Laminin‐111 Inhibits Bovine Fertilization but Improves Embryonic Development in vitro, and Receptor Integrin‐β1 is Involved in Sperm–Oocyte Binding

Abstract

This study detected the distribution of laminin during embryonic formation by immunofluorescence. To determine the possible function of laminin on developmental ability of in vitro fertilized embryos, the presumptive zygotes were divided and transferred to CR1aa medium supplemented with different concentrations (0 μg/ml, 5 μg/ml, 10 μg/ml and 20 μg/ml) of laminin. To explore the association with sperm-oocyte fusion, oocytes and/or sperm were pre-incubated with laminin or anti-β1 antibody before insemination. Laminin was absent in mature oocytes and could be detected first at the 8-cell stage and then displayed an increasing tendency. Adding 10 μg/ml laminin to the culture medium improved embryonic development including cleavage rate, blastocyst rate, total cell numbers in the blastocyst and cell numbers in the inner cell mass. Laminin inhibited sperm-oocyte fusion when incubated with oocytes and/or sperm before in vitro fertilization, and only integrin-β1 of sperm was involved in sperm-oocyte binding. Inhibition may be caused by blocking β1, but why laminin inhibits fertilization is still unknown. The results suggest that laminin plays an important role during embryonic formation and has a negative function in sperm-oocyte fusion, but improves embryonic development. However, only integrin-β1 is involved in sperm-oocyte binding.

Role of Integrins in Sperm Activation and Fertilization

“…In addition, in documented oocyte experiments, wild-type sperm were used for in vitro fertilization and wild-type males were used for mating and monitoring fertilization success in vivo. As subsequent experiments have shown, incubation of mouse sperm with anti-α6 [16], anti-αV, or anti-β3 [18] integrin antibodies, or bovine sperm with anti-β1 [118] or anti-β5 [119,120] integrin antibodies, reduced the ability of sperm to bind to the oocyte. In mice, this effect was more pronounced when both gametes were incubated with the antibodies prior to their interaction.…”

Evaluation of fertilization capability of frozen-thawed completely immotile spermatozoa collected from a white bengal tiger after interspecific ICSI with bovine oocytes

“…Oocyte collection and in vitro maturation were performed as described previously (Lin et al, 2016). Bovine ovaries were collected from a local slaughterhouse.…”