A propensity score matched analysis of liver transplantation outcomes in the setting of preservation solution shortage.

The recent shortage of the University of Wisconsin (UW) solution prompted increased utilization of histidine-tryptophan-ketoglutarate (HTK) solution for liver graft preservation. This contemporary study analyzed deceased donor liver transplant outcomes following preservation with HTK vs UW. Patients receiving deceased donor liver transplantations between January 1, 2019, and June 30, 2022, were retrospectively identified utilizing the Organ Procurement and Transplant Network database, stratified by preservation with HTK vs UW, and a propensity score matching analysis was performed. Outcomes assessed included rates of primary nonfunction, graft survival, and patient survival. There were 4447 patients in each cohort. Primary nonfunction occurred in 60 (1.35%) patients in the HTK group vs 25 (0.54%) in the UW group (P < .001). HTK was associated with lower 90-day graft survival (94.39% vs 96.09%; P < .001) and 90-day patient survival (95.97% vs 97.38%; P = .001). Unmatched donation after cardiac death-specific analysis of HTK vs UW demonstrated respective rates of primary nonfunction of 1.63% vs 0.82% (P = .20), 90-day graft survival of 92.50% vs 95.29% (P = .069), and 90-day patient survival of 93.90% vs 96.35% (P = .077). These results suggest that HTK may not be an equivalent preservation solution for deceased donor liver transplantation.

Assessing Kidney Transplantation Using ECMO-Supported Donors Within a KDPI-Based Allocation System.

Background: Organ donors supported by extracorporeal membrane oxygenation (ECMO) have historically been considered high-risk and are judiciously utilized. This study examines transplant outcomes using renal allografts from donors supported on ECMO for nondonation purposes. Methods: Retrospective review of the Gift of Life (Pennsylvania, New Jersey, Delaware) organ procurement organization database, cross-referenced to the Organ Procurement and Transplantation Network database, assessed kidney transplants using donors supported on venoarterial (VA) and venovenous (VV) ECMO for nondonation purposes. Transplants using VA- and VV-ECMO donors were compared with Kidney Donor Profile Index (KDPI)-stratified non-ECMO donors. Regression modeling of the entire ECMO and non-ECMO populations assessed ECMO as predictive of graft survival. Additional regression of the ECMO population alone assessed for donor features associated with graft survival. Results: Seventy-eight ECMO donors yielded 128 kidney transplants (VA: 80, VV: 48). Comparing outcomes using these donors to kidney transplants using organs from KDPI-stratified non-ECMO donors, VA- and VV-ECMO donor grafts conferred similar rates of delayed graft function and posttransplant renal function to KDPI-matched non-ECMO counterparts. VA-ECMO kidneys demonstrated superior graft survival compared with the lowest-quality (KDPI 86%-100%) non-ECMO kidneys and similar graft survival to KDPI <85% non-ECMO kidneys. VV-ECMO showed inferior graft survival to all but the lowest-quality (KDPI 86%-100%) non-ECMO kidneys. VV-ECMO, but not VA-ECMO, was associated with increased risk of graft loss on multivariable regression (hazard ratios-VA: 1.02, VV: 2.18). Higher KDPI, advanced age, increased body mass index, hypertension, and diabetes were identified as high-risk features of ECMO donors. Conclusions: Kidney transplantation using appropriately selected ECMO donors can safely expand the donor pool. Ongoing studies are necessary to determine best practice patterns using kidneys from these donors.

Extracorporeal membrane oxygenation for cardiopulmonary failure in organ donation: Assessing liver transplant outcomes.

