Objective: To examine human embryos at various stages of preimplantation development for simultaneous expression of matrix metalloproteinases (MMPs) and tissue inhibitor of matrix metalloproteinases (TIMPs).
Design: mRNAs of specific MMPs and TIMPs were examined in single human embryos, at different stages of preimplantation development, by reverse transcription-polymerase chain reaction (RT-PCR). Single embryo immunohistochemistry was applied to examine the protein expression.
Setting: University-affiliated IVF-ET program.
Patient(s): Couples, attending the university-affiliated IVF-ET program, electing to donate poor prognosis embryos with anomalous morphology.
Main outcome measure(s): The expression of MMP-1, MMP-2, MMP-9, TIMP-1, TIMP-2, and TIMP-3 in preimplantation embryos.
Result(s): The MMP-2 mRNA was expressed consistently during development from one-cell to blastocyst stage. The TIMP-1 and TIMP-3 mRNAs were detected in embryos at all stages; however, in the later preimplantation developmental stages, an increasing proportion of embryos expressing TIMP-1 and TIMP-3 mRNA were noted. The MMP-1, MMP-9, and TIMP-2 mRNAs were detected in only a minority of human embryos studied. Immunohistochemistry showed MMP-1 and TIMP-1 protein expression in preimplantation embryos.
Conclusion(s): The existence of MMP and TIMP mRNA expression in human preimplantation embryos argues for a role for these metalloproteinases and their inhibitors during the process of implantation in humans.