See-through zebrafish, new imaging method puts blood stem cells in the high-resolution spotlight

Tracing features in a large 3D electron microscopy dataset reveals a zebrafish blood stem cell (in green) and its surrounding niche support cells, a group photo method that will help researchers understand the factors that contribute to healthy blood stem cells, which in turn could help develop therapies for blood diseases and cancers. 1 credit

For the first time, researchers can get a high-resolution view of single blood stem cells with a little help from microscopy and zebrafish.

Researchers from the University of Wisconsin-Madison and the University of California, San Diego have developed a method that allows scientists to track a single blood stem cell in a living organism and then describe the ultrastructure, or l architecture, of this same cell using electron microscopy. This new technique will help researchers develop therapies for blood diseases and cancers.

“Currently, we’re looking at stem cells in tissue with a limited number of markers and at low resolution, but we’re so lacking in information,” says Owen Tamplin, assistant professor in the Department of Cellular and Regenerative Biology at UW-Madison. , a member of the Stem Cell & Regenerative Medicine Center, and co-author of the new study, which was published Aug. 9 in eLife. “Thanks to our new techniques, we can now see not only the stem cell, but also all the surrounding niche cells that are in contact.”

The niche is a microenvironment found in tissues like bone marrow that contain the blood stem cells that support the blood system. The niche is where specialized interactions between blood stem cells and their neighboring cells occur every second, but these interactions are difficult to track and not clearly understood.

In the new study, Tamplin and co-lead author Mark Ellisman, professor of neuroscience at UC San Diego, identified a way to integrate multiple types of microscopic imaging to study a cell’s niche. . With the newly developed technique that uses confocal microscopy, X-ray microscopy and serial scanning electron microscopy, researchers will now be able to track the once elusive cell-cell interactions that occur in this space.

“This allowed us to identify cell types in the microenvironment that we didn’t even know were interacting with stem cells, opening new directions for research,” says Tamplin.

In this study, Tamplin and his colleagues, including co-first authors Sobhika Agarwala and Keunyoung Kim, identified dopamine beta-hydroxylase-positive ganglion cells, which were previously an uncharacterized cell type in the niche of blood stem cells. This is crucial, because understanding the role of neurotransmitters like dopamine in regulating blood stem cells could lead to better therapeutics.

“Transplanted blood stem cells are used as a curative therapy for many blood diseases and cancers, but blood stem cells are very rare and difficult to locate in a living organism,” says Tamplin. “It is therefore very difficult to characterize them and understand how they interact and connect to neighboring cells.”

While blood stem cells are difficult to locate in most living organisms, the transparent zebrafish larva offers researchers a unique opportunity to more easily visualize the inner workings of the blood stem cell niche.

“That’s what’s really great about zebrafish and the ability to image cells,” Tamplin says of the animal’s transparent quality. “In mammals, blood stem cells develop in utero in the bone marrow, making it virtually impossible to see these events happening in real time. But, with zebrafish, you can actually watch the stem cell happen through traffic, find the niche, get attached to it and then go lodge there.”

While the zebrafish larva makes it easier to see the development of blood stem cells, specialized imaging is needed to find these small cells and then detail their ultrastructure. Tamplin and his colleagues have spent more than six years perfecting these imaging techniques. This allowed them to see and track the real-time development of a blood stem cell in the microenvironment of a living organism, and then zoom in even closer on the same cell using electron microscopy.

“First, we identified single fluorescently labeled stem cells by light sheet or confocal microscopy,” says Tamplin. “Next, we processed the same sample for serial scanning electron microscopy. We then aligned the 3D optical and electron microscopy datasets. By crossing these different imaging techniques, we were able to see the ultrastructure of unique rare cells deep inside a tissue. This also allowed us to find all surrounding niche cells that come into contact with a blood stem cell. We believe that our approach will be broadly applicable for correlative light and electron microscopy in many systems.

Tamplin hopes this approach can be used for many other types of stem cells, such as those from the intestine, lung and tumor microenvironment, where rare cells need to be characterized at nanometer resolution. But, as a developmental biologist, Tamplin is particularly excited to see how this work can improve researchers’ understanding of how the microenvironment of blood stem cells is formed.

“I think it’s really exciting because we generate all of our blood stem cells during embryonic development, and depending on what organism you are, a few hundred or maybe a few thousand of those stem cells will eventually produce hundreds billions of new blood cells every day throughout your life,” says Tamplin.

“But we really don’t know much about how stem cells first find their home in the niche where they are going to stay for the rest of the life of the organism. This research will really help us understand how stem cells behave and A better understanding of stem cell behavior and regulation by surrounding niche cells could lead to better stem cell therapies.


Mystery cells that create blood stem cells in mammals identified


More information:
Sobhika Agarwala et al, Defining hematopoietic stem cell niche ultrastructure by correlative light and electron microscopy, eLife (2022). DOI: 10.7554/eLife.64835
Journal information:
eLife


Provided by the University of Wisconsin-Madison


Quote: Transparent Zebrafish, New Imaging Method Puts Blood Stem Cells in the High-Resolution Spotlight (August 10, 2022) Retrieved August 10, 2022 from https://phys.org/news/2022-08-see- through-zebrafish-imaging-method-blood.html

This document is subject to copyright. Except for fair use for purposes of private study or research, no part may be reproduced without written permission. The content is provided for information only.

Comments are closed.