Amrit for the muscles: the secret lies within

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.

Photo by Nikolett Emmert

Chasing after fireflies in the dark night

So, the resolution to write more frequently did not really materialize. There are too many other less interesting distractions. But it’s a good time to glance back before forging ahead.

 
I started with no thought of money (or rather funds, as scientists seem to call it), generously helped by supportive colleagues. Then joined the mainstream, wrote network projects (as the funding agency calls them) and now it was funds galore. Oh, but like Cinderella there was a deadline…when the clock strikes midnight the carriage will turn to a pumpkin and the funds will all vanish. So dutifully, we stuffed our freezers and emptied our pockets. Then you are told, go play with your existing toys, no new toys for you for six months. The fairy godmother visits but rarely. So, until then we shall do predictable research, and dream of all those ‘urgent’ experiments.

I started with one student who had accidentally strayed into my web. Now I have a team of 10 assorted students. I started with a one-gene-one-protein dogma. Then it turned out that one gene could give rise to many RNA. Some may not even code for a protein and some could be simply transcriptional runoffs and still others might have hitherto unknown functions. I learnt that you need a large diversity in the genome to create complexity.

I started with wonderful colleagues, supportive mentors and friends all around. I passed through distress and disillusionment and came out on the other side with the realization that, oh yes, we are all just humans and don’t let us pretend to be anything more. I have honed my survival skills through shouting matches with colleagues in the corridor, volcanic eruptions in small committee meetings and one-on-one heated arguments in the privacy of gypsum walled offices. I had once, long ago, complained that my life was too boring.

Today I am thinking about fireflies and yes, their luciferase. The lure of the luciferase that draws you to one, you lunge and grab and there is none there. But just there on the periphery of your vision you see another winking only to lunge and fail. I have a dozen fireflies in my field of vision now. Each a story, each a secret of nature’s that she like a small child holds in her cupped hands only to allow a tantalizing glimpse. The moment you stretch you finger out to touch it, the light blinks, the palm closes and you are not even sure if you really did see it.

It was almost four years and a month ago that I was lying back and watching fireflies blink around (see synapses alive and crackling). Today I am chasing those fireflies in the dark night and hoping I will catch one to open a tiny window into nature’s workings. But for all else that goes on the light of the fireflies do not dim and the magic of the chase keeps me here.  

Stem cells

Adult body is a specialized machine with each part perfected for its intended function. Most cells in the adult body are irreversibly differentiated to form parts of this machine. Such as the heart, where the myocardial cells form an interconnected bundle that can contract in unison upon receiving instructions from the cardiac pacemaker. Or the brain, which contains millions of neurons connected through synapses designed for this command centre to integrate and control all the activities of the organism from digestion to perspiration to locomotion to reproduction to introspection.

The life of every animal starts off from a single cell known as the zygote. This single cell divides prolifically to give rise to the embryo, where progressively cells exit cell cycle, specialize for a particular function and differentiate. However, there are organs in the body that undergo regular wear and tear and require continuous repair and replacement of lost cells. Examples include the skin, gut lining, blood etc. These organs retain a small population of reserve cells that do not differentiate. These cells proliferate, repair, renew and regenerate the organs as and when required. These are the ‘stem cells’. 

In 1877, the famous German biologist Ernst Haeckel used the term ‘‘Stammzelle’’ (German for stem cell) in his book Anthropogenie to mean the zygote as the originator of all cells in the organism. Towards the end of the century, scientists studying hematopoiesis arrived upon a cell that they called the ‘stem cell’, which was capable of giving rise to all the diverse lineages of blood cells viz. the erythrocytes (red blood cells) and leukocytes (T-cells, B-cells, macrophages, neutrophils, eosinophils etc.). This modern concept of stem cell, as a cell that can divide and self-renew indefinitely and that could differentiate into a number of different cell types was introduced and demonstrated by James Till and Ernest Mcculloch in 1960s. Mice irradiated with high dose of X-ray die rapidly because the radiation kills blood cells essential for oxygen transport and immunity.  Till and Mcculloch found that these mice could be rescued by injection of bone marrow from a normal mouse. The bone marrow contained ‘hematopoietic stem cells’ (HSC) that could recolonize the marrow of the irradiated mice and thus provide a steady supply of all blood lineages for life.

