It’s easy to forget that every second thousands of events occur in your body just to keep you alive. Perhaps one of the more obvious of these is the beat of your heart, which amongst many things requires the functioning of a specialized type of cell called pacemakers. These keep everything “pulsing”.
When pacemaker cells stop working properly heartbeat can become slow, irregular, or stop altogether. This type of heart failure can be detected using an Echocardiogram (ECG), and can be treated using an amazing little device called an artificial pacemaker. It does the job the pacemaker cells are meant to do. Of course, as with any mechanical device, problems can develop so implanted pacemakers have to be checked every so often to ensure they are still working properly.
Recently, scientists conducted a very cool little experiment that could lead to artificial pacemakers being replaced with a special protein and light (doi: 10.1016/j.bpj.2011.08.004). Channelrhodopsin-2, a protein found in algae sits on the surface of the cell and provides a “gated” channel of entry into its interior cytoplasm. This particular protein channel opens up its gate when light hits it, causing a tiny electrochemical pulse that the cell uses to communicate. Humans have many different gated protein channels that are found almost everywhere in the body. The algae’s channelrhodopsin-2 light-stimulated channel is a very special way to open these gates and researchers have been trying to see if we can harness this mechanism in animal and human cells.
Ok so now that you’ve got the basics, here’s the exciting part. Scientists have taken the channelrhodopsin-2 from algae and expressed them in embryonic stem cells. These stem cells have the potential to become any type of cell – eg. muscle cell, skin cell, liver cell…but these were differentiated into heart-muscle cells. Basically, this means that they got channelrhodopsin-2 onto the surface of cells that make up the heart muscle. Then, using light, they stimulated the protein so that the gates on the cells could open…and they did! The light caused the heart cells to contract, or “pulse”. Scientists say that this elegant experiment demonstrates that heart failure treatment could one day involve light and channelrhodopsin-2 instead of an artificial pacemaker.