Kidney transplantation following iliac revascularization in severe atherosclerosis: a comparative study.

BACKGROUND: Kidney transplantation (KT) has become the standard of care for patients with end-stage renal disease. However, as atherosclerosis progresses with time on dialysis, it causes increasing difficulties in implanting the graft. This is a comparative study analyzing complications and graft survival of recipients with iliac revascularization before transplantation. METHODS: Between January 2006 and December 2015, 1691 kidney transplants were performed at our institution. We retrospectively analyzed eighteen patients with peripheral arterial disease (PAD) with the necessity of vascular revascularization before kidney transplantation to protect the inflow to the renal graft and to optimizing blood supply to the extremities. The primary endpoint included patient survival and graft survival. The secondary endpoints evaluate perioperative and early postoperative complication rates after kidney transplantation. RESULTS: All patients enrolled in this study underwent two consecutive surgical procedures. No patient reported limb loss, and there was no additional perioperative morbidity or mortality related to the vascular procedure. Primary endpoints such as graft survival without dialysis and overall patient survival show 1-month survival of 100%, 1-year survival of 94.1%, and 5-year survival of 84.70%, respectively. One graft failure occurred 8 months after transplantation due to acute rejection, and there were two deaths over follow-up period due to myocardial infarction. CONCLUSIONS: Vascular repair before kidney transplantation is safe, and results are suggestive that it prolongs graft survival. These promising results should encourage other centers to address vascular repair before the transplantation to optimize blood supply to the extremity and the future graft. Although, the interpretation of our results must be cautiously because of the small and heterogeneous sample size, and the limitations of retrospective study design. Prospective trials with larger study populations are needed to confirm the results of this study and to identify significant differences.

Robotic surgery and liver transplantation: A single-center experience of 501 robotic donor hepatectomies.

BACKGROUND: Over the past two decades robotic surgery has been introduced to many areas including liver surgery. Laparoscopic liver surgery is an alternative minimally invasive approach. However, moving on to the complexity of living donor hepatectomies, the advantages of robotic versus laparoscopic approach have convinced us to establish the robotic platform as a standard for living donor hepatectomy. METHODS: From November 2018 to January 2022, 501 fully robotic donor hepatectomies, including 177 left lateral donor lobes, 112 full left lobes and 212 full right lobes were performed. Grafts were donated to 296 adult recipients and 205 pediatric recipients. Donor age, sex, body weight, body mass index (BMI), graft weight, graft to body weight ratio (GBWR), operative time, blood loss, first warm ischemic time, pain score, length of intensive care unit (ICU) stay and hospital stay, and complications were retrospectively analyzed based on a prospectively kept database. Recipients were evaluated for graft and patient survival, age, sex, BMI, body weight, model of end-stage liver disease score, blood loss, transfusions, operative time, cold ischemic time, length of hospital stay and complications. RESULTS: There was no donor mortality. Two cases needed to be converted to open surgery. The median blood loss was 60 mL (range 20-800), median donor operative time was 6.77 h (range 2.93-11.53), median length of hospital stay was 4 days (range 2-22). Complication rate in donors classified following Clavien-Dindo was 6.4% (n = 32) with one grade III complication. Three-year actual recipient overall survival was 91.4%; 87.5% for adult recipients and 97.1% for pediatric recipients. Three-year actual graft overall survival was 90.6%; 87.5% for adult recipients and 95.1% for pediatric recipients. In-hospital mortality was 6%, 9.1% (27/296) for adult recipients and 1.4% (3/205) for pediatric recipients. The recipients' morbidity was 19.8% (n = 99). Twenty-eight recipients (5.6%) had biliary and 22 (4.4%) vascular complications. Six (12.0%) recipients needed to be re-transplanted. CONCLUSIONS: With growing experience it is nowadays possible to perform any donor hepatectomy by robotic approach regardless of anatomical variations and graft size. Donor morbidity and quality for life results are encouraging and should motivate other transplant centers with interest in minimally invasive donor surgery to adopt this robotic technique.

Career intentions of female surgeons in German liver transplant centers considering family and lifestyle priorities.

