How Stem Cells can Support Bone Repair

As soon as stem cell research emerged in the early 2000s, scientists began to look at ways of tapping into the regenerative potential of adult stem cells for bone repair, especially in older people affected by lower bone mineral density and a higher incidence of joint surgeries. Rapidly, scientist documented the crucial role played by various growth factors in attracting stem cells to the fracture site and promoting bone repair. In case of distraction fracture involving bone elongation, scaffolds were developed in which various growth factors were embedded, which resulted in significantly enhanced bone repair.[8,9]

Endogenous Stem Cell Mobilization for Bone Repair

Given the natural ability of stem cells to migrate to the site of a bone fracture, scientists also investigated the effect of simply stimulating stem cell release from the bone marrow on bone repair.  These studies were first done in animals and they revealed that this simple approach was quite promising.  Endogenous Stem Cell Mobilization (ESCM) significantly improved bone volume, bone density and overall bone repair.[10,11,12] One group of scientists even reported that ESCM could provide an effective alternative strategy to cell transplantation for enhancing bone regeneration.[13]

When this approach was repeated in humans, similar results were obtained.

One such study was performed with human patients undergoing complex knee surgeries.  It was documented that triggering the release of the patients’ own stem cells led to significant improvement in bone repair and integration of the bone graft.[14]

ESCM and Bone Density

One aspect of bone health that has been amply documented is the significant decline in bone mineral density with age, especially in women. While many factors contribute to the decrease in bone density, such as lack of physical activity and hormonal changes following menopause, one factor that is oftentimes overlooked is the age-related decline in the number of circulating stem cells, which in turn reduces the day-to-day ability of bones to repair and maintain a healthy density.[15,16,17]

A group of scientists documented that the age-related decline in the bones’ ability to repair, at least in women, maybe linked to menopause. They documented that mice made to be menopaused not only had lower bone density, but they released much fewer stem cells in response to bone fracture, further delaying bone repair[18]. Another study on osteoporosis reported that releasing one’s own stem cells can in fact help maintain bone density.[19]

Conclusion

Stem cells play a crucial role in bone repair, regardless of the type of fracture. And like any other tissue, there is a link between the number of circulating stem cells and the ability of bones to repair.  Increasing the number of circulating stem cells could also assist the body in maintaining health bone density.