Johannes Bargehr

Reconstruction of the mouse extrahepatic biliary tree using primary human extrahepatic cholangiocyte organoids

The treatment of common bile duct (CBD) disorders, such as biliary atresia or ischemic strictures, is restricted by the lack of biliary tissue from healthy donors suitable for surgical reconstruction. Here we report a new method for the isolation and propagation of human cholangiocytes from the extrahepatic biliary tree in the form of extrahepatic cholangiocyte organoids (ECOs) for regenerative medicine applications. The resulting ECOs closely resemble primary cholangiocytes in terms of their transcriptomic profile and functional properties. We explore the regenerative potential of these organoids in vivo and demonstrate that ECOs self-organize into bile duct–like tubes expressing biliary markers following transplantation under the kidney capsule of immunocompromised mice. In addition, when seeded on biodegradable scaffolds, ECOs form tissue-like structures retaining biliary characteristics. The resulting bioengineered tissue can reconstruct the gallbladder wall and repair the biliary epithelium following transplantation into a mouse model of injury. Furthermore, bioengineered artificial ducts can replace the native CBD, with no evidence of cholestasis or occlusion of the lumen. In conclusion, ECOs can successfully reconstruct the biliary tree, providing proof of principle for organ regeneration using human primary cholangiocytes expanded in vitro.

Preexisting atrial fibrillation and cardiac complications after liver transplantation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, and it is associated with increased cardiovascular morbidity and all‐cause mortality. Our aim was to determine the impact of preexisting AF on patients undergoing liver transplantation (LT). A retrospective case‐control study was performed. Records from patients who underwent LT between January 2005 and December 2008 at Mayo Clinic Florida were reviewed. Patients with preexisting AF were identified and matched to patients who did not have a diagnosis of AF. Thirty‐two of 717 LT recipients (4.5%) had AF before LT. These patients were compared to a control group of 63 LT recipients. Pre‐LT left ventricular hypertrophy (P = 0.03), a history of congestive heart failure (P = 0.04), and a history of stroke or transient ischemic attack (P = 0.03) were significantly more prevalent in patients with AF versus controls. Intraoperative adverse cardiac events (P = 0.02) and AF‐related adverse postoperative events (P < 0.001) were more common in the recipients with known AF. Six patients with paroxysmal AF (19%) developed chronic/persistent AF postoperatively. Graft survival and patient survival were similar in the groups. Although patients with AF had a higher incidence of intraoperative cardiac events, a higher cardiovascular morbidity rate, and a complicated postoperative course, this did not affect overall graft and patient survival. Liver Transpl 21:314–320, 2015.

Liver Transplantation in Patients With Atrial Fibrillation

In this study we described survival and incidence of perioperative and postoperative complications in liver transplant recipients with known atrial fibrillation. A total number of 717 patients underwent liver transplantation between January 2005 and December 2008 at our institution. In this population, preoperative paroxysmal or chronic-persistent atrial fibrillation was diagnosed in 32 patients (4.5%). Of these, 12 patients died during follow-up and 4 patients required liver retransplantation. Perioperative cardiac complications occurred in 10 patients (31%) resulting in 3 cardiac-related deaths. Median patient survival was 1613 days (range, 22-2492) and median graft survival was 1524 days (range, 10-2492). Twenty patients are still alive with a median survival of 1861 days (range, 1189-2492) after liver transplantation.

