*Scientists reverse muscle wastage in old miceSCIENTISTS have recorded two major breakthroughs in regenerative medicine.In the first study published in the journal Nature, scientists say a small African mammal with an unusual ability to regrow damaged tissues could be the key to the next breakthrough in regenerative medicine.Salamanders have long been studied for their ability to regrow lost limbs. However, amphibian biology is so different from human biology that experts have found it difficult to translate their findings into medical therapies for humans.But the African spiny mouse is a mammal and therefore far closer on an evolutionary scale to humans.The second research also published in Nature suggests that drugs could one day be used to reverse the muscle-wasting effects of ageing.Scientists have identified a key process responsible for muscle weakening in old age and used a chemical to block it in mouse studies. The findings could pave the way to body-building anti-ageing drugs that keep people strong and fit near the end of their lives.A team of British and United States researchers looked at the way stem cells in muscle repair damaged tissue by dividing and developing into numerous new muscle fibres.Strenuous activity, such as lifting weights, results in minor damage that triggers this response and builds up muscle. The end result is bulging biceps and rippling torsos. But as people age, muscle loses its ability to regenerate itself, leading to limbs that are puny and weak.Studying old mice, the researchers found that the number of dormant stem cells in muscle reduces with age. They traced the effect to excessively high levels of FGF2 (fibroblast growth factor 2) - a protein that stimulates cells to divide.In ageing muscle, the protein was continuously awakening the dormant stem cells for no reason.The supply of stem cells depleted over time, so not enough were available when they really were needed. As a result, the ability of muscle to regenerate was impaired.The scientists found that a drug that inhibits FGF2 prevented the decline of muscle stem cells. Treating old mice with the drug, called SU5402, dramatically improved the ability of aged muscle tissue to repair itself.SU5402 is purely manufactured for laboratories and not licensed for therapeutic use. But scientists hope the research, published in the latest online issue of the journal Nature, will lead to future treatments.The leader of the first study, Ashley Seifert, from the University of Florida, United States, said: 'The African spiny mouse appears to regenerate ear tissue in much the way that a salamander regrows a limb that has been lost to a predator.He said that the genes that direct regeneration in salamanders are probably switched off in mammals, but have been switched back on in the African mice. Locating this mechanism could have exciting potential for wound healing in people.In most mammals the gap created by a wound is filled by scar tissue. However, it lacks the functionality of the original tissue and has low elasticity. Internal scar tissue can prevent organs from working properly.Seifert was studying scar-free healing in amphibians when a colleague told him that a small rodent he had observed in Africa seemed capable of autotomy, a defense mechanism whereby the animal self-amputates a body part to escape a predator.'Autotomy in skinks, geckos and some salamanders is well known,' Seifert said. 'But it is very rare in mammals, and so far we've only seen it in a few rodents that can jettison their tail.'Seifert travelled to Nairobi, Kenya, where he documented the first known case of skin autotomy in a mammal. But it was how the animals' injuries appeared to be healing that really got his attention.He used a tiny biopsy punch, half a centimetre across to puncture holes in the ears of the mice to see if they would regenerate. 'The results were astonishing,' he said.
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