Tomorrow's pacemakers could be powered by lightS

The emerging field of optogenetics — which enables scientists to control your body's cellular function, using different colored lights — is rapidly changing the way we study and understand the human body.

And new research reveals how optogenetics can help us better understand complications with the human heart, and how the modern metal pacemaker may one day be supplanted by a more bio-compatible, light-powered device.

Optogenetics has its origins in the field of neuroscience, but now researchers across a variety of fields are beginning to implement optogenetics in truly groundbreaking ways, and a light-powered pacemaker could be one of the most amazing.

Here's how it works. Heart-muscle cells, commonly known as cardiomyocytes, are a pretty tightly-knit group of coworkers. Not because they like each other, but because they have to be.

The fact of the matter is that when cardiomyocytes are pumping blood through your body, it pays off for their activity to be synchronized. This requirement has given rise to a feature in cardiomyocytes that makes them different from many of the other cells in your body: the ability to synchronize their activity by communicating with each other.

It was this so called "coupling" feature in cardiomyocytes that led SUNY bioengineer Emilia Entcheva to investigate how these special cells might serve to benefit from the optogenetics toolbox.

Technology Review's Courtney Humphries explains one of the challenges faced by scientists looking to implement optogenetics techniques in their research, and how cardiomyocytes provide a unique way of circumventing this complication:

One of the obstacles in using optogenetics as a clinical tool is the need to introduce genes into cells. To get around the problem, the researchers in the current study...decided to take advantage of the tight communication between heart-muscle cells.

Rather than having to modify every cell in the heart to respond to light, Entcheva says, it's possible to inject a small population of light-sensitive donor cells, and allow those cells to couple with, and orchestrate, the beating of the normal tissue.

In their paper, which is published in the latest issue of Circulation: Arrhythmia & Electrophysiology, Entcheva's research team demonstrated her claim by genetically engineering a number of light-sensitive cells and pairing them with normal, unmodified heart cells — a technique the team refers to as a Tandem Cell Unity (TCU) strategy.

An example of TCU in action is shown in the image up top; genetically modified, light-activated cells have been fluorescently labeled in green, while the unmodified heart cells are shown in red.

When the mix of normal and genetically engineered cells was stimulated with light, the entire cell population was observed to contract in synchronized waves. What's more, the researchers were able to demonstrate that these contractions were "quantitatively indistinguishable from electrically-triggered waves," in other words, they were similar to what you might expect from a modern day pacemaker.

Entcheva's team's findings have immediate applications as a research tool, but looking to tomorrow, the researchers imagine that a similar technique could soon be used to create a light-powered, optical pacemaker.

The team expects that such a device, which would use thin fiber-optic cables to deliver light, would not only be more biocompatible than today's metal electrodes, but would likely lead to marked improvements in energy consumption — a feature they note is important for extending the battery life in implanted devices.

Circulation: Arrhythmia & Electrophysiology via MIT's Technology Review
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Top image generously provided by Z. Jia & E. Entcheva