But scientists will need to arrange those diverse cells into the right patterns if they want the heart to beat. The basic idea is simple: tissue engineers hope to induce stem cells, the powerful, general-purpose cells from which all cell types derive, to grow into the various specialized cells that form a liver, kidney or heart. While neuroscientists might someday adapt this methodology to study neuronal patterning in the human brain, the Stanford researchers believe the technique could be more usefully applied to the emerging field of tissue engineering. Study co-authors Jian Qin, an assistant professor of chemical engineering, and postdoctoral scholar Xian Kong developed a computational model to show that this complex network of functional neighborhoods stems from the tendency of neurons to pack together as closely as possible without being too close to other neurons of the same type. The researchers found that this pattern repeats over and over across the entire flatworm brain to form a continuous neural network. This unique arrangement means that no single neuron sits flush against its twin, while still allowing different types of complementary neurons to be close enough to work together to complete tasks. What they found was that each neuron is surrounded by roughly a dozen neighbors similar to itself, but that interspersed among them are other kinds of neurons. They then used high-resolution microscopes to capture images of the whole brain вЂ“В glowing neurons and all вЂ“ and analyzed the patterns to see if they could extract from them the mathematical rules guiding their construction. First, Wang and Margarita Khariton, a graduate student in his lab, used fluorescent stains to mark different types of neurons in the flatworm.

The brain they chose to examine belonged to a planarian, a millimeter-long flatworm that can regrow a new head every time after amputation. We surprised ourselves when we discovered there was, in fact, such a rule.вЂќ вЂњWe chose to answer that question by studying a brain because it had been commonly assumed that the brain was too complex to have a simple patterning rule. вЂњHow do cells with complementary functions arrange themselves to construct a functioning tissue?вЂќ said study co-author Bo Wang, an assistant professor of Bioengineering. The researchers wanted to uncover the invisible growth patterns that enable the right kinds of neurons to arrange themselves into the right positions to build a brain. Their study, published in Nature Physics, builds on the fact that the brain contains many different types of neurons and that it takes several types working in concert to perform any tasks. Similar rules could guide the development of other cells within the body, and understanding them could be important for successfully bioengineering artificial tissues and organs. By employing advanced microscopy and mathematical modeling, Stanford researchers have discovered a pattern that governs the growth of brain cells or neurons. Using this technique, they hope to find patterns that guide the growth of cells in other parts of the body in order to pave the way to bioengineer artificial tissues and organs.

Stanford researchers used advanced microscopy and mathematical modeling to discover a pattern that governs the growth of neurons in the flatworm brain, shown here.

Neurons in the brain