Scientists have cultivated tiny human brain organoids in space to explore new treatments for Alzheimer’s disease, Parkinson’s disease, and spinal cord injuries.
The low-gravity environment of the International Space Station (ISS) enabled researchers to develop brain organoids in just 72 hours, a process that typically takes months on Earth.
These organoids, which are artificially grown cell masses mimicking the structure and function of human organs, allowed researchers to test a novel approach for curing currently incurable neurological diseases.
The promising new treatment, developed by biotechnology company Axonis Therapeutics, uses a reprogrammed virus to deliver beneficial gene therapy to cells in the central nervous system (CNS).
These modified viruses, known as viral vectors, could be particularly useful for treating Alzheimer’s and Parkinson’s diseases, as well as spinal cord injuries. Nearly 600,000 Americans are diagnosed with Alzheimer’s or Parkinson’s each year, alongside approximately 18,000 new spinal cord injuries annually in the United States.
Tests indicated that the proposed treatment was effective in mice. However, gene therapies that work in rodent models often fail in humans. Axonis Therapeutics needed to conduct tests using an accurate model of the human CNS, prompting them to attempt to grow human brain organoids in space.
While scientists can grow CNS cells on Earth, gravity forces them to organize into flat, two-dimensional layers, complicating the cultivation of the three-dimensional structure and functional complexity of brain cell groups.
The organoids cultivated in space quickly provided a highly accurate model of the human brain, allowing ISS researchers to effectively test the efficacy of the new viral vector treatment.
“Conducting research in space is not something one would typically consider,” said Shane Hegarty, co-founder and chief scientific officer of Axonis Therapeutics. “But the opportunity to leverage microgravity conditions can unlock significant untapped potential by pushing the boundaries of science in a unique environment,” he added.
In August 2023, Axonis Therapeutics sent frozen vials of its viral vector, mature neurons, and astrocytes—cells that support and maintain nerve cells—aboard a resupply mission to the ISS. A team of researchers then injected these materials into a specialized cell culture system called BioCell.
They loaded the viral vector with a fluorescent protein gene. If successful, the neurons would glow green after the gene was implanted.
In just 72 hours, the cells not only organized into three-dimensional human brain organoids but also exhibited fluorescence.
NASA astronaut Mike Barratt is processing brain organoid samples aboard the ISS for another research project this year.
ISS researchers utilized the BioCell system to cultivate brain organoids and test the viral vector's efficacy. “The pivotal day was when the crew performed microscopy and we saw large aggregates of green, glowing 3D tissues,” said Sheila Nielsen, a researcher from BioServe Space Technologies, which developed BioCell. “Shane and I were sending images of the organoids back and forth, and we were quite thrilled because it was not something they had ever seen in the field,” she added.
Viruses are highly effective at infecting cells and inserting genetic material, which can damage cells and trigger an immune response. However, scientists can reprogram viruses to deliver beneficial gene therapies, providing targeted treatment for diseases or injuries.
This study demonstrated that Axonis Therapeutics' viral vector could deliver gene therapy to human neurons. “It was very exciting: we were able to both validate the targeting capability of the gene therapy and show that we rapidly formed 3D assembloid models of the human brain,” said Hegarty. “The major breakthrough lies in the ability to rapidly self-assemble mature neurons and astrocytes to form a brain model in microgravity conditions, which cannot be achieved on Earth.”