Citrin-deficient patient-derived induced pluripotent stem cells as a pathological liver model for congenital urea cycle disorders.

Citrin deficiency is a congenital secondary urea cycle disorder lacking useful disease models for effective treatment development. In this study, human induced pluripotent stem cells (iPSCs) were generated from two patients with citrin deficiency and differentiated into hepatocyte-like cells (HLCs). Citrin-deficient HLCs produced albumin and liver-specific markers but completely lacked citrin protein and expressed argininosuccinate synthase only weakly. In addition, ammonia concentrations in a medium cultured with citrin-deficient HLCs were higher than with control HLCs. Sodium pyruvate administration significantly reduced ammonia concentrations in the medium of citrin-deficient HLCs and slightly reduced ammonia in HLCs differentiated from control iPSCs, though this change was not significant. Our results suggest that sodium pyruvate may be an efficient treatment for patients with citrin deficiency. Citrin-deficient iPSCs are a pathological liver model for congenital urea cycle disorders to clarify pathogenesis and develop novel therapies.

Efficient protocol for the differentiation of kidney podocytes from induced pluripotent stem cells, involving the inhibition of mTOR.

The mechanistic/mammalian target of rapamycin (mTOR) is involved in a wide range of cellular processes. However, the role of mTOR in podocytes remains unclear. In this study, we aimed to clarify the role of mTOR in podocyte differentiation from human induced pluripotent stem cells (hiPSCs) and to establish an efficient differentiation protocol for human podocytes. We generated podocytes from hiPSCs by modifying protocol. The expression of the podocyte-specific slit membrane components nephrin and podocin was measured using PCR, western blotting, flow cytometry, and immunostaining; and the role of mTOR was evaluated using inhibitors of the mTOR pathway. Nephrin and podocin were found to be expressed in cells differentiated from hiPSCs, and their expression was increased by mTOR inhibitor treatment. S6, a downstream component of the mTOR pathway, was also found to be involved in podocyte differentiation. we evaluated its permeability to albumin, urea, and electrolytes. The induced podocytes were permeable to the small molecules, but only poorly permeable to albumin. We have shown that the mTOR pathway is involved in podocyte differentiation. Our monolayer podocyte differential protocol, using an mTOR inhibitor, provides a novel in vitro model for studies of kidney physiology and pathology.

The Induction of Parathyroid Cell Differentiation from Human Induced Pluripotent Stem Cells Promoted Via TGF-α/EGFR Signaling.

The parathyroid gland plays an essential role in mineral and bone metabolism. Cultivation of physiological human parathyroid cells has yet to be established and the method by which parathyroid cells differentiate from pluripotent stem cells remains uncertain. Therefore, it has been hard to clarify the mechanisms underlying the onset of parathyroid disorders, such as hyperparathyroidism. In this study, we developed a new method of parathyroid cell differentiation from human induced pluripotent stem (iPS) cells. Parathyroid cell differentiation occurred in accordance with embryologic development. Differentiated cells, which expressed the parathyroid hormone, adopted unique cell aggregation similar to the parathyroid gland. In addition, these differentiated cells were identified as calcium-sensing receptor (CaSR)/epithelial cell adhesion molecule (EpCAM) double-positive cells. Interestingly, stimulation with transforming growth factor-α (TGF-α), which is considered a causative molecule of parathyroid hyperplasia, increased the CaSR/EpCAM double-positive cells, but this effect was suppressed by erlotinib, which is an epidermal growth factor receptor (EGFR) inhibitor. These results suggest that TGF-α/EGFR signaling promotes parathyroid cell differentiation from iPS cells in a similar manner to parathyroid hyperplasia.

A multiple-funnels cell culture insert for the scale-up production of uniform cell spheroids.

