Strex Systems Help Provide Insights into Gut Muscle Mechanical Forces in Tissue Regenerative Medicine

User Case Study

At Strex, we strive to gain valuable perspectives on our clients’ applications. In our case study of the research of Dr. Tyler Huycke, a Postdoctoral Fellow at the University of California, San Francisco (UCSF), he graciously shared his experience with the Strex ST-1400 Automated Cell Stretching System. In his previous position at Harvard Medical School, he used the automated stretch device to explore the mechanical forces that underlie interactions between gut smooth muscle cells and their surrounding tissue during development. As he sets up his new laboratory, Dr. Huycke will be implementing the ST-1400 and other Strex systems to explore these forces further, aiming to build a foundation for the fast-growing field of tissue regenerative medicine. Our interview with him has been edited for formatting.

What issues in healthcare is your lab going to tackle?

Dr. Tyler Huycke is a developmental biologist investigating how cells, which he considers the engineers of tissue architecture, generate forces in a repeated, robust, and organized way across cellular and supracellular scales to build tissue during an organism’s developmental phase. His research has crucial implications for tissue engineering and regenerative medicine, paving the way for elucidating the tissue building mechanisms, and harnessing these mechanisms for therapeutic tissue regeneration following trauma or disease. “If we want to rebuild tissues,” he explains, “or to spark their natural abilities to regenerate, a good roadmap is to understand how nature has figured out how to do this.” One aspect of these mechanisms that he is focused on is the collection of mechanical forces exerted on and by smooth muscle cells in the gastrointestinal tract.

What was your focus of research at Harvard University?

Dr. Huycke began his work in tissue mechanics while completing his PhD at Harvard University. “We were really interested, as classic developmental biologists are, about how genes and their products influence how our tissues form.” Genetics are not the only factor driving tissue formation, however. “The physical basis of developmental biology,” he tells us, “is how forces are integrated into this picture to sculpt our tissues during development.” Focusing on the tissue comprising the gut wall, he explains that it is a three-layer cake consisting of the epithelial layer, mesenchymal stroma, and the smooth muscle. In his model at Harvard, he used chicken embryo-derived epithelial and mesenchymal cells differentiating into smooth muscle cells. These progenitor cells would undergo applied forces from surrounding tissue at critical windows of development that influenced their differentiation and alignment within the intestines’ muscle. As the smooth muscle forms and begins contracting cyclically, it also exerts repeated forces that impact the organization and differentiation of surrounding tissue layers. To interrogate these two-way influences, Dr. Huycke needed a reliable in vitro system that could model the in vivo cyclic forces experienced by cells in smooth muscle and other types of gut tissue. “We needed ways to directly apply these forces to these cell types and these tissues, and even organoids,” he recounts. A holistic understanding of the different cell types and forces working in concert required comprehensive examination of whole tissue. “I wanted to take into account how all of these cell types are interacting together.”

The gut wall consists of multiple highly organized layers of cells, each influencing the growth of the other two through poorly understood mechanical forces. Blue = smooth muscle layers; orange = neurons; purple = nuclei. Reference: T. Huycke, unpublished.

What were the major roadblocks that you experienced?

“We’ve learned a lot by isolating cells and studying them in 2D, and then moving to organoids in 3D matrices,” says Dr. Huycke. However, in vitro analysis of the conditions experienced by gut smooth muscle in vivo was limited by the fact that cells were isolated in a controlled environment. “The biggest challenge is that they’re not acting in isolation,” he explains. “Morphogenesis and development is about the collective activity of all these cells, so how forces generated in one tissue layer impact another tissue layer and so on.” His research needed a more complex view of tissue interactions and was further complicated by the very nature of developmental biology. “We need to be able to study this in multi-layered tissues with multiple cell types. And of course, in developing tissue this is all happening mainly in utero, so it’s really hard to access these processes as they’re occurring in their native environment.” His primary concern was recapitulating these systems ex vivo to study the cells and apply forces to them, but a lot of work remained in setting up a paradigm that would allow him to do that.

