Grow a new brain: First steps to lab-made grey matter

BIOENGINEERS dream of growing spare parts for our worn-out or diseased bodies. They have already succeeded with some tissues, but one has always eluded them: the brain. Now a team in Sweden has taken the first step towards this ultimate goal.

Growing artificial body parts in the lab starts with a scaffold. This acts as a template on which to grow cells from the patient's body. This has been successfully used to grow lymph nodes, heart cells and voice boxes from a person's stem cells. Bioengineers have even grown and transplanted an artificial kidney in a rat.

Growing nerve tissue in the lab is much more difficult, though. In the brain, new neural cells grow in a complex and specialised matrix of proteins. This matrix is so important that damaged nerve cells don't regenerate without it. But its complexity is difficult to reproduce. To try to get round this problem, Paolo Macchiarini and Silvia Baiguera at the Karolinska Institute in Stockholm, Sweden, and colleagues combined a scaffold made from gelatin with a tiny amount of rat brain tissue that had already had its cells removed. This "decellularised" tissue, they hoped, would provide enough of the crucial biochemical cues to enable seeded cells to develop as they would in the brain.

When the team added mesenchymal stem cells taken from another rat's bone marrow to the mix, they found evidence that the stem cells had started to develop into neural cells (Biomaterials, doi.org/qfh).

The method has the advantage of combining the benefits of natural tissue with the mechanical properties of an artificial matrix, says Alex Seifalian, a regenerative medicine specialist at University College London, who wasn't involved in the study.

There is a long way to go before any sort of clinical application could be considered, but Macchiarini envisages that a scaffold seeded with neural cells could help people with neurodegenerative disease. The death of brain cells is what causes symptoms in conditions such as Parkinson's and Alzheimer's.

It might also be possible one day to use transplants of bioengineered tissue to replace parts of the brain damaged, for example, by a gunshot, Macchiarini says, and to provide a matrix for native cells to grow into.

"We expect that a patient's central nervous system cells could migrate into the implanted scaffold, adhere to it, grow and contribute to neural tissue regeneration," he says.

Seifalian says that in someone with cell loss from a neurodegenerative disease or brain damage, a scaffold such as this would be useful as a last resort. Of the numerous stages to go through before this method gets to the clinic, not least is the need to confirm the degree of integration of the scaffold within natural tissue in the brain, he says. There also needs to be a way to measure any functional improvement in brain activity.

Charles Lieber at Harvard University says the work could represent a significant advance for neural tissue engineering and regenerative neural treatments.

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Grow a new brain: First steps to lab-made grey matter