INTRODUCTION: Formation of cell spheres is an important procedure in biomedical research. A large number of high-quality cell spheres of uniform size and shape are required for basic studies and therapeutic applications. Conventional approaches, including the hanging drop method and suspension culture, are used for cell sphere production. However, these methods are time consuming, cell spheres cannot be harvested easily, and it is difficult to control the size and geometry of cell spheres. To resolve these problems, a novel multiple-funnel cell culture insert was designed for size controlling, easy harvesting, and scale-up production of cell spheres. METHODS: The culture substrate has 680 micro-funnels with a 1-mm width top, 0.89 mm depth, and 0.5 mm square bottom. Mouse embryonic stem cells were used to test the newly developed device. The seeded embryonic stem cells settled at the downward medium surface toward the bottom opening and aggregated as embryoid bodies (EBs). For cell sphere harvest, the bottom of the culture insert was put in contact with the medium surface in another culture dish, and the medium in the device flowed down with cell spheres by hydrostatic pressure. RESULTS: Compact cell spheres with uniform size and shape were collected easily. The diameter of the spheres could be controlled by adjusting the seeding cell density. Spontaneous neural differentiation (nestin and Tju1) and retinoic acid-induced endodermal differentiation (Pdx-1 and insulin I) were improved in the EBs produced using the new insert compared to those in EBs produced by suspension culture. CONCLUSIONS: This novel cell culture insert shall improve future studies of cell spheres and benefit clinical applications of cell therapy.

Effects of Activin in Embryoid Bodies Expressing Fibroblast Growth Factor 5.

Nodal/activin signaling is indispensable for embryonic development. We examined what activin does to the embryoid bodies (EBs) produced from mouse embryonic stem cells (mESCs) expressing an epiblast marker. The EBs were produced by culturing mESCs by the hanging drop method for 24 hours. The resulting EBs were transferred onto gelatin-coated dishes and allowed to further differentiate. The 24-hour EBs showed a stronger expression of fibroblast growth factor (FGF)5 and Brachyury (specific to the epiblast) in comparison with mESCs. Treating the transferred EBs with activin A maintained transcript levels of FGF5 and Oct4, while inhibiting definitive endoderm differentiation. The activin A treatment reversed the endoderm differentiation induced by retinoic acid (RA), while the inhibition of nodal/activin signaling promoted RA-induced endoderm differentiation. Inhibition of nodal/activin signaling in EBs, including epiblast-like cells, promotes differentiation into the endoderm, facilitating the transition from the pluripotent state to specification of the endoderm.

Electrofusion of mesenchymal stem cells and islet cells for diabetes therapy: a rat model.

Islet transplantation is a minimally invasive treatment for severe diabetes. However, it often requires multiple donors to accomplish insulin-independence and the long-term results are not yet satisfying. Therefore, novel ways to overcome these problems have been explored. Isolated islets are fragile and susceptible to pro-apoptotic factors and poorly proliferative. In contrast, mesenchymal stem cells (MSCs) are highly proliferative, anti-apoptotic and pluripotent to differentiate toward various cell types, promote angiogenesis and modulate inflammation, thereby studied as an enhancer of islet function and engraftment. Electrofusion is an efficient method of cell fusion and nuclear reprogramming occurs in hybrid cells between different cell types. Therefore, we hypothesized that electrofusion between MSC and islet cells may yield robust islet cells for diabetes therapy. We establish a method of electrofusion between dispersed islet cells and MSCs in rats. The fusion cells maintained glucose-responsive insulin release for 20 days in vitro. Renal subcapsular transplantation of fusion cells prepared from suboptimal islet mass (1,000 islets) that did not correct hyperglycemia even if co-transplanted with MSCs, caused slow but consistent lowering of blood glucose with significant weight gain within the observation period in streptozotocin-induced diabetic rats. In the fusion cells between rat islet cells and mouse MSCs, RT-PCR showed new expression of both rat MSC-related genes and mouse ß-cell-related genes, indicating bidirectional reprogramming of both ß-cell and MSCs nuclei. Moreover, decreased caspase3 expression and new expression of Ki-67 in the islet cell nuclei suggested alleviated apoptosis and gain of proliferative capability, respectively. These results show that electrofusion between MSCs and islet cells yield special cells with ß-cell function and robustness of MSCs and seems feasible for novel therapeutic strategy for diabetes mellitus.

Immunoisolation effect of polyvinyl alcohol (PVA) macroencapsulated islets in type 1 diabetes therapy.

