These New Stem Cells Could Change the Face of Plastic Surgery

So how could this new cell have eluded scientists and doctors for so long? In other words, it didn’t. Plikus and his graduate student scoured the scientific literature over the centuries to find every lost eagle. They found information in a German book from 1854 written by Franz Leydig, a contemporary of Charles Darwin. “Anything and everything he could stick under the microscope, he did,” says Plikus. Leydig’s book describes fat-like cells in a model of cartilage from the ears of rats. But the equipment of the 19th century could not go beyond this observation, and, realizing that an accurate measurement of skeletal muscle could be important in medicine, Plikus decided to solve the case.

His team began their research by looking at the cartilage in the middle of the thin skin of a mouse’s ear. A green dye that normally stains fat molecules revealed a group of squishy blobs. They isolated these lipid-laden cells and analyzed their contents. All of your cells have the same library of genes, but those genes don’t always work. What genes did these cells express? What proteins are involved? The data revealed that lipochondrocytes look very different, molecularly, from fat cells.

He then asked how lipochondrocytes behave. Fat cells have a little-known function in the body: storing energy. When your body conserves energy, the cellular stores of lipids swell; When your body burns fat, cells shrink. Lipochondrocytes, it was found, do not. The researchers studied the mice’s ears to put on high-fat foods versus calories. Although they grew faster or lost weight, the lipochondrocytes in the ears did not change.

“This suggests that they must have a very different role that is unrelated to metabolism,” says Plikus. “It has to be structural.”

Lipochondrocytes are like balloons filled with vegetable oil. They are soft and amorphous but resist compression. This is very helpful in the formation of cartilage. According to data from rats, the strength, stiffness, and hardness of cartilage increased 77 to 360 percent compared to cartilage tissue and without lipochondrocytes-which means that these cells make cartilage more stable.

And the gifts of nature seem to benefit all species. For example, outside the long-tongued Pallas bat’s ear, the Pallas’s bat has a series of tiny pores that scientists believe are responsible for making sounds.

The team also found lipochondrocytes in human fetal cartilage. And Lee says the findings seem to explain what reconstructive surgeons are seeing: “Cartilage is always a little slippery,” he says, especially in young children. “You can hear it, you can see it. It’s obvious.”

These findings suggest that lipochondrocytes effectively regulate the biomechanics of some of our cartilage. A solid layer of cartilage protein without lipids is very strong and is used to build the heavy bones in your neck, spine, and—yes, you’ve got it—ribs, one of the traditional cartilage materials for implants. “But when it comes to complex things that need to be flexible, flexible, flexible—the ears, the tip of the nose, the nose,” says Plikus, that’s where lipocartilage shines.

In a process that involves changing these parts of the body, Plikus will one day see the growth of lipocartilage organoids in a plate and 3D print them in any way they want. Lee, however, cautions: “Despite 30 or 40 years of study, we’re not really good at building complex muscles,” he says.

Although such an operation is a long way off, this study shows that it is possible to grow lipochondrocytes from embryonic stem cells and isolate them for transplantation. Lee reckons that regulators won’t give the green light to using embryonic cells to grow muscles because it’s not life-threatening, but he says he’ll be optimistic if the researchers can grow the transplanted tissue from patient-derived stem cells. (Plikus claims a new patent application he filed using adult-type stem cells.)

Lipochondrocytes change our understanding of what cartilage should look and feel like—and why. “When we try to make, say, a nose, sometimes we can use (lipid-rich cells) to cook it a little bit.” Lee says. Lipocartilage may one day fill that void as a larger, more flexible cartilage — or it may inspire better biomimicking devices. He said: “It can be both. “It’s fun to think about. Maybe that’s one thing we’ve been missing.