Amnion-derived mesenchymal stromal cells show angiogenic properties but resist differentiation into mature endothelial cells.

Mesenchymal stromal cells derived from the human amnion (hAMSC) currently play an important role in stem cell research, as they are multipotent cells that can be isolated using noninvasive methods and are immunologically tolerated in vivo. The objective of this study was to evaluate their endothelial differentiation potential with regard to a possible therapeutic use in vascular diseases. hAMSC were isolated from human term placentas and cultured in Dulbecco's modified Eagle's medium (DMEM) (non-induced hAMSC) or endothelial growth medium (EGM-2) (induced hAMSC). Induced hAMSC changed their fibroblast-like toward an endothelial-like morphology, and were able to take up acetylated low-density lipoprotein and form endothelial-like networks in the Matrigel assay. However, they did not express the mature endothelial cell markers von Willebrand factor and vascular endothelial-cadherin. Gene expression analysis revealed that induced hAMSC significantly downregulated pro-angiogenic genes such as tenascin C, Tie-2, vascular endothelial growth factor A (VEGF-A), CD146, and fibroblast growth factor 2 (FGF-2), whereas they significantly upregulated anti-angiogenic genes such as serpinF1, sprouty1, and angioarrestin. Analysis of protein expression confirmed the downregulation of FGF-2 and Tie-2 (27%±8% and 13%±1% of non-induced cells, respectively) and upregulation of the anti-angiogenic protein endostatin (226%±4%). Conditioned media collected from hAMSC enhanced viability of endothelial cells and had a stabilizing effect on endothelial network formation as shown by lactate dehydrogenase and Matrigel assay, respectively. In summary, endothelial induced hAMSC acquired some angiogenic properties but resisted undergoing a complete differentiation into mature endothelial cells by upregulation of anti-angiogenic factors. Nevertheless, they had a survival-enhancing effect on endothelial cells that might be useful in a variety of cell therapy or tissue-engineering approaches.

Oxygen modulates the response of first-trimester trophoblasts to hyperglycemia.

Pregestational diabetes retards early embryonic growth. Placental and fetal growth are closely associated, suggesting that placental growth is also impaired. During the first trimester of gestation, oxygen tension rises steeply, leading to excessive production of reactive oxygen species (ROS), which is exacerbated in diabetes and may affect placental development. We hypothesized that oxygen modifies hyperglycemic effects on ROS formation, resulting in decreased first-trimester trophoblast growth. This was tested using a first trimester trophoblast-derived cell line (ACH-3P). Normoglycemia did not alter ACH-3P proliferation at 2.5%, 8%, and 21% oxygen. Hyperglycemic conditions for up to 3 days reduced cell number by 65% and resulted in cell cycle (G(1)- and S-phase) changes but only at 21% oxygen. Proliferation reduction could be partially restored by an inhibitor of mitogen-activated protein kinase (MAPK) ERK1/2 but not of Akt/PkB. Intracellular ROS elevation under hyperglycemia was oxygen independent, whereas mitochondrial superoxide levels were enhanced under hyperglycemia only at 21% oxygen. Intervention to modulate cytosolic and mitochondrial ROS, using ROS formation inducers and inhibitors, did not alter cell growth under hyperglycemia at 21% oxygen. The combination of hyperglycemia and high oxygen levels (21%) reduces proliferation of human first-trimester trophoblasts in a ROS-independent manner involving MAPK. This may account for reduced placental growth and, therefore, also for embryonic growth during the first-trimester pregestational diabetic pregnancies when the oxygen tension increases.