Advancing Cellular Understanding

If only human embryonic stem cells could sprout anew from something other than a human embryo. Researchers could harvest them and perhaps harness their great biomedical potential without destroying what some consider to be a budding human life.

But like a low-calorie banana split or the proverbial free lunch, there is no such thing as an embryo-free embryonic stem cell.

Or is there?

In recent months, a number of researchers have begun to assemble intriguing evidence that it is possible to generate embryonic stem cells without having to create or destroy new human embryos.

The research is still young and largely unpublished, and in some cases it is limited to animal cells. Scientists doing the work also emphasize their desire to have continued access to human embryos for now. It is largely by analyzing how nature makes stem cells, deep inside days-old embryos, that these researchers are learning how to make the cells themselves.

Yet the gathering consensus among biologists is that embryonic stem cells are made, not born -- and that embryos are not an essential ingredient. That means that today's heated debates over embryo rights could fade in the aftermath of technical advances allowing scientists to convert ordinary cells into embryonic stem cells.

"That would really get around all the moral and ethical concerns," said James F. Battey, chief of the stem cell task force at the National Institutes of Health. The techniques under study qualify for federal grant support because embryos are not harmed, he noted. And eventually the work could boost the number of stem cell colonies, or lines, available for study by taxpayer-supported researchers.

The transformation of ordinary body cells into extraordinary stem cells is not a matter of alchemy but molecular biology. All human cells, be they stem or otherwise, have the same basic complement of genes. What is different about stem cells -- and what gives them their remarkable capacity to proliferate and morph into whatever kind of cell the body may need -- is the specific pattern of activity of their genes. It is all about which genes are working and which are dormant.

As cells mature during embryonic and fetal development, certain genes in those cells are switched either on or off. Depending on the new pattern of activity, each cell becomes skin, heart muscle, nerve or some other kind of specialized cell.

Now scientists are exploring methods for resetting the genetic switches inside various cells to the positions that will make them embryonic again. Both of the two major approaches now under study use existing embryonic stem cells (widely available from previously destroyed embryos and eligible for study using federal funds) to help ordinary cells become stem cells.

In one approach pioneered by Robert Lanza and colleagues at Advanced Cell Technology in Worcester, Mass., researchers pluck single cells from eight-cell embryos -- embryos so young they do not have stem cells yet.