新技术“看”和保护移植成功的糖尿病动物模型

在霍普金斯大学的研究人员已经找到一种方法来克服一个主要的障碍，发展为I型糖尿病患者胰岛素细胞移植成功。

传统的细胞移植，伴随着必要的免疫抑制药物，具有高度可变的结果，从良好的耐受性差。霍普金斯研究人员说，问题的一部分，是一种无法跟踪细胞，所谓的胰腺β细胞，一旦他们体内的。

现在一项新的技术将胰岛细胞磁胶囊，使用FDA批准的铁化合物与标签外使用，它可以通过磁共振成像（MRI）跟踪。该产品，在猪和糖尿病小鼠进行测试，同时也避免了免疫系统的排斥反应，可能是移植失败的主要原因。这工作将于下周在网上发布自然医学。

"We’re really excited because we can track where we put the cells and make sure their protective housing stays intact and that the cells don’t move。 This could solve the mystery of why current transplantation techniques work only for so long," says one of the study’s authors, Aravind Arepally, M。D。, assistant professor of radiology and surgery at Hopkins。

Type I diabetes-the most common childhood sort-causes a person’s immune system to destroy the pancreatic beta cells that make insulin。 Without insulin, blood sugar levels can become dangerously high and lead to complications that include blindness or kidney failure。 Careful monitoring of blood sugar levels paired with insulin injections can manage the condition, but transplanting healthy beta cells holds more promise for the moment-to-moment fine-tuning of insulin levels, says Arepally。

Current experimental cell transplantation techniques are done "naked and blind," only lasting a short period of time, according to co-author Jeff Bulte, Ph。D。, a professor of radiology and chemical and biomolecular engineering at Hopkins。 The unprotected transplanted cells are vulnerable to attack by the recipient’s immune system, and researchers cannot see the cells to figure out why they stop making insulin after a while。

To address both of these challenges, the research team captured beta cells in tiny porous capsules made from a mixture of alginate, a gooey material made from seaweed, and Feridex, a magnetic iron-containing material visible under MRI。 They then used a machine that oozes droplets of this mixture to surround and encapsulate individual islet clusters each containing about 500 to 1,000 insulin-producing beta cells。 Once the cells are encapsulated, the shell hardens, creating a "magnetocapsule" that measures less than 1/128 of an inch across。

"They’re tiny spheres with nano-scale pores just big enough too let the good stuff out but keep the bad from getting in," says lead author Brad Barnett, medical student and Howard Hughes fellow at Hopkins。 The openings in the magnetocapsule are so small that the body’s immune system sentinels cannot reach and attack the transplanted cells。

The team first transplanted magnetocapsules into the abdomens of mice engineered to develop diabetes。 Blood sugar levels in the animals returned to normal within a week and stayed that way for more than two months。 In contrast, more than half of untransplanted diabetic mice died, and the rest had very high blood sugar levels。

To mimic human transplantation, the researchers then implanted magnetocapsules into the livers of swine with the help of MRI fluoroscopy, special reflective screens and a computer monitor that provide real-time imaging。 The liver was chosen, rather than the usual pancreatic home of beta cells, because it contains many blood vessels that can deliver insulin quickly to the rest of the body。

"Getting the magnetocapsules into the right place requires hand-eye coordination normally required when playing video games," says Arepally。 The team threaded a long needle-like tube into a large vein near the upper thigh and guided the tube upward, across and into a neighboring blood vessel, ending in the body of the liver。

The pigs underwent MRI and blood tests three weeks after magnetocapsule transplantation。 MRI showed that the magnetocapsules remained intact in the liver, and blood tests revealed that the cells were still secreting insulin at levels considered functional in people。

"We hope that our magnetocapsules will make tissue-type matching and immunosuppressive drugs problems of the past when it comes to cell-based therapies for type 1 diabetes," says Bulte。

The research was funded by the National Institutes of Health and the Howard Hughes Medical Institute。

Authors on the paper are Barnett, Arepally, Parag Karmarkar, Di Qian, Wesley Gilson, Piotr Walczak, Valerie Howland, Leo Lawler, Cal Lauzon, Matthias Stuber, Dara Kraitchman and Bulte, all from Hopkins。

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