To a large degree the future of medicine is the future of control over cells. Plus some other stuff around the edges relating to clearing up after cells, removing some of the metabolic waste and misfolded proteins that they can't deal with. These items aside, near all of disease and aging might be tamed with a sufficiently good ability to repair and direct the behavior of our cells as they go about the business of life. That is the ultimate goal of medicine: to prevent all death, suffering, and disability, and provide the option of remaining alive and in good health for as long as you desire.
In some ways these are still the very earliest days in the control of cells, despite more than a century of serious work on the topic. The research community is barely starting on programming cells for specific activities or outcomes, and the technologies to do so have only existed for a handful of years. Yet progress in cell biotechnology is accelerating rapidly. Given the knowledge that researchers have today it is not unreasonable to look ahead to envisage very specific technologies that will enable sophisticated cellular control, not just over individual cells in the lab, but eventually for every cell in the body, all at once. This will happen a matter of a few decades from now. Tomorrow's researchers will mass-produce merged assemblies of novel protein nanomachines and natural cell components to improve, repair, and direct cells in very sophisticated ways.
The advances of today are modest in comparison with this vision for decades to come, and the tools used to change cell behavior very crude in comparison. But this progress is important, and the resulting treatments provide real benefits. Present day stem cell medicine is just a first pass at doing something useful, and yet where it is proven it is life-changing and life-saving for patients. Much more interesting and effective therapies lie ahead. Here is a random selection of some recent work in the field of cell biotechnology:
Limbal stem cells reside in the eye's basal limbal epithelium, or limbus, and help maintain and regenerate corneal tissue. Their loss due to injury or disease is one of the leading causes of blindness. In the past, tissue or cell transplants have been used to help the cornea regenerate, but it was unknown whether there were actual limbal stem cells in the grafts, or how many, and the outcomes were not consistent.
In this study, researchers were able to use antibodies detecting ABCB5 to zero in on the stem cells in tissue from deceased human donors and use them to regrow anatomically correct, fully functional human corneas in mice. "Limbal stem cells are very rare, and successful transplants are dependent on these rare cells. This finding will now make it much easier to restore the corneal surface. It's a very good example of basic research moving quickly to a translational application."
The gold standard is human embryonic stem cells (ES cells) cultured from discarded embryos generated by in vitro fertilization, but their use has long been limited by ethical and logistical considerations. Scientists have instead turned to two other methods to create stem cells: Somatic cell nuclear transfer (SCNT), in which genetic material from an adult cell is transferred into an empty egg cell, and induced pluripotent stem cells (iPS cells), in which adult cells are reverted back to a stem cell state by artificially turning on targeted genes.
Until now, no one had directly and closely compared the stem cells acquired using these two methods. The scientists found they produced measurably different results. "The nuclear transfer ES cells are much more similar to real ES cells than the iPS cells. They are more completely reprogrammed and have fewer alterations in gene expression and DNA methylation levels that are attributable to the reprogramming process itself."
"If you believe that gene expression and DNA methylation are important, which we do, then the closer you get to the patterns of embryonic stem cells, the better. Right now, nuclear transfer cells look closer to the embryonic stem cells than do the iPS cells. I think these results show that the SCNT method is a far superior candidate for cell replacement therapies. I truly believe that using this method of producing stem cells will someday help us cure and treat a wide range of diseases that are defeating us today."
Red blood cells (RBCs) are an attractive vehicle for potential therapeutic applications for a variety of reasons, including their abundance - they are more numerous than any other cell type in the body - and their long lifespan (up to 120 days in circulation). Perhaps most importantly, during RBC production, the progenitor cells that eventually mature to become RBCs jettison their nuclei and all DNA therein. Without a nucleus, a mature RBC lacks any genetic material or any signs of earlier genetic manipulation that could result in tumor formation or other adverse effects.
Exploiting this characteristic, [researchers] introduced genes coding for specific slightly modified normal red cell surface proteins into early-stage RBC progenitors. As the RBCs approach maturity and enucleate, the proteins remain on the cell surface, where they are modified. Referred to as "sortagging," the approach relies on the bacterial enzyme sortase A to establish a strong chemical bond between the surface protein and a substance of choice, be it a small-molecule therapeutic or an antibody capable of binding a toxin. The modifications leave the cells and their surfaces unharmed.
"Because the modified human red blood cells can circulate in the body for up to four months, one could envision a scenario in which the cells are used to introduce antibodies that neutralize a toxin. The result would be long-lasting reserves of antitoxin antibodies."