UIC researchers zoom in on tiny cellular messengers
Urine, blood, sweat, saliva. While unpleasant to dwell on, bodily fluids are a wellspring of health information. For example, particles called extracellular vesicles, which are in all bodily fluids, can signal chronic inflammation, cancer and neurodegenerative diseases like Parkinson’s.
In a new ACS Nano study, UIC researchers published a guide for capturing and analyzing the extracellular vesicles that immune and cancer cells create. The work advances noninvasive early detection of disease.
“By studying these tiny vesicles, we can monitor a disease throughout its lifetime and track its response to treatment,” said lead researcher Ying Hu, an associate professor of chemistry in the College of Liberal Arts and Sciences and affiliate of the University of Illinois Cancer Center.
A diagnostic gold mine
Almost every cell in the body secretes extracellular vesicles: tiny bloblike sacs that deliver molecular messages from cell to cell. Extracellular vesicles travel through fluids like blood and carry proteins, lipids, DNA and RNA.
Broadly, extracellular vesicles fall into two categories: exosomes, which are produced inside the parent cell, and the larger ectosomes, which form in the cellular membrane. Each vesicle is topped with a unique assortment of proteins that determines its identity.
Extracellular vesicles are molecularly like their parent cells. If a parent cell is sick or cancerous, that’s reflected in the extracellular vesicles. That’s what makes them valuable as a tool for early detection of disease.
Isolating and analyzing extracellular vesicles
But that information is difficult to come by. Extracellular vesicles exist at the nanoscale, thousands of times narrower than a strand of hair and impossible to distinguish without magnification.
The researchers needed a way to look at each one individually.
“Think about the city of Chicago,” Hu said. “From an airplane, you see the city as a single entity. But zoom in, and you get different neighborhoods, streets, communities, buildings, art and architecture. That’s the level we need to be at with individual EVs.”
Understanding a single vesicle’s inner ecosystem is the key, but a major barrier is the difficulty in physically isolating a vesicle from its surroundings.
Currently, scientists attempting this isolation reach for an ultra-fast centrifuge, which uses centrifugal force to pull extracellular vesicles out of their surroundings like a salad spinner pulls water off lettuce. However, the rapid revolutions of a centrifuge can damage extracellular vesicles, and in any case, most labs can’t afford the necessary hardware.
It’s all about the process
So Hu and graduate student Dinethri Herath adapted two methods to isolate extracellular vesicles from their parent immune and liver cancer cells.
The first method is to mix a liquid solution containing extracellular vesicles with synthetic polymers, let it sit overnight and spin it in a tabletop centrifuge the next morning. This forces the vesicles to separate out.
The second method uses a physical filter to separate the extracellular vesicles. Some larger vesicles might be unintentionally excluded, yet this method yielded better results than with the first.
“I saw so many extracellular vesicles in one field. All different sizes, different shapes — hundreds of them,” said Herath, whose research image of the extracellular vesicles was featured in ACS Nano.
After isolating the extracellular vesicles, the researchers used a fluorescence super-resolution microscopy method, called dSTORM, to map the protein distribution atop individual vesicles. They were able to look at the extracellular vesicles at a resolution of roughly one-thousandth the size of a human cell. That allowed them to zoom in on the vesicles’ protein distribution signatures track them back to the parent cell membrane.
Looking east, west and ahead
Hu and Herath envision a future where clinicians can easily diagnose chronic inflammation, cancer and neurodegenerative diseases by examining extracellular vesicles from a liquid biopsy.
“Developing the process for future studies is a first step for us,” Hu said. “The most important thing is establishing a reliable workflow to isolate EVs for ultrasensitive phenotyping.“
He said this initial study succeeded due to collaboration between the University of Chicago; UIC’s cancer research center; and UIC’s colleges of liberal arts and sciences, engineering and medicine.
“Chemistry and medicine came together to make this possible,” Hu said. “It’s a testament to the power of scientific collaboration.”
Additional authors include Haoran Jing from the UIC College of Liberal Arts and Sciences and Mingyang Li and Joseph Franses from UChicago Medicine.
Research reported in this article was supported by the College of Liberal Arts and Sciences and the National Institute of General Medical Sciences (R35GM146786).
