A CAPSULE packed with human eye cells has been turned into a drug factory for treating the inherited eye disease retinitis pigmentosa. Trials on people could start within a year.
Encapsulated cells have long been hailed for their potential to deliver a continuous, local dose of drugs to treat conditions as diverse as Parkinson鈥檚 disease and chronic pain. Because the capsule protects the cells from immune attack, the same cell line can be implanted in any patient.
The few trials in the past have been disappointing, admits Weng Tao of biotech company Neurotech of Paris and Boston. But key lessons have been learned over the past decade. 鈥淣ow I think we can translate the technology into a practical entity,鈥� Tao says.
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One lesson was not to target a disease that affects large organs, such as the brain. Instead, Tao鈥檚 group focused on the eye, for which far smaller drug doses will suffice. They also picked the cells for their factory carefully, using human retinal cells that are adapted to the environment in which they would be implanted.
They chose to treat retinitis pigmentosa, a disease that destroys the retina. It affects millions worldwide, and while the genetic cause is often known, there is no effective treatment. A variety of substances have been shown to halt the disease in the lab 鈥� the problem is how to deliver them to the eye continuously and at the proper dose.
That鈥檚 where the encapsulated cells come in. Tao and her colleagues genetically engineered eye cells to produce the protein ciliary neurotrophic factor (CNTF). About a half million cells making CNTF were encased in a plastic tube measuring 1 centimetre by 1 millimetre, with pores large enough to let CNTF out but too small for antibodies to get in. These were implanted in one eye each of dogs with the disease, in a simple 15-minute procedure.
After seven weeks, tissue destruction in the treated eyes had halted, while the untreated eyes had lost about half their light-sensitive cells (Investigative Ophthalmology & Visual Science, vol 43, p 3292). And the implanted cells continue to thrive after a year, Tao told 快猫短视频.
鈥淭he slow, timed release of small amounts of drug is an important improvement,鈥� says Peter Dudley of the National Eye Institute near Washington DC. 鈥淎 single large injection to the eye doesn鈥檛 work nearly as well.鈥�
Since dogs and people have similar-sized eyes, the capsule should be suitable for humans, Tao says. It could also be adapted to treat other eye diseases by engineering cells to produce different substances.
Tao thinks encapsulated cells have a clear advantage over gene therapy, a rival way of treating such diseases. 鈥淚n gene therapy, once the genes are in, they are in to stay. But if in five years we have a better model of our cells or a problem develops, we can pull them out.鈥