Hacking Our Cells to Produce Solar Power Could Make Humans Heal Faster
Kinda like Wolverine.
Image: Chris Beckett/Flickr
Much like a gas-powered car, the human body relies on carbon-based fuels for energy. But for automobile engines and our cellular engines alike, burning carbon has intrinsic inefficiencies.
If we could upgrade our cells to run on solar power, the age-old restrictions of using carbon and oxygen to produce energy might be overcome. The idea sounds outlandish, but to Christopher Powell, founder of the new biotech startup BiPlastiq, it's not. Powell established his company to accomplish a single, radical goal: Hacking human mitochondria—our cellular engine—to gain additional power from light.
Powell believes the hack could dramatically increase cellular power output, transforming our bodies into regenerative machines and extending human lifespans by decades.
"Futurists often talk about [how] we'll reinvent our biology so that our cells have an immediate energy supply," Powell said. "But the fact is, our biology doesn't currently work that way. Right now, this futurist vision lacks the rationale for how our cells can access power instantaneously."
Within each of our cells, a specialized compartment called the mitochondria acts like a generator, converting the chemical energy contained in our food into an energy-storage molecule called ATP.
ATP is the cell's energy currency—it's used for everything from building new proteins to repairing and regenerating old and broken parts. But the rate at which our mitochondria can produce ATP is inherently limited, because it depends on both the breakdown of calories and the availability of oxygen. Powell proposes to overcome this limitation by essentially installing a biological solar panel into our mitochondria, so that they can produce ATP using nothing but light.
The idea may have the ring of science fiction, but the concept of using radiant energy to power cells has been around since the 1960s, when doctors first discovered that they could accelerate wound healing and reduce pain by applying near-infrared laser light. Low level laser therapy (LLLT) is still considered an unconventional medical practice, but there's now a large body of scientific research to support its beneficial effects.
While the cellular mechanisms behind LLLT are not fully established, it's believed that laser light directly energizes our mitochondria, temporarily speeding up cellular ATP production. LLLT may also have indirect and longer-term effects by influencing the expression of genes that regulate cell proliferation.
"Light therapy is a slow process, one that takes days to weeks," said Dr. Michael Hamblin, a researcher at Wellman Center for Photomedicine at Massachusetts General Hospital. Hamblin is currently involved with a new research effort to evaluate whether LLLT can repair damaged brain tissue in patients who have suffered traumatic brain injuries. "But we've shown that this treatment can protect cells from dying and enhance their proliferation. And the mitochondria are the key players."
Drawing inspiration from the field of LLLT, Powell's proposed technology takes things one dramatic step further. If a cell's power output can be enhanced by light therapy alone, could it be accelerated even further if our mitochondria were light-receptive by design? As it happens, there's an entire family of light-receptive proteins that have evolved for the precise purpose of giving their cells a little extra boost. These proteins are called rhodopsins, and they're found in almost every bacterium living in the surface ocean.
"A bacterium that can generate energy from light can maintain its activity independent of calories or oxygen supply," microbial ecologist Ed DeLong of MIT told me. "Opsin proteins are found everywhere because they confer organisms a huge selective advantage."
Using new genomics technologies in the early 2000s, DeLong was among the first to demonstrate just how ubiquitous light-activated rhodopsins are in marine microbial communities. When I spoke with him over the phone, he explained how rhodopsin, a single protein that embeds itself in cell membranes, can act as a supplemental generator for microbes that get the bulk of their energy through carbon metabolism.
"A bacterium that only uses carbon for fuel is like a gas-powered car," DeLong told me. "But as soon as it acquires these opsin genes, an organism that could only grow by eating carbon can also make ATP from sunlight. Bacteria with opsins are like little hybrid cars with solar cells—they still get around by burning gas, but now they can use sunlight to go a little further."
And it wasn't long after bacterial rhodopsins were discovered that researchers began hacking the light-driven protein into new organisms.
