A search under the term “stem cells low back” will turn up many studies that can seem to be able to regenerate worn out low back discs with stem cells. Does this work? If you believe a recent meta-analysis of 6 animal studies all it takes to restore a bad disc is a stem cell injection. However, based on our decade long experience and the existing human clinical trials data, it only works really well if you happen to be rabbit.
Degenerative disc disease is a big problem. The spinal discs are like shock absorbers between the bones. They have a soft inner center (Nucleus Pulposis or NP) that’s good at holding onto water and a tough fibrous outer covering. When the NP cells die off and don’t produce a special chemical to hold onto water (GAG or glycoaminosglycan), the disc dries out and loses height. This can also happen when the NP herniates (slipped or herniated disc).
If the disc becomes degenerated because the cells inside it die, why not just replace the cells? This has been a dream of medicine for decades. When stem cells came on the scene about a decade or more ago, there were a number of animal studies that showed that you could do this by injecting stem cells into the disc. In fact, this caught my attention in early 2005 and launched our interest and early studies in stem cells.
The most recent review paper of this research paints a rosy picture. The researchers pooled the results of 6 studies and found an that an intervertebral disc stem cell transplant was associated with 23.6% increase in disc height! This is great, as increasing the height of the disc can help all sorts of things like arthritis in the spine joints (facets) and pinched nerves. In addition, of all the six studies, none showed a decrease of disc height in the transplant group compared with the control group. Finally, the increase of disc height was statistically significant in all individual studies. Where do I sign up?
All of this sounds fantastic and this optimistic animal data has launched many biotech companies hoping to cash in on the next big revolution in one of man’s most common ailments. There’s just one catch, it doesn’t work in humans. We tried to replicate these animal studies as far back as 2006-7 and it failed miserably. Not a single patient saw a significant increase in disc height. In addition, a recent biotech company (Mesoblast) has also failed miserably. While their early clinicaltrials.gov outcome endpoint was to improve disc height and restore degenerated discs through an injection of someone else’s stem cells, they have seen no such results, just a very expensive reduction in pain.
Why did this not work so well in humans and why will these companies spending hundreds of million on FDA clinical trials ultimately fail? The animal models are poor surrogates for the real disease. While my patients come to the office with discs that took years to degenerate, the animal models are the equivalent of being abducted by space aliens and having your NP sucked out and then getting a stem cell injection weeks later. Meaning the chronic disease and all that caused it (too much sitting, weight, smoking, lifting, etc…) produces a nasty challenging chemical environment to regenerate while the young and healthy rats or rabbits have an acute traumatic injury that doesn’t exist in humans (sudden loss of the NP through a lab worker to make the disc degenerate artificially). In addition, we humans are bipeds and these animals are all quadrupeds, so our disc architecture is quite different than a rabbit.
The upshot? While we have had great success in using stem cells to help get rid of disc bulges and platelets to help patients avoid epidural steroids or other spinal injections, despite this meta-analysis, restoring a pristine lumbar disc with a magic stem cell injection isn’t going to happen anytime soon. Will it happen some day? Absolutely. But it will take many years of clinical experience with stem cells before it does.