Islet transplantation has shown great success in the treatment of type 1 diabetes since the Edmonton protocol was established. However, it still has two major problems to overcome: the lack of organ donors and the side effects of immunosuppression. Encapsulated islets have emerged as a potential option for islet transplantation because it can, at least partly, overcome these two problems. Wistar rat islets suspended in 3% polyvinyl alcohol (PVA) hydrogel were frozen-thawed to make macroencapsulated islets (MEIs). The recovery rate, insulin content, and morphological change in culture medium with/without fresh human plasma (FHP) were measured in MEIs and free islets in vitro. In vivo, MEIs of either Wistar or Lewis rats were transplanted into the peritoneal cavity of streptozotocin (STZ)-induced diabetic Lewis rats and nonfasting blood glucose (NFBG), body weight, and histological evaluations were processed. FHP destroyed rat free islets but did not affect the islet morphology, islet recovery rate, or insulin content of rat MEIs. The transplantation of MEIs decreased the NFBG level and prevented body weight loss without a significant difference between the donor strains. Insulin-positive islets were observed in PVA MEIs 24 weeks after allotransplantation. These results suggest that PVA MEIs may be used as a cure for type 1 diabetes.

Difficulty in sustaining hepatic outflow in left lobe but not right lobe living donor liver transplantation.

BACKGROUND: Hepatic outflow block is one of the major complications leading to severe graft dysfunction after left lobe living donor liver transplantation (LDLT). METHODS: Medical records of 46 recipients of a left lobe LDLT were reviewed. The method of outflow reconstruction and post-transplant morphological changes of hepatic veins were investigated. The subjects were followed up until September 2008, with a median follow-up period of 2.0 yr (range: 0.5-5.9 yr). RESULTS: There were no multiple outflow tracts to be reconstructed, and the median caliber of the single orifices with or without venoplasty was 32.0 mm. The difference between the angle of hepatic veins to the sagittal plane measured on computed tomography was calculated for pre-operative donors and post-operative recipients a month after LDLT. Both left and middle hepatic veins showed a significantly greater change in angle than the right hepatic vein. Both left and middle hepatic veins more frequently showed a nearly flat wave form on Doppler study one month after LDLT. In the 46 recipients of left lobe grafts, three developed outflow block (6.5%). CONCLUSIONS: The middle and left hepatic veins tend to distort and stretch during graft regeneration. These characteristics seem to be associated with outflow disturbances.

Reduction of left-lateral segment from living donors for liver transplantation in infants weighing less than 7 kg: technical aspects and outcome.

LLS reduction has been frequently used in infants weighing <7 kg. Twenty recipients weighing <7 kg at the time of LDLT, median age 11.0 months and body weight 5.6 kg, were treated with an RLLS (n = 12) or LLS (n = 8) graft. Absolute indication of size reduction was that the estimated GRWR was >4.0%. Even if the preoperative GRWR was <4.0%, the RLLS graft was considered to ensure a size match. A flatfish-type LLS was preferred to a blowfish-type to make an RLLS graft for such a small infantile population. The RLLS recipients had significantly more flatfish-type grafts, while the LLS recipients had more blowfish-type grafts. Primary full-layer wound closure could be performed successfully in all LLS recipients, while in the RLLS group, two patients were forced to have partial skin closure. There were no graft losses related to graft compression. Reducing an LLS is a useful procedure to promote the comfortable accommodation of the graft in an infant weighing <7 kg. Flatfish-type LLS allowed more flexibility to make the suitable volume.

The in vivo performance of polyvinyl alcohol macro-encapsulated islets.

Islet transplantation is a method for the treatment of type 1 diabetes mellitus (DM) and has been widely performed around the world. The long-term cryopreservation of islets shows many advantages in the field of islet transplantation. Previous studies have described the development of sheet-type polyvinyl alcohol (PVA) macro-encapsulated islets (MEI) to treat type 1 DM without any immunotherapy. The present study examined their beneficial effects on islet cryopreservation. PVA MEI of Wistar rats were divided into three groups of 1-day, 7-day and 30-day cryopreservation at -80 degrees C. The 30-day group showed a lower recovery rate of the islet number and impaired insulin release in comparison to the 1-day group, whereas no significant differences of the in vitro results were observed between the 1-day and 7-day groups. The MEI transplantation recipient mice in the 1-day and 7-day groups reached normoglycemia for a 4-week observation period, and the recipients in 30-day group also showed a significant decrease followed by a slightly higher non-fasting blood glucose level. These results suggest that the PVA MEI are useful for islet long-term cryopreservation, and that the use of cryopreserved PVA MEI may, therefore, be a promising modality for performing DM therapy.

Massive ascites after living donor liver transplantation with a right lobe graft larger than 0.8% of the recipient's body weight.

