On the surface, a stem cell–based cure for Parkinson’s disease seems straightforward.

Parkinson’s causes tremors, slowed movement, and muscle rigidity. This is because a specific group of dopamine‑producing neurons in the brain dies over time. Replacing those lost cells with stem‑cell‑derived dopamine neurons would seem like an obvious way to restore dopamine levels and relieve symptoms.

Easier said than done

Well, it hasn’t been that easy. Early fetal brain cell transplants in the 1980s and 1990s showed initial promise, but larger trials found no meaningful benefit and even worsened symptoms for some patients. One likely issue was the variable composition of fetal tissue. In addition, fetal tissue is limited, and it yields very few usable cells.

More recently, researchers have worked to generate purer populations of dopamine neurons from human embryonic stem cells and induced pluripotent stem cells. Progress has been strong, but the field still struggles to produce enough dopamine neurons quickly and reliably for therapeutic use.

Cutting out the pluripotent “middle man”

This week, a research team at the University at Buffalo reported in Nature Communications about a much more efficient method. This finding could strongly push stem cell-based therapy development for Parkinson’s disease.

The team bypassed the need to start with hESCs or iPSCs by converting skin cells directly into dopaminergic neurons. A detailed analysis confirmed the cells were functional and matched the dopamine neurons lost in Parkinson’s disease.

Direct reprogramming—pioneered by several groups, including CIRM grantees—has advantages over differentiating hESCs or iPSCs. It is faster, doesn’t require cell division, and reduces concerns about introducing DNA mutations or tumor formation. It also raises the possibility of converting one cell type into another inside the body, rather than manipulating stem cells in the lab.

Despite these benefits, direct reprogramming has been inefficient. That’s where the University at Buffalo team made progress.

Bringing down the gatekeeper

The team, led by Jian Feng, Ph.D., made key modifications to improve the efficiency of converting skin cells into dopaminergic neurons. First, they reduced p53 levels. Known as the “guardian of our genes,” p53 controls cell division and DNA repair and helps suppress tumors.

Lowering p53 greatly increased the efficiency of reprogramming skin cells into dopaminergic neurons. Because this conversion occurs within days, the researchers had to time the introduction of neuron‑specific nutrients carefully. Together, these refinements improved on earlier methods. As Feng noted in a University at Buffalo press release:

“The best previous method took two weeks to produce 5 percent dopamine neurons. With ours, we got 60 percent in ten days.”

IMHO (In my humble opinion)

Researchers know this method for deriving dopaminergic neurons from skin will require more development before it reaches the clinic. The approach uses a deactivated virus to deliver neuron‑specific genes into skin cells, but viral DNA can insert randomly into chromosomes and potentially activate cancer‑causing genes. Clinical use will require a non-viral delivery method.

Because p53 suppresses uncontrolled cell division and helps prevent tumors, it’s also critical to ensure that reducing p53 does not create long‑term risks, including transplanting cells with cancerous potential.

Still, this large increase in efficiency for generating functional dopaminergic neurons—and identifying p53 as a key reprogramming control point—is an exciting advance for a field committed to finding cures.

Related links:

From the Stem Cellar archives: blogs about direct reprogramming
Video: CIRM Grantee Marius Wernig discusses direct reprogramming
Video: Thirty-second elevator pitch describing direct reprogramming