Giving human organs the ability to regrow themselves after becoming diseased or damaged would be a boon for modern science, not to mention for scientists selling the commercial rights to the technology. With the FDA's approval last month of the world's first clinical trial using human embryonic stem cells (it had been on hold for a year), the quest for so-called "regenerative medicine" is plowing forward. But many new regenerative techniques don't require the embryonic stem cells that are so ethically objectionable. Sometimes they don't use stem cells at all.
Two new experiments illustrate: Drawing inspiration from newts and salamanders, which can regrow limbs (humans only regrow livers), a team from the Stanford University School of Medicine in California suppressed two genes in mouse muscle cells and caused the cells to multiply as if they were young again. With further development, the technique could be used to coax damaged muscle tissue into regrowing itself. As a next step, the Stanford team plans to try healing the muscle-wasting disease muscular dystrophy in mice.
In the other experiment, a team from the Gladstone Institute of Cardiovascular Disease, also in California, used a virus and three genes to transform fibroblast cells into muscle cells-both from a mouse heart. The fibroblasts, which make up about half of the heart's cells, give the organ its structure, while the beating muscle cells do all the work. During a heart attack the beating cells can die, leading to long-term heart failure. The Gladstone concept of converting the remaining fibroblasts into muscle cells could be used to reverse heart failure one day.
Both experiments were performed with mouse cells and primarily in lab dishes. It remains to be seen how effective the techniques will prove within the body-and any human applications are probably years away. Yet some biologists think these cell transformation techniques could make stem cells unnecessary for regenerative medicine.
Certainly not all scientists think so, and the many medical applications of ethical "adult" stem cells are too clear to ignore. Just a few months ago doctors in London performed a groundbreaking surgery on a 10-year-old Irish boy who was born with a constricted windpipe: They grew a new one inside the boy's neck using his own stem cells.
A clue about the single-celled alga Oophila amblystomatis can be found in its name: It means "salamander egg lover." Since the 1940s these algae have been known to enjoy a mutually beneficial relationship with the offspring of the spotted salamander, a shy amphibian with yellow spots that lays its jelly-like eggs in eastern U.S. ponds at night. The algae live inside the egg sac of the embryos, which grow more quickly because of the oxygen and carbohydrate produced by the algae during photosynthesis. In turn, the algae feed on the nitrogen-saturated waste of the embryo.
But only now have scientists noticed Oophila lurking inside the embryo itself-in its very cells. Although marine invertebrates like coral are known to harbor algae in their cells (coral bleaching is what happens when the algae die), this is the first instance of such intracellular symbiosis between algae and a vertebrate. The scientists' additional discovery of algae in the oviducts of an adult female spotted salamander has led them to speculate that the algae are passed directly from mother to egg.