Recent news that scientists in Japan and the United States have converted skin cells into stem cells that are similar to human embryonic stem cells surprised the world. Drawing from information derived from human embryonic stem cells, these researchers found that they could reprogram certain genes in these skin cells to produce cells they have termed "induced pluripotent stem cells."
Their hope is that specific kinds of cells -- for example, bone, muscle, blood, kidney -- can be developed from such cells and used to treat patients with serious diseases.
Does this mean that research on human embryonic stem cells now can be ended? Some maintain that this is the case. Stem cell scientists, however, respond that the era of human embryonic research cell is not over. They give several reasons why it should continue.
First, there is concern that induced pluripotent cells might produce cancerous cells in patients to whom they were transferred.
This is because one of the genes inserted into the skin cells to induce them to change into these new sorts of cells is associated with cancerous tumors.
Moreover, the retroviruses used to insert these genes into the skin cells also are associated with cancer. It is unclear at this time whether there is a way of getting around these obstacles so that induced pluripotent stem cells could be used safely in patients.
Second, stem cell scientists believe that we need to use human embryonic stem cells as a control against which to compare and assess the capabilities and safety of induced pluripotent stem cells.
Third, scientists do not know yet whether these new cells have the capacity to change into as wide a range of specialized cells as human embryonic stem cells. If not, they clearly would not make a satisfactory substitute for the latter cells.
Fourth, while induced pluripotent stem cells would provide immunological matches for the specific patients from whom they were derived, it might be very expensive to develop the millions of such cells that would be needed to allow the individual treatment of each of the multitude of patients in the United States.
Finally, scientists estimate that in five to 10 years they will have refined and improved their knowledge of human embryonic stem cells to a point where they can transplant cells derived from them to patients safely. It will take even more time, some believe, to assess the capabilities of induced pluripotent stem cells.
In addition, human embryonic stem cells are needed for certain kinds of research for which induced pluripotent stem cells are not suitable, such as that into the development of human embryos. This sort of research is needed if we are to learn about the causes of serious diseases and disabilities in newborn babies.
The real impetus behind calls to drop human embryonic stem cell research lies in the concerns of some about the destruction of early human embryos that it entails. Such embryos, which have been developed outside the body in a glass dish during in vitro fertilization (IVF), are four to five days old and have about 50 to 150 cells. More of them are developed than will be used in one IVF cycle so that women will not have to go through the discomforting and sometimes risky procedures of ovarian stimulation and extraction again in the future.
Spare embryos of good quality can be frozen for later IVF attempts. However, some are of poor quality and therefore never will be used in future attempts at IVF; others will not be used because those for whom they were developed have succeeded in becoming pregnant and do not plan to use these spare embryos to have more children.
There is considerable debate about whether such early embryos should be viewed as individual human beings who must be transferred to a woman's body in order to be saved from destruction. Yet no one argues that women should be forced to accept these embryos into their bodies.
Couples and individuals who do not believe that these early embryos are individual human beings, and who do not plan to have additional children, have donated them for stem cell research instead of discarding them or donating them to others. Scientists at several research centers have found that they can derive human embryonic stem cells from such embryos, even those of poor quality.
Stem cell oversight committees have developed specific guidelines about the sorts of information that should be provided to those considering the donation of their spare embryos for stem cell research and about measures that must be taken to ensure that they give such embryos voluntarily.
Those who do believe that these spare embryos are individual living human beings have sought to donate them to others, with some success, rather than to give them to stem cell research.
The discovery of induced pluripotent stem cells has not made human embryonic cells a relic whose time has passed.
There is a need for extensive research using both kinds of cells if we are to develop new treatments for those who are desperately ill and to learn more about why certain roadblocks to healthy growth appear during embryonic development.