Expression of tissue type and urokinase type plasminogen activators as well as plasminogen activator inhibitor type-1 and type-2 in human and rhesus monkey placenta

The distribution of mRNAs and antigens of tissue type (t) and urokinase typ e (u) plasminogen activators (PA) plus their corresponding inhibitors, type -1 (PAI-1) and type-2 (PAI-2) were studied in human and rhesus monkey place ntae by in situ hybridisation and immunocytochemistry. Specific monkey cRNA and antibodies against human tPA, uPA, PAI-1 and PAI-2 were used as probes . The following results were obtained. (1) All the molecules tPA, uPA, PAI- 1 and PAI-2 and their mRNAs were identified in the majority of the extravil lous cytotrophoblast cells of the decidual layer between Rohr's and Nitabuc h's striae and in cytotrophoblast cells of the chorionic plate, basal plate , intercotyledonary septae and cytotrophoblast cells of the chorionic villo us tree. (2) Expression of uPA and PAI-2 was noted in villous trophoblast w hereas tPA and PAI-1 were mainly concentrated where detachment from materna l tissue occurs. (3) No expression of tPA, uPA, PAI-1 and PAI-2 was observe d in the basal plate endometrial stromal cells, chorionic plate connective tissue cells, septal endometrial stromal cells or villous core mesenchyme. (4) The distribution of probes observed following in situ hybridisation is generally consistent with the immunofluorescence pattern of the correspondi ng antigens and no significant interspecies differences were noted. It is p ossible that both decidual and extravillous trophoblast cells of placentae of human and rhesus monkey are capable of producing tPA, uPA, PAI-1 and PAI -2 to differing extents. Coordinated expression of these genes in the tissu e may play an essential role in the maintenance of normal placentation and parturition. The differences in distribution we observed are consistent wit h the suggestion that coordinated expression of tPA and its inhibitor PAI-1 may play a key role in fibrinolytic activity in the early stages of placen tation and separation of placenta from maternal tissue at term. On the othe r hand, uPA with its inhibitor PAI-2 appears mainly to play a role in degra dation of trophoblast cell-associated extracellular matrix, and thus may be of greatest importance during early stages of placentation.