By Eileen McCluskey
Illustrations by Janet Dreyer

Seated on an examining table, a woman with diabetes rolls up her sleeve. In a matter of seconds, her doctor has given her an intravenous injection of stem cells derived from eggs removed from her ovaries.

With no side effects, the stem cells will correct her body's inability to produce insulin. The woman may need to visit her doctor every year or so for additional infusions. But with these infrequent interventions, she is essentially cured of an illness suffered by, the U.S. Department of Health and Human Services estimates, more than 18.2 million Americans. An illness that would otherwise require daily monitoring and insulin injections, and perhaps cause serious secondary complications, such as eye, kidney, and circulatory ailments.

Embryonic stem (ES) cell researchers are confident such a remarkable cure will one day be possible, and not only for diabetics. As they grow stem cells from ova, scientists are, in truth, putting eggs into many baskets, hoping to reverse diseases such as Parkinson's, Alzheimer's, even cancer. And that's not all. Stem cells could help people with spinal-cord injuries walk again. Turn the tide on heart and liver diseases.

Carol Warner works passionately to hasten these advancements from the research bench to the bedside. The Matthews Distinguished University Professor in biology has been studying eggs and preimplantation embryos for thirty-four years. A year ago, she added stem cells to her areas of exploration. Unlocking the mysteries of all these microscopic cell clusters, she believes, will bring about revolutionary medical treatments, not to mention better in vitro fertilization (IVF) results.

But the research has been hampered by what some view as a crippling stricture. Back in 1998, when ES cells were first cultivated in a lab, the U.S. government decided not to permit federal funds to go to the study of human ES cells.

Three years later, on August 9, 2001, the Bush administration announced it would begin to allow the use of federal funds for human ES cell research, but only for cell lines created on or before that date. A step forward, perhaps, yet Warner and many others believe it advances ES cell research very little, since most of those previously existing lines have died out, and all of them were grown using mouse feeder cells. As a result, these are stem cells that could never be used to treat humans, because of a high risk of viral and other infections.

Though funding limits are applauded by those who believe human ES cell research violates the sanctity of human life, they are viewed with dismay by scientists like Warner, who are intrigued by stem cells' therapeutic potential. Warner derives much of her funding from federal agencies, such as the National Institutes of Health and the National Science Foundation, so she's had to content herself with working largely with mouse ES cells.

"It's a travesty that this country has put political constraints around such critically important research," she says, shaking her head. "Although we can learn a lot from mouse stem cells, it's much slower to have to make inferences from the mouse system to humans. We would accelerate the science tremendously if we could work with human ES cells."

Plastic fantastic stem cells

What are embryonic stem cells? In simplest terms, they're "blank" cells—cells in their youngest stages, before they've passed through a differentiation process that turns them into brain cells, or blood cells, or bone cells.

But ES cells have to be harvested and grown before they can cure and mend. Four or five days after fertilization by sperm (or activation without sperm), a dividing egg turns into a hollow ball of cells known as a blastocyst. The blastocyst—which measures about 100 microns, or the size of the head of a pin—includes a structure called the inner cell mass (ICM). This group of about thirty cells is the critical mass that will become all the different tissues and cells in the human body.

For ICM cells to become curative stem cells, they must first be extracted from the blastocyst and carefully grown in a lab. After a painstaking six months of cultivation, the original thirty ICM cells will yield millions of ES cells. These astonishingly fecund ES cells have the capacity to multiply indefinitely.

Some adult tissues and organs maintain their own supply of stem cells. Skin, sperm, blood, bone marrow, and the lining of the stomach and the intestines all contain cells that are capable of making new members of their communities. In a sense, stem-cell treatments began fifty years ago, when bone-marrow transplants were first used to treat leukemia.

Yet many of the body's tissues and organs cannot repair themselves. Though researchers have found small numbers of stem cells in the pancreas, the brain, the eye, the spinal cord, the heart, and the kidney, they have not been able to grow them in sufficient quantities to use them to counteract disease or injury.

Someday, experts hope, they'll find a way to harvest and grow enough stem cells from adult tissues to engineer medical treatments. Even so, most believe ES cells play an essential role in stem-cell therapy.

What's so wondrous about ES cells? "Their plasticity," says Warner. "They have the potential to give rise to all cell types. ES cells hold great promise for repair of neurologic diseases such as spinal-cord injury and retinal degeneration."

