Researchers have demonstrated a successful and fairly straightforward stem cell therapy for osteoporosis in mice, though it remains a question mark as to exactly how it works under the hood. Osteoporosis is the name given to the age-related loss of bone mass and strength, with the primary proximate cause being a growing imbalance between the activities of osteoblasts that deposit bone and osteoclasts that absorb it. There are other factors involved, such as persistent cross-linking that makes the molecular structure of bone more fragile, but so far the best results in the laboratory have arisen from increasing osteoblast activity, reducing osteoclast activity, or both in conjunction.
With age-related osteoporosis, the inner structure of the bone diminishes, leaving the bone thinner, less dense, and losing its function. But how can an injection of stem cells reverse the ravages of age in the bones? Researchers had in previous research demonstrated a causal effect between mice that developed age-related osteoporosis and low or defective mesenchymal stem cells (MSCs) in these animals. "We reasoned that if defective MSCs are responsible for osteoporosis, transplantation of healthy MSCs should be able to prevent or treat osteoporosis."
To test that theory, the researchers injected osteoporotic mice with MSCs from healthy mice. Stem cells are "progenitor" cells, capable of dividing and changing into all the different cell types in the body. Able to become bone cells, MSCs have a second unique feature, ideal for the development of human therapies: these stem cells can be transplanted from one person to another without the need for matching (needed for blood transfusions, for instance) and without being rejected. After six months post-injection, a quarter of the life span of these animals, the osteoporotic bone had astonishingly given way to healthy, functional bone. "We had hoped for a general increase in bone health. But the huge surprise was to find that the exquisite inner "coral-like" architecture of the bone structure of the injected animals - which is severely compromised in osteoporosis - was restored to normal."
The study could soon give rise to a whole new paradigm for treating or even indefinitely postponing the onset of osteoporosis. While there are no human stem cell trials looking at a systemic treatment for osteoporosis, the long-range results of the study point to the possibility that as little as one dose of stem cells might offer long-term relief. "It's very exciting. We're currently conducting ancillary trials with a research group in the U.S., where elderly patients have been injected with MSCs to study various outcomes. We'll be able to look at those blood samples for biological markers of bone growth and bone reabsorption." If improvements to bone health are observed in these ancillary trials, larger dedicated trials could follow within the next 5 years.