Why we need fetal tissue research

![Figure][1] PHOTO: SUZANNE KAWOLA, NSCI ![Figure][1] PHOTO: DONNA COLEMAN PHOTOGRAPHY A vocal minority in the United States is intent on stopping federal funding for research using human fetal tissue, citing stem cell–based or other alternatives as adequate. This view is scientifically inaccurate. It ignores the current limitations of stem cell research and disregards the value of fetal tissue research in finding therapies for incurable diseases. If there is to be continued rapid progress in treating cancer, birth defects, heart disease, and infectious diseases, then we need fetal tissue research. ![Figure][1] Fetal brain tissue PHOTO: STEVE GSCHMEISSNER/SCIENCE SOURCE > “…fetal tissue remains an essential resource for many applications.” Life-saving advances, including the development of vaccines against rubella, rabies, and hepatitis A viruses, and antiviral drugs that prevent HIV/AIDS, required fetal tissue research. Today, fetal tissue is being used to develop new medicines including vaccines for HIV/AIDS, preventives for Zika virus, and immunotherapies to battle untreatable cancers. Although research into alternatives is worthwhile, there are several aspects of fetal tissue research for which alternatives do not and will not exist. For example, to discover which fetal cells go awry and cause childhood cancers such as retinoblastoma, a cancer of the eye, or rhabdomyosarcoma, a muscle cancer, we must understand which cells are the culprits. For that, we need access to relevant fetal tissues. Zika virus can cross the placenta and attack specific fetal brain cells. To determine the mechanism of viral entry, which cell types are vulnerable, and how to prevent infection and damage, we need access to fetal brain tissue. Beyond diseases affecting children, some forms of hereditary Alzheimer's disease cause neural impairments in utero that persist over decades and manifest later in life. Without access to fetal cells, we cannot understand and effectively combat diseases that begin in utero. Fetal tissue alternatives for some applications may be developed as science advances, but this will take time. The transition to any new model of research should be data-driven and based on scientific evidence. Opponents of fetal tissue research state that human stem cell–derived organoids are adequate models, supplanting fetal tissue research, but that is incorrect. Organoids typically do not fully mirror the complex cellular composition and architecture of fetal organs. Although organoids may prove valuable to model some diseases, critically, access to fetal tissue is required for validation of these and any proposed alternatives. For example, mice that model the human blood system are produced through transplants of human fetal liver and/or thymus tissue to provide a near full complement of long-lived human blood cells. These animal models are needed to develop therapies that involve the immune system, such as HIV vaccines and new chimeric antigen receptor (CAR) T cell–based cancer treatments. Alternative mouse models using human neonatal thymus are being explored but may lack the variety and sustained production of blood cells produced from fetal liver or autologous bone marrow, and supply is limited to thymus taken from infants undergoing congenital heart surgery, sometimes associated with concomitant immune problems that confound results. It would be a grave injustice to the patients and families afflicted by diseases that benefit from this research to prematurely halt production of fetal tissue models. Although alternatives may be established in some cases, fetal tissue remains an essential resource for many applications. It is important to remember that the fetal tissue used in research would otherwise be discarded and thus unavailable in the fight against disease. U.S. researchers also follow rigorous, well-established medical and ethical standard practices for this research. Fetal tissue research has been supported for decades by both Republican and Democratic administrations and congresses. Rigorous U.S. government–sponsored review processes have also concluded that this research is ethical and valuable. If we are to achieve medical advances for currently incurable diseases, the path forward must include fetal tissue research, for which continued public support is most critical at this time. [1]: pending:yes