With the exception of the brain, the human eye is the single most complex organ in the human body.
It has 2 million working parts and accounts for an estimated 90% of the information we learn during our lifetimes.
Throughout the average life span, the eyes will transmit nearly 24 billion separate visual images of the world. They will also occupy 65% of the pathways to the brain and 40% of its cells.
As such prominent extensions of our brains, our eyeballs have been considered by many to be the basic foundation of human intelligence. Just about everything we know has started at the eye, so it’s no wonder these organs need to be incredibly complex.
The human eye is so intricate that it’s often used by creationists as an argument for intelligent design, the idea being that there is simply no way a structure so sophisticated could have been created through natural selection.
English clergyman and philosopher William Paley called the eye a “miracle of design” in 1802, and even Charles Darwin wrote in his Origin of Species that the evolution of the eye seemed, at first glance, to be “absurd in the highest possible degree.”
But I’m not here to argue about evolution — I’m simply highlighting that the construction of the eye was undeniably an incredible feat.
Regardless of whether it is the product of intricate design or the long and arduous process of natural selection, the sophistication of the eye is remarkable.
Perhaps even more extraordinary than the initial construction of the eye, though, are recent advancements in science that have given us the ability to grow parts of it on demand.
Just a few days ago, a BBC headline caught my eye: “Scientists use stem cells to regenerate human corneas.”
The article reported:
“Limbal stem cells (LSC) are crucial for healthy eyesight – these cells work to maintain, repair and completely renew our corneas every few weeks.
Without them the cornea – the transparent outermost layer of the eye – would become cloudy and our vision disrupted.
A deficiency of these cells due to disease or damage through injury to the eye are among the commonest reasons behind blindness worldwide.
But the cells have so far been extremely difficult to identify, buried in a matrix of other structures in the limbal part of the eye – the junction between the cornea and the white of the eye (the sclera).
Now scientists from the Massachusetts Eye and Ear Infirmary, Boston Children’s Hospital, Brigham and Women’s Hospital and the VA Boston Healthcare System have identified a key tracer molecule – known as ABCB5 – naturally present on the surface of limbal stem cells.
Though ABCB5 has been known about for some time in other parts of the body, this is the first time it has been spotted on LSCs, helping to single out these elusive cells.
Researchers have been able to tag these cells with fluorescent molecular flags.
In their study, the scientists used this tagging technique to instantly identify a pool of LSCs on donated human corneas.
After being transplanted to mice, these cells were able to generate fully functioning human corneas.”
Of course, the cornea is just one part of the eye. What about more sophisticated areas such as the retina?
Well, you might be surprised to hear that stem cells are working wonders on this front as well.
According to a news release from Johns Hopkins Medicine last month, a group of researchers has successfully used stem cells to create light-sensitive retinas in a petri dish.
Study leader M. Valeria Canto-Soler, Ph.D., explains:
“We have basically created a miniature human retina in a dish that not only has the architectural organization of the retina but also has the ability to sense light.”
Regrowing the retina is a particularly difficult task because the tissue and structure is highly complex. The retina is comprised of six major cell types, including five different kinds of neurons, all organized into precise layers.
The success of the study was so extraordinary that even Canto-Soler and her team were surprised by the results:
“We knew that a 3-D cellular structure was necessary if we wanted to reproduce functional characteristics of the retina, but when we began this work, we didn’t think stem cells would be able to build up a retina almost on their own. In our system, somehow the cells knew what to do.”
As the lead researcher also noted, this research “advances opportunities for vision-saving research and may ultimately lead to technologies that restore vision in people with retinal diseases.”
Of course, it will be years before we can regrow entire eyeballs, let alone successfully transplant these man-made organs into the human body.
Biotechnology company Organovo (NYSE: ONVO) is already bio-printing human tissue for research and therapeutic purposes, but it remains focused on much simpler structures such as liver and bone. And even with these less complicated structures, the company is finding it impossible to turn a profit.
In the near term, profitable stem cell ventures will not lie in the full reproduction of organs, but rather in simpler treatments that target specific ailments.
Among these are therapeutics in the pipeline focused on treating paralysis, heart disease, and vision loss.
These treatments won’t give you a new heart or spine, but they may very well be the key to many age-related ailments. After all, that’s really what regenerative medicine is all about.
Turning progress to profits,
Jason Stutman
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