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  • 1
    ISSN: 1432-1440
    Keywords: Key words Islet transplantation ; Microencapsulation ; Immunoalteration ; Diabetes ; Alginate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recently, we reported successful transplantation (Tx) of microencapsulated (mc) islets. However, graft failure observed in several cases was associated with an increased foreign body reaction compared to long-term functioning grafts. This study was performed to investigate the impact of an immunoalterating islet pretreatment (12–14 days culture at 22°C) on graft function. After microencapsulation in barium alginate beads the islets were cultured for another day. Diabetic LEWIS rats (blood glucose 〉19 mM) were transplanted with 3500 immunoaltered mc-Wistar islets intraperitoneally. Controls were transplanted with 3500 non-cultured syngeneic or allogeneic mc-islets. Additional syngeneic and allogeneic controls were transplanted with 6000 non-cultured, non-encapsulated islets intraperitoneally. Seventy percent of the recipients of microencapsulated, long-term low temperature cultured islets maintained normoglycemia at least for 15 weeks, while this was true in only 17% of those animals receiving microencapsulated non-pretreated allogeneic islets. Islets in non-encapsulated controls were rejected within several days. Graft function correlated with histologically proven viable islets within the capsules. Microencapsulation of islets markedly prolonged allograft survival compared to non-encapsulated islets; application of an immunoaltering low-temperature culture further improved graft function significantly. These data may support the hypothesis of induction of a reaction against microcapsules by the antigen release from the graft which may be avoided by immunoaltering islet pretreatment.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-5233
    Keywords: Alginate ; Islets of Langerhans ; Macroencapsulation ; Microencapsulation ; Transplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have recently demonstrated long-lasting normoglycaemia after transplantation of barium alginate microencapsulated rat and porcine islets. Nevertheless the transplantation results obtained with different microencapsulation techniques have been controversial. Little is known about possible immune interactions between host and encapsulated islet. This study demonstrates in vitro stimulation of lymphoid cells by encapsulated islets that is similar to that of unencapsulated islets. This stimulation was reduced by a 4-day culture with unencapsulated islets only. After macroencapsulation of islets in hollow fibres a stimulatory effect was also observed, but this was less pronounced than after microencapsulation. Empty microcapsules as well as macrocapsules induced lymphoid proliferation as a result of mitogenic impurities in the encapsulation materials themselves. In the same donor-recipient combination in which we have shown successful transplantation, we found activation of the sensibilization arm of the immune system. This suggests that microencapsulation results in protection of the transplanted islets from the action of the effector arm. This lymphoid activation could be triggered by the mitogeniticity of the encapsulation material itself. In the case of alginates these mitogenic factors could not be abolished by culture (i.e. dialysis).
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-5233
    Keywords: Rat Islets ; Transplantation ; Bioartificial Pancreas ; Microencapsulation ; Insulin Secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Immuno-isolated transplantation offers the attractive prospect of being able to transplant xenogeneic islets without immunosuppression. This study introduces a completely new method of coating single islets using a homogenous alginate membrane approximately 10 μm thick. During glucose challenge (perifusion and static incubation) encapsulated islets show the same pattern and quantity of insulin release as non-encapsulated controls. This encapsulation method markedly reduces the amount of transplanted material by reducing the size of the capsule. It is suggested that encapsulated islets may be transplanted into sites such as the renal capsule or omentum or even by intraportal injection into the liver.
    Type of Medium: Electronic Resource
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