BACKGROUND: There are only limited data on post-transplant ascites unrelated to small-sized grafts in living donor liver transplantation (LDLT). METHODS: The subjects were 59 adult patients who had received right lobe LDLT with a graft weight-to-recipient weight ratio (GRWR)>0.8%. Patients were divided into either Group 1 (n=14, massive ascites, defined as the production of ascitic fluid>1000 mL/d that lasted longer than 14 d after LDLT) or Group 2 (n=45, no development of massive ascites). Patients were followed for a median period of 3.0 yr (range, 0.5-7.5 yr). RESULTS: Group 1 had both higher Model for End-Stage Liver Disease score and Child-Pugh score than Group 2. Portal venous flow volume just after reperfusion was significantly greater in Group 1 than Group 2 (307.8±268.8 vs. 176.2±75.0 mL/min/100 g graft weight, respectively; p<0.05). Post-transplant infectious complications including ascites infection developed more frequently within the first post-transplant month in Group 1. Massive ascites was significantly associated with early graft loss (p<0.05). CONCLUSION: Post-transplant massive ascites associated with portal over-perfusion into the graft liver can develop in patients with a GRWR over 0.8%. Recipients with post-transplant massive ascites require careful management to prevent infection.

Rapamycin inhibits proliferation and migration of hepatoma cells in vitro.

BACKGROUND: Systemic immunosuppression represents the major factor for cancer recurrence after orthotopic liver transplantation for hepatocellular carcinoma (HCC). Rapamycin is an immunosuppressant with unique antitumoral properties. Although rapamycin has been successfully used in HCC patients after liver transplantation, the detailed mechanisms of rapamycin action on tumor cells are poorly understood. METHODS: Two HCC cell lines (PLC5 and HuH7) were used to evaluate the effect of rapamycin. Tumor cell proliferation was analyzed using cell counting and BrdU incorporation assay. Expression of phosphorylated Akt was studied using enzyme linked immunosorbent assay. Digital time-lapse microscopy was utilized to measure tumor cell migration in vitro. RESULTS: Rapamycin induced a strongly dose-dependent inhibition of tumor cell proliferation in both HCC cell lines. Additionally, rapamycin inhibited activation of Akt phosphorylation and tumor cell migration after prolonged treatment. CONCLUSIONS: Rapamycin suppresses tumor progression due to inhibition of phosphorylated Akt, cell proliferation, and migration. The data of the present study strengthen clinical implications of rapamycin after liver transplantation with HCC.

Gastric volvulus as a complication in the recipients after adult living donor liver transplantation.

BACKGROUND: We report 4 adult cases of mesenteroaxial gastric volvulus after living donor liver transplantation (LDLT). RESULTS: All 4 recipients were female with a median age of 31 years (range, 21-69). All had undergone right lobe LDLT. Gastric volvulus developed on postoperative days (POD) 4-30, and all were successfully treated with an endoscopic correction procedure. Two of 4 needed a repeated correction procedure and 1 needed a surgical revision for the recurrent volvulus. CONCLUSION: Although this type of the complication is unusual, earlier post-transplant endoscopic intervention is useful to reverse the pyloroantral obstruction. These cases let us recognize that gastric volvulus is one of the complications after right lobe LDLT.

How to handle a huge portosystemic shunt in adult living donor liver transplantation with a small-for-size graft: report of a case.

Little attention has been paid to a ligation of the spontaneous portosystemic shunt in adult living donor liver transplantation (LDLT). A 33-year-old Japanese man with cryptogenic liver cirrhosis accompanied by a huge splenorenal shunt underwent LDLT. Acute cellular rejection produced "to and fro" portal venous flow on postoperative day (POD) 10. Steroid bolus therapy reversed the rejection, but the recovery of the portal venous flow was incomplete and the recipient subsequently started to have episodes of encephalopathy. Angiography showed portal hypoperfusion and portal flow steal via a huge splenorenal shunt. The patient underwent a shunt occlusion on POD 58. Portography showed marked improvement of the portal hypoperfusion. The encephalopathy thereafter dramatically reversed and the patient was discharged with no complications related to shunt ligation on POD 110. This case suggested that a ligation of a huge portosystemic shunt should therefore be considered at the time of transplantation, even when a relatively small graft is implanted.

Revisited impact of recipient age on the outcome of living donor liver transplantation for biliary atresia in the recent "transplantation era" in Japan.

