Study On The Relationship Between BDNF And Preimplantation Embryo Development

Part1Relation between BDNF in Follicle Fluid and the Outcome of IVF and the Embryo DevelopmentObjectiveThe aim of the study was to evaluate the correlation between BDNF and oocyte maturation and to verify whether BDNF could predict in vitro fertilization (IVF) outcome. Methods The blood and follicle fluid (FF) for BDNF, E2and P assay were obtained from59patients undergoing intracytoplasmic sperm injection (ICSI). The women were divided into two groups by pregnancy outcome and their clinical and lab data were compared. And the correlation of BDNF with E2, P, age, and IVF data were analyzed.Results There was no statistically significant difference in any items in the pregnant and non-pregnant group. There waspositive correlationbetween serum BDNF and E2, P. Serum BDFN was positively correlated with the oocytes collected and mature oocytes collected. There was positive correlationbetweenBDNF and E2, but there was no correlation with P in follicle fluid.BDNF in FF was positively correlated with the rate of mature oocytes collected and cleavage rate.ConclusionsThe BDNF could not predict IVF outcome, but BDNF might play an important role in the maturation of oocyte and development of oocyte into preimplantation embryo. Part2Expression of Brain-Derived Neurotrophic Factor in Preimplantation Embryo and Effect on the Embryo Development in MouseObjective:Some studies showed that the preimplantation embryo was not so good in vitro as in vivo and the blastocyst formation rate is lower in vitro than in vivo. It was important to find some way to increase ability of the preimplantation embryos to developto the good blastocysts, which is very important in the process of in vitro fertilization. Studies showed that the reproductive tract or preimplantation embryo could produce a number of growth factors and cytokines, which could promote the preimplantation embryo development through autocrine or paracrine pathway by combining with the specific receptors. Brain-Derived Neurotrophic Factor (BDNF) not only played an important role in the neural system, but could promote ovarian development, oocyte maturation and early embryo development in reproductive system. Therefore, the objective of this study was to investigate the expression and distribution of BDNF in preimplantation embryos, to test theimportance of BDNF signaling during early embryonicdevelopment and implantation progress in mice, and to provide some theoripeutical basis for increase the ability of the development of preimplantation embryos, Three main points were to:1) To determine if TrkB activation is required for embryodevelopment in vitro; and2) To determine if BDNF supplementation increases embryo development in vitro; and3) if BDNF could improve embryo development, when and how to add BDNF to the culture medium?Methods:The female ICR mice were superovulated and then mated with male mice. On the morning of1st to4th of pregnancy, the embryos in different stage were taken by washing the fallopian tubes or horns of uterus.The total RNA was isolated from embryos of each stage respectively, and mRNA expression of BDNF and TrkB were detected by real time RT-PCR; the expression and distribution of BDNF and TrkB protein in blastocyst was performed by immunocytochemical staining;2cell embryos were collected and cultured with different concentration of BDNF, and the embryo development was observed;2cell embryos were collected and cultured in the medium with BDNF with or without a pan-specific Trkreceptor inhibitor, k252a or k252b, and the embryo development was observed;2cell embryos were collected and cultured with different concentration of k252a or k252b, and the embryo development was observed. The numbers of inner cell mass and trophectoderm cells inblastocystswere counted by the differential labeling technique using twopolynucleotide-specific fluorochromes. K252a or k252b was administrated four times (10μg×4) at72,76,84and88hafter hCG injection, which was correspondence to the development of morula to theblastocyst stages.The number of embryosthat developed to the expanded blastocyst stage and the number of cells in blastocyst was counted. At day14of pregnancy, the embryos that were implanted in uterus and the embryo development was observed.Results:Both BDNF and TrkB were expressed in all stage of preimplantation embryos. Treatment with BDNF promoted thedevelopment of two-cell-stage embryos into blastocysts. The blastocyst formation and hatching rate, as well as the total cell number in the blastocyst were increased, especially in the group of10ng/ml BDNF through the whole progress. The effects of BDNF wereblocked by the Trk receptor inhibitor, K252a. The Trk receptor inhibitor significantly inhibited the formation of blastocysts and the hatching of blastocyst in a dose-dependent manner. In vivoexperiments further demonstrated that K252a treatment suppressed early embryo development by inhibiting blastocyst cell numbers. Conclusions:BDNF/TrkB signaling system plays an important role during the development of preimplantation embryos and implantation process in mice by autocrine and paracrine roles.