Schramm Rene, Scheuer Claudia, Yamauchi Jun-ichiro, Vollmar Brigitte, Menger Michael D
Institute for Clinical and Experimental Surgery, University of Saarland, Homburg/Saar, Germany.
Transplantation. 2002 Dec 15;74(11):1544-50. doi: 10.1097/00007890-200212150-00011.
Revascularization of freely transplanted pancreatic islets is essential for appropriate graft function and survival. During the first days after transplantation, however, islet transplants are avascular, and successful engraftment is believed to be markedly hampered by hypoxia-induced tissue injury. Because heat shock has been shown to induce cell resistance against hypoxia, it seems reasonable to stress pancreatic islets by heat before transplantation. In contrast, hypoxia is a major stimulus for angiogenesis, and thus heat shock preconditioning-induced resistance against hypoxia may decrease stimulation of angiogenesis. The authors therefore studied in vivo whether heat shock preconditioning of isolated islets affects angiogenesis and revascularization after free transplantation.
After collagenase isolation, heat shock-preconditioned islets (42 degrees C for 30 min) were transplanted syngeneically into nontreated skinfold chambers of Syrian hamsters. In a second group of animals, nontreated islets were transplanted into heat shock-preconditioned chambers. Nontreated islets transplanted into nontreated chambers served as controls. Islet angiogenesis and revascularization were quantitatively analyzed during 14 days after transplantation using intravital fluorescence microscopy. Expression of heat shock proteins (HSP) was confirmed by immunohistochemistry and Western blotting.
Immunohistochemistry revealed expression of HSP32 (heme oxygenase [HO]-1), HSP72, and also intracellular insulin in isolated and transplanted pancreatic islets. Western blot analysis showed enhanced HSP32 but slightly decreased HSP72 expression in heat shock-preconditioned islets when compared with controls. Intravital microscopy revealed appropriate vascularization of control islets within 14 days after transplantation. Heat shock preconditioning of the host tissue (i.e., the skinfold chambers) did not affect islet vascularization when compared with controls. In contrast, heat shock preconditioning of the isolated islets resulted in a significantly (P < 0.05) impaired take rate, a reduced (P < 0.05) size of the newly formed microvascular network, and thus a smaller area (P < 0.05) of microvascularly perfused endocrine tissue.
These data suggest that heat shock preconditioning of isolated pancreatic islets before transplantation impairs the process of graft angiogenesis and revascularization. Therefore, transient exposure of isolated islets to heat may not be considered a promising tool to improve the outcome of islet transplantation.
自由移植的胰岛血管重建对于移植物的正常功能及存活至关重要。然而，在移植后的最初几天，胰岛移植体是无血管的，且成功植入被认为明显受到缺氧诱导的组织损伤的阻碍。由于热休克已被证明可诱导细胞对缺氧产生抗性，因此在移植前对胰岛进行热应激似乎是合理的。相反，缺氧是血管生成的主要刺激因素，因此热休克预处理诱导的对缺氧的抗性可能会降低对血管生成的刺激。因此，作者在体内研究了分离的胰岛进行热休克预处理是否会影响自由移植后的血管生成和血管重建。
胶原酶分离后，将经热休克预处理的胰岛（42℃，30分钟）同基因移植到叙利亚仓鼠未处理的皮褶小室中。在第二组动物中，将未处理的胰岛移植到经热休克预处理的小室中。将未处理的胰岛移植到未处理的小室中作为对照。在移植后14天内，使用活体荧光显微镜对胰岛血管生成和血管重建进行定量分析。通过免疫组织化学和蛋白质印迹法确认热休克蛋白（HSP）的表达。
免疫组织化学显示在分离和移植的胰岛中存在HSP32（血红素加氧酶[HO]-1）、HSP72以及细胞内胰岛素的表达。蛋白质印迹分析表明，与对照相比，经热休克预处理的胰岛中HSP32表达增强，但HSP72表达略有下降。活体显微镜检查显示对照胰岛在移植后14天内有适当的血管化。与对照相比，宿主组织（即皮褶小室）的热休克预处理不影响胰岛血管化。相反，分离的胰岛进行热休克预处理导致摄取率显著降低（P<0.05），新形成的微血管网络大小减小（P<0.05），因此微血管灌注的内分泌组织面积较小（P<0.05）。
这些数据表明，移植前对分离的胰岛进行热休克预处理会损害移植物血管生成和血管重建过程。因此，将分离的胰岛短暂暴露于热中可能不是改善胰岛移植结果的有前景的工具。
