The third installment of Science Savvy is now in print! If you can’t access a paper copy, you can read the online version on the Quest site. We’ve also reprinted the text below with some external links to cool movies and the original articles. We hope you enjoy this article and will appreciate this example of just how important human embryonic stem cell research is.
Eye’ll Be Back
by Jack Craig & Moriah Gottman
In Luc Besson’s 1997 cult film, The Fifth Element, scientists recreate the perfect human from just a few cells. Though we’re far from being able to grow an entire Milla Jovovitch in an incubator, we are closer than ever to growing replacement body parts.
Earlier this year, a Japanese research team showed that it’s possible to generate a retina (the light-sensing part of your eye) in a dish. The scientists grew embryonic stem cells under special conditions and replicated the same processes that generate embryonic eyes during development. They first performed this study with mouse cells and then followed up to show that, with a few modifications, the same procedure works with human cells. This new procedure obviously has massive medical and scientific potential.
Yoshiki Sasai’s group at the RIKEN in Japan followed the physical development of a human eye minute by minute, enabling the study of a process that isn’t normally accessible because it occurs early in human embryonic development. They first saw a mass of tissue ballooning out from the embryonic brain which then doubled back on itself, forming an “optic cup.” The optic cup would give rise to the retina, which sits behind the lens and is surrounded by protective tissue. Here are links to some actual movies of these two stages of eye formation: First, evagination MOVIE1 then invagination MOVIE2.
Critically, the sides of the “balloon” must maintain enough rigidity to act as the outer walls of the newly formed cup while at the same time the center must be elastic enough to double in on itself, forming the inner walls. Additionally, the rim of the cup, formed by a band of cells in the middle of the balloon, would need to act as a hinge between the inner and outer walls, and this area would need to be the most elastic of all. To test their ideas about the importance of tissue flexibility during optic cup formation, Sasai’s team developed a computer model. Their findings suggest that simply changing the biophysical features of a tissue are sufficient to initiate optic cup formation. For more details about the simulations modeling optic cup evagination solely with biophysical forces, click here.
This recent breakthrough opens the door to further research on in-vitro organ development and therapies. In fact, stem-cell-mediated vision restoration in mouse models of retinal degeneration is already promising hope for patients.
Growing retinas in a dish also has implications for another neurodegenerative disease: Parkinson’s. Parkinson’s disease manifests with loss of muscle control, stiffness, trembling, and often dementia. It is the 14th leading cause of death in the US, according to data from the Parkinson’s Disease Association. The cause of Parkinson’s symptoms are linked to loss of dopamine, a neuromodulator that contributes to control of movement, memory, pleasure, and emotion. Areas of the brain rich in dopamine atrophy and die in Parkinson’s patients’ brains. Because retinal neurons make and respond to dopamine, retinas cultured from human stem cells could provide a model system for investigating how loss of dopamine affects neuronal circuits and provide new insights into this debilitating disease.
Can you think of other applications or uses of this technique? What else might embryonic stem cells be used for? Remember that without basic research on embryonic stem cells, these types of promising medical applications are less likely to occur.