To re-evaluate the impact of recipient age on the outcome of LDLT for BA in an era in which LDLT is the established treatment for BA in Japan. Thirty-one patients with BA who underwent LDLT were divided into four groups regarding the age at LDLT: infants <1 yr old (group A; n = 14); young children 1 to 6 yr old (group B; n = 8); school children 6 to 15 yr old (group B; n = 5); and adults > or =15 yr old (group D; n = 4). Pre-, peri-, and postoperative factors were compared among the four groups. There was no significant difference in number of the previous laparotomy among the groups. Cholestasis was the dominant indication in group A. PELD score in group B was lower than that in the other groups, and blood loss in group B was significantly less than in groups A and D. Ratio of the graft weight to the recipient's body weight (GRWR) in group A was significantly higher than in other groups. Duration of operation in group D was lower than in groups A and B, but there was no significant difference in the length of postoperative hospital stay and graft survival. Although the case volume was not big, the age of the recipient did not have any significant impact on the outcome of LDLT in our series.

Biliary reconstruction for infantile living donor liver transplantation: Roux-en-Y hepaticojejunostomy or duct-to-duct choledochocholedochostomy?

Hepaticojejunostomy is a standard biliary reconstruction method for infantile living donor liver transplantation (LDLT), but choledochocholedochostomy for infants is not generally accepted yet. Ten pediatric recipients weighing no more than 10 kg underwent duct-to-duct choledochocholedochostomy (DD) for biliary reconstruction for LDLT. Patients were followed up for a median period of 26.8 months (range: 4.0-79.0 months). The incidence of posttransplant biliary complications for DD was compared with that for Roux-en-Y hepaticojejunostomy (RY). No DD patients and 1 RY patient (5%) developed biliary leakage (P > 0.05), and biliary stricture occurred in 1 DD patient (10%) and none of the RY patients (P > 0.05); none of the DD patients and 5 RY patients (25%) suffered from uncomplicated cholangitis after LDLT (P > 0.05), and 1 DD patient (10%) and 2 RY patients (10%) died of causes unrelated to biliary complications. In conclusion, both hepaticojejunostomy and choledochocholedochostomy resulted in satisfactory outcome in terms of biliary complications, including leakage and stricture, for recipients weighing no more than 10 kg.

Vascular reconstruction and complications in living donor liver transplantation in infants weighing less than 6 kilograms: the Kyoto experience.

Smaller-size infants undergoing living-donor liver transplantation (LDLT) are at increased risks of vascular complications because of their smaller vascular structures in addition to vascular pedicles of insufficient length for reconstruction. Out of 585 child patients transplanted between June 1990 and March 2005, 64 (10%) weighing less than 6 kg underwent 65 LDLTs. Median age and weight were 6.9 months (range: 1-16 months) and 5 kg (range: 2.8-5.9 kg), respectively. Forty-five lateral segment, 12 monosegment, and 8 reduced monosegment grafts were adopted, and median graft-to-recipient weight ratio was 4.4% (range: 2.3-9.7). Outflow obstruction occurred in only 1 patient (1.5%). Portal vein complication occurred in 9 (14%) including 5 with portal vein thrombosis. Hepatic artery thrombosis (HAT) occurred in 5 (7.7%). Patient and graft survivals were 73% and 72% at 1 yr, and 69% and 68% at 5 yr after LDLT, respectively. Thirteen of 22 grafts (58%) lost during the follow-up period occurred within the first 3 months posttransplantation. Overall graft survival in patients with and without portal vein complication was 67% and 65%, respectively (P = 0.54). Overall graft survival in patients with and without HAT was 40% and 67%, respectively. HAT significantly affected graft survival (P = 0.04). In conclusion, our surgical technique for smaller-size recipients resulted in an acceptable rate of vascular complications. Overcoming early posttransplantation complications will further improve outcomes in infantile LDLT.

Development of pulmonary hypertension in 5 patients after pediatric living-donor liver transplantation: de novo or secondary?