Liver transplantation continues to face significant organ shortages and efficient utilization of marginal donors is paramount. This study evaluates the practice patterns and outcomes in liver transplantation when utilizing allografts from marginal donors who required extracorporeal membrane oxygenation (ECMO) support. We performed a retrospective review of the Gift of Life (PA, NJ, DE) organ-procuring organization database for transplants performed using donors supported on ECMO for nondonation purposes. These were cross-referenced to the transplant recipients within the Organ Procurement and Transplantation Network database, and the outcomes of liver transplants using donors on ECMO support were compared with those not requiring ECMO. Organ use and nonuse patterns were then evaluated in ECMO-supported donors, identifying the factors associated with nonuse compared with the factors associated with graft failure. Thirty-nine of the 84 ECMO-supported donors contributing at least one intra-abdominal organ for transplant donated a liver. Graft survival and patient survival up to 5 years were comparable between transplants from ECMO and non-ECMO-supported donors, and no cases of primary nonfunction were seen in the ECMO group. ECMO support was not associated with 1-year graft failure on regression modeling. Additional regression analyses within the ECMO donor population identified bacteremia (HR: 19.81) and elevated total bilirubin at donation (HR: 2.44) as predictive of post-transplant graft failure. Livers from donors supported on ECMO before donation appear safe to use in select transplant settings. Better understanding of the impact of predonation ECMO on liver allograft function will help guide the optimal use of these scarcely used donors.

Reduced Rates of Post-Transplant Recurrent Hepatocellular Carcinoma in Non-Alcoholic Steatohepatitis: A Propensity Score Matched Analysis.

Non-alcoholic steatohepatitis (NASH)-related hepatocellular carcinoma (HCC) has become the second leading cause of HCC-related liver transplantation in the United States. This study investigated post-transplant recurrence and survival for patients transplanted for NASH-related HCC compared to non-NASH HCC etiologies. Retrospective review of the United Network for Organ Sharing (UNOS) Organ Procurement and Transplantation Network (OPTN) database identified 7,461 patients with HCC-1,405 with underlying NASH and 6,086 with non-NASH underlying diseases. After propensity score matching (PSM) to account for patient- and tumor-related confounders 1,175 remained in each group. Primary outcomes assessed were recurrence rate and recurrence-free survival. Recurrent malignancy at 5 years post-transplant was lower in NASH compared to non-NASH patients (5.80 vs. 9.41%, p = 0.01). Recurrence-free survival, however, was similar at 5 years between groups. Patients with NASH-related HCC were less likely to have post-transplant recurrence than their non-NASH counterparts, although recurrence-free survival was similar at 5 years.

Evaluating Outcomes Related to Donor and Recipient Metabolic Environment: Macrosteatotic Allografts and Nonalcoholic Steatohepatitis.

The increasing prevalence of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) affects both recipient and donor populations in liver transplantation. Presently, it is unclear whether transplantation of macrosteatotic allografts is affected by the metabolic milieu of liver transplant recipients. This study investigates fatty liver disease at the intersection of donor and recipient. A retrospective review of the Organ Procurement and Transplantation database identified 5167 NASH and 26,289 non-NASH transplant recipients who received transplants from January 1, 2004, to June 12, 2020. A total of 12,569 donors had allografts with no macrosteatosis (<5%), 16,140 had mild macrosteatosis (5%-29%), and 2747 had moderate to severe macrosteatosis (≥30%). Comparing recipients with NASH to propensity score-matched (PSM) recipients without NASH demonstrated noninferior graft and patient survival up to 10 years in patients with NASH. Similar trends were observed in subgroup analyses of transplants within each strata of allograft macrosteatosis. Assessing allograft macrosteatosis specifically in the NASH population demonstrated that allografts with ≥30% macrosteatosis were associated with reduced early graft survival (30 days, 93.32% versus 96.54% [P = 0.02]; 1 year, 84.53% versus 88.99% [P = 0.05]) compared with PSM grafts with <30% macrosteatosis. Long-term graft survival at 5 and 10 years, however, was similar. The use of carefully selected macrosteatotic allografts can be successful in both recipients with NASH and recipients without NASH. The metabolic environment of patients with NASH does not appear to adversely affect outcomes with regard to the allograft when controlled for numerous confounders. It is, however, important to remain cognizant of the potential for high-risk macrosteatotic allografts to negatively affect outcomes.

Limited Expansion of Human Hepatocytes in FAH/RAG2-Deficient Swine.

