Breaking Boundaries in Skin Research With Biosensors and Optogenetics

 Cory Simpson lab photo
ISCRM faculty member Cory Simpson, MD, PhD

Cory Simpson, MD, PhD is an assistant professor of Medicine/Dermatology, a faculty member in the UW Institute for Stem Cell and Regenerative Medicine (ISCRM), and a practicing dermatologist. While all this keeps him busy, the overlapping roles seem to drive the research, the care, and the scientist all at once.

“It is definitely a two-way street,” says Simpson. “I’ll often encounter a genetic disorder in a patient that we can model in the lab. And of course, I see firsthand the need for relief, especially for people suffering from a rare disease with no effective treatments.”

Fortunately, the Simpson Lab is not alone in the pursuit of discoveries that may lead to better outcomes in the clinic. Last year, Simpson heard a talk from fellow ISCRM faculty member Andre Berndt, PhD, an assistant professor of Bioengineering. Berndt was discussing his lab’s work on protein biosensors and optogenetic tools.

The Berndt Lab develops fluorescent biosensors that enable researchers to detect and study biochemical signals at work in living systems. The sensors are genetically-encoded proteins that can be expressed in almost any cell type, making them broadly applicable. The Berndt Lab has used this technology in neuronal networks but sees possibilities for other organs and tissues.

Simpson was intrigued. Berndt was describing technologies that allow for high-resolution imaging and measurement of signaling mechanisms that cells use to communicate and guide their behavior.

“Inside of a cell there is a complex, dynamic signaling network that regulates whether the cell should divide, or differentiate, or even die,” says Simpson. “Until recently, we would culture cells, preserve them in a fixative, and take a snapshot with a microscope. But what if we didn’t have to hit the stop button? Why can’t we watch this signaling happening in real time with tools that make these processes visible?”

New Possibilities in Dermatological Research

Disruptions in cellular signaling processes can create problems that contribute to many diseases, including skin disorders. Calcium is one important regulator of cellular communication. When a mutation causes an imbalance of calcium within cells, it can lead to misery for a patient. The skin tears and blisters as the structures that hold cells together (known as desmosomes) deteriorate under the surface.

“Patients come into my clinic and there’s nothing we can do to directly address the problems underlying the disease affecting them,” says Simpson, who is now studying two of these diseases with support from an ISCRM Innovation Pilot Award, a state-funded initiative to nurture new research in ISCRM labs.

GFP sensor diagram
A biosensor derived from green fluorescent protein (GFP) is normally not visible (“OFF”), but it glows (“ON”) upon exposure to a signal that increases calcium inside the cell.

Could technology like the tools being developed in the Berndt Lab open up new possibilities in dermatological research? Simpson is optimistic. Citing just one example, he points to a sensor derived from a jellyfish protein that glows in response to certain light wavelengths. Because the sensor was designed to be sensitive to calcium, skin researchers like Simpson can gain crucial insights about fluctuations in calcium levels in skin cells that have been engineered to model a genetic disease using CRISPR gene editing. Simpson suggests if his lab optimizes a precise readout of calcium levels, they could use a library of approved drugs to screen for a clinical treatment.

Another driver of skin disease that interests the Simpson Lab is oxidative stress, which can be triggered when abnormal calcium levels within the cell’s major manufacturing hub, the endoplasmic reticulum, cause misfolded proteins to clog up.  This, in turn, can lead to cell death and skin damage. Simpson notes the Berndt Lab has created sensors that emit light signals in response to oxidative stress and imagines this tool could be used to quantify the buildup of these toxic molecules. He envisions this approach could be used to identify drugs to reduce oxidative stress as potential therapies, which he can test in a pre-clinical human organoid skin model.

Visualizing and Controlling Cellular Signaling

Faculty headshot of Andre Berndt, PhD
ISCRM faculty member Andre Berndt, PhD

The Simpson and Berndt Labs recently described these and other promising applications in a paper published in the Journal of Investigative Dermatology. Simpson and Berndt review how fluorescent biosensors and optogenetic tools can be leveraged to visualize and control dynamic signaling events in real-time within live cells, organoids, and even animal models. The lead author of the article is Shivam Zaver, a graduate student in the Medical Scientist Training Program, who worked in the Simpson Lab to learn more about dermatology, the specialty he recently matched into for clinical training.

“The paper was a way to describe in both words and pictures how biosensors and optogenetics are biologically relevant to skin and to get dermatologists excited about these tools,” says Simpson. “We’re talking about really cool advances in imaging techniques that can be used to ask fundamental questions about how tissues develop and regenerate and about how cellular signals go awry in disease states.”

Berndt emphasizes that the light-activated sensors and actuators, which have been primarily used in the brain, will help break boundaries in other areas of study. “Neuroscience tends to pioneer technology, and we are now at a position where we can observe molecular processes such as neurotransmitter release in moving and behaving animals with single-cell accuracy. I predict that these approaches will provide significant benefits to stem cell research by enabling optical access to the physiology of stem cells and organoids, allowing for real-time observation under a microscope.

Skin organoids
The Simpson Lab grows human cells called keratinocytes into multi-layered organoids, which replicate skin tissue that can be used for microscopy or drug screening.

According to Berndt, being able to work in cells has two advantages. First, it is easier to manipulate cell physiology with drugs, CRISPR/Cas9, shRNA, or viruses than it is in animal models. Second, it allows researchers to conduct investigations in human cells and tissue, which could be a more direct pathway to precision medicine and high-throughput drug screening than animal models.

While biosensors are opening up new possibilities for researchers and clinicians to visualize biological signals, the optogenetic technologies detailed in the paper may represent an even more thrilling game-changer. Typically constructed from endogenous light-sensitive proteins, these laser-activated protein tools give scientists the power to not just witness cellular processes in real time – but to influence them.

“No longer are you merely watching cellular signaling as a passive observer, you’re controlling it,” says Simpson. “You can actually manipulate biology inside of a live cell or even an animal or organoid model. These tools are fundamentally changing the way that we think about what kind of experiments are possible.”