Hampered cumulus expansion of porcine cumulus‐oocyte complexes by excessive presence of alpha2‐macroglobulin is likely mediated via inhibition of zinc‐dependent metalloproteases. (26th January 2017)

• Record Type: Journal Article
• Authors: Appeltant, Ruth; Beek, Josine; Maes, Dominiek; Bijttebier, Jo; Van Steendam, Katleen; Nauwynck, Hans; Van Soom, Ann
• Is Part Of: Animal science journal. Volume 88:Number 9(2017:Sep.)
• Page Start: 1279
• Page End: 1290
• Publication Date: 2017-01-26
• Subjects: alpha2‐macroglobulin -- cumulus expansion -- in vitro maturation -- porcine -- serum; Animal culture -- Periodicals; Livestock -- Periodicals; 636
• DOI: 10.1111/asj.12767
• Languages: English
• ISSNs: 1344-3941

Abstract

Abstract: In vitro maturation (IVM) in serum causes hampered expansion of porcine cumulus‐oocyte complexes (COCs) due to excessive alpha2 ‐macroglobulin (A2M). This study investigated two hypotheses that could explain the effect of A2M: (i) binding of epidermal growth factor (EGF) to A2M, followed by its decreased availability; and (ii) inhibition of zinc‐dependent metalloproteases. Cumulus expansion was evaluated based on the diameter of the COCs, the proportion of COCs participating in a floating cloud and the proportion of COCs with loss of cumulus cells. The first hypothesis of decreased EGF availability was tested by increasing the EGF concentration (20 and 50 ng/mL vs. 10 ng/mL), but was not confirmed because cumulus expansion did not improve. To verify the second hypothesis of inhibited zinc‐dependent metalloproteases, the effect of tissue inhibitor of metalloproteases‐3 (TIMP‐3) on cumulus expansion during IVM with and without A2M was investigated. To immuno‐neutralize A2M, serum was pre‐incubated with A2M antibodies. Impaired cumulus expansion because of TIMP‐3 could only be observed during IVM in 10% of serum with A2M antibodies. No effect of TIMP‐3 was observed in medium without A2M antibodies. These results indicate that A2M and TIMP‐3 share a common target, a zinc‐dependent metalloprotease. Future research is directed toward the identification of the protease involved.