Adult stem cells thus reside in niches, usually within the tissue that they repair and regenerate. In the stem cell jargon they will be defined as ‘multipotent’, i.e. having the potential to differentiate into a number of different cell types. Usually one stem cell population can replenish losses in a few different cell types e.g. the intestinal stem cells that reside in the crypts of the intestinal villi are multipotent. These stem cells continuously undergo cell division and supply the gut with enterocytes (absorptive cells that absorb nutrients from the food), goblet cells (that secrete mucin to form mucus), enteroendocrine cells (that secrete intestinal hormones) and the Paneth cells (that provide defense against microbes). They also replenish the stem cells themselves. However, an adult stem cell does not have ‘pluri’potency; an intestinal stem cell cannot form heart or brain cells.

The zygote is a ‘totipotent’ cell; it has the potential to form any tissue or cell type in the animal body, rather the zygote gives rise to the whole animal. Embryonic stem (ES) cells are created by growing young embryos in artificial culture conditions. These cells are ‘pluripotent’ i.e. they have the potential to differentiate into almost all cell types in the animal. By controlling their growth conditions they can be made to differentiate into brain, heart, muscle, pancreas and many other cell types. In 1998 James Thomson of the University of Wisconsin created the first embryonic stem cells from human embryos donated by individuals after informed consent. These embryos had been created by in vitro fertilization (IVF) for fertility treatments. The scientists were able to keep these cells dividing in culture conditions for months and they became established cell lines, being used by scientists around the world even today.

James Thomson’s discovery came in a climate of controversy and regulations. Since 1970s successive American governments headed by Ronald Reagan, George H W Bush, Bill Clinton and George W Bush have instituted a series of bans on embryonic research. In 1993, the United States President Bill Clinton had lifted an existing moratorium on government funding for embryonic research, only to rapidly reverse the order under public pressure. In 1995, the U.S. congress banned federal funding for any research involving the destruction of human embryos under the Dickey-Wicker Amendment. It was during this time that Thomson created the first ES cells using private funding.

The funding and legal problems in working with human embryos and embryonic stem cells had prompted scientists to think about alternatives. In 1960s John Gurdon in Oxford University, U.K., had demonstrated that you could replace the nucleus of a frog oocyte (an immature female reproductive cell) with the genetic material (contained in the nucleus) of an adult frog cell and create a live tadpole. The tadpole was thus a clone of the adult frog, which donated the nucleus.  Gurdon hypothesized that all the genetic information needed to create a whole organism is contained in the differentiated adult cells of the organism. However, you need the ‘reprogramming’ environment of an egg cell to activate this potential. This was the origin of the cloning of ‘Dolly’, the sheep cloned from the udder cells of a Finn-Dorset ewe in 1996.

Thus, the hunt was on to define the reprogramming molecules that were needed to make an adult cell regain its pluripotency. In 2007 using a combination of just four proteins, the Shinya Yamanaka and James Thomson labs simultaneously published the successful generation of pluripotent stem cells from adult human  somatic cells that they called the ‘inducible pluripotent stem cells’ or iPS cells. This has opened the door to patient-specific stem cell therapies for diseases ranging from neurodegenerative diseases, cardiovascular diseases, and accidental damage to tissues such as the spinal-cord and many others.

The creation of iPS cells frees stem cell research from the dependency on human embryos and thus religious and political controversies. However, stem cell therapies will continue to be controversial and will have to be administered with great caution. Stem cells are cells with immense potential for growth, a hallmark of cancer.

Stem Cell Resources

http://stemcells.nih.gov/

http://www.eurostemcell.org/stem-cell-resources

as published in the Manorama Year Book ® 2014

Only as far as we imagine…

Only as far as we imagine…

On a clear night 20,000 years ago a man lay next to the warming fire and gazed upward; he saw a glittering dome that contained the world he lived in. Today when I lounge on my balcony and stare up at a smog-obscured-night-sky, I see an infinite universe, perhaps one of many; a vast nothingness punctuated by millions of insignificant balls of fire with finite life spans, around one of which we spend our precariously short existence. Over the last many thousands of years, we have shattered that domed-roof over our heads and thrown back its limits into the reaches of infinity. And all because we dared to imagine, imagine an infinity, imagine a time even before time.

However, our world is only as big as we can imagine. Our discoveries will remain contained within the boundaries of our imagination. If we cannot imagine it, we shall not discover it. The 17^th century philosopher Benedictus Spinoza once said ‘if a triangle could speak, it would say, in like manner, that God is eminently triangular’. So do we, a carbon-hydrogen-based life-form think that life is where water is. We go hunting for obscure marks of water-that-once-flowed on the surface of far away planets. But is that the limit of possibilities or is that just as far as our imagination can take us?

