Extracellular matrix (ECM) proteins synthesized by human placental mesenchymal cells (PMCs) provide structural support for the villus. Aberrant expression of ECM proteins by PMCs has been associated with intrauterine growth restriction (IUGR). To provide insight into the mechanisms of ECM protein regulation in the stroma of the placental villus, in the current study, we examined the interaction of glucocorticoid (GC) and transforming growth factor-beta (TGFbeta) in the modulation of ECM proteins in cultures of PMCs isolated from human term placentas. Initial results obtained by ELISA showed that combined treatment with dexamethasone (DEX) and TGFbeta enhanced oncofetal fibronectin (FFN) protein levels in serum-free culture medium severalfold in a dose-dependent manner. Northern blotting and real-time polymerase chain reaction (PCR) analyses revealed a similar enhancement in levels of FN mRNA in cells treated with TGFbeta and DEX. Real-time PCR results also revealed that DEX and TGFbeta enhanced collagen (Col) I and Col IV expression, but did not affect levels of Col III or laminin, indicative of selective stimulation of ECM proteins. Hypoxic treatment moderately enhanced FFN levels in control cells but not in those treated with DEX and TGFbeta. In contrast with the results obtained with PMCs, we noted that DEX treatment suppressed FFN levels in untreated and TGFbeta-treated cytotrophoblasts, suggesting that GC and TGFbeta modulate FFN expression in placenta in a cell-type-specific manner. We conclude that GC and TGFbeta are key regulators of ECM protein synthesis in PMCs, suggesting a role in modulating placental architecture in uncomplicated pregnancies and those associated with aberrant ECM protein expression.