The only sure thing in life is that all of us one day will die. Humans have long been trying to achieve immortality, or at least live for 100 years and beyond. Some people think we're getting closer, and new research is sure to bolster that belief: Scientists say they've managed to reverse aging in human cells.

"We can make aged cells younger," said Dr. John Cooke, department chair of cardiovascular sciences at Houston Methodist Research Institute, who is lead author of the paper published Monday in the Journal of the American College of Cardiology. Cooke's team targeted the telomeres of patients' cells—the caps at the ends of chromosomes whose length roughly corresponds to age. Telomeres are a favourite focus of the anti-aging community. But there's still good reason to be skeptical that we've found the fountain of youth.

In the new study, Cooke's team took cells from children with progeria, a rare genetic condition that causes them to rapidly age. "These children lose their hair, they have osteoporosis. They look drawn and older," he told me in a phone call. These kids typically live to their early or mid-teens, when they die of a heart attack or stroke. This patient group is in desperate need of new life-prolonging treatments.

The paper notes that 12 of the 17 participants in this study (aged one to 14 years) had shortened telomeres, similar to what would be seen in cells from a healthy 69-year-old. Cooke said their cells can tell us something valuable about the aging process in healthy humans, too.

Cooke's team used a technology called RNA therapeutics, which delivers RNA directly into cells, to spur cells to produce telomerase, a protein that lengthens telomeres. The technique improved cells' lifespan and function. Before, cells would "multiply very poorly and then die," Cooke said. After the procedure, "cells proliferated normally. It was a dramatic improvement." Markers of aging, such as the release of inflammatory proteins, were reduced.

Video: Houston Methodist/Vimeo

Of course, cells in a dish are different than living breathing humans. Cooke believes that, while there's still plenty of research left to be done, it's a promising sign that could have applications for fighting age-related diseases. "When we lengthen telomeres, that can reverse a lot of the problems associated with aging," he said in an accompanying video.

This study follows other research highlighting telomeres' associations with age, and the potential anti-aging properties of telomerase. In 2010, one high-profile paper in Nature described how mice engineered to lack telomerase got prematurely old, but were young and spry again after the protein was replaced. Telomerase has been of huge interest to the anti-aging community, and supplements claiming to be "telomerase activators" are circulating online.

According to Dr. Peter Lansdorp, a professor of medical genetics at the University of British Columbia and scientist at the BC Cancer Agency, claims of telomere lengthening are mostly "snake oil." He explained that, despite the excitement, there's still a lot to learn.

Telomeres do tend to shrink as we age, but it's not a perfect correlation, according to Lansdorp. "It is not hard to find a 70-year-old with longer telomeres than a teenager," he said in an email. And there's good reason for telomeres to decline as we age: it's a "tumor suppression mechanism," as Lansdorp put it. Our cells stop dividing and die when telomeres become too short. If that didn't happen, it would put us at higher risk of developing cancer.

Cooke thinks we'll see treatments that target "the mechanisms of aging"

Telomerase-activating treatments might hold potential, Lansdorp agreed, under certain defined conditions. "For example, if it was possible to elongate the telomere length in blood forming stem cells, such cells could possibly be used for new therapies of selected patients," he said. Replacing defective hearts and kidneys wholesale from a patient's own cells, though, is still "science fiction," according to Lansdorp.

Cooke, for his part, is hopeful that what he's seen in cells in the lab can be translated to patients—first and foremost, kids with progeria. One challenge, he said, is how to deliver a treatment like this directly into the patients' own cells, possibly through nanoparticles.

Cooke thinks that, within our lifetimes, we'll see treatments that target "the mechanisms of aging," and by extension, the age-related diseases that plague us.

As for whether immortality is on the horizon, Lansdorp is skeptical. Immortality "is not a dream entertained by many serious scientists," he said. Our bodies are mortal by design, so we may just need to upload our minds into robot bodies instead.