Engineers at the University of Wisconsin-Madison have developed a process to generate a new cell type that may aid researchers in understanding the progression and treatment of Alzheimer’s disease and other neurological disorders. The research appears in the journal Science Advances.
For the last two decades, Sean Palecek and Eric Shusta, both professors of chemical and biological engineering at UW-Madison, have worked with human pluripotent stem cells. They’ve developed methods that use chemical signals and other environmental cues to coax these cells, which have the potential to develop into many different types of cells in the body, into cell types found in the blood vessels of the brain.
Blood vessels in the brain exhibit a tight barrier between the blood and the brain, termed the blood-brain barrier (BBB). The BBB protects the brain but also blocks delivery of drugs that could treat neurological disease. Researchers can use BBB cell types derived from human pluripotent stem cells to test how drugs and other therapies cross the BBB to treat brain disease.
In previous work, the researchers developed methods to generate the endothelial cells that line blood vessels in the brain. In the latest study, they sought to produce a different cell type called pericytes, which wrap around capillaries, or the tiny blood vessels that deliver oxygen and other nutrients to cells throughout the body. In the brain, a special type of pericyte derived from a precursor cell type known as the neural crest helps in developing and maintaining the blood-brain barrier by directly interacting with the endothelial cells to reduce molecular transport between and through them.
“These neural pericytes are recognized as a very important cell type because they are thought to be very involved in the process of Alzheimer’s disease,” says Shusta. “Because of that, and their impact on BBB development and function, we’re very interested in trying to derive these cells from human pluripotent stem cells.”
To create cells similar to the pericytes found in the brain, they first needed to coax the stem cells to form neural crest cells, following a technique developed by other researchers. Then, they discovered that turning on a gene in the neural crest called NOTCH3 causes the neural crest to develop into cells that resemble brain pericytes.
To produce the cells, the team used a genetic tool called a lentivirus to add genetic code to the neural crest cells which causes an active form of the NOTCH3 gene to be expressed. Once this gene is delivered to neural crest cells, it induces them to develop into pericyte-like cells.
“Since we’re trying to develop neural pericytes, we started with a process that had been developed by others to take stem cells to this neural crest,” says Palecek. “And then our advance was figuring out how to take those neural crest cells to pericytes in this neural- developmental fashion using NOTCH3.”
Another advantage of the technique is that it’s serum free. Serum is a growth medium supplement used in cell and tissue culturing that can vary widely in its exact chemical makeup. By avoiding the use of serum, the researchers believe their end product will be more consistent and reproducible.
In the future, they hope to make the process of generating pericyte-like cells from human stem cells easier by making it possible to turn NOTCH3 on and off by adding a small signaling molecule. That will make the cell line more user-friendly for those who want to use it in their research.
“I think there’s a lot of interest out there from drug developers and people who research Alzheimer’s disease,” says Shusta, pointing out that the loss of pericytes in Alzheimer’s disease may cause BBB deficits that contribute to disease progression. “You could imagine using these cells as screening tools for drugs that could prevent pericyte loss in Alzheimer’s disease. This could play an important role in researching stroke and other neurological diseases as well.”
Sean Palecek is Milton J. and A. Maude Shoemaker Professor. Eric Shusta is Howard Curler Distinguished Professor and R. Byron Bird Department Chair.
Other UW-Madison authors include Benjamin Gastfriend, Margaret Snyder and Hope Holt. Other authors include Richard Daneman, University of California, San Diego.
The authors acknowledge support from the NIH via awards NS103844 and NS132441, the NIH Biotechnology Training Program, T32 GM008349, and the NSF Graduate Research Fellowship Program, 1747503.
Featured image: Researchers Sean Palecek (seated), Eric Shusta (standing) and their students have developed a method for producing a line of neural pericyte-like cells that could aid research into neurological diseases like Alzheimer’s disease. Credit: Jason Daley.