Discarded stem cells with a future?

Although embryonic stem cells hold the promise for tissue and organ generation, stem cells with early mesenchymal character, which can be obtained at the time of birth from extra-embryonic tissue, may have similar capabilities if manipulated appropriately. These 'perinatal' tissues, such as the umbilical cord or the placenta, which are generally discarded after delivery, contain early mesenchymal stem cells that are believed to have a greater potential for plasticity than postnatal mesenchymal cells, such as those from bone marrow. They express early transcriptional genes, and emerging technologies, such as nuclear reprogramming, could direct their development into tissues of embryonic origin. Hence, these cells, generally discarded after birth, could become a valuable source for future tissue generation.