Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Biology Made Simpler With "Clear" Tissues

06.08.2014

In general, our knowledge of biology—and much of science in general—is limited by our ability to actually see things. Researchers who study developmental problems and disease, in particular, are often limited by their inability to look inside an organism to figure out exactly what went wrong and when.

Now, thanks to techniques developed at Caltech, scientists can see through tissues, organs, and even an entire body. The techniques offer new insight into the cell-by-cell makeup of organisms—and the promise of novel diagnostic medical applications.

"Large volumes of tissue are not optically transparent—you can't see through them," says Viviana Gradinaru (BS '05), an assistant professor of biology at Caltech and the principal investigator whose team has developed the new techniques, which are explained in a paper appearing in the journal Cell.

Lipids throughout cells provide structural support, but they also prevent light from passing through the cells. "So, if we need to see individual cells within a large volume of tissue"—within a mouse kidney, for example, or a human tumor biopsy—"we have to slice the tissue very thin, separately image each slice with a microscope, and put all of the images back together with a computer. It's a very time-consuming process and it is error prone, especially if you look to map long axons or sparse cell populations such as stem cells or tumor cells," she says.

The researchers came up with a way to circumvent this long process by making an organism's entire body clear, so that it can be peered through—in 3-D—using standard optical methods such as confocal microscopy.

The new approach builds off a technique known as CLARITY that was previously developed by Gradinaru and her collaborators to create a transparent whole-brain specimen. With the CLARITY method, a rodent brain is infused with a solution of lipid-dissolving detergents and hydrogel—a water-based polymer gel that provides structural support—thus "clearing" the tissue but leaving its three-dimensional architecture intact for study.

The refined technique optimizes the CLARITY concept so that it can be used to clear other organs besides the brain, and even whole organisms. By making clever use of an organism's own network of blood vessels, Gradinaru and her colleagues—including scientific researcher Bin Yang and postdoctoral scholar Jennifer Treweek, coauthors on the paper—can quickly deliver the lipid-dissolving hydrogel and chemical solution throughout the body.

Gradinaru and her colleagues have dubbed this new technique PARS, or perfusion-assisted agent release in situ.

Once an organ or whole body has been made transparent, standard microscopy techniques can be used to easily look through a thick mass of tissue to view single cells that are genetically marked with fluorescent proteins. Even without such genetically introduced fluorescent proteins, however, the PARS technique can be used to deliver stains and dyes to individual cell types of interest. When whole-body clearing is not necessary the method works just as well on individual organs by using a technique called PACT, short for passive clarity technique.

To find out if stripping the lipids from cells also removes other potential molecules of interest—such as proteins, DNA, and RNA—Gradinaru and her team collaborated with Long Cai, an assistant professor of chemistry at Caltech, and his lab. The two groups found that strands of RNA are indeed still present and can be detected with single-molecule resolution in the cells of the transparent organisms.

The Cell paper focuses on the use of PACT and PARS as research tools for studying disease and development in research organisms. However, Gradinaru and her UCLA collaborator Rajan Kulkarni, have already found a diagnostic medical application for the methods. Using the techniques on a biopsy from a human skin tumor, the researchers were able to view the distribution of individual tumor cells within a tissue mass. In the future, Gradinaru says, the methods could be used in the clinic for the rapid detection of cancer cells in biopsy samples.

The ability to make an entire organism transparent while retaining its structural and genetic integrity has broad-ranging applications, Gradinaru says. For example, the neurons of the peripheral nervous system could be mapped throughout a whole body, as could the distribution of viruses, such as HIV, in an animal model.

Gradinaru also leads Caltech's Beckman Institute BIONIC center for optogenetics and tissue clearing and plans to offer training sessions to researchers interested in learning how to use PACT and PARS in their own labs.

"I think these new techniques are very practical for many fields in biology," she says. "When you can just look through an organism for the exact cells or fine axons you want to see—without slicing and realigning individual sections—it frees up the time of the researcher. That means there is more time to the answer big questions, rather than spending time on menial jobs."

Written by Jessica Stoller-Conrad

A 3-D visualization of fluorescently-labeled brain cells within an intact brain tissue. Through the use of this novel whole-body clearing and staining method, researchers can make an organism’s tissues transparent—allowing them to look through the tissues of an organism for specific cells that have been labeled or stained.Credit: Bin Yang and Viviana Gradinaru/Caltech

Deborah Williams-Hedges | Eurek Alert!
Further information:
http://www.caltech.edu/content/biology-made-simpler-clear-tissues

Further reports about: BIONIC Caltech DNA HIV UCLA biopsy blood proteins skin

More articles from Life Sciences:

nachricht Severity of enzyme deficiency central to favism
26.07.2016 | Universität Zürich

nachricht From vision to hand action
26.07.2016 | Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Self-assembling nano inks form conductive and transparent grids during imprint

Transparent electronics devices are present in today’s thin film displays, solar cells, and touchscreens. The future will bring flexible versions of such devices. Their production requires printable materials that are transparent and remain highly conductive even when deformed. Researchers at INM – Leibniz Institute for New Materials have combined a new self-assembling nano ink with an imprint process to create flexible conductive grids with a resolution below one micrometer.

To print the grids, an ink of gold nanowires is applied to a substrate. A structured stamp is pressed on the substrate and forces the ink into a pattern. “The...

Im Focus: The Glowing Brain

A new Fraunhofer MEVIS method conveys medical interrelationships quickly and intuitively with innovative visualization technology

On the monitor, a brain spins slowly and can be examined from every angle. Suddenly, some sections start glowing, first on the side and then the entire back of...

Im Focus: Newly discovered material property may lead to high temp superconductivity

Researchers at the U.S. Department of Energy's (DOE) Ames Laboratory have discovered an unusual property of purple bronze that may point to new ways to achieve high temperature superconductivity.

While studying purple bronze, a molybdenum oxide, researchers discovered an unconventional charge density wave on its surface.

Im Focus: Mapping electromagnetic waveforms

Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.

Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...

Im Focus: Continental tug-of-war - until the rope snaps

Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases

Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

GROWING IN CITIES - Interdisciplinary Perspectives on Urban Gardening

15.07.2016 | Event News

SIGGRAPH2016 Computer Graphics Interactive Techniques, 24-28 July, Anaheim, California

15.07.2016 | Event News

Partner countries of FAIR accelerator meet in Darmstadt and approve developments

11.07.2016 | Event News

 
Latest News

New movie screen allows for glasses-free 3-D

26.07.2016 | Information Technology

Scientists develop painless and inexpensive microneedle system to monitor drugs

26.07.2016 | Health and Medicine

Astronomers discover dizzying spin of the Milky Way galaxy's 'halo'

26.07.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>