Researchers are managing to grow larger masses of tissue from stem cells of late, with more of the structure of the full organ they came from. See, for example, recent work on liver tissue engineering. This is a small step on the way towards full organ regrowth, and will probably be of greatest immediate benefit to further research, testing of therapies, and the like, as three-dimensional engineered tissues of this sort behave much more like the real thing. The brain is of course an organ just like all the others, grown from a genetic blueprint from a selection of cells - so we should expect to see the same progress here as we see for hearts and livers. It is even conceivable that less vital portions of the brain could be replaced or renewed by transplant or regrowth in the future, as not every part of the brain is essential to either storage of the data of the mind or maintenance of life.
Researchers found that immature brain cells derived from stem cells self-organize into brain-like tissues in the right culture conditions. The "cerebral organoids," as the researchers call them, grew to about four millimeters in size and could survive as long as 10 months. For decades, scientists have been able to take cells from animals including humans and grow them in a petri dish, but for the most part this has been done in two dimensions, with the cells grown in a thin layer in petri dishes. But in recent years, researchers have advanced tissue culture techniques so that three-dimensional brain tissue can grow in the lab. The new report [demonstrates] that allowing immature brain cells to self-organize yields some of the largest and most complex lab-grown brain tissue, with distinct subregions and signs of functional neurons.
[This] is the latest advance in a field focused on creating more lifelike tissue cultures of neurons and related cells for studying brain function, disease, and repair. With a cultured cell model system that mimics the brain's natural architecture, researchers would be able to look at how certain diseases occur and screen potential medications for toxicity and efficacy in a more natural setting.
Other groups are developing three-dimensional brain tissue cultures with the hopes of treating degenerative diseases or brain injury. [One set of researchers] has developed a three-dimensional neural culture to study brain injury, with the goal of identifying biomarkers that could be used to diagnose brain injury and potential drug targets for medications that can repair injured neurons. "It's important to mimic the cellular architecture of the brain as much as possible because the mechanical response of that tissue is very dependent on its 3-D structure."