Advanced Science

CIRM-funded development of stem cell therapy for Canavan disease shows promising results

/ Yimy Villa / Leave a comment
Yanhong Shi, Ph.D., City of Hope

Canavan disease is a fatal neurological disorder, the most prevalent form of which begins in infancy. It is caused by mutation of the ASPA gene, resulting in the deterioration of white matter (myelin) in the brain and preventing the proper transmission of nerve signals.  The mutated ASPA gene causes the buildup of an amino acid called NAA and is typically found in neurons in the brain.  As a result of the NAA buildup, Canavan disease causes symptoms such as impaired motor function, mental retardation, and early death. Currently, there is no cure or standard of treatment for this condition.

Fortunately, CIRM-funded research conducted at City of Hope by Yanhong Shi, Ph.D. is developing a stem cell-based treatment for Canavan disease. The research is part of CIRM’s Translational Stage Research Program, which promotes the activities necessary for advancement to clinical study of a potential therapy.

The results from the study are promising, with the therapy improving motor function, reducing degeneration of various brain regions, and expanding lifespan in a Canavan disease mouse model.

For this study, induced pluripotent stem cells (iPSCs), which can turn into virtually any type of cells, were created from skin cells of Canavan disease patients. The newly created iPSCs were then used to create neural progenitor cells (NPCs), which have the ability to turn into various types of neural cells in the central nervous system. A functional version of the ASPA gene was then introduced into the NPCs. These newly created NPCs were then transplanted inside the brains of Canavan disease mice.

The study also used iPSCs engineered to have a functional version of the ASPA gene. The genetically modified iPSCs were then used to create oligodendrocyte progenitor cells (OPCs), which have the ability to turn into myelin. The OPCs were also transplanted inside the brains of mice.

The rationale for evaluating both NPCs and OPCs was that NPCs typically stayed at the site of injection while OPCs tend to migrate, which might have been important in terms of the effectiveness of the therapy.  However, the results of the study show that both NPCs and OPCs were effective, with both being able to reduce levels of NAA, presumably because NAA can move to where the ASPA enzyme is although NPCs do not migrate.  This resulted in improved motor function, recovery of myelin, and reduction of brain degeneration, in both the NPC and OPC-transplanted Canavan disease mice.

“Thanks to funding from CIRM and the hard work of my team here at City of Hope and collaborators at Center for Biomedicine and Genetics, Department of Molecular Imaging and Therapy, and Diabetes and Metabolism Institute at City of Hope, as well as collaborators from the University of Texas Medical Branch at Galveston, University of Rochester Medical Center, and Aarhus University, we were able to carry out this study which has demonstrated promising results,” said Dr. Shi.  “I hope that these findings can one day bring about an effective therapy for Canavan disease patients, who currently have no treatment options.”

Dr. Shi and her team will build on this research by starting IND-enabling studies using their NPC therapy soon.  This is the final step in securing approval from the Food and Drug Administration (FDA) in order to test the therapy in patients.  

The full study was published in Advanced Science.

Testing a drug is safe before you give it to a pregnant woman

/ Kevin McCormack / Leave a comment
Pregnant woman holding medicine.

When a doctor gives you a medication you like to think that it’s safe, that it has been tested to make sure it will do you some good or, at the very least, won’t do you any harm. That’s particularly true when the patient is a pregnant woman. You hope the medication won’t harm her or her unborn child. Now scientists in Switzerland have found a new way to do that that is faster and easier than previous methods, and it uses cell cultures instead of animals.

Right now, drugs that are intended for use in pregnant women have to undergo some pretty rigorous testing before they are approved. This involves lots of tests in the lab, and then in animals such as rats and rabbits. It’s time consuming, costly, and not always accurate because animals never quite mimic what happens in people.

In the past researchers tested new medications in the lab on so-called “embryoid bodies”. These are three-dimensional clumps of cells developed from embryonic stem cells from mice. The problem is that even when tested in this way the cells don’t always reflect what happens to a medication as it passes through the body. For example, some medications can seem fine on the surface but after they pass through the liver can take on toxic qualities. 

So, scientists at ETH Zurich in Basel, Switzerland, developed a better way to test for toxicity.

They took a cell-culture chip and created several compartments on it, in some they placed the embryoid bodies and in others they put microtissue samples from human livers.  The different compartments were connected so that fluid flowed freely from the embryoid bodies to the liver and vice versa.

In a news release, Julia Boos, a lead author of the study, says this better reflects what happens to a medication exposed to a human metabolism.

“We’re the first to directly combine liver and embryonic cells in a body-on-a-chip approach. Metabolites created by the liver cells – including metabolites that are stable for just a few minutes – can thus act directly on the embryonic cells. In contrast to tests on mice, in our test, the substances are metabolised by human liver cells – in other words, just as they would be in the human body when the medication is administered.”

To see if this worked in practice the researchers tested their approach on the chemotherapy drug cyclophosphamide, which is turned into a toxic substance after passing through the liver.

They compared results from testing cyclophosphamide with the new liver/embryoid body method to the older method. They found the new approach was far more sensitive and determined that a 400 percent lower concentration of cyclophosphamide was enough to pose a toxic threat.

The team now hope to refine the test even further so it can one day, hopefully, be applied to drug development on a large scale.

Their findings are published in the journal Advanced Science