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Hampered cumulus expansion of porcine cumulus-oocyte complexes by excessive presence of alpha2-macroglobulin is likely mediated via inhibition of zinc-dependent metalloproteases

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Ondertitel:Hampered cumulus expansion of porcine cumulus-oocyte complexes by excessive presence of alpha(2)-macroglobulin is likely mediated via inhibition of zinc-dependent metalloproteases
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 epider- mal 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.
Tijdschrift: Animal Science Journal
ISSN: 1344-3941
Issue: 9
Volume: 88
Pagina's: 1279 - 1290
Jaar van publicatie:2017
Trefwoorden:Voedings- en dierkunde en technologie