We are a species capable of unparalleled imagination. In these last 20,000 years our brain has taken us on journeys beyond experience; shading our eyes to gaze outward as far as the edges of universe or peering inward to dissect the minutiae of that brain itself. But these boundaries were not reached in one leap but in steps, some small, some giant.

In his book A short history of nearly everything Bill Bryson says, ‘Once in a great while, a few times in history, a human mind produces an observation so acute and unexpected that people can’t quite decide which is the more amazing ­– the fact or the thinking go it.’ He is talking about Newton, but the same could be said of the other few times that mankind has taken that giant step forward. ‘The thinking of it’ is so amazing, so freeing, that like that first thin stream of water breaching the crack in the dam, it lets the rest of the river of human knowledge burst through, washing away the remnants of the dam. Our imagination leaps ahead into the space opened up, suddenly free and unrestrained, until that is, a new wall is reached. 

The history of science is littered with such ‘feats of thinking’. Like when John Snow was faced with a cholera epidemic decimating 19^th century Londoners. London was a vile place full of disease. Under the ramshackle houses lining the busy streets were cesspits with years of accumulation of refuse and excrement. Snow focused his attention on one street where nearly 500 people had died in a matter of two weeks. In an inspired epidemiological study he identified the commonalities between the patients and proposed that the source of the disease was contaminated water coming from a single pump down the street. In a world that believed diseases were either punishment from the gods or a result of bad air, this required quite a leap of imagination. The authorities were reluctantly persuaded to disable the pump, saving hundreds of lives.

James Hutton lived in 18^th century Britain. He trained to be a medical doctor, became a farmer but is now known to us as the man who founded modern geology. Just as we all do, he too liked a beautiful landscape of mountains and valley and rivers and lakes. But he went further to note that although wind and water constantly erodes mountains and carries the sediments down to the sea and the plains, the world has no dearth of mountains. That sometimes you can find remains of sea-creatures high up on the mountains. The Christian faith maintained that earth was created 6000 years ago and that all change happens by cataclysmic events such as the Great Flood. Hutton’s imagination came up with another explanation. After years of painstaking observation and collection of data from various parts of the Europe, he proposed that the reshaping of earth’s landscape is the result of continuous but slow incremental change wrought over millions of years. These geological changes are constantly restructuring the earths crust, moving not just mountains even continents, thus today’s oceans may become tomorrow’s mountains and vice versa.  In one fell swoop Hutton pushed the age of earth back from a mere 6,000 years to millions of years. 

Most scientific discoveries are made by a handful of people. Another handful of people are intellectually able to understand and critique the discovery. The rest of us merely struggle to interpret the results and how it changes the world as we know it. Nowhere is this more true than the science of the origins of our universe. In early 20^th century, astronomers began to suspect that we live in an expanding universe. In the 1920s Edwin Hubble, after whom the Hubble telescope is named, realized that everywhere you look, galaxies are moving away from us. This led to the idea that, at the beginning of this expansion all the contents of our universe must have been concentrated in one place, from where it shot out in all directions, in other words, in the beginning there was an explosion, the Big Bang. Since we know how far the galaxies are from us today and also the rate at which they are receding from us, we can calculate the time at which it all began, around 13-14 billion years ago. In 1940s George Gamow and colleagues imagined that if the universe did indeed begin with a big bang, there must be residues of the ‘bang’ still reverberating through space. A prediction that was proved correct when in the 1960s Arno Penzias, Robert Wilson and Robert Dicke in their experiments encountered an annoying all-pervasive background radiation that wouldn’t go away. So after 14 billion years our world still resonates with the violence that began our universe.

Our imagination has carried us far. We have discovered much. But each discovery births new questions, new wonders, new boundaries to be breached, new walls to be scaled. As Ralph Sockman said, ‘the larger the island of knowledge, longer the shorelines of wonder’. 

But how much can we discover? Is there a limit to our knowledge? Do we still live inside a dome in the sky, no matter how big? Perhaps that dome is not in the sky, rather we carry it around with us, in our heads. The day we stop imagining, we would have found that dome. Nature is not an easily read book. It allows us only tiny glimpses of its secrets, opening only those windows we knock on. As long as we have the zeal to find a new window to knock, there will be secrets waiting to be discovered.  

Readings:

 A Short History of Nearly Everything by Bill Bryson (an excellent light reading!)

A History of Western Philosophy by Bertrand Russell

Lots and lots of Google!!