City of Hope scientists use stem cells to develop ‘mini-brains’ to study Alzheimer’s and to test drugs in development

Alzheimer’s is a progressive disease that destroys memory and other important mental functions. According to the non-profit HFC, co-founded by CIRM Board member Lauren Miller Rogen and her husband Seth Rogen, more than 5 million Americans are living with Alzheimer’s. It is the 6th leading cause of death in the U.S and it is estimated that by 2050 as many as 16 million Americans will have the disease. Alzheimer’s is the only cause of death among the top 10 in the U.S. without a way to prevent, cure, or even slow its progression, which is it is crucial to better understand the disease and to develop and test potential treatments.

It is precisely for this reason that researchers led by Yanhong Shi, Ph.D. at City of Hope have developed a ‘mini-brain’ model using stem cells in order to study Alzheimer’s and to test drugs in development.

The team was able to model sporadic Alzheimer’s, the most common form of the disease, by using human induced pluripotent stem cells (iPSCs), a kind of stem cell that can be created from skin or blood cells of people through reprogramming and has the ability to turn into virtually any other kind of cell. The researchers used these iPSCs to create ‘mini-brains’, also known as brain organoids, which are 3D models that can be used to analyze certain features of the human brain. Although they are far from perfect replicas, they can be used to study physical structure and other characteristics. 

The scientists exposed the ‘mini-brains’ to serum that mimics age-associated blood-brain barrier (BBB) breakdown. The BBB is a protective barrier that surrounds the brain and its breakdown has been associated with Alzheimer’s and other age-related neurodegenerative diseases . After exposure, the team tested the ‘mini-brains’ for various Alzheimer’s biomarkers. These markers included elevated levels of proteins known as amyloid and tau that are associated with the disease and synaptic breaks linked to cognitive decline.

Research using brain organoids has shown that exposure to serum from blood could induce multiple Alzheimer’s symptoms. This suggests that combination therapies targeting multiple areas would be more effective than single-target therapies currently in development.

The team found that attempting a single therapy, such as inhibiting only amyloid or tau proteins, did not reduce the levels of tau or amyloid, respectively. These findings suggest that amyloid and tau likely cause disease progression independently. Furthermore, exposure to serum from blood, which mimics BBB breakdown, could cause breaks in synaptic connections that help brains remember things and function properly.

Image Description: Yanhong Shi, Ph.D.

In a press release from the Associated Press, Dr. Shi elaborated on the importance of their model for studying Alzheimer’s.

“Drug development for Alzheimer’s disease has run into challenges due to incomplete understanding of the disease’s pathological mechanisms. Preclinical research in this arena predominantly uses animal models, but there is a huge difference between humans and animals such as rodents, especially when it comes to brain architecture. We, at City of Hope, have created a miniature brain model that uses human stem cell technology to study Alzheimer’s disease and, hopefully, to help find treatments for this devastating illness.”

The full results of this study were published in Advance Science.

Dr. Shi has previously worked on several CIRM-funded research projects, such as looking at a potential link between COVID-19 and a gene for Alzheimer’s as well as the development of a therapy for Canavan disease.