Tashiro H, Iwata H, Warnock G L, Takagi T, Machida H, Ikada Y, Tsuji T
National Cardiovascular Center Research Institute, Osaka, Japan.
Ann Transplant. 1997;2(3):33-9.
The bioartificial pancreas was designed to incorporate islet tissues and a selectively permiable membrane that isolates islets from the immune system of the recipient. The efficacy of agarose, a nontoxic polysaccharide, has been evaluated as a material of microcapsules to prevent allo- and xenograft rejection in rodents. The aim of this study is to demonstrate the possibility of the agarose microcapsule containing allo-islets as a bioartificial pancreas in canine model. In vitro viability of islets was determined by glucose challenge during perifusion experiments (n = 4). Insulin secretion from both encapsulated (enc.) and non-encapsulated (non-enc.) canine islets rose from initial basal levels of 0.09 (encap.), 0.07 (non-encap.) to the peak of 0.2 (encap.), 0.1 (non-encap.) in microU/islet/min after 5 minutes, then decreased to the basal level when the glucose challenge was discontinued. Auto-transplantation was performed in two dogs to evaluated in vivo viability and biocompatibility of encapsulated islets implanted into the splenic sinus by venouse reflux. Two weeks after auto-transplantation, the plasma insulin levels in the splenic vein and artery of two dogs were assayed. In the first dog, serum insulin level was 1 microU/ml both in the vein and the artery and increased, after glucagon (1.0 mg) injection, to levels of 9 microU/ml in the vein, but still kept 1 microU/ml in artery, as well as in the second one. Histological and electron-microscopical examination of the spleen revealed that encapsulated islets remained morphologically intact and the surface of agarose capsules showed no significant adherence of fibroblasts and inflammatory cells. Functional efficacy of the microencapsulated islets was determined using five totally-pancreatectomized diabetic dogs as recipients without immunosuppression. Defined quantity of microencapsulated islets from outbred mongrel donors were grafted through the catheter into omental tissue of the pancreatectomized recipients. All dogs had various degrees of reduced insulin requirements. In three of five recipients, the average fasting glucose values were controlled under 120 mg/dl for 28, 42, 49 days without exogenous insulin, which received totally 4.3 x 10(3), 7.3 x 10(3) and 1.0 x 10(4) (IE/kg) of microencapsulated islets, respectively. In conclusion, the present study indicates that the agarose-based microencapsulated islets can function in large diabetic animals, resulting in the independence of exogenous insulin therapy for prolonged periods without the need for immunosuppression.
生物人工胰腺旨在整合胰岛组织和一种选择性渗透膜，该膜可将胰岛与受体的免疫系统隔离开来。琼脂糖是一种无毒多糖，其作为微胶囊材料用于预防啮齿动物的同种异体移植和异种移植排斥反应的效果已得到评估。本研究的目的是在犬模型中证明含同种异体胰岛的琼脂糖微胶囊作为生物人工胰腺的可能性。在灌注实验期间（n = 4），通过葡萄糖刺激测定胰岛的体外活力。封装（enc.）和未封装（non-enc.）的犬胰岛的胰岛素分泌从初始基础水平0.09（封装）、0.07（未封装）在5分钟后升至峰值0.2（封装）、0.1（未封装）微单位/胰岛/分钟，然后在葡萄糖刺激停止时降至基础水平。对两只狗进行自体移植，以评估通过静脉回流植入脾窦的封装胰岛的体内活力和生物相容性。自体移植两周后，测定两只狗脾静脉和动脉中的血浆胰岛素水平。在第一只狗中，静脉和动脉中的血清胰岛素水平均为1微单位/毫升，在注射胰高血糖素（1.0毫克）后，静脉中的胰岛素水平升至9微单位/毫升，但动脉中的胰岛素水平仍保持在1微单位/毫升，第二只狗也是如此。对脾脏进行组织学和电子显微镜检查发现封装的胰岛形态保持完整，琼脂糖胶囊表面未显示有成纤维细胞和炎性细胞的明显附着。使用五只全胰切除的糖尿病犬作为受体且不进行免疫抑制，来确定微封装胰岛的功能效果。将来自杂种供体的特定数量的微封装胰岛通过导管移植到全胰切除受体的网膜组织中。所有狗对胰岛素的需求都有不同程度的降低。在五只受体中的三只中，平均空腹血糖值在28、42、49天内控制在120毫克/分升以下，无需外源性胰岛素，它们分别接受了4.3×10³、7.3×10³和1.0×10⁴（胰岛等效物/千克）的微封装胰岛。总之，本研究表明基于琼脂糖的微封装胰岛可在大型糖尿病动物中发挥作用，从而在无需免疫抑制的情况下长期实现外源性胰岛素治疗的独立性。
