CD45+/CD133+ positive cells expanded from umbilical cord blood expressing PDX-1 and markers of pluripotency.

UCB (human umbilical cord blood) contains cells able to differentiate into non-haematopoietic cell lineages. It also contains cells similar to primitive ESCs (embryonic stem cells) that can differentiate into pancreatic-like cells. However, few data have been reported regarding the possibility of expanding these cells or the differential gene expression occurring in vitro. In this study, we expanded formerly frozen UCB cells by treatment with SCF (stem cell factor) and GM-CSF (granulocyte-macrophage colony stimulating factor) in the presence of VPA (valproic acid). Gene expression profiles for beta cell differentiation and pluripotency (embryo stem cell phenotype) were analysed by RT-PCR and immunocytochemistry. The results show a dramatic expansion (>150-fold) of haematopoietic progenitors (CD45+/CD133+) which also expressed embryo markers of pluripotency (nanog, kfl-4, sox-2, oct-3/4 and c-myc), nestin, and pancreatic markers such as pax-4, ngn-3, pdx-1 and syt-1 (that is regulated by pdx-1 and provides the cells with a Ca++ regulation mechanism essential for insulin exocytosis). Our results show that UCB cells can be expanded to produce large numbers of cells of haematopoietic lineage that naturally (without the need of retroviral vectors or transposons) express a gene pattern compatible with endocrine pancreatic precursors and markers of pluripotency. Further investigations are necessary to clarify, first, whether in this context, the embryogenes expressed are functional or not, and secondly, since these cells are safer than cells transfected with retroviral vectors or transposons, whether they would represent a potential tool for clinical application.