Can we re-grow cartilage in damaged knees? A new Stanford study offers hope

Knee pain is one of the most common afflictions among athletes and among older people in general. I’ve written about treatments for knee pain before, specifically about the many so-called alternative therapies that just don’t work.

(Quick review: the supplements glucosamine and chondroitin don’t work. Injections of hyaluronic acid don’t work. Acupuncture really doesn’t work. Simple pain relievers like ibuprofen work, but only for a short time.)

The problem is that cartilage, which provides a cushion between the large bones of the upper and lower leg, doesn’t regenerate itself. When you have cartilage damage, either from an injury or just wear and tear, you lose that cushion and you get pain and inflammation. Because the cartilage doesn’t really heal, if the damage gets severe, you might eventually need a knee replacement.

There is hope, though. For years now, I’ve been following stem cell research to see if it offers the promise to truly regenerate cartilage (or any other tissue, for that matter). Stem cells are special types of cell that can generate all of the different cells in our bodies, from blood cells to heart cells to lung cells to cartilage. Back in 2006, scientists made a major breakthrough when they discovered how to turn normal cells back into stem cells. Ever since, scientists have been exploring how to turn stem cells into just what we want them to be.

To repair damaged cartilage, what we’d really like is fresh new cartilage grown from our own stem cells. This is what a new study out of Stanford University, just published in the journal Nature Medicine, promises to do.

Here’s how it works. It turns out that the ends of our leg bones do contain stem cells, and if the bones are damaged, those stem cells will create new cells in response. The problem is that the new cells are basically scar tissue, not cartilage. The scar tissue wears out pretty quickly, and doesn’t provide the cushioning that cartilage does.

Stimulating the stem cells to get started is easy, if a bit crude: orthopedic surgeons already do this by drilling very tiny holes in the ends of the bone, a technique called microfracture. This provides some pain relief when the scar tissue appears, but it’s only temporary.

The Stanford team, led by Matthew Murphy, Charles K.F. Chan, and Michael Longaker, decided to use some of the latest findings about stem cells to steer the cells in a different direction after microfracture surgery. They did this by adding two proteins to the ends of the bones. The first one was BMP2 (bone morphogenetic protein 2), which encourages the stem cells to make new bone cells. They also added a second protein, VEGFR1 (vascular endothelial growth factor), which halts the process of bone formation in a way that leaves cartilage instead.

What’s exciting about this therapy is that it actually worked! New cartilage grew from the stem cells, and it appeared to reduce pain. The big caveat here, and this bears emphasis, is that the experiments were done in mice–and many studies that work on mice fail to reproduce in humans. Recognizing this limitation, the Stanford team also conducted experiments using human cells that had been transplanted into mice, showing that the treatment did indeed create human (not mouse) cartilage.

Next up will be studies in humans, to see if this works as well in people as it did in mice. If it does, another big advantage, as Prof. Longaker pointed out, is that both BMP2 and VEGF have already been approved by the FDA for other uses. This should make it easier to get approval for the new treatment as a therapy for aching knees. He suggested that, eventually, doctors might:

“follow a ‘Jiffy Lube’ model of cartilage replenishment. You don’t wait for damage to accumulate — you go in periodically and use this technique to boost your articular cartilage before you have a problem.”

So when can we get this new cartilage-healing treatment? More studies will likely take years.

Well, as Dr. Robert Marx pointed out in the NY Times, there’s nothing to stop orthopedists from trying this treatment out right away, because the drugs required are already on the market. Thus long before we see convincing evidence that it works in humans, doctors might be trying this out. For a patient who has deteriorating cartilage, if given the choice between waiting many years to see how the studies turn out versus trying a promising new treatment right away, the temptation might be too great to resist.

This is where things get tricky. There are already numerous orthopedic practices offering “stem cell therapy for knees” along with “platelet-rich plasma,” which they will inject right into your knees (for a price, of course). It took me less than 30 seconds of Googling to find dozens of practices offering these therapies, with assurances that they “repair the knee naturally ... by stimulating the creation of cartilage.” Note that these clinics are not using the new Stanford technique (not yet, at least), and there’s no good evidence that these injections will re-grow cartilage, despite the testimonials on many websites. So for anyone looking for knee pain treatments, caveat emptor.

Let’s hope this new treatment method works. For those of us (including myself) with aching knees, this new therapy is the most promising one I’ve seen in a very long time.