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| Author(s): |
Elizabeth Maria Costa de Oliveira
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2004-08-06 |
| Examining board members: |
Irene de Lourdes Noronha;
Pio Colepicolo Neto;
Rui Curi;
Pedro Soares De Araujo;
Álvaro Pacheco e Silva Filho
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| Advisor: | Irene de Lourdes Noronha; Mari Cleide Sogayar |
| Abstract | |
Type 1 diabetes mellitus results from insufficient or absence of insulin production, as a consequence of destruction of pancreatic β cells, by an auto-imune mechanism. Treatment for this type of diabetes consists of subcutaneous administration of exogenous insulin. Recently, it has been demonstrated that pancreatic islet cell transplantation is capable of rendering type I diabetic patients independent of exogenous insulin. However, in spite of the success achieved, permanent immunosuppression is still required, being the main barrier to expand this treatment to a large number of patients. Therefore, development of new technologies, such as islet macro and microencapsulation to avoid rejection of the tissue implanted, is still crucial for definitive establishment of islet transplantation as a therapeutic alternative for type I diabetes. In the present work, an animal model was established for in vivo evaluation of the functional ability of human pancreatic islets, which were isolated and purified at the Human Pancreatic Islet Unit of the University of São Paulo Chemistry Institute. Diabetes was induced in NIH nude rats through streptozotocin injection followed by implantation of naked or microencapsulated human pancreatic islets. Biodritin, a new and patented heteropolyssaccaride was used to microencapsulate the islets. The production of uniform and homogeneous microcapsules with diameters in the range of 400µm e 600 µm was successfully established. Reversion of diabetes occurred in 24% of the nude rats transplanted with human pancreatic islets. On the other hand, no reversion of diabetes was observed when encapsulated islets were implanted, although their functional activity in vitro indicated that they secreted insulin and responded to glucose stimulation upon encapsulation. In order to elucidate this effect, empty capsules were implanted in nude rat and in immunocompetent rats, both of which developed an inflammatory process accompanied by a fibrotic process in the site of the implant. Immunohistochemical studies are underway to address the nature and the intensity of these inflammatory processes. (AU) | |