Stretch forces play a large role in how gut smooth muscle cells orient themselves within
surrounding tissue during development. Blue = smooth muscle. Reference: T. Huycke, unpublished.

His lab’s first approach involved a device that applied radial stretch using a vacuum pump. The lab encountered challenges immediately. “It was hard to use, and didn’t work for these whole tissues, which were tens of millimeters and needed to be cultured in a particular way,” he recounts. “They couldn’t be submerged or embedded in matrigel or collagen, because they needed to be at the air-liquid interface.” The lab also found that the vacuum pump systems were bulky and were not as well suited for their incubator, an indispensable tool for maintaining a cell’s environment in vitro. “I couldn’t get these other systems to keep the tissue alive.”

Why did you choose the Strex ST-1400 over other options?

Dr. Huycke had evidence of a mechanism underlying force-driven orientation of smooth muscle cells in development, but he needed a way to test it with cyclic stretching. Needing to move quickly after the setbacks, the lab reached out to Strex. After learning about the ST-1400 Automated Cell Stretching System, incorporating the device into his experiments was a breeze. “We had a demo system up in a couple of weeks, because it’s easy to get up and running. We were collecting meaningful data very quickly.” He recalls its many benefits, including reproducible and rigorous uniaxial stretching and ease of use. “The key difference here was the design,” he says. He found the system’s small footprint to be particularly beneficial when moving the experiment to the incubator. He also highlights the ‘plug-and-play’ nature of the system, with its pre-programmed stretch patterns. “It was just something we could get out of the box and get going right away.” He was able to culture cells directly in the PDMS stretch chambers and image them with brightfield, immunofluorescence, and confocal microscopy. “The PDMS chambers were perfect for growing tissues,” he continues. “You could grow these tissues within this more three-dimensional environment, but still apply stretch across the whole organ.” Once cells were cultured in the chambers, the possibilities were endless. “I wasn’t restricted to 2D cell culture. That was a big thing. I could take them in and out. Manipulate them, put them back in, image them, put them back in.” He was able to precisely image the layers of the embryonic gut smooth muscle layers and examine the effects of applied cyclic or static stretching. “What I saw that was remarkable is that by applying these forces we could reorient the muscles in these intact intestines. This ability to show that these forces were sufficient to drive this supracellular alignment was something that hadn’t been done before,” Dr. Huycke recounts. The ST-1400 offered a novel approach to his research. “There really weren’t techniques to do this.”

Cell Stretching System, STB-1400

The ST-1400 Cell Stretching System can automatically apply uniaxial stretch to cells

What does the future hold for your research?

In his own lab, Dr. Huycke is eager to explore the translational perspectives of developmental biology and tissue regeneration. “I’m working mainly in mammalian tissues. So the mouse model is kind of the workhorse. But I also plan to integrate human intestinal tissues that we can differentiate from human pluripotent stem cells.” The new lab will broaden their investigation beyond the developmental standpoint to examine force-driven effects on cells in adulthood as well, and try to incorporate other types of mechanical forces seen in the gut. “Cells in the lumen of the intestinal epithelial sheets, the crypts and the villi, are experiencing hydrostatic pressures, and they’re constantly pumping in fluids to maintain a certain intraluminal pressure,” he tells us. To model this, he is considering integrating Strex’s Cell Pressure Systems into his model. “We don’t really have any sense of how pressure is impacting the ability of these cells to organize. I’m interested in potentially connecting roles of hydrostatic pressure to the ability of these cells to generate their own forces.”

The team at Strex would like to thank Dr. John Lawler and Dr. Khaled Kamal at the Redox Biology and Cell Signaling Laboratory of Texas A&M University for taking the time to share their story with the ST-1400 Automated Uniaxial Cell Stretching System. Check out their lab’s website for more information on their research, and take a look at their other recent publication in Nature (DOI: 10.1038/s41586-024-07586-8). Click here to learn more about Strex’s Cell Stretching Systems and other products Feel free to reach out and see how we can help you set up your stretching experiments, or click below to request a demo of our products.