Stem cell cure for implants under research at Toronto hospital
TORONTO — To arthritis patients, they still seem like wonders of modern medicine: artificial hip and knee implants that curb chronic pain.
In fact, 14,000 Canadians a year receive hip replacements and more than 21,000 undergo knee replacements, the numbers soaring over the last decade.
If Dr. Nizar Mahomed and colleagues at the University Health Network (UHN) in Toronto succeed with fascinating new research, however, such surgery will eventually become a thing of the past.
The operations are, in fact, anything but panaceas, never really restoring people to their healthiest state, and often requiring replacement when the implant wears out, acknowledges Dr. Mahomed, head of orthopedics at the UHN’s Toronto Western Hospital.
With those limitations in mind, the UHN is pursuing research that aims to find a biological cure for joints decimated by osteo-arthritis, the most common form of the disease. Most dazzling among several experiments is a project that uses stem cells to create bone and cartilage, which researchers hope can be turned into a sort of organic joint implant that would fuse with existing tissue and regenerate diseased knees and hips.
Theoretically, the limits imposed on artificial joint-replacement patients would be forgotten.
“If we can find biological repair options, then basically we’re restoring the joint back to its native health state,” Dr. Mahomed said. “There would be no restrictions. You could go and run a marathon if you’d like. And there’s no concern that it is going to wear out, because we’ve basically restored it back to its [original] state of health.”
The research is prodded along by the reality of a field that in some ways has progressed little in recent decades. Drugs used today for osteo-arthritis simply treat the symptoms and are essentially the same as prescribed 30 years ago, said Dr. Mahomed.
Joint replacements, the last-ditch treatment, have been around for half a century. Neither is anything like a cure.
One of the UHN projects is generating cartilage and bone using both embryonic stem cells and those that can be extracted from bone marrow, blood or even fat of any adult patient.
At this point, the cartilage created in petri dishes is too thin to be helpful, but the team is working at making it more bulky, so it could be integrated with bone and implanted in patients. Once that laboratory work is perfected, the technique would have to be tried in animals. If the idea works on mice, human trials are probably five to 10 years away, said Dr. Mahomed.
Research around stem cells — which have a unique ability to convert into virtually any type of cell — has long been touted as a potential source of huge breakthroughs, from fixing severed spines to repairing diseased hearts. None of those breakthroughs has yet materialized, however.
Dr. Mahomed said he believes the orthopedic applications are much closer at hand. The stem cell-generated cartilage and bone only has to act as a mechanical support, much less complex, for instance, than creating spinal cord tissue that is able to effectively transmit neurons.
“We really do believe this will be a reality, rather than a potential dream,” said Dr. Mahomed.
Other work is looking at injecting a different type of stem cell — called mesenchymal — into the joint, a strategy that has emerged from a key recent discovery of the UHN team: that the most common type of arthritis seems to have an inflammatory component, contrary to earlier thinking.
The mesenchymal-cell injection, it is hoped, would help the joint return to its original, healthy state.