To clarify the mechanisms regulating lipoprotein production by hepatocyte nuclear factors (HNFs), we generated four kinds of transfectants in human bone marrow mesenchymal stem cells: UE7T-13, stably expressing FOXA2 (also known as HNF3 beta), HNF4 alpha, HNF1 alpha or co-expressing HNF4 alpha, and HNF1 alpha (HNF4 alpha/HNF1 alpha). In HNF4 alpha/HNF1 alpha transfectants, cellular contents of triglycerides (TG) and cholesterol were markedly higher than in UE7T-13 cells and comparable to those in human hepatoma HepG2 cells. However, TG and cholesterol, which are secreted from cells as components of lipoproteins, were hardly detected in the medium for any of the transfectants. ApoB100 and MTP, which are essential for the formation and secretion of lipoproteins, were undetectable and detected at low levels, respectively, in HNF4 alpha/HNF1 alpha transfectants. We suggest that enforced co-expression of HNF4 alpha and HNF1 alpha is effective for cellular lipid accumulation, while additional factors are probably required for lipoprotein formation and secretion.