Here are some stem cell stories that caught our eye this past week. Some are groundbreaking science, others are of personal interest to us, and still others are just fun.
Light used to direct stem cell fate. Stem cells respond to a symphony of cellular signals telling them to remain stem cells or to mature into a specific type of tissue. Much of stem cell biology today has researchers hitting various notes in various rhythms until the score produces a reasonable percentage of the desired tissue.
It’s often a rather discordant process because the cell is not a simple keyboard. A team at the University of California, San Francisco, has used a neat light trick to make the music a little easier to understand. They started with two known facts: that the protein made by the BRN2 gene can drive stem cells to become nerves and that the gene is often turned on in stem cells and they ignore it, choosing to remain stem cells. The UCSF team genetically engineered mouse stem cells so that they could turn on the BRN2 gene with light.
They found that the gene could only drive the production of nerve cells when it was turned on for a relatively long time. They then discovered that the stem cells were responding to another note in the score, a protein that kept the cells in the stem cell state but became depleted after a prolonged period of BRN2 expression.
“There’s lots of promise that we can do these miraculous things like tissue repair or even growing new organs, but in practice, manipulating stem cells has been notoriously noisy, inefficient, and difficult to control,” said Mather Thomson, one of the senior authors on the paper published in Cell Systems and quoted in a university press release widely picked up, including by News Medical. “I think it’s because the cell is not a puppet. It’s an agent that is constantly interpreting information, like a brain. If we want to precisely manipulate cell fate, we have to understand the information-processing mechanisms in the cell that control how it responds to the things we’re trying to do to it.”
Stem cells delivering engines. Jan Nolte, one of our grantees at the University of California, Davis, and editor of the journal Stem Cells, likes to refer to mesenchymal stem cells (MSCs) as little ambulances that rush emergency medical kits to sites of injury. These stem cells that normally hang out in the bone marrow can generate bone, cartilage and blood vessels, but also can deliver a number of chemicals that either tamp down inflammation or summons other repair cells to the scene. The Scientist published a good overview on how MSCs deliver a key repair tool: mitochondria, known as the powerhouse of cells, to cells in need of an energy boost.
Mitochondria are very susceptible to stressors like a heart attack and often are the first parts of a cell to succumb to the stress. While researchers have known for a decade that MSCs can deliver mitochondria to cells, they haven’t known how this happens. They are rapidly gathering that knowledge hoping they to find better ways to harness that particular MSC skill for therapy.
The author walks through a number of discoveries over the past couple years that have begun to paint a picture of this paramedic skill. She also briefly discusses some potential therapies that have been tested in animals.
Embryonic stem cell controversy waning. Pacific Standard, which has become my favorite “thought” magazine even though I have never seen a print copy, published a pretty thorough overview of the early controversy about embryonic stem cells (ESCs) and the many recent scientific advances that may make them unnecessary. The author closes with the fact that for now, advancing those alternatives requires the continued use of ESCs.
Leading with the George W. Bush quote about ESCs being “the leading edge of a series of moral hazards,” he goes on to note that the controversy drove the creation of CIRM and helped Democrats take control of the Senate in 2006. But the bulk of the piece focuses on the alternatives starting with the Nobel Prize-winning discovery of reprogramed adult cells called induced pluripotent stem cells that mimic ESCs. It also covers most recent advances in converting one type of adult cell directly into another type of tissue.
The author closes with a caveat on the ongoing importance of ESCs, at least for now.
“The controversy isn’t over quite yet though—while the newer techniques are immediately useful in research, they have yet to yield any therapies. And because embryonic stem cells are useful for studying how different types of cells develop naturally in the body, they still play an important role in ongoing biomedical research.”
However, he does suggest that eventually, technology will end this controversy.
NOVA video on the brain. Alright, this video only tangentially relates to stem cells and only mentions them toward the end. But it does get at one of the pressing problems in advancing our field: actually seeing what stem cells do at the cell-to-cell and molecular level.
If you are even a casual fan of science, how can you not like a video that starts out with two young scientists using phrases like, “crazy idea,” “wild dream” and “told we’re wasting our time.” It even goes on to talk about “your brain on diapers.” It’s got to be worth the five and a half minutes on the NOVA PBS web site.
It let’s two MIT researchers narrate their effort to image the tiniest of cellular interactions in the brain. Since they found limitations in every existing attempt to see smaller detail, they decided to inflate the brain and make the details larger. They did this by adding the same absorbent material found in diapers to thin slices of mouse brain that had different types of tissues dyed in varying colors. When they added water the brain slice swelled expanding the details.
The result: some really cool images and a tool already being used by scientists around the world. It is now called “expansion microscopy.”