The mammalian liver's regenerative ability has led researchers to engineer animals as incubators for expansion of human hepatocytes. The expansion properties of human hepatocytes in immunodeficient mice are well known. However, little has been reported about larger animals that are more scalable and practical for clinical purposes. Therefore, we engineered immunodeficient swine to support expansion of human hepatocytes and identify barriers to their clinical application. Immunodeficient swine were engineered by knockout of the recombinase-activating gene 2 (RAG2) and fumarylacetoacetate hydrolase (FAH). Immature human hepatocytes (ihHCs) were injected into fetal swine by intrauterine cell transplantation (IUCT) at day 40 of gestation. Human albumin was measured as a marker of engraftment. Cytotoxicity against ihHCs was measured in transplanted piglets and control swine. We initially detected higher levels of human albumin in cord blood of newborn FAH/RAG2-deficient (FR) pigs compared with immunocompetent controls (196.26 ng/dL vs. 39.29 ng/dL, p = 0.008), indicating successful engraftment of ihHCs after IUCT and adaptive immunity in the fetus. Although rare hepatocytes staining positive for human albumin were observed, levels of human albumin did not rise after birth, but declined, suggesting rejection of xenografted ihHCs. Cytotoxicity against ihHCs increased after birth by 3.8% (95% CI: [2.1%-5.4%], p < 0.001) and inversely correlated with declining levels of human albumin (p = 2.1 × 10-5, R2 = 0.17). Circulating numbers of T cells and B cells were negligible in FR pigs. However, circulating natural killer (NK) cells exerted cytotoxicity against ihHCs. NK cell activity was lower in immunodeficient piglets after IUCT than in naive controls (30.4% vs. 40.1%, p = 0.011, 95% CI for difference [2.7%-16.7%]). In conclusion, ihHCs were successfully engrafted in FR swine after IUCT. NK cells were a significant barrier to expansion of hepatocytes. New approaches are needed to overcome this hurdle and allow large-scale expansion of human hepatocytes in immunodeficient swine. Impact statement There is currently a need for robust expansion of human hepatocytes. We describe an immunodeficient swine model into which we engrafted immature human hepatocytes (ihHCs). We identified the mechanism of the eventual graft rejection by the intact NK cell population, which has not been previously shown to have a significant role in xenograft rejection. By both improving engraftment and reducing NK cell-mediated cytotoxicity toward the graft through intrauterine cell transfer, we confirmed the presence of residual adaptive immunity in this model of immunodeficiency and the ability to induce hyposensitization in the NK cell population by taking advantage of the fetal microenvironment.

Access to direct-acting antivirals for hepatitis C-negative transplant recipients receiving organs from hepatitis C-viremic donors.

PURPOSE: A barrier to using organs from hepatitis C virus (HCV)-viremic donors is the high cost of direct-acting antivirals (DAAs) and concerns about access for recipients after transplantation. The purpose of this study was to evaluate access, cost, and timing for HCV DAAs following transplantation. METHODS: This was a single-center, retrospective study of HCV-negative adult transplant recipients from June 2017 to December 2019 who received grafts from HCV-viremic and/or HCV-seropositive individuals and became HCV viremic after transplantation. RESULTS: Between June 2017 and December 2019, there were 60 HCV-negative transplant recipients who became viremic after receiving grafts from HCV-viremic or HCV-seropositive donors. Thirty-eight patients met the inclusion criteria (n = 25 with liver transplants, n = 6 with lung transplants, n = 4 with simultaneous liver and kidney transplants, and n = 3 with kidney transplants). Of these patients, 23 had commercial insurance, 13 had Medicare, and 2 had Medicaid. All patients ultimately received insurance coverage for treatment; however, 36 (95%) required prior authorization and 9 (24%) required appeals to obtain insurance coverage. The median time from DAA prescription to insurance approval was 6 days. The median time from transplantation to start of treatment was 29 days (range, 0-84 days). Patients with Medicaid insurance had a significantly longer time to insurance approval (31.5 vs 6 days, P = 0.007). The average out-of-pocket cost to patients was less than $10 a month after patient assistance. All patients who completed treatment and 12-week follow-up after treatment achieved a sustained virologic response (n = 36). CONCLUSION: In this study, all HCV-negative recipients who developed HCV following transplantation had access to DAA therapy, with the majority starting treatment in the first month after transplantation.