PURPOSE: Women represent up to 60 % of students entering the medical profession in many countries in the world. However, the proportion of women to men is not accordingly balanced among surgical residents and especially in leadership positions in surgery. Therefore, we investigated the career goals as well as family and lifestyle priorities of female surgeons in German liver transplant centers. METHODS: A standardized questionnaire was developed using the web-based survey tool SurveyMonkey®. Questionnaires were distributed electronically to 180 female surgeons in 24 German liver transplant centers. A total of 81 completed questionnaires were analyzed. RESULTS: Female surgeons in German liver transplant centers are eager to assume leadership positions and do not wish to follow traditional role models. After finishing training, most female surgeons plan to continue working at a university hospital. About 80 % of the respondents intend to continue working full time and wish to combine career and family. CONCLUSIONS: This is the first survey on career intentions of female surgeons in Germany. In the face of gender changes in the medical profession, we were able to demonstrate that female surgeons are willing to fill leadership positions. Individual and institutional creative modifications are necessary if the advancement of women in surgery is to be promoted.

Liver transplantation in infants with biliary atresia: comparison of primary versus temporary abdominal closure.

INTRODUCTION: Biliary atresia (BA) is the most frequent disease leading to liver transplantation (LT) in infants. Since the patients often require transplantation before reaching a body weight of 10 kg, it is necessary to perform living-related or split liver transplantation by using a left lateral segment. However, this graft often exceeds a graft body weight ratio (GBWR) of 4. Because of the size mismatch and poor portal venous blood flow in most recipients, temporary abdominal closure is often favoured. The aim of the present study is to investigate the feasibility of primary abdominal closure in this group of extremely small infants undergoing LT. PATIENTS AND METHODS: All patients with the diagnosis of BA and a body weight ≤10 kg who underwent LT in our centre between January 2004 and December 2014 were included in this study. Patients who received primary abdominal closure at transplantation (group 1) were compared with those receiving temporary abdominal closure (group 2). The postoperative clinical and biochemical course was analysed. The outcome was determined and correlated with body and graft weight and the GBWR. RESULTS: Sixty-six LTs were performed in 57 patients in the study period (22 male, 35 female). Thirty-six patients received primary closure (group 1). Twenty-eight patients received temporary closure (group 2). Mean age at LT was 10 months (range 3-26) and mean GBWR 4.8 (range 2.9-9.3). A GBWR ≥4 occurred in 61.1 % in group 1 and in 60.9 % in group 2. There was no significant difference between both groups concerning body weight, graft weight or GBWR. Vascular thrombosis occurred in 8 patients (22 %) and 15 patients (42 %) in group 1 and in 10 patients (36 %) and 11 patients (39 %) in group 2, respectively. Six patients (17 %) of group 1 and five patients (18 %) of group 2 developed an intraabdominal infection postoperatively. After a mean follow-up of 4.6 years (range 1 month-11.1 years), patient and graft survival were 90.1 and 75 % in group 1 and 78.3 and 64.3 % in group 2, respectively. CONCLUSION: In our study, primary abdominal closure displays a similar outcome in comparison to temporary abdominal closure.

Training, work, and lifestyle of transplant physicians and surgeons in Germany.

BACKGROUND: International data on training, work, and lifestyle of transplant physicians and surgeons are scarce. Such data might help in development of uniform education paths and provide insights for young clinicians interested in this field. This study aimed at the evaluation of these data in all transplant-associated medical disciplines. METHODS: A survey on professional and academic training, workload, and lifestyle was generated. The questionnaire was distributed to all members of the German Transplant Association (DTG), utilizing the tool SurveyMonkey(®) . RESULTS: A total of 127 members of the DTG responded (male/female 66.1%/33.9%, 45.8±10.3 years). The majority had been working in transplant medicine for more than 10 years (61.9%). Fifteen respondents (11.8%) obtained an official European certification (European Union of Medical Specialists). A total of 57 (48.3%) respondents worked full time on research during training. The research focus was clinical for most respondents (n=72, 61.5%). An average working time of 62±1.5 h/wk was reported. Fifty-eight percent of all respondents complained of inadequate remuneration and 50% reported inadequate acknowledgment of their professional performance. CONCLUSION: This is the first study reporting characteristics of training, work, and lifestyle in an interdisciplinary cohort of German transplant physicians and surgeons. Enormous efforts in clinical and research work were reported, associated with high rates of professional and financial dissatisfaction.

Kidney transplantation from deceased donors with elevated serum creatinine.

