Esophageal tissue engineering:A new approach for esophageal replacement

A number of congenital and acquired disorders require esophageal tissue replacement.Various surgical techniques,such as gastric and colonic interposition,are standards of treatment,but frequently complicated by stenosis and other problems.Regenerative medicine approaches facilitate the use of biological constructs to replace or regenerate normal tissue function.We review the literature of esophageal tissue engineering,discuss its implications,compare the methodologies that have been employed and suggest possible directions for the future.Medline,Embase,the Cochrane Library,National Research Register and ClinicalTrials.gov databases were searched with the following search terms:stem cell and esophagus,esophageal replacement,esophageal tissue engineering,esophageal substitution.Reference lists of papers identified were also examined and experts in this field contacted for further information.All full-text articles in English of all potentially relevant abstracts were reviewed.Tissue engineering has involved acellular scaffolds that were either transplanted with the aim of being repopulated by host cells or seeded prior to transplantation.When acellular scaffolds were used to replace patch and short tubular defects they allowed epithelial and partial muscular migration whereas when employed for long tubular defects the results were poor leading to an increased rate of stenosis and mortality.Stenting has been shown as an effective means to reduce stenotic changes and promote cell migration,whilst omental wrapping to induce vascularization of the construct has an uncertain benefit.Decellularized matrices have been recently suggested as the optimal choice for scaffolds,but smart polymers that will incorporate signalling to promote cell-scaffold interaction may provide a more reproducible and available solution.Results in animal models that have used seeded scaffolds strongly suggest that seeding of both muscle and epithelial cells on scaffolds prior to implantation is a prerequisite for complete esophageal replacement.Novel approaches need to be designed to allow for peristalsis and vascularization in the engineered esophagus.Although esophageal tissue engineering potentially offers a real alternative to conventional treatments for severe esophageal disease,important barriers remain that need to be addressed.

Liver bioengineering:Current status and future perspectives

The present review aims to illustrate the strategies that are being implemented to regenerate or bioengineer livers for clinical purposes.There are two general pathways to liver bioengineering and regeneration.The first consists of creating a supporting scaffold,either synthetically or by decellularization of human or animal organs,and seeding cells on the scaffold,where they will mature either in bioreactors or in vivo.This strategy seems to offer the quickest route to clinical translation,as demonstrated by the development of liver organoids from rodent livers which were repopulated with organ specific cells of animal and/or human origin.Liver bioengineering has potential for transplantation and for toxicity testing during preclinical drug development.The second possibility is to induce liver regeneration of dead or resected tissue by manipulating cell pathways.In fact,it is well known that the liver has peculiar regenerative potential which allows hepatocyte hyperplasia after amputation of liver volume.Infusion of autologous bone marrow cells,which aids in liver regeneration,into patients was shown to be safe and to improve their clinical condition,but the specific cells responsible for liver regeneration have not yet been determined and the underlying mechanisms remain largely unknown.A complete understanding of the cell pathways and dynamics and of the functioning of liver stem cell niche is necessary for the clinical translation of regenerative medicine strategies.As well,it will be crucial to elucidate the mechanisms through which cells interact with the extracellular matrix,and how this latter supports and drives cell fate.

Single vs dual(en bloc) kidney transplants from donors ≤ 5 years of age: A single center experience

AIM: To compare outcomes between single and dual en bloc(EB) kidney transplants(KT) from small pediatric donors. METHODS: Monocentric nonprospective review of KTs from pediatric donors ≤ 5 years of age. Dual EB KT was defined as keeping both donor kidneys attached tothe inferior vena cava and aorta, which were then used as venous and arterial conduits for the subsequent transplant into a single recipient. Donor age was less useful than either donor weight or kidney size in decision-making for kidney utilization as kidneys from donors < 8 kg or kidneys < 6 cm in length were not transplanted. Post-transplant management strategies were standardized in all patients.RESULTS: From 2002-2015, 59 KTs were performed including 34 dual EB and 25 single KTs. Mean age of donors(17 mo vs 38 mo, P < 0.001), mean weight(11.0 kg vs 17.4 kg, P = 0.046) and male donors(50% vs 84%, P = 0.01) were lower in the dual EB compared to the single KT group, respectively. Mean cold ischemia time(21 h), kidney donor profile index(KDPI; 73% vs 62%) and levels of serum creatinine(SCr, 0.37 mg/d L vs 0.49 mg/d L, all P = NS) were comparable in the dual EB and single KT groups, respectively. Actuarial graft and patient survival rates at 5-years follow-up were comparable. There was one case of thrombosis resulting in graft loss in each group. Delayed graft function incidence(12% dual EB vs 20% single KT, P = NS) was slightly lower in dual EB KT recipients. Initial duration of hospital stay(mean 5.4 d vs 5.6 d) and the one-year incidences of acute rejection(6% vs 16%), operative complications(3% vs 4%), and major infection were comparable in the dual EB and single KT groups, respectively(all P = NS). Mean 12 mo SCr and abbreviated MDRD levels were 1.17 mg/d L vs 1.35 mg/d L and 72.5 m L/min per 1.73 m^2 vs 60.5 m L/min per 1.73 m^2(both P = NS) in the dual EB and single KT groups, respectively. CONCLUSION: By transplanting kidneys from young pediatric donors into adult recipients, one can effectively expand the limited donor pool and achieve excellent medium-term outcomes.

