Characterization of Placenta Derived Adherent Cells (PDAC): A Novel Type of Stem Cells Isolated from Human Placenta.

The placenta is a rich source of ethically non-controversial stem cells. In this work, we describe the development of procedures to isolate and culture adherent stem cells from a full term, postpartum human placenta (Placenta Derived Adherent Cells, PDACs). PDACs are isolated from the placenta by one of several methods including physical disruption of tissue from several different anatomical sites within the placenta that include the amniotic membrane, chorion, cord, placental cotyledons, or any combination thereof. PDACs were established in a medium containing low concentrations of fetal calf serum and limited growth factors. Flow cytometry analysis showed that PDACs isolated from certain sites exhibit phenotypes, including for example CD200+ CD105+ CD73+ CD34− CD45− at percentages ≥70%. We found that PDACs differentiate down the adipocyte, chondrocyte and osteocyte lineages. In an induction medium containing IBMX, insulin, dexamethasone and indomethacin, PDACs turned into fat laden adipocytes in 3 to 5 weeks. Under osteogenic induction culture conditions, PDACs were found to form bone nodules and have calcium depositions in their extracellular matrix. Chondrogenic differentiation of PDACs was performed in micropellets and was confirmed by formation of glycosaminoglycan in the tissue aggregates. In addition, we showed that PDACs suppress an MLR consisting of suitable effectors (T cells or NK cells) and target populations (allogeneic irradiated PBMCs or mature DCs). The range of suppression of T cell proliferation was 50 to 95 %. The observed suppression of the MLR is likely cell-to-cell contact dependent in the range of 20%. In summary, the PDACs described herein exhibit in vitro properties of pluripotent stem cells. The placenta is an excellent raw material for the isolation of stem cells.