An average human brain weighs about 3 pounds. It's made up of nearly 75% water, contains some 100 billion neurons, and of those neurons, there are some 1,000 to 10,000 synapses for each neuron. The brain includes no pain receptors within its tissues. There are approximately 100,000 miles of blood vessels in a typical human brain, and it's the fattiest organ in the body comprised of about 60% fat.
The human brain uses 20% of the total oxygen available in the body at any given time, and your brain also uses 20% of the blood circulating in the body. In a waking state, the brain generates between 10 and 23 watts of power and the neocortex makes up about 76% of the human brain to handle language functions and consciousness.
There is archaeological evidence that a form of primitive brain surgery was performed by drilling a hole in the skull as early as 2000 B.C., but the complexity of the brain has made studying it a difficult prospect. While tissues in the human body of simpler construction have been unlocked and re-created using in-vitro 3D tissue cultures by firms like Organovo, functional, brain-like tissues have resisted such efforts – until now.
A team of researchers working at Tufts University have now created a scaffolding they say will lead to the development of three-dimensional tissues which will one day be used to study brain injuries and genetic disorders.
One problem faced by those working to understand how brain tissue functions is the fact that organic matter created in a lab setting typically dies in less than a day, but the Tufts team has managed to create tissue which stays viable for several weeks.
And that's not all. The tissue has been shown to be capable of developing and demonstrating the sort of complex neuronal activity of the living brain tissue on which it's based – and the researchers say the tissue has organized itself into structures reminiscent of the 'gray' and 'white' matter of a real, living brain.
The paper the team wrote, Bioengineered Functional Brain-like Cortical Tissue, details the intricate construction of functional, three-dimensional 'brain-like' cortical tissue featuring architectures which demonstrate electrophysiological function. The tissues are so realistic that, when injured, they responds in vitro with biochemical and electrophysiological reactions which are highly analogous with observations made of the workings of the living brain.
The modular, 3D, brain-like tissue will one day be used as a basis for studies of brain homeostasis and injury.
The process works like this: while previous attempts to create brain matter in a lab relied on a hydrogel as a growth medium, the tissues were limited in size and could only develop on a two-dimensional plane. The Tufts team solved the problem with a process which uses collagen gel and a bio-engineered silk protein. These materials are then used to make a porous scaffolding in which white brain cells can fully develop and differentiate themselves from the 'gray' matter in a typical brain structure.
Interlocking modular structures were generated using a biopsy punch with concentrically arranged rings to punch out layered 'doughnut' shapes, and those structures were separated to prepare for cell seeding and then reassembled into a composite structure with concentric rings. The 'scaffolds' were autoclaved, and coated with poly-L-lysine for one to two hours, washed twice and then dehydrated slightly before being seeded with cells.