“There’s an app for that” is a well-known phrase trademarked by Apple to promote how users can do almost anything they do on a computer on their mobile phone. Apps are so deeply ingrained in everyday life that it’s hard for some people to imagine living without them. (I know I’d be lost without google maps or my Next Bus app!)
An estimated 2.2 million mobile apps exist for iPhones. Imagine if this multitude of apps were instead the number of stem cell models available for scientists to study human biology and disease. Scientists dream of the day when they can respond to questions about any disease and say, “there’s a model for that.” However, a future where every individual or disease has its own personalized stem cell line is still far away.
In the meantime, scientists are continuing to generate stem cell-based technologies that answer important questions about how our tissues and organs function and what happens when they are affected by disease. One strategy involves growing human stem cells on microchips and developing them into miniature organ systems that function like the organs in our bodies.
A group of scientists from Harvard’s Wyss Institute are using organ-on-a-chip technology to model a structure in the human kidney, called a glomerulus, that’s essential for filtering the body’s blood. It’s made up of a meshwork of blood vessels called capillaries that remove waste, toxic products, and excess fluid from the blood by depositing them into the urine.
The glomerulus also contains cells called podocytes that wrap around the capillaries and leave thin slits for blood to filter through. Diseases that affect podocytes or the glomerulus structure can cause kidney failure early or later in life, which is why the Harvard team was so interested to model this structure using their microchip technology.
They developed a method to mature human pluripotent stem cells into podocytes by engineering an environment similar to that of a real kidney on a microchip. Using a combination of kidney-specific factors and extracellular matrix molecules, which form a supportive environment for cells within tissues and organs, the team generated mature podocytes from human stem cells in three weeks. Their study was published in Nature Biomedical Engineering and was led by Dr. Donald Ingber, Founding Director of the Wyss Institute.
3D rendering of the glomerulus-on-a-chip derived from human stem cells. (Wyss Institute at Harvard University)
First author, Samaira Musah, explained how their glomerulus-on-a-chip works in a news release,
“Our method not only uses soluble factors that guide kidney development in the embryo, but, by growing and differentiating stem cells on extracellular matrix components that are also contained in the membrane separating the glomerular blood and urinary systems, we more closely mimic the natural environment in which podocytes are induced and mature. We even succeeded in inducing much of this differentiation process within a channel of the microfluidic chip, where by applying cyclical motions that mimic the rhythmic deformations living glomeruli experience due to pressure pulses generated by each heartbeat, we achieve even greater maturation efficiencies.”
Over 90% of stem cells successfully developed into functional podocytes that could properly filter blood by selectively filtering different blood proteins. The podocytes also were susceptible to a chemotherapy drug called doxorubicin, proving that they are suitable for modeling the effects of drug toxicity on kidneys.
Ingber highlighted the potential applications of their glomerulus-on-a-chip technology,
“The development of a functional human kidney glomerulus chip opens up an entire new experimental path to investigate kidney biology, carry out highly personalized modeling of kidney diseases and drug toxicities, and the stem cell-derived kidney podocytes we developed could even offer a new injectable cell therapy approach for regenerative medicine in patients with life-threatening glomerulopathies in the future.”
There’s an organ-on-a-chip for that!
The Wyss Institute team has developed other organ-on-chips including lungs, intestine, skin and bone marrow. These miniature human systems are powerful tools that scientists hope will “revolutionize drug development, disease modeling and personalized medicine” by reducing the cost of research and the reliance on animal models according to the Wyss Institute technology website.
What started out as a microengineering experiment in Ingber’s lab a few years ago is now transforming into a technology “that is now poised to have a major impact on society” Ingber further explained. If organs-on-chips live up to these expectations, you might one day hear a scientist say, “Don’t worry, there’s an organ-on-a-chip for that!”