Tag Archive | "chimeras"

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Chimeras for Transplant Organs and Third Parent Immunity

Posted on 13 August 2013 by Jerry

How you feel about something may be a function of how broadly you generalize or how narrowly you define it.  We have two scientific situations that specifically sound positive and yet generally may set disturbing precedents.  Each of us should decide how general we think we should be, what are the downsides and who determines outcomes.

In Japan there is a partial governmental ban on experiments that create chimeras, or mix human cells with cells of other animals to create cross species hybrids.  Creation of chimeras is permitted in vitro, a test tube or petri dish involving just cells, for up to fourteen days after which the resulting cells are destroyed.  No experiments are permitted in vivo, or with a whole living organism.

It is just such a whole living organism experiment that has been proposed by Dr. Hiromitsu Nakauchi, a stem cell biologist at the University of Tokyo.  He believes he can grow human organs in a pig fetus by implanting human pluripotent stem cells into a genetically engineered pig fetus that lacks a specific organ.

An article appearing in the June 28, 2013 issue of Science magazine states “Mouse experiments have shown that pluripotent cells can fill the developmental niche opened by the absence of an organ.”  Dr. Nakauchi believes he can eliminate the fear of organ rejection by using the recipient’s own pluripotent cells to be grown in the pig.  After the piglet is born, when the organ is the right size, it would be harvested and transplanted into the human being.

While having received a Japanese government ethics panel endorsement, Dr. Nakauchi will probably wait no longer.  He has just been awarded a $6.2 million grant from the California Institute for Regenerative Medicine and is in discussions to open a new lab at Stanford University.  The California Institute for Regenerative Medicine was formed when voters in the state approved a 2004 ballot proposition providing $3 billion of taxpayer funding for stem cell experimentation.

A different proposal has been approved for trial in the United Kingdom.  It involves a strategy for avoiding a baby inheriting mitochondrial disease from the genes of its biological mother.  The strategy is to merge the nucleus of an egg from the affected mother with the egg of another woman who has no genetic anomaly and then have the merged egg fertilized by the sperm of a man.  This would produce a baby that genetically has three parents but does not develop mitochondrial disease.

The worldwide controversy surrounding this experimental procedure is that it would allow the baby to pass on its altered genetic code to its eventual offspring.  This means the change created by the merged eggs constitutes genetic germline modification.

Marcy Darnovsky, executive director of the Center for Genetics and Society in Berkeley, California, in a July 17, 2013 issue of Nature magazine states “Were the United Kingdom to grant a regulatory (permanent) go-ahead, it would unilaterally cross a legal and ethical line on this issue that has been observed by the entire international community.  This consensus holds that genetic-engineering tools may be applied, with appropriate care and safeguards, to treat an individual’s medical condition, but should not be used to modify gametes or early embryos and so manipulate the characteristics of future children.”

In both of these cases the specifics, especially given the targeted outcomes, clearly offer benefit, if successful, for thousands of people.  Issues arise however, when what happens in the experiments is generalized to permit a host of other experiments with far less compelling outcomes or even risks of serious harm.

These experiments should cause each of us to personally consider what kind of genetic engineering should be allowed.  A series of questions come to mind.  For instance, should the applied science of genetic engineering continue to be largely unregulated?  Should exceptions be made and by whom?  Whom should we appoint to sit in judgment and make decisions for us?  How will those we appoint represent us faithfully and how will they know what we collectively think?  These scientific issues may have a profound effect on our collective future.  They deserve our personal attention.

Use the following links to obtain additional information or see original source documents:

http://www.sciencemag.org/content/340/6140/1509.sumary?sid=ad66cb5e-78e1-449d-936b-79d2d5e8e5a1

http://news.sciencemag.org/health/2013/03/u.k.-agency-cautiously-endorses-mitochondria-replacement

http://www.nature.com/news/a-slippery-slope-to-human-germline-modification-1.13358

http://www.the-scientist.com/?articles.view/articleno/34790/title/uk-may-allow-mitochondrial-replacement

http://www.guardian.co.uk/science/2012/jan/05/chimera-monkeys-combining-several-embryo

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Chimeric Systems: Living and Non-Living Components

Posted on 06 August 2012 by Jerry

As is often the case, the line between one scientific area and another blurs over time.  A prime example is synthetic biology and its new category called a Chimeric System.  A Chimeric System represents the fusion of synthetic non-living material with living tissue.  Three examples spanning 2010 to 2012 show the intersection of regenerated tissue, stem cells, and synthetic biology in the formation of this new category of chimera.

In 2010 scientists from Yale University used a lung’s collagen support structure with lung cells removed, to provide the base for their experiment.  They then took eight or nine types of existing lung cells, cultured them for eight days, and grew new lung tissue on the collagen infrastructure which was subsequently transplanted to living rats where it functioned normally for about two hours.  This is an example of the use of regenerated tissue to artificially create organ tissue.

Taking the lung experiment one step further, scientists and doctors at Karolinska University hospital in Sweden in 2011 implanted a synthetic trachea in a cancer patient.  The synthetic organ was completely lab-grown using a Y-shaped plastic-like “nanocomposite” polymer material for the underlying support structure.  Upon the structure the physicians grew the patient’s own stem cells over a two day period.  This procedure avoided the risk of rejection by the patient’s immune system because of the use of his own stem cell tissue.  This experiment created one of the first of these Chimeric Systems in that it is composed of a synthetic infrastructure upon which living tissue was grown.

The final example represents the use of silicone and heart muscle tissue from a rat to create an artificial jellyfish.  In a series of experiments to understand the inner workings of muscular pumps like a heart muscle, Kit Parker, a biophysicist at Harvard University, led an effort with two groups at Caltech and Harvard to understand how jellyfish swim.  Janna Nawroth a graduate student at Caltech mapped every cell in the bodies of young moon jellyfish.

A July 22, 2012 article in Nature magazine describes the artificial jellyfish as follows, “Nawroth created a structure with the same properties (as a jellyfish) by growing a single layer of rat heart muscle on a patterned sheet of polydimethylsiloxane.  When an electric field is applied across the structure, the muscle contracts rapidly, compressing the medusoid and mimicking a jellyfish’s power stroke….When placed between two electrodes in water, the medusoid swam like the real thing.”  See the identified link below for a connection to an article with an embedded film that shows the artificial jellyfish swimming.

Beyond the three accomplishments mentioned in our May 2012 post of “Troubling Progress for Synthetic Biology” or the creation of a bacterial living shell, an inventory of synthetic genetic parts, and complex molecules of synthetic nucleotides, enzymes, and proteins, these experiments represent significant advances in a new field within Synthetic Biology.  Unlike what many have called the over-reaching ambition of earlier efforts and the perennial risk of negative use, this new field holds great promise for beneficial future developments.  As in any unregulated, scientifically advanced, new area we need to carefully monitor progress and developments to insure we have good outcomes.

Use the following links to obtain additional information:

http://www.nature.com/news/2010/100624/full/news.2010.314.html

http://www.guardian.co.uk/science/2011/jul/08/cancer-patient-synthetic-organ-transplant

http://www.nature.com/nbt/journal/vaop/ncurrent/full/nbt.2269.html

See a link in this article to a film of the artificial jellyfish – http://www.nature.com/news/artificial-jellyfish-built-from-rat-cells-1.11046

http://www.bbc.co.uk/news/science-environment-18953034

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