BACKGROUND: Elevated donor serum creatinine has been associated with inferior graft survival in kidney transplantation (KT). The aim of this study was to evaluate the impact of elevated donor serum creatinine on short and long-term outcomes and to determine possible ways to optimize the use of these organs. METHODS: All kidney transplants from 01-2000 to 12-2012 with donor creatinine ≥ 2 mg/dl were considered. Risk factors for delayed graft function (DGF) were explored with uni- and multivariate regression analyses. Donor and recipient data were analyzed with uni- and multivariate cox proportional hazard analyses. Graft and patient survival were calculated using the Kaplan-Meier method. RESULTS: Seventy-eight patients were considered. Median recipient age and waiting time on dialysis were 53 years and 5.1 years, respectively. After a median follow-up of 6.2 years, 63 patients are alive. 1, 3, and 5-year graft and patient survival rates were 92, 89, and 89 % and 96, 93, and 89 %, respectively. Serum creatinine level at procurement and recipient's dialysis time prior to KT were predictors of DGF in multivariate analysis (p = 0.0164 and p = 0.0101, respectively). Charlson comorbidity score retained statistical significance by multivariate regression analysis for graft survival (p = 0.0321). Recipient age (p = 0.0035) was predictive of patient survival by multivariate analysis. CONCLUSIONS: Satisfactory long-term kidney transplant outcomes in the setting of elevated donor serum creatinine ≥2 mg/dl can be achieved when donor creatinine is <3.5 mg/dl, and the recipient has low comorbidities, is under 56 years of age, and remains in dialysis prior to KT for <6.8 years.

Safely expanding the donor pool: brain dead donors with history of temporary cardiac arrest.

BACKGROUND & AIMS: Cardiac arrest (CA) in deceased organ donors can potentially be associated with ischaemic organ injury, resulting in allograft dysfunction after liver transplantation (LT). The aim of this study was to analyse the influence of cardiac arrest in liver donors. METHODS: We evaluated 884 consecutive adult patients undergoing LT at our Institution from September 2003 to December 2011. Uni- and multivariable analyses was performed to identify predictive factors of outcome and survival for organs from donors with (CA donor) and without (no CA donor) a history of cardiac arrest. RESULTS: We identified 77 (8.7%) CA donors. Median resuscitation time was 16.5 (1-150) minutes. Allografts from CA donors had prolonged CIT (p = 0.016), were obtained from younger individuals (p < 0.001), and had higher terminal preprocurement AST and ALT (p < 0.001) than those of no CA donors. 3-month, 1-year and 5-year survival for recipients of CA donor grafts was 79%, 76% and 57% and 72.1%, 65.1% and 53% for no CA donor grafts (log rank p = 0.435). Peak AST after LT was significantly lower in CA donor organs than in no CA donor ones (886U/l vs 1321U/l; p = 0.031). Multivariable analysis identified CIT as a risk factor for both patient and graft survival in CA donors. CONCLUSION: This analysis represents the largest cohort of liver donors with a history of cardiac arrest. Reasonable selection of these donors constitutes a safe approach to the expansion of the donor pool. Rapid allocation and implantation with diminution of CIT may further improve the outcomes of livers from CA donors.

Using pediatric liver grafts (≤ 6 yr) for adult recipients: A considerable option?

In LT, the common policy is to allocate pediatric liver grafts to pediatric recipients. Pediatric organs are also offered to adults if there is no pediatric recipient. However, they are rarely accepted for adult recipients. So far, there is no information available reporting outcome of LT in adult recipients using pediatric livers from donors ≤ 6 yr. In this study, we included nine adult recipients (seven females and two males) who received grafts from children ≤ 6 yr from January 2008 to December 2013. We evaluated the graft quality, the GBWR and analyzed the recipients' perioperative course. Laboratory samples and graft perfusion were analyzed. Nine adults with a median age of 49 yr (range: 25-65) and a median weight of 60 kg (range: 48-64) underwent LT with a pediatric donor graft. Median donor age was five yr (range: 3-6). Median GBWR was 1.02 (range: 0.86-1.45). After a median follow-up of 3.9 yr (range: 11 months-6.6 yr), patient survival was 100%; graft survival was 89%. One patient needed re-transplantation on the second postoperative day due to PNF. Eight recipients were discharged from the ICU after 2-9 days with a regular graft function. Doppler scans revealed regular flow patterns at any time. Only if denied for pediatric recipients, the use of pediatric livers from donors ≤ 6 yr for adult recipients is a considerable option.

Progressive familial intrahepatic cholestasis-outcome and time to transplant after biliary diversion according to genetic subtypes.

