Broken Hearts - Scientists say experiments in mice show that
a special sort of cell that we all carry around in our blood and
bone marrow can rebuild damaged hearts, and probably other organs
as well. (3/30/01)
Cloning: The Ethics - The United States bars government-funded
scientists from cloning human cells to cure diseases. But the
nation has not outlawed cloning a human being. (10/31/02)
Elsewhere on the web
Stem Cell Information
by the President on Stem Cell Research
Harm: The Coalition of Americans for Research Ethics
The good news about stem cells is that they can develop into any kind of cell
or tissue. The bad news is that scientists have had trouble making them grow
into the kinds of cells they want.
This ScienCentral News video reports that brain scientists have found a solution,
at least when it comes to nerve cells.
Stem Cell Breakthrough
Stem cells have the capability to differentiate into any kind of cell or tissue
in the body. This makes stem cell research fascinating because by studying
them, we may gain information and knowledge about the complex mechanisms involved
in the development of the human body.
to the National Institutes of Health, stem cells have three general properties:
they are capable of dividing and renewing themselves for long periods; they
are unspecialized; and they can give rise to specialized cell types.
Stem cells directed to differentiate into specific cell types could be used
as a renewable source of replacement cells and tissues to treat various diseases,
including Parkinson's, Alzheimer's, amyotrophic lateral sclerosis (ALS, or
Lou Gehrigâ€™s disease), heart diseases, spinal cord injury, stroke, burns,
and various other conditions. However, scientists agree that there is still
much ground to cover between the promise of stem cells and the realization
of these uses. The many technical hurdles will only be overcome by continued
intensive stem cell research.
There are three different types of stem cells: embryonic
stem cells, fetal stem cells, and adult
stem cells. Fetal stem cells are malleable cells harvested from aborted
fetuses. Whether they are embryonic, fetal or adult stem cells, only a few
stem cells develop into neurons when placed in most areas of the brain and
spinal cord. The majority of the cells either fail to develop or grow into
other kinds of cells.
At the University of Texas Medical
Brach at Galveston, Texas, Ping
Wu, assistant professor in the department of Anatomy and Neurosciences,
Coggeshall, and others have successfully made a majority of human fetal
stem cells develop into neurons when implanted in the brains and spinal cord
of rats. Wu, the lead author of the study published in the journal Nature
Neuroscience, believes this is a significant finding as they can now grow
a large quantity of cells that can become neurons with the potential of replacing
lost neurons due to neurodegenerative diseases.
Wu screened many proteins and chemicals that play a role in neuron development,
and developed a blend of two proteins and a sugar-like molecule to make a
protein cocktail. Wu and her team then treated the fetal neural stem cells
in this cocktail in a culture dish for a week. They then injected those cells
into the brains and spinal cords of normal rats. After a month they collected
the tissue samples of the ratâ€™s brain and spinal cord and found that
the majority of the fetal stem cells had developed into a specific type of
pure population neurons.
“The protein cocktail seems to direct the neural stem cells into a particular
plastic stage, and when we transplant those cells into adult ratâ€™s brain
and spinal chord, they then turn into specific type of neurons, in the spinal
chord, also in the cortex, medial septum and hippocampus of the brain,”
says Wu. “And those areas are important for learning and memory.”
Although this is a significant breakthrough, the scientists agree that there
is always the risk of implanted stem cells forming tumors.
“We have not yet waited long enough to make certain that [tumors] donâ€™t
develop,” says Coggeshall. “However since the cells placed into
the nervous system are already differentiated into the young neurons, the
possibility is relatively low. Nevertheless this has to be checked very carefully
before any further steps are undertaken.”
The scientists still have a long way to go before they can test whether the
neural stem cells will grow, survive and develop into neurons when placed
into humans. Next, they are preparing to study animals that have nervous system
diseases. Wu says they also want to know whether, “these human neural
stem cell-derived neurons can make correct connections to their targets. For
example, we want to know if human neural stem cells can become motor neurons
in the damaged spinal cord, and whether those motor neurons can reach their
target muscles. And then finally, we need to know whether these cells, these
new motor neurons, can make those paralyzed animals walk again.”
Wu's research was supported by the John
Sealy Memorial Endowment Fund, the Mission
Connect of the Institute for Rehabilitation and Research Foundation, and
the National Institute
on Drug Abuse.