I still remember the skin on my grandmother’s arms. It had that crumpled-silk feeling that I used to love running my cheeks over. I did not know then that it was called sarcopenia or muscle wasting, often seen in the very elderly or children with progeria, as was Auro in the film Paa.
Muscle is what gives us our youthful limbs, the full cheeks and the expressive faces. Making up nearly 30% of our body mass, skeletal muscle or voluntary muscle enables us to walk, run, lift, blink, smile and breathe. Among the largest cells in the body, skeletal muscle cells connect to the bones through tendons. Each muscle is a bundle of muscle cells stretched from tendon to tendon, contracting in sync. Each muscle cell is packed with micro-bundles of proteins known as actin and myosin that slide against each other like in the boom of a telescopic crane. This sliding results in the contraction or expansion of the muscle, forcing the leg to bend, the lips to curve or the chest to expand.
In an active human, the skeletal muscles are constantly in motion and are subject to daily wear-and-tear. How do they keep themselves well oiled and in working condition? In the skeletal muscle, resides a population of specialized reserve cells known as the Satellite cells. Upon receiving chemical signals from torn or injured muscle in the neighbourhood the otherwise dormant satellite cells get ‘activated’ and start dividing to generate (1) muscle cells that will fuse with existing fibres to repair the damage and (2) more satellite cells that will retreat to the wings to wait for the next crisis to enter centre stage again. ‘Body building’ relies on this response of satellite cells, as exercise or working-out causes minor injuries to the muscles and fusion of more and more satellite cells to muscle fibres leads to a larger muscle mass.
As people age, their muscles become more prone to degeneration or atrophy. So, why did my grandmother’s muscles not regenerate the same as mine do? Nearly a decade ago scientists had shown that chemicals in the young blood could improve regeneration in old muscle. This they proved by creating a shared blood circulatory system, or parabiosis, between young and old mice. The success of this experiment generated hope that drugs could one day replace these blood ‘factors’. Now, two independent studies published early this year in Nature and Nature Medicine reveal more about aging muscles and offer real possibilities in treating sarcopenia.
Scientists took satellite cells from geriatric mice and transplanted them into a young mouse and discovered that the ‘aged’ satellite cells were inherently defective. Satellite cells from the donor mice were engineered to emit light such that the recipient muscle would glow in the dark if the donor cells helped their regeneration. They discovered that the satellite cells from old mice become ‘senescent’ and lost their abilities to repair injured muscle. This prompted the researchers to ask if there is a way to reverse this process; could the satellite cells be made youthful again?
The answer is yes. First they took the aging satellite cells and grew them. To prevent them from losing their satellite cell-like properties, chemical engineers designed a soft, porous, gel-like matrix that could mimic the elasto-rigidity of the animal muscle to grow them on. This expanded pool of satellite cells were then treated with drugs that could suppress senescence and further transplanted into mouse muscle. And hey presto! The rejuvenated satellite cells grew and repaired the muscle!
These studies have revealed that the problem lies within the aging satellite cells themselves and that the defect can be corrected with some chemistry and some engineering. The dream cure, a drug that can be injected into the aging muscle to improve regeneration, would await a better understanding of how the satellite cells and the environment in the young muscle differs from the old muscle.
But these studies show us that there is hope for Auro and for grandmother. But grandchildren would perhaps always rue the days when grandma’s skin was soft and wrinkly; proof of a lifetime’s love stored up, just for them.
Muscle is what gives us our youthful limbs, the full cheeks and the expressive faces. Making up nearly 30% of our body mass, skeletal muscle or voluntary muscle enables us to walk, run, lift, blink, smile and breathe. Among the largest cells in the body, skeletal muscle cells connect to the bones through tendons. Each muscle is a bundle of muscle cells stretched from tendon to tendon, contracting in sync. Each muscle cell is packed with micro-bundles of proteins known as actin and myosin that slide against each other like in the boom of a telescopic crane. This sliding results in the contraction or expansion of the muscle, forcing the leg to bend, the lips to curve or the chest to expand.
In an active human, the skeletal muscles are constantly in motion and are subject to daily wear-and-tear. How do they keep themselves well oiled and in working condition? In the skeletal muscle, resides a population of specialized reserve cells known as the Satellite cells. Upon receiving chemical signals from torn or injured muscle in the neighbourhood the otherwise dormant satellite cells get ‘activated’ and start dividing to generate (1) muscle cells that will fuse with existing fibres to repair the damage and (2) more satellite cells that will retreat to the wings to wait for the next crisis to enter centre stage again. ‘Body building’ relies on this response of satellite cells, as exercise or working-out causes minor injuries to the muscles and fusion of more and more satellite cells to muscle fibres leads to a larger muscle mass.
As people age, their muscles become more prone to degeneration or atrophy. So, why did my grandmother’s muscles not regenerate the same as mine do? Nearly a decade ago scientists had shown that chemicals in the young blood could improve regeneration in old muscle. This they proved by creating a shared blood circulatory system, or parabiosis, between young and old mice. The success of this experiment generated hope that drugs could one day replace these blood ‘factors’. Now, two independent studies published early this year in Nature and Nature Medicine reveal more about aging muscles and offer real possibilities in treating sarcopenia.
Scientists took satellite cells from geriatric mice and transplanted them into a young mouse and discovered that the ‘aged’ satellite cells were inherently defective. Satellite cells from the donor mice were engineered to emit light such that the recipient muscle would glow in the dark if the donor cells helped their regeneration. They discovered that the satellite cells from old mice become ‘senescent’ and lost their abilities to repair injured muscle. This prompted the researchers to ask if there is a way to reverse this process; could the satellite cells be made youthful again?
The answer is yes. First they took the aging satellite cells and grew them. To prevent them from losing their satellite cell-like properties, chemical engineers designed a soft, porous, gel-like matrix that could mimic the elasto-rigidity of the animal muscle to grow them on. This expanded pool of satellite cells were then treated with drugs that could suppress senescence and further transplanted into mouse muscle. And hey presto! The rejuvenated satellite cells grew and repaired the muscle!
These studies have revealed that the problem lies within the aging satellite cells themselves and that the defect can be corrected with some chemistry and some engineering. The dream cure, a drug that can be injected into the aging muscle to improve regeneration, would await a better understanding of how the satellite cells and the environment in the young muscle differs from the old muscle.
But these studies show us that there is hope for Auro and for grandmother. But grandchildren would perhaps always rue the days when grandma’s skin was soft and wrinkly; proof of a lifetime’s love stored up, just for them.
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