Islet cell transplantation

Importância da microcirurgia experimental para transplantes de órgãos

A microcirurgia experimental é uma área relativamente nova e seu desenvolvimento foi um marco importante para o desenvolvimento da pesquisa imunológica e de técnicas cirúrgicas de transplante, pois permitiu a utilização de modelos animais de pequeno porte; mais apropriados para pesquisa, e com menor custo. A microcirurgia exige bastante habilidade técnica e treinamento continuo. Além disso contribui para formação do cirurgião de transplantes na medida que promove o desenvolvimento de habilidade manual, interesse científico e cooperação interdisciplinar. Esse artigo relata alguns aspectos históricos, a importância e as vantagens e limitações da microcirurgia experimental.

Address by the Honorary Founding President of the Xenotransplantation Society. The eye of an eagle: xenobiology and the quest for bioadvantage

My purpose in these remarks is to stimulate us to consider the vast array that nature has provided us in the differentiation of species, and to examine the possibility that some of these differences might prove useful in other species, including man.

Successful methods of pancreas transplantation in the rat using a cuff technique

Two models of pancreas transplantation were examined in the rat with a view to choosing one for regular use in functional experiments. A cuff technique applied to the renal vessels of the recipient was used. The histology and endocrine functioning of whole pancreas-duodenal transplant (Tx) plus bladder drainage (drainage model), and the pancreatic duct ligated segmental pancreas Tx (ligated model) were examined. Syngeneic operations were performed using either Lewis or Wistar rats. Streptozotocin (STZ) 60 mg/kg intravenously (i.v.) was used to render the recipient rats diabetic. A cuff technique was used with both models to anastomose the grafts to the renal vessels instead of the conventional technique of hand suturing to the abdominal vessels. This allows a shorter warm ischaemia time for the donor pancreas and leaves the systemic circulation intact leading to a high success rate for both techniques. Operation survival rates were 93% (n = 30) and 90% (n = 10) in the ligated and drainage models, respectively. The recipients in both groups were normoglycaemic for > 100 days. Histological examination revealed atrophic exocrine tissue early in the ligated group but only two from the drainage group showed exocrine atrophy at > 100 days. There was no statistical difference in i.v. glucose tolerance tests with both models showing a normal pattern. Thus, endocrine function remained independent of exocrine function. Both models are quicker than the conventional techniques. The duct ligation model was a simpler transplant to perform, suggesting that this should be the technique of choice in future experiments.

Pancreas transplantation in the rat using Lee's technique: a reliable model in experimental microsurgery

Numerous unresolved problems, both technical and immunological, in pancreas transplantation stimulate experimental studies. Dogs have been routinely used in experimental studies but today rats are more commonly used. However, pancreas transplantation in the rat presents complex technical problems and requires a good knowledge of microsurgical techniques. In 1983 Squifflet undertook an experimental study aimed at evaluating the technical aspects of pancreas transplantation in the rat and calculating the success rates using different methods. The comparison of four methods revealed to our surprise that 100% of the rats operated on using Lee's technique had complications, with a 0% survival rate. In our study we report our experience using Lee's technique which we had the opportunity of mastering directly under the supervision of Professor Lee. We performed 100 pancreas transplantations using Lee's technique and divided our study in two phases. In the first phase we performed 70 pancreas transplantations and overall survival, after 1 week, was 42 rats (60%). In the second phase on 30 rats diabetes was induced by administering 70 mg/kg of streptozotocin. These 30 diabetic rats underwent pancreas transplantation and overall survival, after 1 week, was 25 (83.3%). We believe that our successful survival rates could probably be explained by the close collaboration between Lee and our department. Moreover, we noted the importance of constant training in obtaining better results, and in our opinion Lee's technique of pancreas transplantation is a reliable experimental model which can be used to resolve problems linked to pancreas transplantation.

Long-term studies of pancreas allotransplantation in experimental diabetes mellitus

Pancreaticoduodenal (PD) allografts (Brown Norway-alloxan-diabetic rats, n = 190) were treated with cyclosporin A (Cy-A) 10 mg/kg/daily and compared with nondiabetics with Cy-A treatment (n = 55), diabetics (n = 50), and diabetics with Cy-A treatment (n = 45). Body weight, blood sugar, blood insulin, blood urea nitrogen (BUN), and creatinine were monitored periodically; there were marked elevations of BUN and creatinine levels, indicating probably nephrotoxicity of Cy-A at this dosage. Some islet cell atrophy in the PD allografts was noted at the conclusion of the study. With respect to the immunosuppressive effect of Cy-A in alloxan diabetic rats, Brown Norway PD transplants into Lewis rats were successful and free of rejection for as long as 15 months post-transplantation. The body weight of these PD transplanted rats, however, never approached values representative of the nondiabetic rats. In our experience, the PD allograft model is acceptable in the clinical situation, particularly in children if the microsurgical technique is mastered and if the Cy-A regimen is used in combination with other immunosuppressant(s).

Technical aspects of segmental pancreatic grafting in rats

Four techniques for segmental pancreatic transplantation were used sequentially in rats. The success rate and the incidence and type of technical complications that developed in each group of recipients were determined and attempts were made to improve the microsurgical technique. A strict comparison of the relative merits of the four different techniques was not made, but rather the development of an approach to an original technique that resulted in a high success is rate presented. The various modifications and details of this experience are documented. The various complications, each of which results in a typical postoperative pattern of weight and plasma glucose changes and each of which is preventable by the use of proper microsurgical techniques, are also analyzed.