Biomedical engineers at Duke University have developed an ultrathin silk-based membrane that can be used in organ-on-a-chip models to better mimic the natural environment of the body’s cells and tissues. When used in a kidney organ-on-a-chip platform, the membrane helped tissues grow to recreate the functionality of both healthy and diseased kidneys.
By allowing cells to grow closer together, this new membrane helps researchers better control the growth and function of key cells and tissues in any organ, allowing them to more accurately model a wide range of diseases and test therapies. .
The research appears June 4 in the magazine. Scientific advances.
Often no larger than a USB flash drive, organ-on-a-chip (OOC) systems have revolutionized the way researchers study the underlying biology of the human body, whether creating dynamic models of tissue structures, studying organ functions or modeling diseases. These platforms are designed to stimulate cell growth and differentiation in a manner that best mimics the organ of interest. Researchers can even populate these tools with human stem cells to generate patient-specific organ models for preclinical studies.
But as the technology has evolved, problems have also arisen in chip design, especially with the materials used to create the membranes that form the support structure for specialized cells to grow. These membranes are usually composed of polymers that do not degrade, creating a permanent barrier between cells and tissues. While the extracellular membranes of human organs are typically less than a micron thick, these polymeric membranes are between 30 and 50 microns, making communication between cells difficult and limiting cell growth.
“We want to handle the tissues on these chips just as a pathologist would handle biopsy samples or even live tissue from a patient, but this was not possible with standard polymeric membranes because the extra thickness prevented the cells from forming structures that more closely resemble themselves. look like tissues in the human body,” said Samira Musah, assistant professor of biomedical engineering and medicine at Duke. “We thought, ‘Wouldn’t it be nice if we could get a protein-based material that mimicked the structure of these natural membranes and was thin enough that we could cut it up and study it?'”
This question led Musah and George (Xingrui) Mou, a doctoral student in Musah’s lab and first author of the paper, to silk fibroin, a protein created by silkworms that can electronically spin to form a membrane. When examined under a microscope, silk fibroin looks like spaghetti or a Jackson Pollock painting. Made from long, intertwined fibers, the porous material better mimics the structure of the extracellular matrix found in human organs and has previously been used to create structures for purposes such as wound healing.
“Silk fibroin allowed us to reduce the thickness of the membrane from 50 microns to five or less, which brings us an order of magnitude closer to what we would see in a living organism,” Mao explained.
To test this new membrane, Musah and Mao applied the material to their kidney chip models. Made of clear plastic and about the size of a quarter, this OOC platform is intended to resemble a cross section of a human kidney, specifically the glomerular capillary wall, a key structure in the organ made up of groups of blood vessels that are responsible. to filter the blood.
Once the membrane was in place, the team added derivatives of human induced pluripotent stem cells to the chip. They observed that these cells could send signals through the ultrathin membrane, helping the cells differentiate into glomerular cells, podocytes, and vascular endothelial cells. The platform also triggered the development of endothelial fenestrations in the growing tissue, which are holes that allow fluid to pass between cell layers.
By the end of the trial, these different types of kidney cells had assembled into a glomerular capillary wall and could efficiently filter molecules by size.
“The ability of the new microfluidic chip system to simulate in vivo-like tissue-tissue interfaces and induce the formation of specialized cells, such as fenestrated endothelium and mature glomerular podocytes from stem cells, has significant potential to advance in our understanding of human organ development and disease progression and therapeutic development,” Musah said.
As they continue to optimize their model, Musah and his colleagues hope to use this technology to better understand the mechanisms behind kidney disease. Despite affecting more than 15 percent of American adults, researchers lack effective models for the disease. Patients are also typically not diagnosed until their kidneys have suffered substantial damage and often must undergo dialysis or receive a kidney transplant.
“Using this platform to develop kidney disease models could help us discover new biomarkers of the disease,” Mao said. “This could also be used to help us screen drug candidates for various models of kidney disease. The possibilities are very exciting.”
“This technology has implications for all organ-on-a-chip models,” Musah said. “Our tissues are made up of membranes and interfaces, so you can imagine using this membrane to improve models of other organs, such as the brain, liver and lungs, or other diseases. That’s where the power of our platform”.
This work was supported by a Whitehead Fellowship in Biomedical Research, Duke University Department of Medicine Chair Research Award, MEDx Pilot Grant on Biomechanics in Injury or Injury Repair, PDEP Career Transition Ad Hoc Award from the Burroughs Fund Wellcome, Duke Incubation Fund from the Duke Innovation and Entrepreneurship Initiative, Genetech Research Award, a George M. O’Brien Renal Center Pilot Grant (P30 DK081943), an NIH Director’s New Innovators Grant (DP2DK138544).