Island cells in practical cling packaging
Researchers have developed complex carbohydrate beads to protect insulin-producing islet cells. In her opinion, this improves the chances of success of islet cell transplantation to treat diabetes. These beads are made from a complex carbohydrate known as alginate. Their development could solve one of the main problems that has stood in the way of successful islet cell transplantation: These beads have pores large enough for glucose to enter and insulin to exit. At the same time, the pores are small enough to prevent the immune cells from entering the beads and attacking the islet cells, said Emmanuel Opara, assistant professor of experimental surgery and leader of the research project at Duke University.
In animal experiments, the researchers found that the isolated islet cells produced exactly the right amount of insulin in tests for the respective glucose concentration. Insulin is a hormone made and secreted by special cells in the pancreas called islets of Langerhans. It breaks down sugar, starch and other foods, releasing energy for cell metabolism. These islets of Langerhans show a malfunction in insulin deficiency diabetes, diabetes type I. Diabetics therefore have to inject their own insulin.
In the experiments, the scientists obtained islet cells from the pancreas of a donor animal by treating them with enzymes that digest everything except islet cells. The isolated cells were then placed in an alginate solution. This was pressed through a fine cannula with the aid of a droplet generator. This formed tiny spheres that hardened as soon as they dropped into a calcium solution. Each bead contained one or two cells. At this stage of the process, the entire bead was solid. It was then provided with a layer of amino acids as spacers and then covered with alginate. We then chemically treated the beads in a so-called chelation process. This made the inner alginate core liquid again explains Opara. The liquid center provides an ideal environment for the islets to work within a protective shell.
The researchers tested the islet cells' ability to produce adequate amounts of insulin in three sets of experiments: the first group lived in liquid spherical nuclei, the second group lived in solid nuclei, and the third group consisted of packaged islet cells that lived for 24 hours preserved in a solution of nutrients and antibiotics but contained in spheres with a solid core.
The islets in the first group responded to variable glucose concentrations like normal islet cells would, while the second group had no response at all," Opara said. The third group showed a small but insignificant reaction; therefore, we believe that keeping it in a nutrient solution can improve cell function.
Since 1966, surgeons have transplanted more than 7,000 human pancreases. This has enabled many diabetics to stop injecting insulin. Unfortunately, there are not enough organs to support all diabetics.
Researchers are considering isolating islet cells from pigs, millions of which are slaughtered for their meat each year. In order to keep the defense reaction of the human immune system low, they want to work with a special breed of pig that carries human genes. However, Harland believes that islet cell transplantation could become a reality in the near future. At the moment we don't know how long the islet cells will work. But even if we had to implant new cells every six months or once a year, that would still be better for patients than having to inject themselves with insulin several times a day.
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