As kids, most of us got a bang out of blowing soap bubbles and watching them float around. Biologists have learned that some of our cells do that too. On the right, you can see two cells (greenish yellow) in the process of forming bubbles, or plasma membrane vesicles (PMVs). During this blebbing process, a cell’s membrane temporarily disassociates from its underlying cytoskeleton, forming a tiny pouch that, over the course of about 30 minutes, is “inflated” with a mix of proteins and lipids from inside the cell. After the PMVs are fully filled, these bubble-like structures are pinched off and released, like those that you see in the background. Certain cells constantly release PMVs, along with other types of vesicles, and may use those to communicate with other cells throughout the body.
This particular image, an entrant in the Biophysical Society’s 2017 Art of Science Image Contest, was produced by researchers working in the NIH-supported lab of Jeanne Stachowiak at the University of Texas at Austin. Stachowiak’s group is among the first to explore the potential of PMVs as specialized drug-delivery systems to target cancer and other disorders .
Until recently, most efforts to exploit vesicles for therapeutic uses have employed synthetic versions of a different type of vesicle, called an exosome. But Stachowiak and others have realized that PMVs come with certain built-in advantages. A major one is that a patient’s own cells could in theory serve as the production facility.
For example, researchers might remove healthy skin or blood cells from a cancer patient’s body, insert genes into the cells that code for proteins that will enable their PMVs to home in on cancer cells, and stimulate the cells to bleb in a laboratory dish. The resulting lab-grown PMVs could then be filled with drugs or other therapeutic agents and infused back into a patient’s body, where they would seek out and destroy cancerous cells while leaving healthy cells unscathed.
As one step on this path, Chi Zhao, a graduate student in the Stachowiak lab, recently showed that PMVs engineered with epidermal growth factor could bind to several breast cancer cells in culture that specifically expressed a receptor for this protein.
And, just in case you’re curious about the technical details of what went into making the image above, these PMVs are giant plasma membrane vesicles derived from Chinese hamster ovary (CHO) cells, a cell line used by many laboratories. The image was captured by David Busch, a former postdoctoral researcher in the lab, and enhanced using 3D reconstruction by Zhao.
Courtesy: Dr. Francis Collins, NIH, USA