Exosomes are lipid vesicles that shuttle proteins and genetic information between both neighboring and distant cells.
Millions of tiny bubbles, released from cells and packaged with molecular mail, are racing through your bloodstream right now. And until recently, only a handful of researchers gave them any thought.
Called exosomes, these lipid vesicles shuttle proteins and genetic information between both neighboring and distant cells. They are just a ubiquitous fact of our biology, according to experts.
Exosomes Nature
Exosomes can deliver therapies into cells that would otherwise be hard to reach. Now they’re positioned to become a widespread tool for drug delivery.
Scientists have known about exosomes for decades, but as recently as 2006, only 508, mostly obscure, papers referred to them.
The research explosion is due, in part, to Swedish scientist Jan Lötvall from the University of Gothenburg. Exosomes had long been viewed as merely tiny trash sacs tossed from cells, but Lötvall showed in 2007 that some cells use exosomes to transfer genetic material — messenger RNAs to make proteins and microRNAs to regulate the expression of genes — between each other.
That discovery set scientists searching for ways that exosomes might be involved in health and disease and even be used as treatments.
“There was huge skepticism at first, and there is still some out there,” Lötvall says.
Now it is clear that Lötvall’s study wasn’t a fluke. The vesicles are implicated in spreading diseases, including cancer, and metabolic conditions, like diabetes and obesity.
A recent study even points to exosomes as a culprit for distributing amyloid-β, the plaque-forming protein that accumulates in the brains of people with Alzheimer’s disease. If exosomes can so easily carry molecules that spread disease, scientists began thinking they might be useful to carry molecules that stop the disease.
Certain research suggests the exosomes themselves, when derived from stem cells, could become a new branch of regenerative medicine. Several firms have already convinced big pharma companies to use their technology.
The sudden spurt of interest is shocking. Just two years ago, people would say we are pretty close to understanding biology but a ways off from the therapeutics and diagnostics. Yet already, exosome-based cancer diagnostics are available, and multiple exosome therapies could begin testing in clinical trials next year.
Exosome Powers
A team of scientists has demonstrated that human mesenchymal stem cells (MSCs) — adult stem cells that can turn into many kinds of cells — can treat animal models of lung disease by reducing inflammation and repairing lung tissue.
Their first guess was that the MSCs work by melding with the damaged tissue and becoming lung cells. But a closer look revealed that the donor stem cells didn’t stick around.
That led the team on a years-long quest to explain the cells’ regenerative properties. In 2012, the researchers finally showed that extracellular vesicles released from MSCs were preventing lung damage in mice.
The group then spent several years learning how to isolate and purify exosomes from stem cells. Last year, they showed that MSC-derived exosomes are responsible for the healing effect in mice with serious lung disease.
Right now scientists collect exosomes that are spit out from cells grown in the lab.
As some scientists grapple with the wide diversity of exosomes produced from a single cell line, others are seeking diversity. One start-up is hunting for new kinds of exosomes from bacteria, fungi, plants, and animals. Another group is developing fruit-derived exosome therapies to deliver cancer drugs.
Almost everyone working on exosome therapies is tackling a different disease, with different exosomes. And they’re doing it fast.
Scientists who weathered years of skepticism are optimistic. Experts see the migration toward exosomes as the result of scientists chasing down the basic biology of a disease, developing a diagnostic, or trying to find a better way to deliver drugs.
It speaks to the fact that they are important in almost every aspect of biology and medicine. The potential here is huge.
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