Transient exposure to calcium ionophore enables in vitro fertilization in sterile mouse models

Abstract

Mammalian sperm acquire fertilizing capacity in the female tract in a process called capacitation. At the molecular level, capacitation requires protein kinase A activation, changes in membrane potential and an increase in intracellular calcium. Inhibition of these pathways results in loss of fertilizing ability in vivo and in vitro. We demonstrated that transient incubation of mouse sperm with Ca2+ ionophore accelerated capacitation and rescued fertilizing capacity in sperm with inactivated PKA function. We now show that a pulse of Ca2+ ionophore induces fertilizing capacity in sperm from infertile CatSper1 (Ca2+ channel), Adcy10 (soluble adenylyl cyclase) and Slo3 (K+ channel) KO mice. In contrast, sperm from infertile mice lacking the Ca2+ efflux pump PMACA4 were not rescued. These results indicate that a transient increase in intracellular Ca2+ can overcome genetic infertility in mice and suggest this approach may prove adaptable to rescue sperm function in certain cases of human male infertility.

CatSperζ regulates the structural continuity of sperm Ca2+ signaling domains and is required for normal fertility

“…Moreover, a short (10 min) exposure to A23187 can rescue defects in hyperactivated motility and the fertilizing capability of CatSper1 -null sperm in vitro (Navarrete et al, 2016). We tested the relation of calcium transients to hyperactivated motility in CatSperz -het and null sperm.…”

CatSper channels are regulated by protein kinase A

“…Whereas P2X2 KO mice are fertile, lack of CatSper results in complete sterility (14,41,42). Recently, we have shown that the lack of hyperactivation and infertility phenotypes can be overcome elevating [Ca 2ϩ ] i pharmacologically by exposing CatSper KO sperm to A23187 for a short period of time (43). Although the role of CatSper is well established in sperm function, how this channel complex is regulated is still not fully understood.…”

Flagellar hyperactivation of bull and boar spermatozoa

“…In particular, calaxin is indispensable to the Ca 2+ ‐dependent antisymmetrisation of flagellar bending and directly decelerates the sliding of microtubules in ascidian spermatozoa. Meanwhile, a treatment with A23187 rescues the ability to fertilize oocytes (including the capacity to undergo hyperactivation) in spermatozoa from infertile CatSper1 ‐, Adcy10 ‐, or Ksper ( Slo3 )‐KO mice, but does not recover it in spermatozoa from infertile Pmaca (Ca 2+ efflux pump on the plasma membrane)‐KO mice, suggesting importance of a transient increase in cytoplasmic Ca 2+ in the expression of fertilizing ability including the ability to undergo hyperactivation . Thus, it may be also necessary to focus on roles of the clearance of cytoplasmic Ca 2+ in the occurrence of hyperactivation.…”

“…Pmaca (Ca 2+ efflux pump on the plasma membrane)-KO mice, suggesting importance of a transient increase in cytoplasmic Ca 2+ in the expression of fertilizing ability including the ability to undergo hyperactivation. 81 Thus, it may be also necessary to focus on roles of the clearance of cytoplasmic Ca 2+ in the occurrence of hyperactivation. Technology Center for Agriculture, Forestry and Fisheries), and students and staffs of our laboratory for their significant contribution to our research projects.…”