Simultaneous liver kidney allocation policy and the Safety Net: an early examination of utilization and outcomes in the United States.

Rates of simultaneous liver kidney (SLK) transplantation in the United States have progressively risen. On 8/10/17, the Organ Procurement and Transplantation Network implemented a policy defining criteria for SLK, with a "Safety Net" to prioritize kidney allocation to liver recipients with ongoing renal failure. We performed a retrospective review of the United Network for Organ Sharing (UNOS) database to evaluate policy impact on SLK, kidney after liver (KAL) and kidney transplant alone (KTA). Rates and outcomes of SLK and KAL transplants were compared, as was utilization of high-quality kidney allografts with Kidney Donor Profile Indices (KDPI) <35%. Here, SLK transplants comprised 9.0% and 4.5% of total postpolicy liver and kidney transplants compared to 10.2% and 5.5% prior. Policy enactment did not affect 1-year graft or patient survival for SLK and KAL populations. Less postpolicy SLK transplants utilized high-quality kidney allografts; in all transplant settings, outcomes using high-quality grafts remained stable. These findings suggest that policy implementation has reduced kidney allograft use in SLK transplantation, although both SLK and KAL rates have recently increased. Despite decreased high-quality kidney allograft use, SLK and KAL outcomes have remained stable. Additional studies and long-term follow-up will ensure optimal organ access and sharing.

Robotic Full Lobe Hepatectomy With Natural Orifice Extraction: Case Series Describing the Novel Technique of Robotic Major Hepatectomy and Transvaginal Specimen Extraction.

MINI-ABSTRACT: A minimally invasive approach to partial hepatectomy with transvaginal specimen extraction is safe and feasible with the potential to improve the cosmetic outcome, minimize postoperative narcotic utilization, and shorten hospital length of stay. This series describes the initial experience using this novel technique.

Kidney Allocation Policy: Past, Present, and Future.

Despite an increase in the number of kidney transplants performed annually, there remain more than 90,000 individuals awaiting transplantation in the United States. As kidney transplantation has evolved, so has kidney allocation policies. The Kidney Allocation System, which was introduced in 2014, made significant strides to improve utility and equity, but regional and geographic disparities remain. Further modifications eliminating donor service areas have been introduced. Moving forward, systems involving continuous distribution and artificial intelligence may provide further advancement toward an ideal allocation system.

Hepatitis C-positive donor liver transplantation for hepatitis C seronegative recipients.

BACKGROUND: The opioid crisis has led to an increase in hepatitis C virus-positive donors in the past decade. Whereas historically hepatitis C seropositive organs were routinely discarded, the advent of direct-acting antiviral agents has notably expanded the utilization of organs from donors with hepatitis C. There has been growing experience with liver transplantation (LT) from hepatitis C seropositive donors to hepatitis C seropositive recipients. However, data remain limited on LT from hepatitis C seropositive or hepatitis C ribonucleic acid positive donors to hepatitis C seronegative recipients. METHODS: We performed a retrospective study of 26 hepatitis C seronegative recipients who received hepatitis C seropositive donor livers followed by preemptive antiviral therapy with direct-acting antiviral treatment at the Johns Hopkins Hospital Comprehensive Transplant Center from January 1, 2017, to August 31, 2019. RESULTS: Twenty-five of the 26 recipients are alive with proper graft function; 20 of them received livers from hepatitis C nucleic acid testing positive donors. All 12 recipients who completed their direct-acting antiviral courses and have reached sufficient follow-up for sustained virologic response have achieved sustained virologic response. Nine of our recipients have either completed direct-acting antiviral treatment without sufficient follow-up time for sustained virologic response or are undergoing direct-acting antiviral treatment. One patient is awaiting antiviral treatment initiation pending insurance approval. Of note, 11 of 12 patients with sustained virologic response received a hepatitis C nucleic acid testing positive donor liver. CONCLUSION: Hepatitis C seronegative patients who receive a hepatitis C seropositive or hepatitis C nucleic acid testing positive liver allograft can enjoy good short-term outcomes with hepatitis C cure following direct-acting antiviral treatment.

