Our neurons’ growth can be shaped by tiny cues from spinning microparticles in the fluids that surround them, a new study reports.
The branching and growth of neurons is based on several kinds of guides, including their chemical environment, their location within the brain, and the dense network of glial cells that support and protect them. But as it turns out, they’re also surprisingly responsive to fluid dynamics, turning in response to the rotation of nearby microparticles – a bit like the way a vine can climb a fence-post.
Since the early days of neuroscience, researchers have dreamed of growing and shaping neurons for specific purposes – to patch gaps in damaged neural networks, for example; or just to test their workings under controlled lab conditions.
But it’s only in the past few years that technologies like microfluidic chambers and pluripotent stem cells have enabled researchers to grow healthy, living neurons according to precise specifications, and study those cells’ responses to all kinds of stimuli. In fact, it looks like it won’t be much longer ’til doctors can implant networks of artificially grown neurons directly into living adult brains.
But as the journal Nature Photonics reports, the big breakthrough this time comes from Samarendra Mohanty at The University of Texas at Arlington, who found that neuron growth can respond to physical cues – spinning particles in fluid, for instance – as well as to chemical ones.
Mohanty’s team discovered this by using a tiny laser to direct the spin of a microparticle positioned next to the axon of a growing neuron. The spinning particle generated a miniature counterclockwise vortex in the fluid – and wouldn’t ya know it; the axon started wrapping around the spinning particle as the neuron grew:
Circularly polarized light with angular momentum causes the trapped bead to spin. This creates a localized microfluidic flow … against the growth cone that turns in response to the shear.
In short, this is the first time a scientific team has used a mechanical device – a “micro-motor,” as they call it – to directly control and precisely adjust the growth of a single axon:
The direction of axonal growth can be precisely manipulated by changing the rotation direction and position of this optically driven micromotor.
So far, the micromotor only works 42 percent of the time – but the team is optimistic that future tests will lead to greater reliability and more precise control. In the near future, micromotors like this one could be used to turn the growth of an axon back and forth – or even to funnel growth through “gauntlets” of spinning particles.
Most conveniently of all, the particles could be injected, re-positioned, and removed as needed – providing a much simpler, more modifiable architecture than any other neuron-shaping technology in use today.
And for the slightly more distant future, Mohanty’s lab is hard at work on a system for providing long-range, long-term guidance to entire neural networks through completely non-invasive optical methods.
Until then, though, isn’t it amazing to stop and think about all the neurons that are growing and reshaping themselves – all the delicate intertwining lattices relaying millions of mysterious coded messages, right now, within the lightless interior of your own head?
Call me self-centered, but I think it’s just about the coolest thing on planet Earth.