Background: Progressive familial intrahepatic cholestasis (PFIC) is a heterogeneous disease characterized by progressive cholestasis in early childhood. Surgical therapy aims at preventing bile absorption either by external or internal biliary diversion (BD). Several different genetic subtypes encode for defects in bile transport proteins, and new subtypes are being discovered ongoingly. Overall, the literature is scarce, however, accumulating evidence points to PFIC 2 having a more aggressive course and to respond less favorable to BD. With this knowledge, we aimed to retrospectively analyze the long-term outcome of PFIC 2 compared to PFIC 1 following BD in children at our center. Methods: Clinical data and laboratory findings of all children with PFIC, who were treated and managed in our hospital between 1993 and 2022, were analyzed retrospectively. Results: Overall, we treated 40 children with PFIC 1 (n = 10), PFIC 2 (n = 20) and PFIC 3 (n = 10). Biliary diversion was performed in 13 children (PFIC 1, n = 6 and 2, n = 7). Following BD, bile acids (BA) (p = 0.0002), cholesterol (p < 0.0001) and triglyceride (p < 0.0001) levels significantly decreased only in children with PFIC 1 but not in PFIC 2. Three out of 6 children (50%) with PFIC 1 and 4 out of 7 children (57%) with PFIC 2 required liver transplantation despite undergoing BD. On an individual case basis, BA reduction following BD predicted this outcome. Of the 10 children who had PFIC 3, none had biliary diversion and 7 (70%) required liver transplantation. Conclusion: In our cohort, biliary diversion was effective in decreasing bile acids, cholesterol levels as well as triglycerides in the serum only in children with PFIC 1 but not PFIC 2. On an individual case level, a decrease in BA following BD predicted the need for liver transplantation.

First Experience in Living Liver Donation From Donors With Sickle Cell Trait.

Living donor liver transplantation is the main source of organs in the Middle East. Therefore, well balanced criteria are needed to avoid unnecessary exclusion of potential donors, while prioritizing donor safety. We face a high incidence of sickle cell trait (SCT; and disease). Therefore, there is vast experience in general and cardiac surgeries in SCT carriers at our center. After studying their management in detail, we considered accepting SCT carriers as living liver donors, on an exceptional basis. This the first single-center case series of living donor liver transplantation with SCT. Methods: Between January 2012 and September 2021, 20 donors with SCT were reviewed for age, gender, relation to the recipient, hemoglobin, hemoglobin S (HbS), surgical approach, intensive care unit stay, donor and recipients' complications, and graft and recipient survival. Results: Average age of donors was 28.4 y. Sixteen donated the left lateral segment, 4 the left lobe. Recipients were related children or adults. HbS ranged from 21.2% to 39.9%, being ≥30% in 14 donors. HbS was reduced by phlebotomy or exchange transfusion. We performed 7 open, one laparoscopic, and 12 robotic donor surgeries. Operating room time, blood loss, and intensive care unit stay were comparable to non-SCT donors. There was no SCT-related complication. All donors are alive and free of thromboembolic events. Graft and recipient survival is 100% until follow-up. Conclusion: Our experience should encourage other countries with high incidence of SCT to report their experience with this donor population.

Implications for the usage of the left lateral liver graft for infants ≤10 kg, irrespective of a large-for-size situation--are monosegmental grafts redundant?

Organ donor shortage for infant liver transplant recipients has lead to an increase in splitting and living donation. For cases in which even transplantation of the left lateral graft (Couinaud's segments II + III) results in a "large for size situation" with an estimated graft body weight ratio (GBWR) of >4%, monosegmental liver transplantation was developed. This, however, bears complications because of greater parenchymal surface and suboptimal vascular flow. We exclusively use the left lateral graft from living donors or split grafts. Temporary abdominal closure is attempted in cases of increased pressure. We report of 41 pediatric transplants in 38 children ≤10 kg. Within this group, there were 23 cases with a GBWR of ≥4, and 15 cases with a GBWR <4. There was no statistical difference in vascular or biliary complications. Despite a more frequent rate of temporary abdominal closure, we did not find a higher rate of intra-abdominal infections. Overall, patient and graft survival was excellent in both groups (one death, three re-transplants). We noticed, however, that the ventro-dorsal diameter of the graft appears to be more relevant to potential graft necrosis than the actual graft size. In conclusion, the usage of monosegmental grafts seems unnecessary if transplantation of left lateral grafts is performed by an experienced multidisciplinary team, and temporary abdominal closure is favored in cases of increased abdominal pressure.

Preimplantation-stage stem cells induce long-term allogeneic graft acceptance without supplementary host conditioning.

