August 25, 2009

Stem Cell Research and Cloning

By Father Thomas Berg *


Now let's continue with the Q & A style update on current happenings in stem cell research we began last week.

What drives the continued interest in cloning human embryos?

The technical name for cloning is somatic cell nuclear transfer.  In this process, a cell, such as a skin cell, is taken from a donor; the nucleus of that cell (which contains the donor's DNA) is inserted into an enucleated egg, and the product is stimulated to begin embryonic development. Tissues derived from the clone would be genetically identical to the donor, obviating the immune-rejection issues normally associated with tissue transplants. Such is the therapeutic gold mine sought by pro-cloning researchers.  Some remaining technical hurdles have recently been surmounted but a more immediate obstacle is the dearth of human eggs required for this research which leads to the next question.
Why is New York going to pay women to give their eggs for stem-cell related research?  

Today it would take an estimated 150 eggs to accomplish a successful human cloning.  Recent history has shown that altruism runs low among potential human egg providers when it comes to stem cell research. New York State, via the Empire State Stem Cell Board (on which I sit) is now poised to pay women directly for their eggs (to the tune of ten thousand dollars per "donation") under the ruse of labeling such exchanges of cash "reimbursement for time and burden." The potential for exploitation of women in such a scenario, not to mention their being submitted to grave and little studied long-term health consequences, is very real.

Have there been human trials with tissues derived from human embryonic stem cells?  

Last January, the FDA gave a first-ever approval to Geron, a San Francisco based biotech company, to conduct a clinical trial using human subjects with tissues derived from human embryonic stem cells. In previous years, Geron had announced an "imminent" first-time-ever human trial, boosting its stock prices every time. But the jump from human embryonic stem cell research to an actual clinical trial with human subjects has been an enormously difficult passage given the inherent risks facing those subjects.  A subdued but growing chorus of concern from the scientific community over their safety finally appears to have won the day since Geron announced last Tuesday that the FDA has temporarily called off the trials.  

What is the current status on human reprogramming (iPS cell research)?

The advent of induced pluripotent stem (iPS) cells by a process called reprogramming opened the door to an ethically and scientifically acceptable alternative to cloning.  A recent development this summer, while good news for reprogramming efforts, also entails a potential dark side. A total of three teams, beginning with researchers in China, have taken skin cells from mice, reprogrammed them, and then combined them to undergo embryonic development and eventual birth as mouse pups in a process known as tetraploid complementation (TC).  Successful TC is actually the gold-standard test researchers use to demonstrate the pluripotency of a batch of stem cells. But given that TC done with iPS cells constitutes a new way to clone organisms, it would be morally illicit to attempt it with human cells. That will take more explaining which I hope to do in a future column.
The other iPS news this summer is that researchers are finding ways to directly reprogram cells so they will be safe for use in humans.  Rather than having to manipulate the genome itself by inserting viruses into the cells to be reprogrammed -- hazardous to humans -- researchers have identified ways to turn on the pluripotency genes in those cells simply by manipulating the chemical environment of the culture surrounding the cells.

Now, it is not known whether iPS cells will yield treatments for human diseases. But at least one reprogramming expert I know was optimistic that clinical trials with human subjects using iPS-derived tissues should not be more than a year or two away.  If that proves true, iPS research will have essentially caught up with embryonic stem cell research as regards therapeutic applications in less than half the time it has taken embryonic stem cell researchers to get there -- if they ever do.




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