Computer engineer Andrew Cohen (pictured right) was designing software to use in high-performance graphics when he left industry for academia and decided to apply his work to a field where the stakes are somewhat higher.
Now, the assistant professor at the University of Wisconsin–Milwaukee (UWM) is creating software that offers a completely novel approach to analyzing time-lapse images capturing live stem cell behaviors. It could lead to new stem cell-based therapies and also new research into causes of cancer, which involves cells that continuously self-renew.
Cohen’s software program not only predicts the types of specialized cells a stem cell will produce, but also foresees the outcome before the stem cell even divides.
“This is a brand-new set of tools for developmental biologists,” says Cohen, “and it supports an area where no other predictive solutions exist.”
Stem cells play a key role in human development, and also offer the potential to repair tissues or organs damaged by disease or injury. But, in order to use stem cell-based therapies, biologists need to better understand the mechanisms that control stem cell differentiation.
Co-authors of the paper are Michel Cayouette and Francisco Gomez, neurobiologists at the Institut de recherches cliniques de Montréal, and Badri Roysam, a computer engineering professor at Rensselaer Polytechnic Institute.
The software is 87 percent accurate in determining the specific “offspring” a stem cell will ultimately produce, and 99 percent accurate in predicting when self-renewal of these stem cells will end in specialization.
It is very rare for engineers to publish in Nature journals, says Michael Lovell, dean of UWM’s College of Engineering & Applied Science (CEAS). “This achievement signifies the quality of our faculty and the value of interdisciplinary work in biomedical technology,” he says.
A Hunt for Markers
As an example of the software’s utility, Cohen cites using stem cells to treat the eye disease macular degeneration. The stem cells would need to produce more photoreceptor neurons for treatment to succeed. “But if you simply implant the stem cells into the retina, there are other types of cells that could develop,” he says, “and that could potentially make the patient’s vision worse.”
Finding a solution has been hampered by the fact that there are very few markers that can predict cell division outcomes.
Subtle behaviors that characterize populations of stem cells with different fates are difficult or impossible for human observers to recognize. Cohen’s tool, which runs on a standard PC, is able to track and generate predictions for up to 40 cells in real time. It outperforms the human eye in detecting differences in how the cells change over time.
Current methods of observing live cells produce terabytes of data, a volume that requires massive amounts of computation to find the most relevant information. A new computer cluster in CEAS was acquired for just this kind of research. To manage the predictive aspects of the program, Cohen uses a uniquely sensitive mathematical approach based on algorithmic information theory.
Answers in DNA
Scientists know little about the programming of stem cell outcomes except that it is a multifaceted process.
“In many cases, stem cells take their developmental cues from their environment,” says Cohen. “Part of the programming mechanism is determined by surrounding cells. But once these cells begin to develop in a particular way, their offspring continue down that path even if the environment changes. So at some point they have been programmed to their fate.”
The researchers designed the software to be used for isolating the genes and proteins that control the specialization process, which could allow researchers to identify and ultimately manipulate these programmed mechanisms.
Brian Link is a developmental biologist at the Medical College of Wisconsin who works with Cohen but is not an author on the paper. The two will be putting the software to the test to study behaviors of organelles within the cell as indicators of stem cell fate.
“The method isn’t perfect,” says Link. “It doesn’t tell us about the influence of the behaviors. It tells us that a particular behavior is important, but it doesn’t tell us how.”
Still, the tool has already proven itself, he says. In a study of stem cells from the retinas of rats, Cohen’s software independently confirmed the significance of at least one of the cell behaviors that Link’s lab had previously identified using a gene manipulation technique.
“Working with Andy was a good marriage of different approaches,” he says.
Illustration: Doctoral student Mark Winter (pictured left) and Andrew Cohen, an assistant professor of electrical engineering, examine a color-coded “map” formed from tracking stem cell activity. –University of Wisconsin-Milwaukee.
University of Wisconsin-Milwaukee News Release (02/07/10)
Science Daily (02/23/10)
Abstract (Nature Methods; 7, 213-218 (02/07/10))