Fortunately, Warner's study of eggs and embryos is helping to facilitate the creation of these microscopic marvels of nature. "Healthy embryonic cells," she explains, "make healthy stem cells."

Warner works with genetics and imaging techniques to pinpoint which fertilized eggs will evolve into healthy embryos. Such knowledge would serve the dual purpose of making IVF a safer process for mothers and babies, and opening an avenue toward reliable sources of ES cells.

Scientists have long known the number of cells in a dividing egg is strongly associated with its health and viability. Warner significantly advanced this knowledge in 1978; working with mice, she identified the gene that regulates cleavage, or cell division, in blastocysts—which are also known as preimplantation embryos, because for a time they are free-floating in the body.

Warner dubbed her discovery the Ped gene, short for preimplantation embryo development gene.

Fifteen years later, in 1993, Warner's Northeastern team identified the protein, Qa-2, that the Ped gene encodes. "Scientific discovery takes a lot of time," she says, smiling.

A proxy mouse

Warner had kept up the search because she knew the protein could provide new information about why some activated eggs continue in their development while others die. "Mice that express the Qa-2 protein also have an overall reproductive advantage that extends to higher birth weight and a better chance at surviving weaning," she says.

Once she'd found Qa-2 in mice, Warner turned her attention to determining if a comparable protein works similarly in humans. Using grants totaling $10.6 million from the National Institutes of Health, the National Science Foundation, and private sources, Warner discovered the human equivalent, a protein called HLA-G.

But because she's barred from using federal funds if she works with activated human eggs, Warner is looking at HLA-G by studying a mouse that's been genetically engineered to express the human protein. This transgenic mouse, originally created by Anatolij Hruska at the Medical College of Georgia, is now being bred in Warner's lab.

Martina Comiskey, a PhD candidate in biology who works in the lab, is examining HLA-G on the transgenic mouse embryos. "It would of course be better to be able to work with human embryos, so we wouldn't have to go through these convolutions," Comiskey says. Nonetheless, through diligent research, she's proven that HLA-G inserts itself into the egg's membrane in the same way that Qa-2 does.

Comiskey's next goal: To show whether HLA-G encourages the fertilized egg to divide quickly. Preliminary results indicate it does.

How does HLA-G get the egg to divide so abundantly? Answering this question would help scientists better understand the mechanisms behind healthy embryos and enable more accurate predictions of which embryos will survive the critical preimplantation days.

"For the past eleven years," says Warner, "we've been working to figure out how Qa-2's—and now HLA-G's—molecular mechanism works." Somehow, from its perch on the dividing egg's exterior, HLA-G gives a go-ahead for copious division. Warner and her team are trying to discern how those signals get inside the cell.

It's a daunting challenge, because every cell contains thousands of signaling pathways, and very little is understood about these lines of communication.

"We're taking a series of approaches," Warner says. She adds with a laugh, "Including lucky guesses."

Small wonder, then, that Warner's laboratories literally hum with activity. Some of the buzz comes from a slew of state-of-the-art machinery, from cell incubators and small centrifuges, to an ultrasonic machine that dismantles cells for close inspection, to a laser scanner that searches for Qa-2 and HLA-G on cell surfaces.

Then there are the scientists and students hard at work amid the hardware, each trying to nail down particular pieces of information.

Sally De Fazio, for instance, a senior research scientist, is examining how Qa-2 tells cells to divide faster. "I'm looking at known signal pathways into the cytoplasm [the cell's innards] and even into the nucleus of the cell," says De Fazio. "I'm also looking at the very top of the signaling pathway, to see with which other molecules Qa-2 associates."

Since Qa-2 originates inside the cell, master's degree student Paula Lampton is exploring how it ends up on the cell's exterior. She's looking at whether a particular protein, called MHC, ushers Qa-2 out to its surface location.

Counting on healthy babies

Other members of Warner's team are engaged in an effort that could revolutionize both stem-cell research and IVF. They are working on ways to count the number of cells in a cleaving egg.

The IVF process already seems pretty miraculous to hopeful moms and dads. But it still carries risks that IVF clinics, and Warner, would like to eradicate. Chief among these are the perils associated with multiple births.

At most of the nation's 400-plus fertility clinics, a woman undergoing IVF treatment is implanted with three embryos to increase her chances for pregnancy. The resulting 20-fold increase in the likelihood of twins—and 400-fold increase in the likelihood of triplets—can wreak havoc on mothers and babies alike.

