Westward Whoa!

Stem cell restrictions could send Texas Medical Center researchers fleeing to California

Getting down to the corporeal nitty-gritty of why embryonic stem cell research is wrong, most opponents present a simple, even graceful secular argument: All that any petri dish embryo needs to grow into an adult is time and nourishment. Boswell's analogy: "I have the potential to be an old lady," she says, "but you put me out in the desert with no food and no water and the poor conditions, I'm going to die…That doesn't make me any less human."

Prompted by his mother, Riley summarizes the problem this way: "You have to kill babies."

Ultimately, the research is all the more atrocious, opponents say, because it isn't even necessary. Boswell is convinced that embryonic stem cells will never cure diabetes. A handout distributed by Texas Right to Life points out a variety of problems with the cells, such as their tendency to form strange tumors consisting of clumps of teeth, eyes and hair. "Some scientists think that stem cells extracted from cloned human embryos will be useful for the treatment of human diseases," it says. These "claims are unfounded."

After conventional treatments offered no relief, stem 
cell therapy helped Ruth Pavelko's heart problems.
Daniel Kramer
After conventional treatments offered no relief, stem cell therapy helped Ruth Pavelko's heart problems.
Geng (shown with computer images of stem cells) 
says therapeutic cloning advances will prolong life.
Daniel Kramer
Geng (shown with computer images of stem cells) says therapeutic cloning advances will prolong life.

Physically speaking, the foundation for Geng's science is a petri dish filled with gel and proteins -- nourishment for a smattering of embryonic cells. In his expansive laboratory on the ninth floor of the Texas Heart Institute, Geng plucks one of these dishes from a refrigerator and places it beneath a microscope.

The view, a few years ago, admittedly might have been a Frankenstein mix of skin, bone and intestine cells -- almost anything the cells wanted to form. But Geng has refined the mixture of proteins to direct the cells' growth. "These are heart muscle cells," he says, "derived from the stem cells."

A nearby computer shows a strangely recognizable video of the cells' movements. Every second or so, they throb in unison. "The mature cardio cells are spontaneously beating; they have a pulse," Geng says. "It's like you grow a heart, in vitro, in a petri dish. A small, tiny heart."

Eventually, Geng wants to know whether embryonic stem cells can be grown into full-sized hearts for patients who need transplants. But in the near term, he's investigating how well the cells repair existing hearts. The investigation mirrors the ones he's conducting with adult stem cells in human patients such as Pavelko. "What we want to do is find out how we can use embryonic stem cells and adult stem cells," he says, "and which ones can do better."

The work is time-consuming and expensive.

After the cells in the petri dish mature and multiply, Geng's lab techs remove them, concentrate them in a vial and insert them into a flow cytometer. The photocopier-like machine costs about as much as Geng's home. It attaches the cells to antibodies, activating fluorescent marker genes, which identify different cell types. They might glow green for vascular cells, for example, or red for muscle cells. Another machine across the street at M.D. Anderson, priced competitively with a house in River Oaks, uses the colored markers to separate out each cell type.

Like preparing a mixed drink, scientists next assemble a fortifying cocktail of the different types of cells. Recipients are diseased mice, dogs or pigs, which have been given severe atherosclerosis and other heart problems. Their ailing hearts are injected with a catheter through the coronary artery to transmit the cells. Taking root and differentiating into veins and tissue, the cells hopefully will make the needed repairs.

Several months later, Geng's scientists kill the animals and remove their hearts to examine the results. Adult stem cells so far have done a better job patching things up than embryonic cells. Despite Geng's ability to control the embryonic cells in the early stages, they often revolt once injected into the mice and form cancerlike tumors. Geng's opponents, it seems for the moment, are correct.

But Geng thinks he can overcome this hurdle. Research on embryonic cells is incredibly young -- they were only discovered in 1998 -- while adult stem cells have been studied for decades. Given more time, he says, he will be able to develop "molecular manipulation pathways" to guide the cells' development. "Using these techniques," he says, "we can selectively change these cells into heart muscle cells or vascular cells -- so-called tissue-specific development."

To Geng's credit, some of the shortcomings in his embryonic stem cell work are due less to science than to a lack of political support. Geng's embryonic cells come by necessity from one of the lines preapproved by President Bush, but those cells don't differentiate into heart cells as well as newer, unfunded lines of cells. All of the Bush-approved cells are also contaminated with mouse viruses and thus can't be used in clinical trials in humans.

"We need better stem cells," Geng says. "I hope that the Texas government can provide us with some funding for this."

Geng suspects that adult stem cells ultimately will face firmer limitations. So far, they've just been made to differentiate into only a small range of cell and tissue types, which means that researchers who want to grow a kidney from scratch or cure diabetes, for instance, might not be able to use them. And though adult stem cells work in patients such as Pavelko, they don't work in all patients, especially older ones, who lack enough stem cells in their bone marrow to harvest for treatments.

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