Pediatric deceased donor kidney transplant outcomes under the Kidney Allocation System.

The Kidney Allocation System (KAS) has resulted in fewer pediatric kidneys being allocated to pediatric deceased donor kidney transplant (pDDKT) recipients. This had prompted concerns that post-pDDKT outcomes may worsen. To study this, we used SRTR data to compare the outcomes of 953 pre-KAS pDDKT (age <18 years) recipients (December 4, 2012-December 3, 2014) with the outcomes of 934 post-KAS pDDKT recipients (December 4, 2014-December 3, 2016). We analyzed mortality and graft loss by using Cox regression, delayed graft function (DGF) by using logistic regression, and length of stay (LOS) by using negative binomial regression. Post-KAS recipients had longer pretransplant dialysis times (median 1.26 vs 1.07 years, P = .02) and were more often cPRA 100% (2.0% vs 0.1%, P = .001). Post-KAS recipients had less graft loss than pre-KAS recipients (hazard ratio [HR]: 0.35 0.540.83 , P = .005) but no statistically significant differences in mortality (HR: 0.29 0.721.83 , P = .5), DGF (odds ratio: 0.93 1.321.93 , P = .2), and LOS (LOS ratio: 0.96 1.061.19 , P = .4). After adjusting for donor-recipient characteristics, there were no statistically significant post-KAS differences in mortality (adjusted HR: 0.37 1.042.92 , P = .9), DGF (adjusted odds ratio: 0.94 1.412.13 , P = .1), or LOS (adjusted LOS ratio: 0.93 1.041.16 , P = .5). However, post-KAS pDDKT recipients still had less graft loss (adjusted HR: 0.38 0.590.91 , P = .02). KAS has had a mixed effect on short-term posttransplant outcomes for pDDKT recipients, although our results are limited by only 2 years of posttransplant follow-up.

Autologous Gene and Cell Therapy Provides Safe and Long-Term Curative Therapy in A Large Pig Model of Hereditary Tyrosinemia Type 1.

Orthotopic liver transplantation remains the only curative therapy for inborn errors of metabolism. Given the tremendous success for primary immunodeficiencies using ex-vivo gene therapy with lentiviral vectors, there is great interest in developing similar curative therapies for metabolic liver diseases. We have previously generated a pig model of hereditary tyrosinemia type 1 (HT1), an autosomal recessive disorder caused by deficiency of fumarylacetoacetate hydrolase (FAH). Using this model, we have demonstrated curative ex-vivo gene and cell therapy using a lentiviral vector to express FAH in autologous hepatocytes. To further evaluate the long-term clinical outcomes of this therapeutic approach, we continued to monitor one of these pigs over the course of three years. The animal continued to thrive off the protective drug NTBC, gaining weight appropriately, and maintaining sexual fecundity for the course of his life. The animal was euthanized 31 months after transplantation to perform a thorough biochemical and histological analysis. Biochemically, liver enzymes and alpha-fetoprotein levels remained normal and abhorrent metabolites specific to HT1 remained corrected. Liver histology showed no evidence of tumorigenicity and Masson's trichrome staining revealed minimal fibrosis and no evidence of cirrhosis. FAH-immunohistochemistry revealed complete repopulation of the liver by transplanted FAH-positive cells. A complete histopathological report on other organs, including kidney, revealed no abnormalities. This study is the first to demonstrate long-term safety and efficacy of hepatocyte-directed gene therapy in a large animal model. We conclude that hepatocyte-directed ex-vivo gene therapy is a rational choice for further exploration as an alternative therapeutic approach to whole organ transplantation for metabolic liver disease, including HT1.

Lentiviral Vector-mediated Gene Therapy of Hepatocytes Ex Vivo for Autologous Transplantation in Swine.

