Live-Cell Computer Tomography: New Imaging Technology for Advance Disease Diagnostics
- A 3D image of a live human myelogenous leukemia cell stained for the nucleus (blue-green) and mitochondria (orange-red). The image shows the mitochondrial network distribution with respect to the nucleus. The 3D image was computationally reconstructed from a set of 2D projections taken on a novel computed tomography-based platform. (Image credit: Arizona State University - Biodesign Institute)
Medical imaging technology like MRIs and CT scans have revolutionized the way patients are diagnosed with injuries and disease by enabling doctors to non-invasively look beneath the patient’s skin. Now, similar imaging advances may soon propel discoveries for the biomedical research community with a new technology ---called live-cell, CT (or LCCT) --- that was recently developed by a team of ASU inventors to enable biologists to explore the inside of living, single cells.
With a premise that the very root of most diseases begins within a single cell, the advance of LCCT promises to usher in a new imaging tool important in the early diagnosis of cancer and in fostering a better understanding cellular processes in cancer and many other diseases.
“Because of LCCT’s capability to perform imaging of live, suspended cells and the relative ease of implementation, we expect the LCCT method to become a powerful new tool for the biomedical research community,” said Deirdre Meldrum, Ph.D., project leader, and co-inventor of the new technology, director of the Biodesign Biosignatures Discovery Automation at ASU’s Biodesign Institute and professor in the Ira A. Fulton Schools of Engineering.
And the ASU innovations may be coming to a clinic sooner than one might think since it was designed from the start with biomedical translation in mind.
“One of our main goals was to design an LCCT system to advance toward clinical and commercial applications in any research or clinical laboratory,” said Meldrum.
World in motion
LCCT imaging is a powerful new tool because it can highlight the key architectural features of single living cells much like MRIs and CTs have done for our bodies.
In this case, think of each cell as an unknown planet where only its surface features were known. Now, with LCCT technology, they are ripe for exploration to reveal their innermost secrets.
At the heart of the technology, the optical live cell CT approach is based on acquiring 2D images from different perspectives of the cell, like moving a camera around to take pictures from a 360-degree rotational axis.
Each 2D image has the same resolution (known as isotropic resolution) and can be computed into the 3D image of the cell with high fidelity and high spatial resolution.
The fact that this resolution is the same along all three spatial dimensions is what empowers researchers to interrogate the dynamics of cells in the disease process.
“We wanted to develop a robust technology where we look at the global, 3D architecture of a cell in its natural state, which is pivotal for the next level of analysis of cellular function and measuring responses to external stimuli or stressors,” said Meldrum.
With that in mind, Meldrum’s team first wanted to demonstrate proof-of-concept of their technology in two important cell biology areas that are revolutionizing medicine: immune and cancer cells, which may be tipping the scales in the fight against cancer with immunotherapies.
On the main stage
To best see the cells in 3D, they had to find a way to carefully spin them around without damaging them.
The cell rotation issue was solved by placing the cell inside of a 3D high-frequency electric field. The electric field creates a torque on the cell turning it slowly at speed of 1 to about 3 revolutions per minute. Typically, 300 to 500 projections can be collected from just one full rotation (360°), which are then used to reconstruct the 3D image.
“We found that the electric field approach produced the most satisfying results in terms of stability, rotation speed, and minimal cell stress,” said Laimonas Kelbauskas, Ph.D., an assistant research professor at Biodesign who co-invented the technology, conceived and designed the study, and co-developed the technological platform and image reconstruction software.
By putting the cells into their “electrocage” they were able to precisely rotate live cancer and immune cells. Next, after establishing a reproducible and stable cell rotation, they performed a series of imaging experiments with live leukemia and immune sentinel cells known as macrophages, with the goal of characterizing the spatial and temporal resolution limits of LCCT.
They used standard fluorescent dyes, that glow when excited by a light source to reconstruct 3D images and time-lapse movies of single cells. With the dyes, they could see depicts segmentation of the nuclear and mitochondrial features of the cell.
Next, they treated the cells with a chemical that is known to prevent segregation of the cell’s powerhouse, the mitochondria, and observed the changes they could see in the brains of the cell too, the nucleus.
Every 30 seconds, they were able to resolve structural details of the cell that are about 300 times smaller than the diameter of a human hair.
They found striking changes to the shape of the mitochondria that had never been seen before.
“We believe that this is the first report of immune system cells imaged in their natural state -suspended in aqueous medium, as opposed to attached to a glass slide, - with fully isotropic 3D spatial resolution,” said Meldrum. “Our experimental findings indicate that a majority of mitochondria in suspended cells are highly interconnected, forming a complex and dynamic filamentous network.”
The pill-shaped mitochondria had previously been thought to be independent operators, and showing the evidence of an interconnected network may cause cell biologists to rethink the ways mitochondria work within the cell.
“We, therefore, conclude that the observed mitochondrial morphology can be attributed to the cell type specificity and/or the fact that the cells are imaged suspended in 3D space rather than adhered on a planar substrate. The conventional 2D imaging of cells on glass slides may become obsolete as 3D imaging of cells in suspension supersedes the 200-year old approach of 2D conventional microscopy,” said Meldrum.
In addition, because they measure and see precise changes within the cell, it may open up LCCT technology to identify the exact cell types found within cancer cells that lead to metastasis, or the immune response to infectious agents. This may lead to better and more targeted disease therapies.
“The quantification of mitochondrial and nuclear remodeling over time enables direct multiparameter comparisons between individual cells or cell types, offering a unique way for rare cell identification with high accuracy,” said Kelbauskas.
For the next series of experiments, the team will expand on their studies to look at more cells types. They can expose cells to environmental stressors, measure responses to drug treatments and use different imaging methods to further improve the spatial and temporal resolution of the technology.
The Meldrum team will also continue to collaborate with industry toward clinical impact.
“In summary, we feel the LCCT is a breakthrough, powerful and versatile tool for investigating individual cellular dynamics and enabling quantitative studies of cellular architecture dynamics, and could be used for combined nuclear and mitochondrial organization studies in response to different treatment regimens,” said Meldrum.
Laimonas Kelbauskas, Rishabh Shetty, Bin Cao, Kuo-Chen Wang, Dean Smith, Hong Wang, Shi-Hui Chao, Sandhya Gangaraju, Brian Ashcroft, Margaret Kritzer, Honor Glenn, AQ1 Roger H. Johnson, Deirdre R. Meldrum: Optical computed tomography for spatially isotropic four-dimensional imaging of live single cells, Sci. Adv. 2017;3: e1602580 (8 December 2017)