“‘Is this too good to be true?’ is the question I often ask,” says Dr. Michael Sheetz, an award-winning mechanobiologist who has taught at Duke Medical School, Columbia and now at the University of Texas. His astonishment at this therapy’s effectiveness is understandable because it reverses a key driver of aging – senescent cells, sometimes called zombie cells.
Researchers are testing drugs to see if they can flush these aging and disease promoting cells from the body. But Dr. Sheetz’s approach is quite different. He’s not aiming to eliminate these zombie cells, but to revitalize them.
In our sixties and beyond senescent cells lose the ability to divide. Instead of dying off however, they remain in a zombie-like state, secreting inflammatory and toxic molecules that drive the aging process and contribute to chronic disease.
Targeting these zombie cells is seen as a promising anti-aging strategy, so researchers have developed drugs called senolytics to wipe them from the body. But senescent cells aren’t all bad news.
When newly formed, they perform important functions in wound healing. Therefore, Dr. Sheetz doesn’t want to wipe them out and lose their beneficial properties, but rather transform them back to normal, healthy cells. The method he uses is to blast them with ultrasound.
Ultrasound extends healthy cell division
While ultrasound is a diagnostic imaging technique best known for its use in pregnancy and the diagnosis of cancer, it can also be used therapeutically as a treatment. Here’s how: An electric current creates sound waves that travel through the skin. The energy from the waves has been shown in studies to promote healing in patients with a variety of musculoskeletal issues.
For his cellular and animal research Dr. Sheetz used an ultrasound frequency of less than 100 kHz. This is well below the 2000 kHz or so used for medical imaging. After directing the waves at senescent cells taken from monkeys and humans, the cells resumed dividing. For instance, human foreskin cells usually show signs of senescence after about 15 divisions, but after ultrasound they reached 24 divisions with no sign of abnormality and without secreting toxic, disease-causing chemicals.
The animal experiment utilized mice aged between 22 and 25 months, which is equivalent to around 63 and 72 in human years. Since ultrasound waves lose less power traveling through water than through air, the mice were placed in water covering half their bodies.
The results were exciting.
Compared to untreated mice, those receiving ultrasound demonstrated better performance in physical tests, some of which were dramatic. For instance, one elderly hunch-backed mouse couldn’t move well in the initial tests. Then Dr. Sheetz explained what happened when the mouse was zapped by sound waves. “We treated it twice with ultrasound and it was back to behaving normally. I don’t think that rejuvenation is too strong a term.”
Using dyes that bind to senescent cells, the team was also able to show how these zombie cells declined in the kidneys and pancreas of the treated mice.
How does ultrasound reverse senescence and rejuvenate mice? Dr. Sheetz can’t provide a definitive answer, but he does have a theory. Although he says aspects of this are “still mystifying,” he believes the distortion of cells by the sound waves has effects like exercise, one of which is to reactivate autophagy – the cells’ waste disposal system – which grinds to a halt in senescent cells.
Since bones and lungs block the transmission of ultrasound waves, it won’t be straightforward to apply the ultrasound to human patients in every case. But the researchers are planning to test it in those with specific health troubles such as osteoarthritis and diabetic foot ulcers and are hopeful of positive results. I’ll keep you posted on any new and exciting developments.