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Differential Secretion of Matrix Metalloproteinase-2 and -9 After Selective Infection With Group B Streptococci in Human Fetal Membranes

Direction of Research and Neonatology Branch, Instituto Nacional de Perinatologia, Mexico City, Mexico; Biomedical Research Institute, Universidad Nacional Autónoma de México, Mexico City, Mexico; zaga{at}universo.com

Horacio Merchant-Larios, PhD

Guadalupe García-López, BSc

Rolando Maida-Claros, MD

Felipe Vadillo-Oretega, MD,PhD

Direction of Research and Neonatology Branch, Instituto Nacional de Perinatologia, Mexico City, Mexico; Biomedical Research Institute, Universidad Nacional Autónoma de México, Mexico City, Mexico.

Objective: This study evaluated the secretions of zymogen and active forms of matrix metalloproteinase (MMP)-9 and MMP-2 and their specific inhibitors, TIMP-1 and TIMP-2 by fetal membranes stimulated with group B Streptoccocci (GBS).

Methods: We used an in vitro experimental model that allowed us to estimate the individual contribution of the amnion (AM) and the choriodecidua (CHD) to the microbial insult. Membranes were obtained after delivery by elective cesarean delivery from women at 37 to 40 weeks of gestation without evidence of either active labor of intrauterine infection. Membranes were mounted in Transwell devices (Costar, New York, NY), physically separating the upper and lower chambers; 1 x 10⁶ CFU of GBS was added to either AM or CHD and the secretions and gelationlytic activity of MMP-2 and MMP-9 were measured in both compartments by enzyme-linked immunosorbent assay (ELISA) and zymography. TIMPs secretion was measured by ELISA. Both MMPs were immunolocalized in tissue sections.

Results: The simultaneous stimulation at both sides was followed by increases of proMMP-9 (85.0 ± 18.63 pg/mL) and proMMP-2 (4.10 ± 1.90 ng/mL) in the CHD (P < .05). When only one side of the membrane was stimulated, the secretion level of proMMP-2 increased 2.3-fold and that of proMMP-9 2.5-fold in the CHD. The active forms of the both enzymes did not change with any modality of stimulation. The secretion levels of both TIMPs remained without significant changes. CHD and AM were positive for immunoreactive MMP-2 and MMP-9.

Conclusion: We propose that infection of fetal membranes with GBS is followed by active secretion of MMP and the CHD is the principal source of these mediators of extracellular matrix degradation.

Key Words: Matrix metalloproteinases • intrauterine infection • extracellular matrix • chorioamniotic membranes

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