The most innovative discoveries in the world of biotechnology often arise at the intersection of physics, biology and technology. The story of how light has been used to keep human cells beating is truly a product of interdisciplinary scientists working together to solve a problem. Genetic and biomedical engineers have developed a genetically targeted tool that allows light to alter the neural activity within stem cells.

Electrically responsive cell types are essential for many biological processes involved in normal, everyday functions, but to target these cells using traditional electrical stimulation techniques can be difficult or nearly impossible. The cells are often embedded deep within heterogeneous tissue, an obstacle that led physiologists, neuroscientists and biomedical engineers to search for a new technology. Their objective was to target specific neurons using photostimulation. The new technology was born from a microscopic organism with sensitivity to light.

The source of the genetic material for this new technology came from a naturally occurring protein found in green algae. The protein, called Channelrhodopsin-2, or ChR2 for short, has a fast-acting cation channel that is stimulated by light. In other words, the gene for ChR2 protein is activated by light energy, similarly to how a light bulb is activated by an electrical impulse. When the light-sensitive gene is delivered to mammalian stem cells, the neural activity within those cells responds to light pulses. A high-energy optical switch combined with genetically targeted delivery of ChR2 to stem cells was the logical next step to solve the problem at hand.

When researchers at Stanford University in California delivered the algal-based gene into human stem cells, the cells could essentially be controlled with a light switch. These researchers were working with stem cells that ultimately became heart muscle cells. This “light switch” technology gave scientists the ability to control neuron spiking, excitatory and inhibitory synapses on a millisecond timescale. The Stanford University researchers successfully inserted the ChR2 gene into these stem cells and demonstrated how light pulses could keep heart cells beating.

What researchers have developed is a form of cellular gene therapy for hard-to-target, electrically excitable cell types. The research began with a group of neuroscientists and bioengineers who tested various biological, physical and behavioral responses in standard specimens such as C. elegans, Drosophila and mice in 2005 and 2006. Normal functions like muscle contraction and disease resistance have been tested with this technology in mammalian stem cells. Combined with advancements in stem cell research and human genome studies, the future of genetic and bioengineering will be exciting to say the least; perhaps some day, green algae Channelrodopsin just might save your life.