Gene therapy is an ideal choice to cure many inborn errors of metabolism of the liver. Ex-vivo, lentiviral vectors have been used successfully in the treatment of many hematopoietic diseases in humans, as their use offers stable transgene expression due to the vector's ability to integrate into the host genome. This method demonstrates the application of ex vivo gene therapy of hepatocytes to a large animal model of hereditary tyrosinemia type I. This process consists of 1) isolation of primary hepatocytes from the autologous donor/recipient animal, 2) ex vivo gene delivery via hepatocyte transduction with a lentiviral vector, and 3) autologous transplant of corrected hepatocytes via portal vein injection. Success of the method generally relies upon efficient and sterile removal of the liver resection, careful handling of the excised specimen for isolation of viable hepatocytes sufficient for re-engrafting, high-percentage transduction of the isolated cells, and aseptic surgical procedures throughout to prevent infection. Technical failure at any of these steps will result in low yield of viable transduced hepatocytes for autologous transplant or infection of the donor/recipient animal. The pig model of human type 1 hereditary tyrosinemia (HT-1) chosen for this approach is uniquely amenable to such a method, as even a small percentage of engraftment of corrected cells will lead to repopulation of the liver with healthy cells based on a powerful selective advantage over native-diseased hepatocytes. Although this growth selection will not be true for all indications, this approach is a foundation for expansion into other indications and allows for manipulation of this environment to address additional diseases, both within the liver and beyond, while controlling for exposure to viral vector and opportunity for off-target toxicity and tumorigenicity.

Association between kidney intracapsular pressure and ultrasound elastography.

BACKGROUND: Kidney congestion is a common pathophysiologic pathway of acute kidney injury (AKI) in sepsis and heart failure. There is no noninvasive tool to measure kidney intracapsular pressure (KIP) directly. METHODS: We evaluated the correlation of KIP with kidney elasticity measured by ultrasound surface wave elastography (USWE). We directly measured transcatheter KIP in three pigs at baseline and after bolus infusion of normal saline, norepinephrine, vasopressin, dopamine, and fenoldopam; infiltration of 2-L peritoneal dialysis solution in the intra-abdominal space; and venous, arterial, and ureteral clamping. KIP was compared with USWE wave speed. RESULTS: Only intra-abdominal installation of peritoneal dialysis fluid was associated with significant change in KIP (mean (95% CI) increase, 3.7 (3.2-4.2)] mmHg; P < .001). Although intraperitoneal pressure and KIP did not differ under any experimental condition, bladder pressure was consistently and significantly greater than KIP under all circumstances (mean (95% CI) bladder pressure vs. KIP, 3.8 (2.9-4.) mmHg; P < .001). USWE wave speed significantly correlated with KIP (adjusted coefficient of determination, 0.71; P < .001). Estimate (95% CI) USWE speed for KIP prediction stayed significant after adjustment for KIP hypertension (-0.8 (- 1.4 to - 0.2) m/s; P = .008) whereas systolic and diastolic blood pressures were not significant predictors of KIP. CONCLUSIONS: In a pilot study of the swine model, we found ultrasound surface wave elastography speed is significantly correlated with transcatheter measurement of kidney intracapsular and intra-abdominal pressures, while bladder pressure overestimated kidney intracapsular pressure.

Margin Proximity Correlates with Local Recurrence After Mastectomy for Patients Not Receiving Adjuvant Radiotherapy.

