EXTRACELLULAR-MATRIX INTERACTIONS IN EARLY HUMAN EMBRYOS - IMPLICATIONS FOR NORMAL IMPLANTATION EVENTS

Objective: To study the role of extracellular matrix (ECM) proteins in supporting the development-and implantation competence of human embry os. Design: Expression of an implantation site adhesive glycoprotein, oncofetal fibronectin, and basement membrane collagen-degrading matrix metalloproteinase-2 and -9 were studied in cultured human embryos. Th e ability of exogenously added laminin and fibronectin to enhance hatc hing and matrix metalloproteinase-2 expression was quantitated also. P atients: Fifty-four women with tubal factor infertility enrolled in th e IVF program at the University Hospital of Oulu agreed to participate by providing 20 residual oocytes and 227 residual early embryos for t his study. Main Outcome Measures: The presence of oncofetal fibronecti n immunoreactive protein was assayed by immunocytochemical staining wi th two specific monoclonal antibodies, FDC-6 and X18A4. These antibodi es bind to specific and distinct epitopes within tumor and trophoblast -derived oncofetal fibronectin. Changes in embryo matrix metalloprotei nase-2 production were measured by zymography and confirmed by immunoc ytochemical staining. Results: Intracellular oncofetal fibronectin was identified within blastomeres of early stage embryos. The immunoreact ivity of oncofetal fibronectin in the zona pellucida was associated wi th fragmentation and dissolution of the zona. Exogenously added lamini n or adult-type fibronectin significantly increased the hatching rate of the cultured embryos. Embryos cultured with added adult-type fibron ectin or trophoblast-derived oncofetal fibronectin stimulated the matr ix metalloproteinase-2 production (72-kd type TV collagenase) by 2.25 +/- 0.16-fold when compared with control embryos (mean +/- SD). Conclu sions: Embryonic production of specific ECM proteins, such as oncofeta l fibronectin, appears to be important for the morphological and bioch emical development of human preimplantation embryos. Moreover, ECM pro teins promote acquisition of the adhesive and degradative properties r equired by human embryos for successful implantation.