Hematopoietic stem cells have been successfully employed for tolerance induction in a variety of rodent and large animal studies. However, clinical transplantation of fully allogeneic bone marrow or blood-borne stem cells is still associated with major obstacles, such as graft-versus-host disease or cytoreductive conditioning-related toxicity. Here we show that when rat embryonic stem cell-like cells of WKY origin are injected intraportally into fully MHC-mismatched DA rats, they engraft permanently (>150 days) without supplementary host conditioning. This deviation of a potentially alloreactive immune response sets the basis for long-term graft acceptance of second-set transplanted WKY cardiac allografts. Graft survival was strictly correlated with a state of mixed chimerism, which required functional thymic host competence. Our results provide a rationale for using preimplantation-stage stem cells as vehicles in gene therapy and for the induction of long-term graft acceptance.

Solubility and aggregation behavior of dendronized poly(p-benzamide)s.

A series of Fréchet dendronized poly(p-benzamide)s have been synthesized. To attach the dendron-functionalities to the poly(p-benzamide) backbone, a propargyl side chain was introduced to p-aminobenzoic acid. Then, copper catalyzed azide-alkyne cycloaddition was used to click a first generation (G(1)), respectively, a second generation (G(2)) Fréchet-dendron azide onto the amino acid monomer. The resulting amino acids were polymerized using triphenylphosphite to obtain a poorly organo-soluble G(1)-dendronized polymer and a non-aggregating G(2)-dendronized polymer showing good organo-solubility. Furthermore, a strictly alternating non-aggregating G(1)-TEG-dendronized polymer with good organo-solubility was synthesized. The aggregation behavior of these polymers was investigated by dynamic light scattering.

Synthesis of a functional metal-chelating polymer and steps toward quantitative mass cytometry bioassays.

We describe the synthesis and characterization of metal-chelating polymers with a degree of polymerization of 67 and 79, high diethylenetriaminepentaacetic acid (DTPA) functionality, M(w)/M(n) ≤ 1.17, and a maleimide as an orthogonal functional group for conjugation to antibodies. The polymeric disulfide form of the DP(n) = 79 DTPA polymer was analyzed by thermogravimetric analysis to determine moisture and sodium-ion content and by isothermal titration calorimetry (ITC) to determine the Gd(3+) binding capacity. These results showed each chain binds 68 ± 7 Gd(3+) per chain. Secondary goat antimouse IgG was covalently labeled with the maleimide form of the DTPA polymer (DP(n) = 79) carrying (159)Tb. Conventional ICPMS analysis of this conjugate showed each antibody carried an average of 161 ± 4 (159)Tb atoms. This result was combined with the ITC result to show there are an average of 2.4 ± 0.3 polymer chains attached to each antibody. Eleven monoclonal primary antibodies were labeled with different lanthanide isotopes using the same labeling methodology. Single cell analysis of whole umbilical cord blood stained with a mixture of 11 metal-tagged antibodies was performed by mass cytometry.

Case Report: Hepatic Adenoma in a Child With a Congenital Extrahepatic Portosystemic Shunt.

Congenital extrahepatic portosystemic shunts (CEPS), previously also described as Abernethy malformations, are rare malformations in which the extrahepatic portal system directly communicates with the vena cava inferior, thereby bypassing the liver. A hypoplastic portal vein (PV) exists in most cases. CEPS have been associated with the development of liver nodules, ranging from mostly focal nodular hyperplasia (FNH) to hepatic adenoma (HA) and even hepatocellular carcinoma (HCC). Tumor development in CEPS may be due to changes in perfusion pressures, oxygen supply or endocrine imbalances. It is important to rule out CEPS in children with liver tumors, because resection could impede future shunt occlusion procedures, and benign masses may regress after shunt occlusion. Here, we review the case of a 9-years-old male with CEPS and hepatic nuclear Factor 1-alpha (HNF-1-alpha) inactivated HA to raise awareness of this condition and review histopathological changes in the liver of CEPS.

Administration of donor-derived transplant acceptance-inducing cells to the recipients of renal transplants from deceased donors is technically feasible.

Patient KW, a 36-yr-old male renal transplant recipient, received transplant acceptance-inducing cells (TAICs) as an adjunct immunosuppressive therapy. In the weeks post-transplantation, the patient's conventional immunosuppressive treatment was gradually minimized, such that, from the 21st wk post-transplantation onwards, the patient was stably maintained on tacrolimus monotherapy. Treatment with TAICs was without complication, both at the time of administration and in the four-yr follow-up period. It is concluded that the production and administration of TAICs to recipients of kidney transplants from deceased donors is technically feasible.

Computed tomography donor liver volumetry before liver transplantation in infants ≤10 kg: does the estimated graft diameter affect the outcome?

