SYNTHESIS OF TISSUE FACTOR PATHWAY INHIBITOR IN HUMAN SYNOVIAL-CELLS AND CHONDROCYTES MAKES JOINTS THE PREDILECTED SITE OF BLEEDING IN HEMOPHILIACS

The synthesis of tissue factor pathway inhibitor (TFPI) was investigat ed in cloned human synovial cells and human chondrocytes. TFPI-specifi c DNA transcription products of these cells were isolated, and a full- length cDNA of about 1000 base pairs was amplified by reverse transcri ption and polymerase chain reaction. The amplified DNA was cloned into the Vector pUC 18. The TFPI coding sequence was confirmed by double s tranded sequencing and was identical with that previously published fo r human TFPI coding nucleotide sequence from human placental cDNA (1). The inhibitory activity of TFPI in the cell medium of cultivated huma n chondrocytes and cloned human synovial cells was determined by a spe cific chromogenic substrate assay of factor Xa activity. The inhibitor y activity of TFPI in the medium of human chondrocytes and cloned huma n synovial cells was 630-720 mU/10(8) cells and 1080-1665 mU/10(8) cel ls, respectively. In addition, TFPI activity in cell culture media of human chondrocytes and cloned human synovial cells was suppressed by a polyclonal goat anti-TFPI antibody directed against the inhibitory do main I and domain II. In the chromogenic substrate assay, the anti-TFP I antibody completely suppressed the inhibitory activity of TFPI in th e samples.