The development of portopulmonary hypertension (PH) in a patient with end-stage liver disease is related to high cardiac output and hyperdynamic circulation. However, PH following liver transplantation is not fully understood. Of 617 pediatric patients receiving transplants between June 1990 and March 2004, 5 (median age 12 yr, median weight 24.5 kg) were revealed to have portopulmonary hypertension (PH) after living-donor liver transplantation (LDLT), as confirmed by echocardiography and/or right heart catheterization. All children underwent LDLT for post-Kasai biliary atresia. In 2 patients with refractory biliary complications, PH developed following portal thrombosis; 2 with stable graft function, who had had intrapulmonary shunting (IPS) before LDLT, were found to have PH in spite of overcoming liver dysfunction due to hepatitis. PH developed shortly after distal splenorenal shunting in 1 patient, who suffered liver cirrhosis due to an intractable outflow blockage. The onset of PH ranged from 2.8 to 11 yr after LDLT, and mean pulmonary artery pressure (mPAP) estimated by echocardiography at the time of presentation ranged from 43 to 120 mmHg. Three of the 5 patients are alive under prostaglandin I2 (PGI2) treatment. Of these, 1 is prepared for retransplantation for an intractable complications of liver allograft, while the other 2 with satisfactory grafts are being considered for lung transplantation. Even after LDLT, PH can develop with portal hypertension. Periodic echocardiography is essential for early detection and treatment of PH especially in the recipients with portal hypertension not only preoperatively but also postoperatively.

Cold preservation of islets in UW solution--with special reference to apoptosis.

BACKGROUND: Apoptosis progresses in cultured islets. Little is known with regard to apoptosis under cold preservation. We examined viability and function of islets in University of Wisconsin (UW) solution. MATERIALS AND METHODS: Isolated rat islets were cultured overnight (overnight group) and further treated with 7-day culture in RPMI 1640 medium at 37 degrees C (culture group) or 7-day preservation in UW solution at 4 degrees C (preservation group). They were evaluated by glucose-stimulated insulin secretion test. Apoptosis was examined by TdT-mediated dUTP-biotin nick end-labeling (TUNEL) assay. Expression of caspase mRNA and the ratio of Bax to Bcl-2 were evaluated by reverse-transcriptase polymerase chain reaction (RT-PCR). RESULTS: Islet recovery after 7 days was significantly lower in culture group than in preservation group (44.0 +/- 3.7% versus 75.0 +/- 4.9%, P < 0.05). The stimulation index in the culture group was significantly lower than in the overnight group (2.1 +/- 0.2 versus 4.1 +/- 0.4, P < 0.05). The apoptotic index in the culture group was significantly higher than both in the overnight group and in the preservation group (38.0 +/- 3.0% versus 10.8 +/- 2.0 and 27.0 +/- 4.0%, P < 0.05). Caspase 3, 8, and 9 mRNA in the culture group expressed more than in the other groups. Bax/Bcl-2 in the culture group was significantly lower than in the overnight group (3.2 +/- 0.66 versus 8.1 +/- 0.95, P < 0.05), suggesting that apoptosis had been already destined early after isolation. CONCLUSIONS: The preservation group showed better recovery and function than the culture group. Apoptosis contributed to islet loss under culture and it was significantly suppressed under cold preservation.

Current role of liver transplantation for the treatment of urea cycle disorders: a review of the worldwide English literature and 13 cases at Kyoto University.

To address the current role of liver transplantation (LT) for urea cycle disorders (UCDs), we reviewed the worldwide English literature on the outcomes of LT for UCD as well as 13 of our own cases of living donor liver transplantation (LDLT) for UCD. The total number of cases was 51, including our 13 cases. The overall cumulative patient survival rate is presumed to be more than 90% at 5 years. Most of the surviving patients under consideration are currently doing well with satisfactory quality of life. One advantage of LDLT over deceased donor liver transplantation (DDLT) is the opportunity to schedule surgery, which beneficially affects neurological consequences. Auxiliary partial orthotopic liver transplantation (APOLT) is no longer considered significant for the establishment of gene therapies or hepatocyte transplantation but plays a significant role in improving living liver donor safety; this is achieved by reducing the extent of the hepatectomy, which avoids right liver donation. Employing heterozygous carriers of the UCDs as donors in LDLT was generally acceptable. However, male hemizygotes with ornithine transcarbamylase deficiency (OTCD) must be excluded from donor candidacy because of the potential risk of sudden-onset fatal hyperammonemia. Given this possibility as well as the necessity of identifying heterozygotes for other disorders, enzymatic and/or genetic assays of the liver tissues in cases of UCDs are essential to elucidate the impact of using heterozygous carrier donors on the risk or safety of LDLT donor-recipient pairs. In conclusion, LT should be considered to be the definitive treatment for UCDs at this stage, although some issues remain unresolved.