AIM OF THE STUDY: Living donor liver transplantation (LDLT) is regularly performed in small-sized infants. Computed tomography (CT)-based donor liver volumetry is used to estimate the graft size. The aim of our study was to assess the results of CT liver volumetry and their impact on the clinical outcome after LDLT in extremely small-sized infants. PATIENTS AND METHODS: In this study, we included all patients with a body weight of ≤10 kg who underwent living related liver transplantation at our centre between January 2004 and December 2014. In all cases of LDLT, a preoperative CT scan of the donor liver was performed, and the total liver and graft volumes were calculated. The graft shape was estimated by measuring the ventro-dorsal (thickness), cranio-caudal, and transversal (width) diameter of segment II/III. We assessed the impact of CT donor liver volumetry and other risk factors on the outcome, defined as patient and graft survival. RESULTS: In the study period, a total of 48 living related liver transplantations were performed at our centre in infants ≤10 kg [20 male (42%), 28 female (58%)]. The mean weight was 7.3 kg (range 4.4-10 kg). Among the recipients, 33 (69%) received primary abdominal closure and 15 (31%) had temporary abdominal closure. The patient and graft survival rates were 85% and 81%, respectively. In CT volumetry, the mean estimated graft volume was 255 mL (range 140-485 mL) and the actual measured mean graft weight was 307 g (range 127-463 g). The mean ventro-dorsal diameter of segment II/III was 6.9 cm (range 4.3-11.2 cm), the mean cranio-caudal diameter was 9 cm (range 5-14 cm), and the mean width was 10.5 cm (range 6-14.7 cm). The mean graft-body weight ratio (GBWR) was 4.38% (range 1.41-8.04%). A high graft weight, a GBWR >4%, and a large ventro-dorsal diameter of segment II/III were risk factors for poorer patient survival. CONCLUSION: Preoperative assessment of the graft size is a crucial investigation before LDLT. For extremely small-sized recipients, not only the graft weight but also the graft shape seems to affect the outcome.

Novel implications in the treatment of hepatocellular carcinoma.

Worldwide hepatocellular carcinoma remains one of the leading causes of cancer-related death, associated with a poor prognosis due to late diagnosis in the majority of cases. Physicians at care are frequently confronted with patients who are ineligible for curative treatment such as liver resection, transplantation or radiofrequency ablation. Besides established palliative locoregional therapies, such as ablation or chemoembolization, new treatment options, such as microwave ablation, drug-eluting bead transarterial chemoembolization or selective internal radiation therapy, are emerging; however, data from randomized controlled trials are still lacking. In order to achieve optimal tumor control, patients should receive tailored treatment concepts, considering their tumor burden, liver function and performance status, instead of strictly assigning patients to treatment modalities following algorithms that may be partly very restrictive. Palliative locoregional pretreatment might facilitate downstaging to ensure later curative resection or transplantation. In addition, the combined utilization of different locoregional treatment options or systemic co-treatment has been the subject of several trials. In cases where local tumor control cannot be achieved, or in the scenario of extrahepatic spread, sorafenib remains the only approved systemic therapy option. Alternative targeted therapies, such as immune checkpoint inhibitors have shown encouraging preliminary results, while data from phase III studies are pending.

Derivation, maintenance, and characterization of rat embryonic stem cells in vitro.

The in vitro differentiation of mouse embryonic stem (ES) cells into different somatic cell types such as neurons, endothelial cells, or myocytes is well established, and many mouse ES cell lines have been created so far. The establishment of rat ES cell lines, however, has proven to be difficult. Most attempts to culture rat ES cell lines and maintain them in an undifferentiated state have failed, so researchers were forced to abandon this system and use mouse ES cells. This chapter describes the long-term cultivation of an alkaline phosphatase-positive rat embryonic stem cell-like line (RESC) and their differentiation into neuronal, endothelial, and hepatic lineages. The RESCs can be characterized by typical growth in single cells as well as embryoid bodies when cultivated in the presence of leukemia inhibitory factor. RESC expressed stage-specific-embryonic antigen 1 and the major histocompatibility class 1 molecule. Neuronal differentiation is achieved by standard retinoic acid treatment and endothelial differentiation can be reproducibly induced by growth on or within Matrigel for 14 d. To induce expression of hepatocyte-specific antigens, RESCs were either grown in hepatocyte-conditioned media or in media containing different combinations of growth factors. The characterization of differentiated cells was done primarily by immunohistochemistry, enzyme-linked immunosorbent assay, and polymerase chain reaction.