Umbilical cords were obtained between 2006 and 2008 from healthy full-term newborns with written parental informed consent according to the guidelines of the medical and ethical committees of Hospices Civils de Lyon and of Agence de Biomedecine, Paris, France. Ethics Committee approval for this study was not required according to institutional guidelines and French law Nu2004-800, from 6 August 2004 -art 12 ORF 7.08.2008, Article L1245-2, allowing the utilization of the placenta and umbilical cords in scientific and therapeutic purpose when their donors do not express any opposition.