LAMININ-2 AND LAMININ-4 ARE EXPRESSED BY HUMAN DECIDUAL CELLS

During pregnancy, the resident stromal cells of the endometrium differ entiate to become decidual cells and produce a pericellular basement m embrane. We used immunofluorescence and Western blotting with a panel of monoclonal Ab specific for various laminin subunits to examine the composition of decidual laminin. The stromal cell basement membrane co ntained subunits alpha 2 (M), beta 1 (B1), beta 2 (S), and gamma 1 (B2 ). Low levels of alpha 1 could also be detected. The glandular and vas cular basement membranes of decidual tissue contained subunits alpha 1 (A), beta 1, and gamma 1. An extract was produced from decidual extra cellular matrix. Western blots of nonreducing gels showed the presence of high molecular weight complexes containing alpha 2, beta 1, beta 2 , and gamma 1. These data indicated that laminins 2 and 4 are coexpres sed by decidual cells. Laminin 1 was present in the extract as a minor component. In contrast, cultured stromal cells expressed laminin 1 as the major secreted variant. Immunolocalization was carried out using tissue from various stages of the nonpregnant cycle. The alpha 2 chain polypeptide was absent in the proliferative phase of the cycle but pr esent in late secretory phase in perivascular areas where predecidual differentiation occurs. Reverse transcriptase-PCR experiments confirme d the presence of alpha 2 chain mRNA in decidua but showed that this t ranscript is detectable throughout the the nonpregnant cycle. The resu lts showed that laminins 2 and 4 are hormonally regulated products of decidual cells. The composition of the vascular and epithelial basemen t membranes remained constant throughout the cycle.