How to Replace the Neurons that Die off in Parkinson’s Disease

When disease or old age ravage the body, it would be great to turn back the clock by swapping out the damaged cells, replacing them with new ones, like for like. Pluripotent stem cells (PSCs) self-replicate and have the potential in the human body to develop into almost any cell type. As such, they have long held potential in the development of regenerative medicines. But obtaining a steady supply of PSCs proved challenging for a number of reasons.

In 2006, researchers introduced a method to reprogram adult cells into a pluripotent state. These induced pluripotent stem cells (iPSCs) could then be coaxed to differentiate into different cell types. Fifteen years on, iPSC technology has become the basis for many drug development efforts, and it could one day change the outlook for millions of people.

iPSC-based therapies could replace, for example, the neurons that die off in Parkinson’s disease or the retinal tissue damaged by macular degeneration. Or perhaps they could obviate the need for a heart transplant. The technology is a marked change for big pharma.

Neurons, derived from stem cells, have potential to replace those lost to Parkinson’s disease. But delivering the cells, and ensuring they survive and integrate, are still big challenges

This is a completely different way of looking at medicine—replacing diseased cells rather than drugging them. And we’re right on that precipice,” says Seth Ettenberg, Chief Executive Officer of BlueRock Therapeutics, a biotechnology company headquartered in Cambridge, MA, and a Bayer subsidiary. “It’s an incredibly exciting time for the field.

Using tools such as gene-editing, researchers are seeking to make iPSC-based treatments more effective. The past few years have seen significant progress in the development of treatments.

Parkinson’s disease (PD) is a neurodegenerative disorder that affects more than ten million people worldwide, characterized by the progressive loss of dopamine-producing midbrain neurons, which causes tremors and other motor and neurological symptoms. Mainstay treatments can alleviate symptoms, but do not halt disease progression.

Researchers hope that iPSC-based therapies could replace the neurons killed as Parkinson’s disease progresses. Dopamine-producing neurons derived from iPSCs have been shown to improve behaviour in a rat model of PD. In one patient, dopamine cells from autologous iPSCs seemed to stabilize or even slightly improve motor symptoms 18-24 months after transplantation.

The brain is a difficult organ to access, however. “Cells will be administered to the midbrain via neurosurgery using devices designed to ensure cells are not damaged during delivery,” says Stefan Frank, associate director of Bayer’s iPSC platform strategy. “The cells then need to stay there, survive and integrate.”


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