It starts off simple: one cell meets another cell. They make the preliminary introductions, and, taking a liking to each other, they unite and become a new cell, full of promise for the future. The cell divides, divides again, and five days later it is a hollow ball of 200 or so cells, a prodigious result from its humble beginnings of sperm and egg. It is from there that things start to get complicated.

Attached to the inside of that hollow blastocyst are 30 cells that have provoked more impassioned debate than arguably any other scientific development in recent memory. In the midst of the national conversation over these precious embryonic stem cells, one is liable to wonder how something so small ­­— smaller than the period at the end of this sentence — has come to carry so much hope, or fuel so much outrage.

Like vaccines, birth control, or genetic engineering, the march of science has yet again forced society to confront difficult issues or to ignore them at its own peril. In considering the question of conducting research on human embryonic stem cells, scientists, ethicists, legislators, religious leaders, the afflicted and the rest of the country see the need to reach a decision on what it means to be a human, and at what point something is no longer — or not yet — human.

Immortal Cells

In every human body there are around 200 different types of cells, all performing their own specific functions and specially equipped to do so. T-cells circulate in the blood ready to engulf microbe intruders; neurons flash electrical signals back and forth inside the brain to communicate with each other. These cells do their jobs well, but age and eventually die.

A few types of cells, however, are more versatile and able to transform themselves into a few other types of cells. These so-called adult stem cells are scattered in isolated clumps around the body — in teeth, bone marrow, umbilical cord blood and other locations.

Research on adult stem cells is currently one of the areas pursued by scientists at the University. The hope is that these adult stem cells can be coaxed to transform reliably into the types of cells that a diseased patient lacks. Controlling this differentiation is a complex matter of balancing an equation of nutrients, growth factors and environmental conditions.

Sean Morrison, an assistant professor in the Department of Internal Medicine, has seen early success in his work with hematopoietic stem cells. These cells are found in bone marrow and eventually give rise to all red and white blood cells.

“We just published a paper in the journal Cell,” Morrison said. For a time, it was the most downloaded paper on Cell’s website. “This indicates we can do stem-cell research that has an impact nationally.”

Deputy General Counsel Edward Goldman said the controversy is centered on embryonic stem cells.

“There is no ethical argument about the use of adult stem cells. The scientific argument is that they are not as useful as embryonic stem cells,” Goldman said.

It is the other variety of stem cells, those harvested from human embryos, which offer greater scientific promise and catch critical attention. Four or five days after fertilization takes place, the embryo has become a blastocyst containing about 30 embryonic stem cells. Unlike adult stem cells, these are pluripotent, meaning each one has the ability to become any of the body’s different types of cells.

“The benefit would be if you created a cell line, instead of testing potentially toxic drugs in human beings you could test them on the cells which are identical to the patient,” Goldman said. The stem cells could also be grown into replacement organs for transplantation.

Scientists are able to extract embryonic stem cells from the blastocyst and to keep them alive in the lab. These stem cells can then give rise to successive generations, forming a stem-cell line. Under the right conditions, stem cells are essentially immortal, given proper care.

The main issue at present is how to acquire these immensely powerful stem cells. One controversial method is somatic cell nuclear transfer, or “therapeutic cloning,” which transfers the nucleus from a skin cell into an egg cell, and activates it in such a way that causes it to multiply like an embryo. A group in South Korea recently announced their success in using this technique to harvest embryonic stem cells.

Another source is from the embryos stored in deep freeze at in-vitro fertilization clinics.