Sperm Ca2+ signaling and energy pathways in basic science and ART

点击翻译按钮获取中文摘要

Project Summary Infertility and subfertility are critical health problems affecting about 9 % of couples worldwide. Since the first successful “Test-Tube” baby in 1978, over 5 million babies were born using Assisted Reproductive Technology (ART). ART includes such techniques as in vitro fertilization (IVF), intrauterine insemination (IUI), intracytoplasmic sperm injection (ICSI) and embryo transfer techniques. ART is used in humans, and in animals of economic relevance. In humans alone, IVF and ICSI are used ~ 800,000 times per year. In all species, the limiting factor for successful pregnancies to occur is obtaining good quality preimplantation embryos which have a direct influence in implantation and pregnancy rates. Capacitation involves crosstalk between metabolic and signaling pathways. In the previous period, we showed that a short incubation with the Ca2+ ionophore A23187[7] can induce in vitro fertilizing capacity in sperm from sterile knock-out (KO) genetic models. We hypothesized that, at least, in part, A23187's effects were due to changes in metabolism. When sperm metabolism was changed using starvation and rescue protocols, we observed that intracellular Ca2+ was elevated. In addition, we found that, similar to A23187, sperm incubated in the absence of nutrients become immotile. Once nutrients are added back to the incubation media, sperm motility is rescued and those sperm depict higher percentage of hyperactivation and enhanced in vitro fertilization (IVF) rates. Unexpectedly, eggs fertilized with sperm incubated in metabolic enhanced conditions were more efficient in producing blastocysts and those blastocysts generated more implantation sites and produced more pups when transferred to pseudo-pregnant females. This proposal has basic and applied goals. The basic science objective is to understand the molecular basis of these methods with particular emphasis on the crosstalk between calcium and metabolic pathways. At the translational level, our goal is to use novel sperm incubation conditions to improve ART.