Breakthrough image could lead to better therapies

Image of a blood stem cell in its natural environment: Photo courtesy UC Merced

When it comes to using stem cells for therapy you don’t just need to understand what kinds of cell to use, you also need to understand the environment that is best for them. Trying to get stem cells to grow in the wrong environment would be like trying to breed sheep in a pond. It won’t end well.

But for years scientists struggled to understand how to create the right environment, or niche, for these cells. The niche provides a very specific micro-environment for stem cells, protecting them and enabling them to self-renew over long periods of time, helping repair damaged tissues and organs in the body.

But different stem cells need different niches, and those involve both physical and chemical properties, and getting that mixture right has been challenging. That in turn has slowed down our ability to use those cells to develop new therapies.

UC Merced’s Joel Spencer in the lab: Photo courtesy UC Merced

Now UC Merced’s Professor Joel Spencer and his team have developed a way of capturing an image of hematopoietic or blood stem cells (HSCs), inside their niche in the bone marrow. In an article on UC Merced News, he says this could be a big step forward.

“Everyone knew black holes existed, but it took until last year to directly capture an image of one due to the complexity of their environment. It’s analogous with stem cells in the bone marrow. Until now, our understanding of HSCs has been limited by the inability to directly visualize them in their native environment.

“This work brings an advancement that will open doors to understanding how these cells work which may lead to better therapeutics for hematologic disorders including cancer.”

In the past, studying HSCs involved transplanting them into a mouse or other animal that had undergone radiation to kill off its own bone marrow cells. It enabled researchers to track the HSCs but clearly the new environment was very different than the original, natural one. So, Spencer and his team developed new microscopes and imaging techniques to study cells and tissues in their natural environment.  

In the study, published in the journal Nature, Spencer says all this is only possible because of recent technological breakthroughs.

“My lab is seeking to answer biological questions that were impossible until the advancements in technology we have seen in the past couple decades. You need to be able to peer inside an organ, inside a live animal and see what’s happening as it happens.”

Being able to see how these cells behave in their natural environment may help researchers learn how to recreate that environment in the lab, and help them develop new and more effective ways of using those cells to repair damaged tissues and organs.

In living color: new imaging technique tracks traveling stem cells

Before blood stem cells can mature, before they can grow and multiply into the red blood cells that feed our organs, or the white blood cells that protect us from pathogens, they must go on a journey.

A blood stem cell en route to taking root in a zebrafish. [Credit: Boston Children's Hospital]

A blood stem cell en route to taking root in a zebrafish. [Credit:
Boston Children’s Hospital]

This journey, which takes place in the developing embryo, moves blood stem cells from their place of origin to where they will take root to grow and mature. That this journey happened was well known to scientists, but precisely how it happened remained shrouded in darkness.

But now, for the first time, scientists at Boston Children’s Hospital have literally shone a light on the entire process. In so doing, they have opened the door to improving surgical procedures that also rely on the movement of blood cells—such as bone marrow transplants, which are in essence stem cell transplants.

Reporting in today’s issue of the journal Cell, Boston Children’s senior investigator Leonard Zon and his team developed a way to visually track the trip that blood stem cells take in the developing embryo. As described in today’s news release, the same process that guides blood stem cells to the right place also occurs during a bone marrow transplant. The similarities between the two, therefore, could lead to more successful bone marrow transplants. According to the study’s co-first author Owen Tamplin:

“Stem cell and bone marrow transplants are still very much a black box—cells are introduced into a patient and later on we can measure recovery of the blood system, but what happens in between can’t be seen. Now we have a system where we can actually watch that middle step.”

And in the following video, Zon describes exactly how they did it:

As outlined in the above video, Zon and his team developed a transparent version of the zebrafish, a tiny model organism that is often used by scientists to study embryonic development. They then labeled blood stem cells in this transparent fish with a special fluorescent dye, so that the cells glowed green. And finally, with the help of both confocal and electron microscopy, they sat back and watched the blood stem cell take root in what’s called its niche—in beautiful Technicolor.

“Nobody’s ever visualized live how a stem cell interacts with its niche,” explained Zon. “This is the first time we get a very high-resolution view of the process.”

Further experiments found that the process in zebrafish closely resembled the process in mice—an indication that the same basic system could exist for humans.

With that possibility in mind, Zon and his team already have a lead on a way to improve the success of human bone marrow transplants. In chemical screening experiments, the team identified a chemical compound called lycorine that boosts the interaction between the zebrafish blood stem cell and its niche—thus promoting the number of blood stem cells as the embryo matures.

Does the lycorine compound (or an equivalent) exist to boost blood stem cells in mice? Or even in humans? That remains to be seen. But with the help of the imaging technology used by Zon and the Boston Children’s team—they have a good chance of being able to see it.