"With multiple births," says Warner, "there is a very large increase in perinatal mortality and disease." A whopping 42 percent of IVF triplets, for example, have cerebral palsy. As for mothers, Warner says, "many women undergoing IVF are in their late thirties and early forties, and tend to suffer tremendous physical and emotional stress with multiple births."

This is why, Warner explains, IVF clinics around the world are pressing hard to develop new techniques for assessing embryo health, so that prospective mothers can receive one healthy embryo, instead of three of uncertain viability.

But to pinpoint which preimplantation embryos are healthy, Warner and her team must first be able to count the number of cells in an embryo without harming it. This is tricky, since cells die when scientists try to get a good look at them using standard techniques, such as staining.

Yet Warner seems well on her way to a solution, thanks to collaborative work with Charles DiMarzio, associate professor of electrical and computer engineering, through Northeastern's Center for Subsurface Sensing and Imaging Systems (CenSSIS).

In a major CenSSIS initiative, funded by a $750,000 grant from the Keck Foundation, Warner and DiMarzio created a design for a new three-dimensional fusion microscope (3DFM). Graduate student Dan Townsend then spent two and a half years building the wonder machine.

The recently completed microscope, which fills a four-by-eight-foot table in the Egan Engineering/Science Research Center, combines five imaging modalities. As a result, the 3DFM lets scientists view composite images of living cells on a single platform. This is not mere convenience. "Preimplantation embryos were dying when we ran them all over town to view them under different microscopes," Warner says. "They're too fragile to withstand so much disturbance. Now we've solved that problem."

Of the microscope's five modalities, its quadrature tomographic microscopy (QTM) instrument seems to hold the most promise for counting cells in preimplantation embryos. Developed by Northeastern engineers, the QTM tool is the only one of its kind in the world, and allows scientists to count cells non-invasively, without stains or sectioning, leaving them unharmed.

Warner says her team has "not yet hit upon the best mathematical algorithm for cell counting." But, she says, "we're very close. The next year or two will show we have something valuable." Once they've established a reliably accurate way of counting embryonic cells using QTM, the process could take place on site in IVF clinics.

Eggs for all

While she hones the cell-counting process, Warner is moving ES cell science forward on another front, through a collaboration with Ann Kiessling, an associate professor of surgery at Harvard Medical School, and the founder and director of the Bedford Stem Cell Research Foundation. Because the foundation is privately funded, Kiessling is able to work with human ES cells.

Kiessling is something of an ES cell activist, promoting the science through public appearances and publications. In 2003, she cowrote Human Embryonic Stem Cells, a book that explains everything from the basic biology of the activated egg, to the status of current research, to the social and political issues roiling around ES cell research in the United States.

One of the book's goals is to give pro-research scientists a voice in the debate. "As a nation," Kiessling says, "we have to face the fact that we fertilize eggs in dishes in IVF clinics. Any embryos that aren't used get frozen or thrown away."

In other words, though there are no restrictions on tossing unused IVF embryos, the federal government discourages using those same embryos to conduct life-saving medical research. "We must have a public discussion about the issues raised by this reality," she says.

In her work with Kiessling, Warner is trying to grow eggs from human ES cells. If this research is successful, it "could accelerate the pace of stem-cell research by making a plentiful supply of eggs readily available," Warner says.

Such an egg bounty would help scientists provide genetically compatible stem cells for every individual who needs them. This is significant, since ES cells, like those used in bone-marrow transplants, must be tissue-matched to every patient.

From a harvest of eggs from the lab, researchers envision, stem cells could be developed for individual patients through one of two methods: parthenogenesis or nuclear transfer. In parthenogenesis, eggs are activated by chemical or electrical stimulation. The ensuing "parthenote" divides and becomes a blastocyst. Its inner cell mass could be harvested to produce stem cells that could then be tissue-matched to patients.

Nuclear transfer would avoid the constraints of hit-or-miss matching. In this process, a cell nucleus from the person needing the stem cells would be implanted in an egg whose chromosomes have been removed. After the egg was activated, the resulting stem cells would genetically match the person whose cell nucleus was transferred to the egg. This process would benefit any patients who couldn't produce their own eggs—men, obviously, but also older women.

However, step one in Warner and Kiessling's path of discovery is determining how to coax stem cells to produce eggs. This means they need to understand the earliest stages of stem-cell differentiation.

In Warner's lab, PhD student Judy Newmark places mouse stem cells in a culture medium where they hover, indefinitely undifferentiated. As soon as the cells are removed from the medium, they begin to choose their paths toward becoming various tissues and organs.