BACKGROUND: Although considerable evidence exists regarding margin status and reexcision for patients undergoing breast conservation therapy, few data address the impact of a close margin for patients undergoing mastectomy without postmastectomy radiotherapy. METHODS: This retrospective review identified 1147 patients who underwent 1206 mastectomies with negative final margins for breast cancer from 2006 to 2010. Margin distance was analyzed as a continuous variable and dichotomized variable ((≤2 vs >2 mm). Patients undergoing adjuvant radiation therapy were excluded from the study. Uni- and multivariable analyses were used to assess the association of reexcision, proximity of the final margin, adjuvant therapy, and other clinical and pathologic factors with local recurrence (LR). RESULTS: In 158 mastectomies (13.1%), a reexcision was performed for a close (n = 90) or positive (n = 68) margin. All but one were identified intraoperatively using frozen section analysis. The reexcision rates for skin- and nipple-sparing mastectomy (SSM/NSM) were higher than for simple mastectomy (SM) (19.8 vs 9.3%; p < 0.001). The overall 5-year risk for an LR was 3.8%. The risk was 3.1% for a margin greater than 2 mm and 11.2% for a margin of 2 mm or smaller. In the multivariable model, proximity of the final margin measured as a continuous variable was found to be a significant risk factor for LR (p = 0.009), whereas adjuvant endocrine therapy was found to be protective (p = 0.03). Intraoperative reexcision was not significant in the multivariable model (p = 0.23). CONCLUSIONS: For patients undergoing mastectomy for breast cancer, a wider final margin correlated with a reduced risk for LR. The rates for LR were similar between SSM/NSM and SM despite higher rates of intraoperative reexcision for SSM/NSM.

Distinguishing between Hepatic Inflammation and Fibrosis with MR Elastography.

Purpose To investigate the utility of magnetic resonance (MR) elastography-derived mechanical properties in the discrimination of hepatic inflammation and fibrosis in the early stages of chronic liver diseases. Materials and Methods All studies were approved by the institutional animal care and use committee. A total of 187 animals were studied, including 182 mice and five pigs. These animals represented five different liver diseases with a varying combination and extent of hepatic inflammation, fibrosis, congestion, and portal hypertension. Multifrequency three-dimensional MR elastography was performed, and shear stiffness, storage modulus, shear loss modulus, and damping ratio were calculated for all animals. Necroinflammation, fibrosis, and portal pressure were either histologically scored or biochemically and physically quantified in all animals. Two-sided Welch t tests were used to evaluate mean differences between disease and control groups. Spearman correlation analyses were used to evaluate the relationships between mechanical parameters and quantitative fibrosis extent (hydroxyproline concentration) and portal pressure. Results Liver stiffness and storage modulus increased with progressively developed fibrosis and portal hypertension (mean stiffness at 80 Hz and 48-week feeding, 0.51 kPa ± 0.12 in the steatohepatitis group vs 0.29 kPa ± 0.01 in the control group; P = .02). Damping ratio and shear loss modulus can be used to distinguish inflammation from fibrosis at early stages of disease, even before the development of histologically detectable necroinflammation and fibrosis (mean damping ratio at 80 Hz and 20-week feeding, 0.044 ± 0.012 in the steatohepatitis group vs 0.014 ± 0.008 in the control group; P < .001). Damping ratio and liver stiffness vary differently with respect to cause of portal hypertension (ie, congestion- or cirrhosis-induced hypertension). These differentiation abilities have frequency-dependent variations. Conclusion Liver stiffness and damping ratio measurements can extend hepatic MR elastography to potentially enable assessment of necroinflammatory, congestive, and fibrotic processes of chronic liver diseases. © RSNA, 2017 Online supplemental material is available for this article.

Chronic Phenotype Characterization of a Large-Animal Model of Hereditary Tyrosinemia Type 1.

Hereditary tyrosinemia type 1 (HT1) is an autosomal recessive disease caused by deficiency in fumarylacetoacetate hydrolase, the last enzyme in the tyrosine catabolic pathway. In this study, we investigated whether fumarylacetoacetate hydrolase deficient (FAH-/-) pigs, a novel large-animal model of HT1, develop fibrosis and cirrhosis characteristic of the human disease. FAH-/- pigs were treated with the protective drug 2-(2-nitro-4-trifluoromethylbenzoyl)-1, 3 cyclohexandione (NTBC) at a dose of 1 mg/kg per day initially after birth. After 30 days, they were assigned to one of three groups based on dosing of NTBC. Group 1 received ≥0.2 mg/kg per day, group 2 cycled on/off NTBC (0.05 mg/kg per day × 1 week/0 mg/kg per day × 3 weeks), and group 3 received no NTBC thereafter. Pigs were monitored for features of liver disease. Animals in group 1 continued to have weight gain and biochemical analyses comparable to wild-type pigs. Animals in group 2 had significant cessation of weight gain, abnormal biochemical test results, and various grades of fibrosis and cirrhosis. No evidence of hepatocellular carcinoma was detected. Group 3 animals declined rapidly, with acute liver failure. In conclusion, the FAH-/- pig is a large-animal model of HT1 with clinical characteristics that resemble the human phenotype. Under conditions of low-dose NTBC, FAH-/- pigs developed liver fibrosis and portal hypertension, and thus may serve as a large-animal model of chronic liver disease.

