judet classification system. RESULTS: Only seven (20%) of 35 patients who received digastric osteotomies had hip abduction precautions applied during the postoperative period. All study patients were shown to have radiographic union at the trochanteric osteotomy site (100% union rate, n=47). Hip abduction precautions intended to protect the osteotomy site and reduce the risk of nonunion and fixation failure were infrequently applied to patients with digastric osteotomies (20%) in this cohort. Multiple protective factors against nonunion were present in this study population compared with previous arthroplasty studies from other institutions. CONCLUSIONS: Trochanteric osteotomies are not associated with a significant nonunion rate, and digastric osteotomies might be safely managed without hip abduction precautions.

Essential metabolites of Mycobacterium tuberculosis and their mimics.

An organism requires a range of biomolecules for its growth. By definition, these are essential molecules which constitute the basic metabolic requirements of an organism. A small organic molecule with chemical similarity to that of an essential metabolite may bind to the enzyme that catalyzes its production and inhibit it, likely resulting in the stasis or death of the organism. Here, we report a high-throughput approach for identifying essential metabolites of an organism using genetic and biochemical approaches and then implement computational approaches to identify metabolite mimics. We generated and genotyped 5,126 Mycobacterium tuberculosis mutants and performed a statistical analysis to determine putative essential genes. The essential molecules of M. tuberculosis were classified as products of enzymes that are encoded by genes in this list. Although incomplete, as many enzymes of M. tuberculosis have yet to be identified and characterized, this is the first report of a large number of essential molecules of the organism. We identified essential metabolites of three distinct metabolic pathways in M. tuberculosis and selected molecules with chemical similarity using cheminformatics strategies that illustrate a variety of different pharmacophores. Our approach is aimed at systematic identification of essential molecules and their mimics as a blueprint for development of effective chemical probes of M. tuberculosis metabolism, with the ultimate goal of seeking drugs that can kill this pathogen. As an illustration of this approach, we report that compounds JFD01307SC and l-methionine-S-sulfoximine, which share chemical similarity with an essential molecule of M. tuberculosis, inhibited the growth of this organism at micromolar concentrations.