How does the transformation work? Like all questions asked by Warner's team, this one leads into uncharted waters. Again, the 3DFM instrument is helping the scientists see into a mysterious realm. "There's been very little imaging of this process," Newmark says, "but we seem to be making progress."

Although these stem-cell production methods are still in their earliest experimental stages, they hold tremendous potential for curing disease. "If you put a cell nucleus into an egg, you could have a new line of stem cells for your patient in two or three weeks," says Kiessling.

Such quick turnaround would be a boon to stem cell therapy for any disease or injury, but especially for those requiring quick response, such as heart attacks and bone injuries.

Talking cure

The nitty-gritty mechanics—and the ethical overtones—of human ES cell research have galvanized the nation's opinion leaders. Politicians, religious figures, celebrities, and scholars have lined up to either promote or condemn the activity.

For Warner, the choice seems straightforward. "If you think it's wrong to use ES cells in treating diseases, you don't have to benefit from the technology," she says, shrugging.

To add historical perspective, she points to the uproar over organ transplantation when it was originally introduced. "Back in 1954," she says, "there was outrage over the first kidney transplant. Some people said it was against God's will. Now, it's touted as a wonder of science and medicine, which it is.

"Organ transplants—kidney, liver, and heart transplants—save many lives every day," Warner says. "But it took years of research to make organ transplants reliable and lifesaving." Most major medical breakthroughs, she says, routinely require twenty years to be realized.

ES cell therapies will be even longer in development, Warner holds, if the research continues to be restricted to mouse embryos. "At some point, you have to bite the bullet and work on human ES cells," she says.

In the wake of President George W. Bush's re-election, this possibility seems to Warner ever more remote. "I'm deeply disappointed with the outcome of the election," she says. "The one bright spot is that California passed a $3 billion, ten-year initiative to fund ES cell research in that state."

Warner continues, "Since Massachusetts has about one-third the population of California, it makes sense that Massachusetts should pass a similar measure for $1 billion over ten years. However, I believe state-funded research is just a stopgap measure. It is imperative that the federal government take over this funding in the long run."

Kiessling thinks moving U.S. stem-cell research into green-light mode will hinge on talk and more talk. "It is healthy that as a nation we respect life and want to protect it," she says. "But we have not yet had the public debate, as other countries have, that will allow us to work out our differences on the stem-cell issue.

"It's a discussion that's long overdue."

Eileen McCluskey, MBA'86, is a freelance writer who regularly contributes to the magazine's "Recruiting Employees" section.

Common misconceptions about stem-cell research

Erroneous assumptions and misinformation frequently litter the landscape of the stem-cell debate. Carol Warner, the Matthews Distinguished University Professor in biology, here addresses what she considers the biggest misconceptions the general public has about embryonic stem (ES) cell research.

Cures or treatments using stem cells will soon be available to combat diseases ranging from Alzheimer's, to diabetes, to cancer.

Not right away, says Warner. There's still a lot of study and testing that needs to happen. "It seems we're looking at a twenty-year horizon until stem-cell therapies would be ready for clinical use," she explains. "And that is if the laws were changed today to allow for federally funded research." Despite the length of time involved, Warner emphasizes that the optimistic predictions of stem cells' capacity to cure "are not overblown."

Excess embryos in IVF clinics should not be donated to ES cell research because they could be used to produce children at some point.

False. "If you don't use them, the unused IVF embryos will be thrown away," Warner says. "We're wasting the chance to do something useful with them, to save lives and cure serious illnesses."

Scientists don't need to create new ES cell lines. They already have enough cells with which to develop cures for diseases.

Unfortunately, says Warner, "the existing human embryonic stem-cell lines allowed to be studied under the Bush guidelines are contaminated with mouse cells and are therefore of no clinical use," meaning they can be used for research but not for therapy.

International stem-cell research will advance even if the United States doesn't participate.

Not true, says Warner. Experts widely believe that only the United States has the biomedical infrastructure to move the science forward.

Last June, Warner attended the second annual meeting of the International Society for Stem Cell Research, held in Boston. "At the meeting, Dr. Alan Trounson, from Australia, implored the U.S. to fund ES cell research," Warner recalls. "He said that, without the U.S., the field cannot possibly move ahead at an appropriate speed." Only the United States, Warner says, can "put enough resources into ES cell research to bring it from the lab to the clinic."

— Eileen McCluskey