Mesenchymal stem cells (MSCs) have been shown to exert therapeutic effects on various autoimmune diseases. However, such therapeutic effect is not always achieved. Among many reasons, MSC culture methodologies may account for the these differences. It is known that oxygen concentration could profoundly affect the properties of MSCs. Therefore, we compared human umbilical cord derived MSCs cultured under hypoxic and normoxic conditions. We used microarrays to profile the gene expression of human umbilical cord derived MSCs under 10% oxygen and normoxia conditions. Overall design: MSCs were cultured under different oxgen tension were applied to microarray analysis