CLAMPS holds future of neuroendocrine research

The neuroendocrine system translates nerve signals into hormonal effects, enabling long-lasting changes in our bodies in response to quick changes in our needs.

Magnocellular neurons (MCNs) are a specialized type of brain neuroendocrine cell that produces oxytocin and vasopressin. These hormones are essential for a wide variety of processes, from regulating child labor and lactation to maintaining blood volume and urination.

That means that understanding how MCNs work could lead to better therapies for a range of illnesses, including post-traumatic stress disorder, depression, migraines, sepsis, and multiple types of diabetes.

Unfortunately, it has been nearly impossible to study MCNs outside the brain in controlled conditions.

“MCNs simply do not grow on conventional cell culture preparations or manufactured surfaces,” said Larry Millet, a research associate professor in the University of Tennessee, Knoxville's Department of Civil and Environmental Engineering. “Without cultivating these cells in controlled ways, it’s extremely difficult to understand how they function or how to manipulate them therapeutically.”

Now, thanks to years of careful chemical and material studies, Millet and his students are ushering in a new era of MCN research. They have developed a new experimental framework that achieves Cell-Like Adhesion through Matrix-Polymer Substrates (CLAMPS), a custom process that allows MCNs to grow on their own.

The new platform could revolutionize how scientists study not only MCNs but many other important cell types that have long resisted culture outside the body.

“For more than 40 years, we haven’t had a reliable way to grow these cells in controlled conditions,” Millet said. “CLAMPS shifts the paradigm.”

Co-Culture Hides Interesting Features

Neurons are asymmetrical cells with many long branches. Signal molecules travel across the gaps (synapses) between the branch tips and the bodies of other neurons, letting neurons send information quickly over long distances.

One of the features that makes MCNs particularly interesting is that they may release hormones from other parts of their cells, not just at synapses. If so, how and where those hormones are released is an important factor in how these cells regulate hormone levels across different parts of the brain and body.

For decades, the only way to grow MCNs in a lab was to grow them in co-culture alongside other cell types present in the brain, known as “feeder layers.” Co-culturing was the only known way to get MCNs to grow and function at all, but the feeder layers introduced unwanted challenges and variability into experiments, complications that obscured the neuroendocrine mechanisms that make MCNs interesting.

Millet and students spent years testing multiple synthetic carbon-based materials, polymers, and amino-acid combinations, then systematically engineering a chemical-material interface with the ones that were most likely encouraging MCNs to grow. The CLAMPS framework uses a thin film of defined, synthetic compounds that allow the MCNs to grow on their own for the first time.

Impacts Beyond the Brain

By removing the feeder layer, CLAMPS will enable highly controlled, high-resolution MCN research for the first time. Researchers will be able to analyze gene expression, visualize long-term neuronal activity, and even track hormone release in real time.

In fact, Millet’s team has already begun using the new framework to visualize oxytocin-related activity in living MCNs, beginning to unravel the mechanisms that let these specialized neurons release hormones.

The team is also working to expand the CLAMPS approach to encompass other important cell types that currently have to be grown in coculture systems, including induced pluripotent stem cell-derived neurons. Future directions include testing CLAMPS ability to support liver cells and pancreatic islet cells, which are promising for treatment of Type 1 diabetes.

Millet has presented the new framework at multiple conferences internationally, including the 29th International Conference on Miniaturized Systems for Chemistry and Life Sciences (MicroTAS) in Australia last November and the Microphysiological Systems World Summit in Washington, DC, this May.

“CLAMPS gives us the opportunity to access biological systems that were previously out of reach,” Millet said. “If we can define the conditions that allow these cells to grow and function, we can begin to understand their behavior—and eventually control it—in ways that weren’t possible before.”