Editors' ChoiceBONE REPAIR

More and Better Bone Formation for the Elderly

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Science Translational Medicine  07 Aug 2013:
Vol. 5, Issue 197, pp. 197ec128
DOI: 10.1126/scitranslmed.3007133

According to the global health observatory, the average life expectancy worldwide is 70 years. In 2011, 11% of the world’s population consisted of people over 60 years old, and this percentage is projected to double by 2050. Osteoporosis and osteoarthritis are already two major health burdens in our modern societies. These bone-affecting diseases have a tremendous impact on life quality of aged individuals and their caregivers. Bone repair is impaired in the elderly, and yet, compatible grafts from younger donors or use of growth factors to improve healing are options not free of safety concerns.

Leucht et al. propose a clinical alternative to improve repair of critical-size bone defects in aged patients. The authors used bone-marrow grafts from young and aged syngeneic mice and rabbits to study the repair of critical-size bone defects in both animal models. All grafted cells were green fluorescent protein–positive, remained within the injury site, and showed indistinguishable proliferation rates. Grafts from aged animals, however, produced significantly less new bone after 7 days. Wnt gene expression and responsiveness to Wnt—which is indicative of bone marrow fatty degeneration—were reduced in bone marrow from aged donors as compared with young controls. Then, bone grafts from aged animals were treated with liposomal Wnt3a in an attempt to recover their osteogenic potential. The treatment was done ex vivo to avoid the oncological risk associated with growth factors use in vivo. Seven days after implantation, new bone formation in recipients with Wnt3a-treated bone grafts doubled that of defects filled with untreated grafts. More interestingly, Wnt3a treatment resulted into new bone of a better quality—that is, woven bone with little fatty degeneration. How did the rejuvenated bone originate? Millions of elderly suffering from bone fractures may be asking themselves the same question.

P. Leucht et al., Wnt3a reestablishes osteogenic capacity to bone grafts from aged animals. J. Bone Joint Surg. Am. 95,1278–1288 (2013). [Abstract]

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