Regenerative medicine technology applied to gastroenterology:Current status and future perspectives

This special issue of World Journal of Gastroenterology has been conceived to illustrate to gastroenterology operators the role that regenerative medicine(RM) will have in the progress of gastrointestinal(GI) medicine.RM is a multidisciplinary field aiming to replace,regenerate or repair diseased tissues or organs.The past decade has been marked by numerous ground-breaking achievements that led experts in the field to manufacture functional substitutes of relatively simple organs.This progress is paving the ground for investigations that aims to the bioengineering and regeneration of more complex organs like livers,pancreas and intestine.In this special issue,the reader will be introduced,hand-in-hand,to explore the field of RM and will be educated on the progress,pitfalls and promise of RM technologies as applied to GI medicine.

Pancreas transplantation: The Wake Forest experience in the new millennium

AIM: To investigate the Wake Forest experience with pancreas transplantation in the new millennium with attention to surgical techniques and immunosuppression. METHODS: A monocentric, retrospective review of outcomes in simultaneous kidney-pancreas transplant(SKPT) and solitary pancreas transplant(SPT) recipients was performed. All patients underwent pancreas transplantation as intent-to-treat with portal venous and enteric exocrine drainage and received depleting antibody induction; maintenance therapy included tapered steroids or early steroid elimination with my-cophenolate and tacrolimus. Recipient selection was based on clinical judgment whether or not the patient exhibited measureable levels of C-peptide. RESULTS: Over an 11.25 year period, 202 pancreas transplants were performed in 192 patients including 162 SKPTs and 40 SPTs. A total of 186(92%) were primary and 16(8%) pancreas retransplants; portalenteric drainage was performed in 179 cases. A total of 39 pancreas transplants were performed in African American(AA) patients; of the 162 SKPTs, 30 were performed in patients with pretransplant C-peptide levels > 2.0 ng/m L. In addition, from 2005-2008, 46 SKPT patients were enrolled in a prospective study of single dose alemtuzumab vs 3-5 doses of rabbit antithymocyte globulin induction therapy. With a mean follow-up of 5.7 in SKPT vs 7.7 years in SPT recipients, overall patient(86% SKPT vs 87% SPT) and kidney(74% SKPT vs 80% SPT) graft survival rates as well as insulin-free rates(both 65%) were similar(P = NS). Although mortality rates were nearly identical in SKPT compared to SPT recipients, patterns and timing of death were different as no early mortality occurred in SPT recipients whereas the rates of mortality following SKPT were 4%, 9% and 12%, at 1-, 3- and 5-years follow-up, respectively(P < 0.05). The primary cause of graft loss in SKPT recipients was death with a functioning graft whereas the major cause of graft loss following SPT was acute and chronic rejection. The overall incidence of acute rejection was 29% in SKPT and 27.5% in SPT recipients(P = NS). Lower rates of acute rejection and major infection were evidenced in SKPT patients receiving alemtuzumab induction therapy. Comparable kidney and pancreas graft survival rates were observed in AA and non-AA recipients despite a higher prevalence of a "type 2 diabetes" phenotype in AA. Results comparable to those achieved in insulinopenic diabetics were found in the transplantation of type 2 diabetics with detectable C-peptide levels.CONCLUSION: In the new millennium, acceptablemedium-term outcomes can be achieved in SKPT and SPTs as nearly 2/3rds of patients are insulin independent following pancreas transplantation.

Composite hepatocellular and hemangiosarcomatous tumor: The prognosis is determined by the sarcomatous component

Nowadays, mixed liver tumors are more frequently diagnosed due to better imaging, advanced immunohistochemistry (IHC) staining techniques and better knowledge of hepatic tumorigene- sis [1–3] . Such tumors represent a mosaic of components with dis- tinct histogenesis and carcinogenic pathways. As their occurrence in the liver is very rare, their behavior and natural history are difficult to determine, and their management remains empirical. An uncommon case of a composite tumor harboring hepatocellular carcinoma (HCC) and hepatic hemangiosarcoma (HHS) components in a liver transplant (LT) recipient is reported herein.

Kidney regeneration: Where we are and future perspectives

In 2012,about 16487 people received kidney transplants in the United States,whereas 95022 candidates were on the waiting list by the end of the year.Despite advances in renal transplant immunology,approximately 40%of recipients will die or lose graft within10 years.The limitations of current therapies for renal failure have led researchers to explore the development of modalities that could improve,restore,or replace the renal function.The aim of this paper is to describe a reasonable approach for kidney regeneration and review the current literature regarding cell sources and mechanisms to develop a bioengineering kidney.Due to kidneys peculiar anatomy,extracellular matrix based scaffolds are rational starting point for their regeneration.The perfusion of detergents through the kidney vasculature is an efficient method for delivering decellularizing agents to cells and for removing of cellular material from the tissue.Many efforts have focused on the search of a reliable cell source to provide enrichment for achieving stable renal cell systems.For an efficient bioengineered kidney,these cells must be attached to the organ and then maturated into the bioractors,which simulates the human body environment.A functional bioengineered kidney is still a big challenge for scientists.In the last ten years we have got many improvements on the field of solid organ regeneration;however,we are still far away from the main target.Currently,regenerative centers worldwide have been striving to find feasible strategies to develop bioengineered kidneys.Cell-scaffold technology gives hope to end-stage renal disease patients who struggle with morbidity and mortality due to extended periods on dialysis or immunosupression.The potential of bioengineered organ is to provide a reliable source of organs,which can be refunctionalized and transplanted.