What is encapsulation?
Wrapped in a protective coating, these encapsulated islets (insulin-producing cells) would be able to do the same job as healthy islets in the pancreas: detecting changes in glucose levels, and producing insulin on demand.
This works because the protective capsule is a little like a sieve – tiny holes in the coating allow nutrients to fit through, enabling the cells to live and work well, but are not big enough to allow anything as big as an immune cell to get close to the precious islets.
What are these special capsules made of?
The first projects we funded on encapsulation used a gel-like material called ‘alginate’ to protect the beta cells. Because you can only see this sort of capsule using a microscope, this approach is sometimes called ‘micro-encapsulation’. Alginate is ‘biologically inert’, which means that the immune system doesn’t respond to it – it’s essentially creating an invisibility cloak for the cells inside!
But alginate doesn’t provide all the answers, so we’re testing other materials as well. We’ve been working with biotechnology company ViaCyte to help drive the development of a physical device to protect and contain new cells. Called the ‘Encaptra’ system, the device is designed to be surgically implanted into the abdomen. The advantage of a much bigger capsule like this one is that it can be retrieved from the body if needed – which is particularly important during the early stages of research when we want to be able to see how well the cells inside are doing. As this approach involves a device big enough to hold in your hand, this is known as ‘macro-encapsulation’.
And in London, Professor Peter Jones completed a project in 2016 to develop coating for cells as thin as possible – this technique is known as ‘nano-encapsulation’. This approach involves weaving a web of different molecules around each set of islets, creating an ultra-fine coating that would still protect the islets from immune cells, but could also incorporate drugs that would keep the cells inside healthy for longer. Find out more about this project.
Where do you get the cells to go inside the capsules?
The beauty of the idea of encapsulation is that as the cells are contained and protected from the rest of the body, a wider array of cells can be placed inside them than would be safe for ‘normal’ transplantation.
For the micro-encapsulation approach, we’ve been working with New Zealand-based company Living Cell Technologies. The islet cells encased in alginate in these studies have come from specially-bred pigs. Having been shown to be safe in the first phase of clinical testing, the DIABECELL product has now entered phase 2 trials, investigating whether it is effective at helping people with type 1 to control their glucose levels.
The ViaCyte Encaptra device has been developed to contain PEC-01 cells. These cells are grown from human embryonic stem cells to become immature pancreatic cells. Once implanted into a person with type 1, the cells, held safely inside the Encaptra device, develop into fully functional islets. The combination of the Encaptra device and the specially grown cells is known as VC-01 and began the first phase of clinical testing in late 2014.