Embryological Origin of Human Smooth Muscle Cells Influences Their Ability to Support Endothelial Network Formation

Vascular smooth muscle cells (SMCs) from distinct anatomic locations derive from different embryonic origins. Here we investigated the respective potential of different embryonic origin‐specific SMCs derived from human embryonic stem cells (hESCs) to support endothelial network formation in vitro. SMCs of three distinct embryological origins were derived from an mStrawberry‐expressing hESC line and were cocultured with green fluorescent protein‐expressing human umbilical vein endothelial cells (HUVECs) to investigate the effects of distinct SMC subtypes on endothelial network formation. Quantitative analysis demonstrated that lateral mesoderm (LM)‐derived SMCs best supported HUVEC network complexity and survival in three‐dimensional coculture in Matrigel. The effects of the LM‐derived SMCs on HUVECs were at least in part paracrine in nature. A TaqMan array was performed to identify the possible mediators responsible for the differential effects of the SMC lineages, and a microarray was used to determine lineage‐specific angiogenesis gene signatures. Midkine (MDK) was identified as one important mediator for the enhanced vasculogenic potency of LM‐derived SMCs. The functional effects of MDK on endothelial network formation were then determined by small interfering RNA‐mediated knockdown in SMCs, which resulted in impaired network complexity and survival of LM‐derived SMC cocultures. The present study is the first to show that SMCs from distinct embryonic origins differ in their ability to support HUVEC network formation. LM‐derived SMCs best supported endothelial cell network complexity and survival in vitro, in part through increased expression of MDK. A lineage‐specific approach might be beneficial for vascular tissue engineering and therapeutic revascularization.

Reversible non-ischaemic cardiomyopathy and left ventricular dysfunction after liver transplantation: A single-centre experience

Non‐ischaemic cardiomyopathy (NIC) is an early complication of liver transplantation (LT). Our aims were to define the prevalence, associated clinical factors, and prognosis of this condition.

Predictors of Suboptimal Gain in Exercise Capacity After Cardiac Rehabilitation

Cardiac rehabilitation (CR) improves exercise capacity (EC), but not all CR participants achieve such improvements. Our primary aim was to develop a tool to identify those with suboptimal improvement in EC after CR. We retrospectively analyzed 541 patients enrolled in a phase-II CR program after a cardiac event or intervention from 2003 to 2014. EC was assessed with the 6-minute walk test. We developed a multivariate linear regression model and corresponding nomogram to predict EC after CR. The predictors included in the final model were age, gender, baseline EC, primary referral diagnosis, body mass index, systolic blood pressure at rest, triglycerides, low-density lipoprotein cholesterol, lipid-lowering medication use, and an interaction term of low-density lipoprotein cholesterol with lipid-lowering therapy. The prediction model was internally validated using bootstrap methods, and a nomogram was created for ease of use. In conclusion, this tool helps to identify those patients with suboptimal improvement in EC who could be targeted for individualized interventions to increase their performance.

25 Embryological origin of human smooth muscle cells influences their ability to support vasculogenesis

Background We hypothesised that the distinct embryonic origins of vascular smooth muscle cells (SMCs) at different anatomic locations, contribute to differences in vascular development and disease. Here we investigated the respective vasculogeneic potential of different embryonic-origin specific SMC derived from human embryonic stem cells (hESCs) to support vasculogenesis in vitro. Methods and results SMCs of three distinct embryonic origins were derived from an mStrawberry-expressing hESC line and were co-cultured with GFP-expressing human umbilical vein endothelial cells (HUVEC) to investigate the effects of distinct SMC subtypes on endothelial network formation. As demonstrated by quantitative data, LM-derived SMCs best supported HUVEC network survival in 3D co-culture in matrigel. In addition, LM-SMCs facilitated more complex endothelial networks, with narrower cords and more branch points, compared with the other SMC types and HUVECs alone. The effects of the LM-SMCs on HUVECs were at least in part paracrine in nature. A TaqMan Array was performed to identify possible mediators responsible for the differential effects of the SMC lineages and a microarray to determine lineage-specific angiogenesis gene signatures. Midkine (MDK) was identified as one important mediator for the enhanced vasculogenic effect of LM-SMCs. Subsequent siRNA-mediated knockdown of MDK in SMCs resulted in a decrease of total HUVEC network area and number of branch points in LM-derived SMC co-cultures. Conclusion SMCs from distinct embryonic origins differ in their ability to support HUVEC network formation. LM-derived SMCs best support vasculogenesis in vitro, in part through increased expression of MDK.