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A new research found that muscle stem cells coming from females are better at generating tissue than the male ones are, a discovery with great impact in the stem technology, aiming at therapies against many diseases and conditions.
Scientists working on muscle stem cells realized that all of the ones they had employed came from female mice. So that they experimented with both male and female cells to see if they would perform similarly.
Embryonic stem cells can turn into any type of body cell; but muscle stem cells, which come from adult muscle tissue, are more limited in what they can generate.
The researchers injected muscle stem cells from healthy mice into individuals that suffered from a disease similar to the human genetic disease Duchene muscular dystrophy, affecting every 3,500 to 5,000 young boys in the United States.
The people present a mutation that impedes them to synthesize the dystrophin protein, the scaffold of the muscle cell. "Their muscle breaks down and is replaced by fat," said co-researcher Bridget Deasy of the University of Pittsburgh School of Medicine.
This condition induces cardiac or respiratory failure as fat replaces muscle tissue in the heart and respiratory muscles.
The disease is generally diagnosed when the boys are five years old, and are wheelchair-bound by their early teens; very few outlive 25 years old.
One possible therapy for this disease would be cell transplantation. After injecting the stem cells, the researchers assessed the cells' ability to grow back muscle fibers that contained dystrophin. The accounts revealed that female cells generated many more fibers than male cells. "Regardless of the sex of the host, the implantation of female stem cells led to significantly better skeletal muscle regeneration," said senior author Johnny Huard, also of the University of Pittsburgh School of Medicine.
The differences linked to sex seem to originate in the cells' stress responses.
At the moment of the transplantation, the tissue gets inflamed and the new cells are attacked by free radicals, which makes the male cells differentiate or stop multiplication. "When you differentiate, you're done. That's the end of the line for a stem cell", said Deasy.
The precise reason for this is still unknown, but the team thinks the differences could be true in other stem cells, including human ones.