Scientists speed up body's repair systems
EU-funded researchers have succeeded in tricking the bone marrow into releasing extra adult stem cells into the bloodstream. The scientists hope that their findings, published in the journal Cell Stem Cell, will eventually lead to the development of new therapies to speed up the treatment of heart disease and broken bones.
EU support for the study came from the INNOCHEM (Innovative chemokine-based therapeutic strategies for autoimmunity and chronic inflammation) project, which is financed under the 'Life sciences, genomics and biotechnology for health' Thematic area of the Sixth Framework Programme (FP6).
When we are ill or injured, our bone marrow ups its production of different types of stem cells to repair our bodies. "The body repairs itself all the time," explained Dr Sara Rankin of the National Heart and Lung Institute at Imperial College London in the UK. "We know that the skin heals over when we cut ourselves and, similarly, inside the body there are stem cells patrolling around and carrying out repair where it's needed. However, when the damage is severe, there are limits to what the body can do of its own accord."
One strategy to increase the numbers of these stem cells in the blood is to harvest them, boost their numbers in the laboratory and return them to the body. However, this technique is beset with a number of practical and technical complications.
The other option is to use drugs to boost the production of these stem cells by the bone marrow. This technique is already used in bone-marrow donors to increase the number of haematopoietic stem cells circulating in their blood. Haematopoietic stem cells eventually turn into blood cells.
In this latest study, the scientists treated healthy mice with one of two growth factors, VEGF or G-CSF. The mice then received a new drug called Mozobil.
When the mice were treated with VEGF and Mozobil, their bone marrow released 100 times more endothelial and mesenchymal stem cells into the blood as untreated mice. Endothelial stem cells can make blood vessels and so could be used to repair damage to the heart. Mesenchymal stem cells can turn into bone and cartilage and also suppress the immune system; this means they could be used to treat autoimmune diseases, such as rheumatoid arthritis, where the immune system goes into overdrive. The group is the first to selectively mobilise these two different types of stem cell in the bone marrow.
Mice treated with G-CSF and Mozobil mobilised large numbers of haematopoietic stem cells; this treatment is already used in bone marrow transplants.
The next step for the scientists is to investigate whether these extra stem cells in the blood really do speed up the rate of tissue regeneration in mice that have suffered a heart attack. If these studies prove successful, the team hopes to try out the new drug combinations in clinical trials in humans within the next decade. The researchers are also keen to probe the impacts of disease and ageing on the ability of the bone marrow to produce different kinds of adult stem cell.
"We hope that by releasing extra stem cells, as we were able to do in mice in our new study, we could potentially call up extra numbers of whichever stem cells the body needs in order to boost its ability to mend itself and accelerate the repair process," commented Dr Rankin. "Further down the line, our work could lead to new treatments to fight various diseases and injuries which work by mobilising a person's own stem cells from within."
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