Pathway to a cure  pg. 5

Wang and colleagues developed an encapsulation method — materials and bioreactor system — and successfully reversed diabetes in a mouse model by transplanting encapsulated rat or pig islets. But their capsules failed in dogs. The investigators have since worked through nearly 20 different engineering parameters, adjusting each in order to optimize performance.

Now, bolstered by a new grant from NASA, they are preparing to test the improved capsules in larger animals, and assuming success, in human beings. “We are starting to see the light at the end of the tunnel,” says Wang. “You can get a little bit edgy though. Is it really the light, or a train coming at me?”

As investigators make progress in shielding transplanted cells from host immune attack, islet transplantation will become all the more desirable as a treatment and cure for diabetes. Translating it into a widespread option, however, will depend on securing a suitable and plentiful source of insulin-producing tissue.

Images of a developing mouse embryo show the ventral (v) and dorsal (d) pancreatic buds as two blue spots (left panel). A section through one of the buds (middle and right panels) shows blue color only in cells that will go on to form the pancreas. Brown color marks cells that not only will form the future pancreas, by also the stomach (s) and gut (g). See story, page 8.
Courtesy of Chris Wright, Ph.D. and colleagues, and Nature Genetics.
Even if xenotransplantation proves workable, the number of donor animals required to meet patient demand for islets would likely be excessive. Insulin-releasing cells that could be produced in unlimited quantities in the laboratory — or pharmaceutical factory — are a more desirable option.

Toward that end, an international group of scientists, assembled together as the NIH-supported Beta Cell Biology Consortium, are working toward the ultimate goal of converting human stem cells into functional beta-like cells or complete pancreatic islets.

Stem cells, the basic building blocks of the body’s many different tissues, offer promise for a variety of ills. They come in two types: embryonic, which normally populate the early embryo and give rise to all the tissues of the body, and adult, which are found in and serve to replenish “mature” tissues — the best known are the bone marrow-residing cells that renew the blood supply. Embryonic stem cells are considered more versatile than their adult stem cell relatives, in terms of the cell types they can become, but they are more controversial.

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