EXPRESSION OF PARATHYROID HORMONE-RELATED PEPTIDE AND ITS RECEPTOR MESSENGER-RIBONUCLEIC-ACID IN HUMAN AMNION AND CHORION-DECIDUA - IMPLICATIONS FOR SECRETION AND FUNCTION

OBJECTIVE: Our purpose was to define the location and packaging of par athyroid hormone-related peptide in amnion-chorion and the potential t arget tissues for its action in fetal membranes. STUDY DESIGN: We stud ied fetal membranes by use of light microscopic immunocytochemistry wi th three monoclonal antibodies against distinct regions of the parathy roid hormone-related peptide molecule. For electron microscopy immunog old analysis with a monoclonal antibody specific to the 109-141 fragme nt was used to observe parathyroid hormone-related peptide intracellul arly in amnion membrane and in the chorion layers. Multiplex reverse t ranscriptase-polymerase chain reaction with Southern blotting was used to identify parathyroid hormone/parathyroid hormone-related peptide r eceptor and control messenger ribonucleic acids in amnion and chorion- decidua. RESULTS: All monoclonal antibodies revealed immunoreactive pa rathyroid hormone-related peptide in the amniotic epithelial cells and in some fibroblast-like cells embedded in the extracellular matrix of the amnion. Parathyroid hormone-related peptide was also found in the chorion in fibroblast and trophoblast layers and in decidua. Ultrastr ucturally immunogold particles were evenly distributed throughout the amniotic epithelial cells and were present in apical microvilli and ne ar the basal membranes. Electron microscopy studies of the chorion cyt otrophoblast also showed freely dispersed immunogold particles of para thyroid hormone-related peptide with no packaging in secretory granule s. Low to undetectable levels of parathyroid hormone/parathyroid hormo ne-related peptide receptor messenger ribonucleic acid were found in a mnion tissue, whereas abundant receptor messenger ribonucleic acid was found in chorion-decidua. CONCLUSIONS: These results suggest the pres ence of a parathyroid hormone-related peptide paracrine system within the human fetal membranes.