Many sorts of cell therapy work because of the signals secreted by the transplanted cells. In most cases, near all such cells die quite quickly, failing to integrate into the recipient tissue. Methods of reliably improving cell survival could be used to make these first generation therapies more effective, but more importantly enable a whole range of second generation therapies that are presently impractical. One approach that seems to be gaining traction is to generate a tissue-like structure in which cells are better supported, and transplant that: heart patches are an example of the type. Another approach is outlined here, in which transplanted cells are encapsulated in alginate, an approach that protects and supports them sufficiently well to allow regenerative therapies, such as the example here involving the use of macrophages to spur regeneration, to become a practical concern.

Researchers have made small capsules from brown algae which hold macrophages, a type of white blood cell. Tests in mice have shown that these algae capsules may be able to increase blood flow in the limbs where tissue has been damaged. The researchers now hope to move this research into human clinical trials to help the people visiting hospital with critical limb ischaemia (CLI). Scientists have been experimenting with cells as a treatment to grow arteries in the leg for years, however, these treatments have not been effective in humans. A big challenge is that many of the cells injected into the injured area die, move away to surrounding areas, or are detected as 'foreign' by the immune system and rejected.

In this study, scientists delivered the new algae-based capsules containing macrophages to areas of injured muscle tissue in the back legs of mice. Alginate from the cell walls of brown algae, which is mainly found in cold waters in the Northern Hemisphere, was used to form the capsules. They found that these macrophages successfully remained in the injured area, new blood vessels formed, and as a result more blood reached the damaged area. Currently, to treat CLI and restore blood flow in the limbs, the blocked section of the artery has to be either bypassed during surgery or widened using a small piece of expandable mesh called a stent. However, in up to a third of patients, these methods will eventually fail or are not possible to begin with and amputation is the only option. The researchers therefore hope that this new way of delivering cells could be the key to creating an effective treatment for people suffering with CLI.