Human placenta: a source of progenitor/stem cells?

Regenerative medicine based on cell therapy and tissue engineering methodologies is a newly emerging, multidisciplinary field i nvolving biology, medicine, and genetic manipulation. This type of therapy is aimed at maintaining, restoring, or enhancing tissue and organ func tion, and is intended to assist in the treatment of a number of human conditions which range in severity from chronic to life threatening. I n diseases where tissue or organ function is compromised, stem cell research holds great promise for providing an efficient avenue for regenerat ive therapy. How- ever, the application of this type of research to the treatment of human disease will not be possible until much more is known about the biological properties of all types of stem cells. In the context of disease treatment, decisions will need to be made as to which is the b est type of stem cell to use. Whether it is better to identify a stem cell able to differentiate into all tissue and organ types as opposed to using com mitted, lineage-specific stem cells, or perhaps embryonic cells are better than adult-derived stem cells, as well as the possible clinical applications of these cells. For some time, these questions have not only required significant scientific and medical consideration, but have also posed important so cial and ethical questions. There is no doubt that stem cells hold great therapeutic potential, however there is still much research required before their use can be accepted as a valuable tool in disease treatment. In particular, it is necessary to identify a source of stem cells that is eas ily accessible, provides a high cell yield and for which cell recovery does not provoke serious ethical debate. The aim of this review is to consider and discuss the findings regarding a new source of “adult” stem cells isolated from human term placenta tissue. So far, the placental tissue has general ly been discarded post partum, but it is now becoming recognised as a potential source of stem and progenitor cells. New findings now show that t his tissue holds visible promise as a source of stem cells which may have widespread clinical applications, but which also circumvents the heate d ethical debate which is associated commonly with the use of embryonically derived stem cells. Aspects including in vitro findings, pre-clinica l experimentation, and immunological properties of stem cells isolated from placental membranes will be discussed in the context of their potentia l clinical applica- tions.