Scientists have introduced a new method for cryopreserving human brain tissue and neural organoids. The groundbreaking technique has allowed scientists to freeze human brain tissue and revive it without damage. This advancement is a game changer in the study of neurological conditions, claim Zhicheng Shao and his team at Fudan University in Shanghai, China.

To be clear from the start, the scientists didn’t freeze and thaw human brains. This effort uses brain organoids — artificially grown, in vitro, tissue resembling parts of the human brain — derived from human embryonic stem cells. These are essentially tiny brain tissues grown in a dish.

Traditionally, freezing brain tissue results in significant cellular damage upon thawing, limiting research capabilities. To address this, the researchers cultivated brain organoids for many weeks and then bathed them in a proprietary blend of chemicals. The organoids, measuring approximately just four millimeters, contained neurons and neural stem cells capable of developing into various functional brain cells.

The MEDY Solution

The key to this breakthrough lies in a chemical blend named MEDY, composed of methylcellulose, ethylene glycol, DMSO, and Y27632. DMSO (Dimethyl Sulfoxide) is a versatile solvent and cryoprotectant that prevents ice crystal formation in cells during freezing, while Y27632 is a small molecule inhibitor that targets ROCK (Rho-associated protein kinase) to improve cell survival and growth.

This concoction was identified after extensive testing with various compounds to find the best preservative during the freezing and thawing process. MEDY was found to minimize cell death and promote growth effectively.

In their experiments, Shao’s team stored the MEDY-treated organoids in liquid nitrogen for at least 48 hours. Upon thawing, they monitored the organoids for two weeks, assessing cell death and the growth of neurites—nerve cell branches. Organoids treated with MEDY showed high similarity in appearance, growth, and function to non-frozen counterparts. This was consistent even after being frozen for 18 months in one particular case.

Why scientists need to freeze brain tissue

Brain diseases pose an enormous cost, financially and in human lives. And over 90% of new candidate drugs fail during clinical trials. This failure is partly due to the challenge of translating drug effects from animal models to humans.

This is where brain organoids come in. These tissues mimic the human brain’s development and function. So, they could prove much more useful than yet another promising study on mice that ends up nowhere. However, their long-term culture and high maintenance costs have limited their widespread use.

MEDY addresses these issues by providing a reliable cryopreservation method that maintains the neural cytoarchitecture and functional activity of brain organoids. One of MEDY’s significant advantages is its applicability to a wide range of brain-region-specific organoids, such as those from the forebrain, spinal cord, and optic vesicle brain. This versatility means that researchers can now preserve and utilize these organoids for extended periods, reducing the preparation time and costs associated with continuous culture.

The successful preservation of brain tissue extends beyond organoids. The team also tested MEDY on 3-millimeter brain tissue cubes from a 9-month-old girl with epilepsy. These tissue samples retained their structure and function post-thaw, remaining active in culture for over two weeks.

Not the sci-fi cryogenic device you were hoping for but who knows what the future has in store

Researchers can now maintain large libraries of brain organoids representing various conditions, facilitating the screening and development of new drugs. Likewise, they could establish a biobank for brain organoids derived from patients with different brain diseases. Such a resource would support personalized medicine approaches, allowing researchers to study disease mechanisms and develop tailored treatments more effectively.

With further research and testing on larger tissues, MEDY could pave the way for preserving entire human brains, although this goal would be like shooting for the stars at this point. The human brain is incredibly complex, many orders of magnitude more challenging to preserve than a tiny slice of neural tissue. Cryopreservation — any billionaire’s wet dream — would also have to work on the entire body because no brain has ever evolved to function in a vat-like environment. Such a goal is impossible with today’s technology, but it’s anyone’s guess the stage of technological advancement a century from now.

For now, this development marks a critical step toward improving the cryopreservation of sensitive tissue. It already has immediate applications in neurodegenerative research. The MEDY technique could transform how scientists study brain development and diseases, ultimately leading to significant medical advancements.

The findings were reported in the journal Cell Reports Methods.