"This is a single protein, and its whole operational system requires only about seven genes," he said. "That means you can convert an organism from not using light to tapping into light quite easily." Now that scientists have successfully inserted rhodopsin into numerous microorganisms, some are exploring the possibility that engineered, light-harvesting microbes can be applied to biofuel production and other industrial processes.
And if we can insert rhodopsin into new microbes, we should theoretically be able to do it in human mitochondria.
"I like to think of mitochondria as bacteria that just got trapped a long time ago," DeLong told me. (That's probably true, according to the leading theory for the origin of eukaryotic cells.) "If we can get these proteins into the membranes of E. coli, getting them to functionally fold and operate in the mitochondria is not that far fetched, at all."
Jan Liphardt, a biophysicist at Stanford University and a colleague of DeLong's, agrees. "From a purely technical perspective, the answer is pretty clear," he said. "You can certainly do this."
In mitochondria, energy production hinges on a series of membrane-embedded proteins called the electron transport chain. These proteins operate like pistons in an engine, shuffling electrons along in order to generate a charge gradient. This charge gradient, coupled with oxygen, drives the production of ATP. Inserting a rhodopsin protein into this system would, in essence, give our cellular engine another piston—one that can continue to do work without calories or oxygen.
"That's one of the key advantages of this technology—the disassociation of energy production from oxygen availability," Powell said. "This could lead to exponential increase in energy productions, in addition to making energy instantaneously available."
(In theory, at least. The actual energy boost a rhodopsin can provide its cell has rarely been quantified, although for microorganisms at least, it's thought to be quite large.)
For Powell and his team, the biggest technical challenge at the moment is getting rhodopsin into the mitochondria of many different cell types, without disrupting natural processes.
"We're only making a small genetic modification, but we need that modification to express itself in different cell environments," he said. "The mitochondria in liver and muscle cells are different. Supporting a variety of cell-based therapeutics is the big challenge."
If that can be achieved, Powell envisions his engineered cells, with their souped-up mitochondria, forming the cornerstone of a new brand of cellular therapy. Injections of light-activated stem cells into injured tissues, in conjunction with light therapy, could vastly accelerate tissue repair and regeneration. This tool could revolutionize any number of nascent biomedical fields, from organ regeneration to anti-aging.
"I'm encouraged by other researchers who have tackled a very specific issue—such as developing the scaffolding structures that can grow organs, or new ways of sequencing genomes," Powell said. "Those initiatives are building the tools to tackle new problems. Even though our proposition seems fantastical, its not. It's challenging, but the rewards are huge."
Indeed, we need only look to nature to find myriad examples of what biological regeneration can offer. There are worms and jellyfish that can regrow their entire bodies from a tiny fragment. There are salamanders and newts that regrow limbs, tails, jaws, eyes and internal organs. And then there are plants, some of which can regenerate their cells and grow new parts more or less indefinitely, living for hundreds to thousands of years.
Powell likens the growth of the regenerative medicine industry to the development of the smartphone ecosystem, which required a number of radical technologies—compact and efficient batteries, solid state memory, and touchscreens—to bring a revolutionary product to market.
"We're not baking the whole cookie, just one ingredient, even though there's barely a market for our cookie yet," he said. "There aren't a lot of cell-based technologies in clinical development, but we anticipate that's going to be the future, and we want to have the tool once the market for cell-based products is actually viable. It's going to take radical propositions like this to raise the bar as to what's possible in regenerative medicine."
So, if you were uneasy about casting aside your meatbag and going full cyborg, you can take comfort in the knowledge that there might yet be a middle-ground in hybrid, solar-powered cells. It'd be a dramatic upgrade, but that fleshy machine you know and love would still look the same. Who knows, maybe even a little better.
Goodbye, Meatbags is a series on Motherboard about the waning relevance of the human physical form. Follow along here.
Update 4/17: This story originally quoted BiPlastiq's Christopher Powell as saying his company's mitochondria modification could help boost cellular energy power production through sunlight. Powell later clarified that his company expects to develop regenerative therapies around specialized light treatments, not simply solar light.