Genetically modified stem cells could enhance Parkinson’s therapy
Replacement cell therapy is expected to land a powerful blow against the progressive, neurodegenerative Parkinson’s disease, and researchers in Aarhus are paving the way to make the treatment more effective by producing high quality cells at the highest possible purity.
Mark Denham, Associate Professor at Aarhus University
By Helen Frost
Parkinson’s disease, which affects over 10 million people worldwide, is characterised by the unrelenting loss of a specific type of neuron in the brain called ‘dopaminergic neurons’. Patients can suffer from tremors, poor muscle control, hallucinations and behavioural changes, and studies show that much of the burden of the disease is carried by loved-ones and family members. There is no cure; currently the only approved treatments relieve symptoms.
Frontier Grants facilitate transitions from basic research to attractive prospects for biotech investors
“The fact that you can restore function in the brain by replacing these dopaminergic brain cells has already been proven”, says assoc. prof. Mark Denham, Aarhus University.
In recent years, scientists have shown that by replacing these specialised cells in the brains of patients, it’s possible to stop the progression of Parkinson’s disease and provide relief from symptoms. However, the supply of human dopaminergic neurons for transplantation is not plentiful - early studies relied on cells purified from foetal tissue. More recently, there have been advances in the production of these cells from lab-grown cultures of stem cells, with laboratory differentiation protocols using chemical factors in the growth medium to stimulate the cells to specialise towards one cell type or another. But, coaxing pluripotent stem cells to become neurons results in a mixture of different, but related, cell types, and the current methods to produce dopaminergic neurons typically result in cultures containing 10-15% cells of interest.
Lineage restriction doubles the number of dopaminergic neurons in the treatment
Assoc. Prof. Mark Denham and his team from Aarhus University have developed and patented a powerful technique to produce dopaminergic neurons of high purity with minimal presence of other unwanted cell types. The technique of ‘lineage restriction’ allows the scientists to modify the genetic code of pluripotent stem cells and direct the cells towards the right destination: specifically, to differentiate into dopaminergic neurons. With this technology, Denham’s group is able to produce double the quantity of the cells of interest.
“There’s an inherent inconsistency in the cell products that are currently being produced and tested, with labs conducting transplantations comprising 10-15% dopaminergic neurons in the brain. We have been able to improve that by over two-fold.”
A pluripotent stem cell doesn’t want to become just one cell type; it really wants to give rise to an entire organism. Controlling that differentiation in the lab is difficult, but we’ve found a way to send them in the right direction
Naturally, during embryonic development, pluripotent stem cells differentiate into increasingly specialised groups of cells, eventually producing the hundreds of different cell types that a human body is made from. During this process, cells switch on and off the expression of a variety of genes, in response to the signals they receive from around them, ensuring that the entire, complex process happens in concert and in the correct sequence. Once a cell begins to differentiate down a pathway, it can no longer turn back and reverse its fate. This applies to brain cells, which begin life as pluripotent stem cells, then become neural stem cells, and later may either branch into the lineage of neural progenitors (which can give rise to the different neurons found in the brain), or may branch instead into other lineages.
“A pluripotent stem cell doesn’t want to become just one cell type; it really wants to give rise to an entire organism. Controlling that differentiation in the lab is difficult, but we’ve found a way to send them in the right direction.”
The project to develop this technology into a treatment is known as UNIPOTENT, and makes use of the exclusive rights to the lineage restriction technology that enhances the production of dopaminergic neurons from stem cells which Denham’s group holds. The process works by knocking out four specific genes in the pluripotent stem cells’ genomes. Without these genes, the stem cells are deterred from differentiating into unwanted lineages and guided towards the dopaminergic neuron fate. Interestingly, even when grown using methods to stimulate specialisation towards a different neural lineage, these engineered cells still produce high quantities of dopaminergic neurons.
“When we genetically alter a stem cell and remove the genes that are expressed in lineages that we don’t want, then we can tailor make a cell type which does one thing, but it does it really well.”
From tinkering in the lab to creating a patient-ready treatment
“By the end of the Frontier Grant the project will be investment-ready. That’s the strength of this grant; we can advance the technology to the point where we can obtain significant investment to take the next step, which typical research grants don’t offer.”
As in many academic labs, Denham’s group initially created the modified cell types using a technology called CRISPR Cas9 applied to research-grade cell lines. This proved the concept can work, but doesn’t give them a product which can be tested in people.
The Lundbeck Foundation Frontier Grant will allow the team to apply their technology to stem cells which have been produced under strictly regulated manufacturing conditions, known as Good Manufacturing Practice, or “GMP”. Denham’s team will apply their technique to GMP stem cells, and will move to a gene editing system that is suitable for licensing.
The scientists will test four different GMP cell lines for suitability, and then they will genetically modify them to knock out the four unwanted genes. Once edited, the cells will be differentiated into the neurons of interest, and then transplanted into the brains of rats experiencing Parkinson’s to test their efficacy - potentially bringing us closer to a treatment for this devastating disease.
“Getting investors on board requires that we demonstrate a clear path to the clinic, and that’s what we’ve been developing for the last 12 months. This Frontier Grant will give us the opportunity to take the first step on that path.”
Focusing on translating research into clinical benefit
For many researchers, rat models of Parkinson’s are an important resource for testing potential treatments. Typically, rats are treated with a drug to create lesions in the brain which mimic the damage in a Parkinsonian brain.
“We showed that we could transplant fewer cells into animals and still achieve a significant recovery from disease. We expect that this will translate into an improved efficacy and safety for patients, by transplanting the smallest number of highest purity cells possible.”
Having cells transplanted directly into the brain is no trivial matter, and ensuring that the dose is as small and effective as possible will serve patients best, Denham believes. Not only in terms of the patient’s experience, but also to satisfy the regulators that the new treatment can be approved for use.
The unique setup of the Frontier Grant means that bringing a new idea towards the clinic might be quicker and easier in the future.
“The first time you try to take the commercial path you spend a lot of time understanding the process, and now that we’ve been through this with the Lundbeck Foundation, our learnings can be directly transferred to another cell therapy.”
Denham has high aspirations for the applications of his technology and imagines that in the future it could be possible to create a bank of differently gene-engineered stem cells which give rise to a variety of different specialised cells when cultured. And beyond this, cocktails of different modified stem cells could be created, in carefully considered ratios, to potentially give rise to complex tissue. Differentiating stem cells are naturally capable of self-organising, so theoretically they could be directed to produce transplantable material to repair damaged or diseased organs. The UNIPOTENT project also benefits from a strong innovation culture at the Department of Biomedicine at Aarhus University, featuring in-house expertise including the support of serial entrepreneur and Innovation Professor Claus Olesen and Senior Innovation Consultant Jane Palsgaard.
“We are interested in pursuing Lineage Restriction for other indications, so having a better idea of what’s important for investors and regulators, means that we can think about those things from the very beginning.”
Working with the Lundbeck Foundation isn’t like writing a traditional research grant, and the strong communication between the scientists and the funders will continue throughout the project.
“It’s clear that the Foundation is keen to make this work successful, which we’ve been really happy with.”
Learn more about the Lundbeck Foundation Frontier Grant:
Frontier Grants facilitate transitions from basic research to attractive prospects for biotech investors
