Expression of gelatinase B by trophoblast cells: down-regulation by progesterone

It is now accepted that gelatinase B (92 kd type IV collagenase) is involved in blastocyst implantation and trophoblast invasion. However, little is known about the regulation of this enzyme at the fetomaternal interface. Progesterone has been demonstrated to inhibit gelatinase B secretion from endometrial cells, myometrium, and cervical fibroblasts. Interestingly, the promotor of gelatinase B contains a progesterone-responsive element that may explain transcriptional activation of this metalloproteinase by progesterone. It may be hypothesized that progesterone secreted from trophoblast cells, representing the fetal part of the fetomaternal interface, may have a role in the regulation of gelatinase secretion and blastocyst implantation.

To this end, use was made of first-trimester trophoblast cells obtained from first-trimester pregnancy terminations. The trophoblast cells were separated by trypsin degradation and fractionation on Percoll gradients. Metalloproteinase activity was measured by zymography, and the expression of the gelatinase B messenger ribonucleic acid was determined by the solution hybridization/ribonuclease protection assay.

Primary cell cultures of trophoblasts from first trimesters of pregnancy constitutively elaborated two species of type IV collagenases (gelatinase A and B) as assessed on a gelatin matrix. Treatment with progesterone decreased the accumulation of a gelatinase B species in a dose-dependent fashion. Administration of a progesterone receptor antagonist onapristone (ZK-98.299) neutralized the progesterone inhibitory effect on the gelatinase B in a dose-dependent fashion, thus supporting the presumption that the progesterone effect is receptor mediated. Progesterone significantly attenuated the expression of gelatinase B by trophoblast cells, an effect that was neutralized by ZK-98.299.

These observations provide strong indirect support for the participation of progesterone in the regulation of gelatinase B in trophoblast cells. It may be an important regulator of gelatinase production at the fetomaternal interface.