Intended for healthcare professionals


Stem cell therapy: hope or hype?

BMJ 2005; 330 doi: (Published 19 May 2005) Cite this as: BMJ 2005;330:1159
  1. Peter Braude, professor of obstetrics and gynaecology (obgyn{at},
  2. Stephen L Minger, director of stem cell biology laboratory,
  3. Ruth M Warwick, consultant haematologist
  1. Stem Cell Group, Division of Reproductive Health, Endocrinology and Development, Guy's Campus, King's College London SE1 9RT
  2. Stem Cell Group, Division of Reproductive Health, Endocrinology and Development, Guy's Campus, King's College London SE1 9RT
  3. Tissue Services, National Blood Service, Edgware HA8 9BD
  • Accepted 13 May 2005

Safety and quality must be assured before this treatment can really benefit patients

The use of human embryonic stem cells has been hailed as the next major step in the battle against serious degenerative disorders, such as diabetes and heart disease, and for some debilitating or lethal neurological diseases, such as Parkinson's and motor neurone disease. News reports and promotional material on websites often convey the impression that this therapy is safe and immediately or imminently available. Whether this is just hype, and how much hope patients should invest in this technology, are issues being discussed at a public debate in London this week.w1

Although the number of human embryonic stem cell lines has increased considerably in the past two years, few of these have been well characterised, and large hurdles still need to be overcome to ensure safety and efficacy.1 These will require substantial further investment and research. Stem cells have not yet been grown in the conditions that would be expected for any pharmaceutical product destined for use in vivo.2 Even the embryos from which human embryonic stem cells could be derived are still cultured in vitro in the presence of human or animal products. The premature use of cell therapy could put many patients at risk of viral or prion diseases unless systems are in place for the appropriate selection and screening of donors and for quality assurance.

The lessons of the premature application of gene therapy, the devastation caused by HIV transmission to people with haemophilia, the clinical and legalw2 problems resulting from hepatitis C infection through blood transfusion, and the crisis caused by bovine spongiform encephalopathyw3 should all be learning opportunities. Expansion of stem cell cultures could allow a single stem cell line to be used for many hundreds, if not thousands of patients, exponentially amplifying the potential risk of disease transmission from a single infected donor. Transmission of malignant, autoimmune, and infectious diseases by organs, tissues, and cells are rare but well documented events.w4 w5 Tissues have transmitted prions,3 and the prion that causes variant Creutzfeldt-Jakob disease (vCJD) has almost certainly been transmitted by blood transfusion.4 5 No blood test for vCJD currently exists, and neither does an effective method of inactivating the causative agent.

Change is on the way, however. Although those working with stem cells in the United Kingdom have non-statutory guidance in the form of a code of practice for tissue banks,6 by April 2006 it will become mandatory for them to comply with the EU directive on tissues and cells.7 Thus all laboratories for in vitro fertilisation and laboratories for producing cell lines with therapeutic intent will have to conform to a new standard of quality even more stringent than the current requirements of the Human Fertilisation and Embryology Authority (HFEA).

The EU directive will cover selection of donors, testing, and procurement of the starting material for cell lines, tracking cells from donor to recipient, use of a specified coding system, and reporting of adverse events. The source of all material will have to be traceable even if it is anonymised at the point of production. A policy collaborative group convened by the English Department of Health, working over two years, enabled key stakeholders from across the United Kingdom to develop guidance to support local implementation of the directive: this guidance will be issued this summer. Furthermore, the Medical Research Council has awarded grants to five units performing in vitro in the United Kingdom to help achieve rigorous standards for the production of therapeutic grade embryonic stem cells.

Potential donors of blood components and blood products are required to give their medical and behavioural histories, and blood samples are tested rigorously at the time of each donation to minimise risk. A novel approach to safety could be used for stem cell lines. Since these lines are potentially immortal and infinitely expandable, it would therefore be possible to test the cell line itself rather than surrogate samples from couples at the time of donation. Clearly, existing tests for viruses or prions would have to be validated in this context before using stem cell lines as the main test analytes.

The drive to be the first to provide cell lines for therapy could compromise safety for recipients and could lead this technology into the realms of quackery. Such fears are already being realised in India8 and Russia,9 where intervention by the governments may be needed to limit or prevent the escalating numbers of clinics offering stem cell cures for all sorts of ills. Despite inadequate preliminary data on clinical safety or from animal experiments, trials using cells derived from autologous bone marrow samples are already being conducted on patients with heart disease,10 with urgency and therapeutic need being cited as the reasons for immediate implementation. However, urgency is not an excuse for bad science. Animal experiments should be conducted to understand further the host destination and integration of transplanted cells, and the risks of neoplasia arising in cells implanted into new environments.1 The ethics of transferring human stem cells into animal hosts in order to develop new therapies for debilitating disorders must be considered as part of the wider stem cell ethical debate.11

Commercial companies are springing up around the world with all the fervour of a new “biological dotcom” era, but with selective memory loss for the fact that unrealistically high expectations burst that bubble. We can only hope that any corporate failure to make immediate financial success out of stem cell research does not drag down a promising technology. Stem cell therapy needs to be nurtured safely and methodically to provide real benefit to patients in the future.


  • Embedded Image Additional references w1-w5 are on

  • Competing interests None declared


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