Toll-like receptor 2 of sperm is involved in sperm attachment to bovine oviductal epithelial cells

Abstract

[Introduction] Sperm binding to oviduct epithelium is essential since it causes favorable effects on sperm motility, storage, survival and fertilizing ability in the oviduct. We have recently shown that, Toll-like receptor 2 (TLR2) partly regulates the attachment of sperm to the oviduct epithelium thereby mediates the Th2 immune response using a bovine sperm-oviduct explant culture model (2019, SRD). Quite recently, we found that TLR2 is localized in bull sperm. Thus, we examined if TLR2 of sperm is involved in sperm attachment to the oviduct epithelial cells. [Materials and methods] To block the TLR2 of sperm, the frozen-thawed active bull sperm after swim-up were pre-treated with TLR1/2 antagonist (TLR2 ant. ⁽⁺⁾) or without (TLR2 ant. ^(-)). To evaluate the sperm organelle functions such as, plasma membrane integrity, acrosomal integrity, and high mitochondrial membrane potential, TLR2 ant. ^(-)/(+) sperm were stained with PI, FITC-PNA, and JC1 respectively. Sperm suspensions were analyzed by the flow cytometer at 0, 1 and 3 hr. To investigate sperm attachment to oviduct epithelial cells, TLR2 ant. ^(-)/⁽⁺⁾ sperm were co-cultured with bovine oviduct epithelial cells (BOECs) and the videos were recorded at 0, 1 and 3 hr. [Results] TLR1/2 antagonist treatment did not affect the sperm organelle functions over the investigated period. The phase-contrast video microscopy data revealed that, lesser number of TLR2 ant. ⁽⁺⁾ sperm were attached to BOECs than TLR2 ant. ^(-) sperm at 3 hr (70% of the TLR2 ant. ^(-) control). The observations suggest that TLR2 of sperm is involved in sperm attachment to BOECs. Further study is necessary to examine by which mechanism of TLR2 both in sperm and BOECs controls sperm-oviduct binding and immune crosstalk.