Debate Around Current Restrictions on the Derivation of New Human Embryonic Stem Cell Lines
By Susan Hawes

Human embryonic stem (ES) cells are unique cells in their ability to become many adult cell types. Scientists are trying to understand the processes involved in this phenomenon. Human embryonic stem cells hold the potential to revolutionize therapies for many different diseases or disorders caused by cellular degeneration or damage. Despite the huge potential of human embryonic stem cells, their availability has been limited. Why do these limitations exist?

Human embryonic stem cells are isolated from early human embryos, called blastocysts, which are generated through assisted reproduction techniques by women or couples trying to have a baby.   Embryos, not used during this process can be donated for research, to generate human embryonic stem cells.

Governments of many countries have instigated legislation regulating research on human embryos and facilitating funding for developing new human embryonic stem cell lines. In the United States, President George Bush announced that no US federal research funds (National Institute of Health ; NIH) would be available to isolate or perform any research on new human embryonic stem cell lines isolated after August 9, 2001. At that time, it was believed that approximately 70 human embryonic stem cells lines existed and were available.

This however, is not the case. Most of the NIH approved human embryonic stem cell lines are not fully characterized yet, and are simply not available for researchers to study. With less than two dozen available cell lines, patent and intellectual property issues are delaying free distribution. Some lines have been derived using funding from private companies or foundations, which is a common practice in scientific research. However, due to legal agreements set up between some companies and universities, the process of obtaining these human embryonic stem cells has been reported to be cumbersome and slow.

Since Professor James Thomson's group derived the first five human embryonic stem cell lines, 32 have been published in the literature including the 17 lines reported by Professor Douglas Melton and his colleagues. Only 19 lines are currently eligible for NIH funding. Research groups all over the world are utilizing about fifteen lines. These have been widely studied for the last five years and are the best characterized to date.

In the past five years, it has been determined that human embryonic stem cells have not been grown under optimum conditions. In addition, some researchers have suggested that human embryonic stem cell lines may differ, which requires further investigation. It is important to note that some of the lines have reportedly developed chromosomal anomalies, which would make them unsuitable for therapeutic use.

These observations make it imperative that more human embryonic stem cell lines be produced. Based on what we have learned from research in the past few years, human embryonic stem cell lines may be isolated using improved techniques, under clinically acceptable conditions, free of mouse feeder layer cells and in serum-free culture conditions. This would eliminate the potential contamination risk from viruses in mice or domestic animals. Improving the efficiency of human embryonic stem cell line derivation protocols is important. Such improved protocols will aid in isolation of human embryonic stem cells after nuclear transfer, where new custom-made embryonic stem cells can be derived for individual patients.

In the UK, human embryonic stem cell lines were generated from embryos during pre-implantation genetic diagnosis (PGD) cycles. PGD involves the removal of one cell from an early embryo created during an assisted reproduction treatment cycle which is then analysed for genetic defects. Affected embryos are discarded. Human embryonic stem cell lines derived from these discarded embryos could allow the study of genetic diseases in the culture dish and could lead to new cures.

Recently, the generation of 17 new human embryonic stem cell lines by researchers at Harvard University, Boston, USA was published in the New England Journal of Medicine . Importantly, these cell lines were generated with funds from private foundations and are being made readily available to research laboratories around the world.   Unfortunately in the United States, because these cell lines were generated after August 9, 2001, only privately funded researchers can work with these cell lines.

To promote rapid progress in the field of human stem cell technology, it is extremely important that new lines are produced in laboratories that allow easy and accessible distribution of the cells for research around the world. The more research groups that study human ES cells and learn how they can become nerve, heart, muscle or insulin producing cells for diabetes, for example, the faster such developments may be utilized clinically to alleviate many disorders affecting millions of people.

Susan Hawes, PhD, is an embryonic stem cell specialist at the Institute of Reproduction & Development at the Monash University in Australia.

References

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Thomson JA, Itskovitz-Eldor J, Shapiro SS, Waknitz MA, Swiergiel JJ, Marshall VS, Jones JM. (1998) Embryonic stem cell lines derived from human blastocysts. Science. 282, 1145-7

Updated: February 2, 2005