Proteinase and proteinase inhibitor localization in the human placenta

Standard immunoperoxidase techniques were used to investigate the distribution of the intracellular proteinase cathepsin D, two serine proteinase inhibitors--alpha 1-antitrypsin (alpha 1-AT) and alpha 1-antichymotrypsin (alpha 1-AChy)--and plasma fibrin stabilizing factor XIII (FXIII) in paraffin-embedded tissues from early and late intrauterine pregnancy and ectopic pregnancy. Localization of cathepsin D, alpha 1-AT, and alpha 1-AChy was identical in ectopic and intrauterine gestation: there was labeling of villous syncytiotrophoblast and a proportion of Hofbauer cells but no labeling of villous cytotrophoblast. The majority of interstitial extravillous trophoblast yielded negative results, but alpha 1-AT and alpha 1-AChy were consistently demonstrated in endovascular trophoblast. FXIII was not found in any trophoblast population but was demonstrated in Hofbauer cells, stromal fibroblasts, and interstitial dendritic cells. Granular, extracellular FXIII reactivity was present among sheets of infiltrating extravillous trophoblast in ectopic pregnancy but only occasionally in early intrauterine pregnancy. The results document further the heterogeneity of trophoblast, with the endovascular trophoblast forming an immunophenotypically distinct population. Furthermore, the pattern of extravillous trophoblastic invasion of maternal tissues in ectopic pregnancy appears to differ from intrauterine pregnancy; the poor decidualization of tubal mucosa in ectopic pregnancy may play a role in this variation.