Enzyme induces adult stem cells to grow bone. Hitherto it has been difficult to induce adult human stem cells to produce bone, e.g. in order to repair bone tissue. Researchers at the University of Twente have shown that if the enzyme PKA is previously activated in the stem cells in the lab, following implantation this results in substantial bone formation. This opens up new ways of repairing bone tissue using cell material from the patient.
In animals, ‘adult’ mesenchymal stem cells have already been used successfully to grow fresh bone. Bone formation using human adult stem cells, e.g. from bone marrow, has been less successful, which has hitherto limited the alternatives hospitals can offer for repairing damaged tissue other than spontaneous healing. Activating the PKA enzyme prior to implantation, however, produces a dramatic improvement in ‘in vivo’ bone growth. The cells can be observed maturing into bone cells already in the lab; once sown on a carrier and implanted in a mouse, the bone grows well.
Encouraging the neighbors
The enzyme protein kinase A (PKA) is responsible for many processes in a cell. The messenger ‘cyclic AMP’ activates PKA: adding it to the stem cells ensures that they stimulate one another, the researchers think. Not only does cyclic AMP promote maturation into bone cells, the cells themselves also secrete various substances that stimulate bone growth. This may explain why mesenchymal stem cells treated with cyclic AMP form significantly more bone than those without the stimulus.
The advantage of administering a bone-growth-stimulating substance in advance is that it can be removed just before implantation. Experiments to date have mainly used high concentrations of a bone-growth-stimulating hormone, e.g. incorporated in the carrier on which the cells are ‘sown.’ In the new approach not only are the hormone concentrations lower, they also more closely resemble the cocktail of hormones normally involved in bone growth.
Illustration: Microsoft clipart.
University of Twente Press Release (05/26/08)
Medical News Today (05/27/08)
Science Daily (05/28/08)
Abstract (Proceedings of the National Academy of Sciences of the United States of America; Vol. 105, No. 20, 7281-7286 (05/20/08))