Silicone retina chip, www.eng.buffalo.edu

Bone marrow stem cells might one day deliver drugs to the eye, halting age- and diabetes-related blindness. The cells can treat a genetic condition that causes mouse retinas to degenerate.

When the stem cells - that usually make blood vessels - were injected into the fluid-filled space of the eye they became part of developing blood vessels in the retina.

Faulty capillary formation is central to both the leading causes of adult blindness in the US: diabetic retinopathy and age-related macular degeneration.

Scientists have worked on mice carrying a genetic mutation for retina development. Normally, these animals start to lose retina blood vessels around two weeks after birth and become completely blind by one month. Bone marrow stem cells stabilized capillaries for up to a month after the injection.

Whether the mice can see, remains to be tested, but the retinas appear normal. "What's so interesting about these cells is that they go directly to where they are needed, incorporate into the normal developing [blood vessels] and just sort of join the party," says ophthalmologist Lois Smith of Harvard Medical School in Cambridge, Massachusetts, who studies blindness in premature babies.

Excess capillaries can also cause blindness. So scientists next exploited the cells' targeting ability to deliver a protein to the retina that stopped blood vessels growing. Before being injected the cells were genetically modified to produce the protein.

This experiment is very much promising in the future. Such therapy could help not only to grow retina, using autologous transplantation of bone marrow cells. This technology could be applied in treating much more diseases than we can imagine possible. Before then, much more work must be done in animal models to rule out dangerous side-effects and new possibilities of this technology.