Curative ex vivo liver-directed gene therapy in a pig model of hereditary tyrosinemia type 1.

We tested the hypothesis that ex vivo hepatocyte gene therapy can correct the metabolic disorder in fumarylacetoacetate hydrolase-deficient (Fah(-/-)) pigs, a large animal model of hereditary tyrosinemia type 1 (HT1). Recipient Fah(-/-) pigs underwent partial liver resection and hepatocyte isolation by collagenase digestion. Hepatocytes were transduced with one or both of the lentiviral vectors expressing the therapeutic Fah and the reporter sodium-iodide symporter (Nis) genes under control of the thyroxine-binding globulin promoter. Pigs received autologous transplants of hepatocytes by portal vein infusion. After transplantation, the protective drug 2-(2-nitro-4-trifluoromethylbenzyol)-1,3 cyclohexanedione (NTBC) was withheld from recipient pigs to provide a selective advantage for expansion of corrected FAH(+) cells. Proliferation of transplanted cells, assessed by both immunohistochemistry and noninvasive positron emission tomography imaging of NIS-labeled cells, demonstrated near-complete liver repopulation by gene-corrected cells. Tyrosine and succinylacetone levels improved to within normal range, demonstrating complete correction of tyrosine metabolism. In addition, repopulation of the Fah(-/-) liver with transplanted cells inhibited the onset of severe fibrosis, a characteristic of nontransplanted Fah(-/-) pigs. This study demonstrates correction of disease in a pig model of metabolic liver disease by ex vivo gene therapy. To date, ex vivo gene therapy has only been successful in small animal models. We conclude that further exploration of ex vivo hepatocyte genetic correction is warranted for clinical use.

Characterization of a porcine model for associating liver partition and portal vein ligation for a staged hepatectomy.

BACKGROUND: Publications using the ALPPS (associating liver partition and portal vein ligation for a staged hepatectomy) procedure have demonstrated a future liver remnant growth of 40-160% in only 6-9 days. The present study aimed to develop and describe the first large animal model of ALPPS that can be used for future studies. METHODS: A total of 13 female domestic pigs underwent ALPPS stage 1 (portal vein division and parenchymal transection) followed by ALPPS stage 2 (completion left-extended hepatectomy) 7 days later. An abdominal computed tomography (CT) scan was performed immediately prior to ALPPS stage 1 surgery and again 7 days later to assess hypertrophy immediately prior to ALPPS stage 2 surgery. Blood samples, as well as tissue analysis for Ki-67, were performed. RESULTS: On CT volumetric analysis, the mean size of the future liver remnant (FLR) prior to ALPPS stage 1 was 21 ± 2% and 40 ± 6% prior to ALPPS stage 2. The median degree of growth was 75% with a mean kinetic growth rate of 11% per day. Liver weights at autopsy correlated well with CT volumetric analysis (r = 0.87). There was no significant difference in mean lab values [asparate aminotransferase (AST), alanine aminotransferase (ALT), ammonia, International Normalized Ratio (INR) or bilirubin] from baseline until immediately prior to ALPPS stage 2. Post ALPPS stage 2 there was a significant increase in INR from baseline 1.1 to 1.6 (P = 0.012). No post-operative deaths secondary to liver failure were observed. CONCLUSION: The present study describes the first reproducible large animal model of the ALPPS procedure. The degree of liver growth and the kinetic rate of growth were similar to that which has been demonstrated in human publications. This model will be valuable as future laboratory studies are performed.