Expression of tissue factor pathway inhibitor in human fetal and placental tissues.

The coagulation system differs markedly between fetuses, neonates, and adults, and fetal and neonatal thrombotic abnormalities are poorly understood. Tissue factor pathway inhibitor (TFPI) is an important inhibitor of the extrinsic pathway of coagulation. To begin examining the role of TFPI in the maternal-fetal relationship, TFPI expression in human fetal and placental tissues was studied by immunohistochemical staining. TFPI was widely expressed in human fetal tissues from 8-24 weeks gestation, particularly in epithelial and endothelial tissues. Fetal liver, lung, kidney, and intestine were notably positive for TFPI staining. Within the tissues, TFPI was expressed in pneumocytes, hepatocytes, renal tubular and glomerular cells, muscle fibers, and enterocytes. In placental tissues, TFPI was expressed in syncytiotrophoblasts, cytotrophoblasts, vascular endothelium, and extravillus trophoblasts from 10 weeks through term. Advancing gestation had little effect on TFPI expression. Further studies are needed to determine the functional role of TFPI in fetal and placental tissues and to define perturbations in its expression during fetal and neonatal disease states.