Transforming growth factor beta (TGF-beta) is a major secretory product of macrophages which, through autocrine/paracrine pathways, play a central role in normal reproductive tissues as well as in disorders such as endometriosis and intraperitoneal adhesion formation. Using TGF-beta antisense oligonucleotides and U937 cells (a promonocytic human cell line) as an in-vitro model, the present study examined the autocrine mediated action of TGF-beta 1 on proliferation, anchor-dependent and -independent cell aggregation and expression of several mRNAs of cell surface adhesion molecules including integrins and platelet-endothelial cell adhesion molecule (PECAM-1). Northern blot analysis and enzyme-linked inmmunosorbent assay (ELISA) revealed that treatment with TGF-beta 1 antisense, but not sense or nonsense oligomers, in a dose-dependent manner (0.1-10 microM) down-regulated the expression of TGF-beta 1 mRNA and protein to undetectable amounts at the highest antisense concentration. TGF-beta 1 antisense at < 1 mM slightly increased, while at > 3 microM significantly inhibited, the rate of DNA synthesis and proliferation of these cells (P < 0.05). Treatment with TGF-beta 1 antisense promoted cell aggregation under anchor-independent culture conditions (plastic dishes), while it suppressed colony formation under anchor-dependent culture conditions (soft agar assay). U937 cells expressed alpha 2, alpha 3, alpha 4, alpha 5, alpha 6, beta 1 and beta 2 integrin mRNA and PECAM-1 mRNA, while alpha v, beta 3 and beta 5 integrin mRNA was undetectable. The relative amount of alpha 2, alpha 3, alpha 4, alpha 6, beta 1 and beta 2 integrin and PECAM-1 mRNA expression were down-regulated in a dose-dependent manner after TGF-beta 1 antisense treatment, while alpha 5 integrin mRNA expression was up-regulated, although it was undetectable at 10 microM antisense. In contrast, TGF-beta 1 antisense up-regulated beta 3 mRNA expression with maximal effect occurring at 10 microM. These results provide evidence that the autocrine loop of monocyte/macrophage-derived TGF-beta 1 action is essential for regulation of growth, aggregation and the expression of adhesion molecules by these cells. We propose that in disorders such as endometriosis and peritoneal fibrous adhesions, significantly higher numbers of tissue macrophages with the capacity to express excess TGF-beta 1 yield an environment able to promote cell-cell and cell-matrix interactions, and thus lead to further complications from these abnormalities. We are currently investigating whether site-specific inhibition of TGF-beta using antisense strategy is a useful tool for management of these lesions, particularly after their post-surgical removal.