脑源性神经营养因子在着床前小鼠胚胎中的表达及其对胚胎发育的影响

Expression of brain-derived neurotrophic factor in preimplantation embryo and its effect on the embryo development

目的检测脑源性神经营养因子（BDNF）及其受体TrkB在植入前胚胎中的表达情况,探讨BDNF对小鼠早期胚胎发育和着床过程中的作用。方法收集小鼠受精后1～4d的胚胎,利用免疫组化和逆转录聚合酶链反应（RT-PCR）检测BDNF及其受体TrkB在各阶段胚胎中的表达情况。将2细胞阶段的胚胎放入添加不同浓度的BDNF的培养基中,添加或不添加TrkB受体阻断剂k252a/k252b,观察胚胎发育情况,并对形成的囊胚进行细胞计数。在注射人绒毛膜促性腺激素（HCG）后72h、76h、84h和88h分别腹腔注射10μg K252a/k252b,收集胚胎,计算扩张期囊胚数和囊胚细胞数。结果 BDNF及TrkB均表达于小鼠植入前各阶段的胚胎中,在培养基中添加BDNF后能够促进小鼠胚胎的体外发育,能够提高囊胚形成率和囊胚孵化率,并能够提高滋养层细胞数,此作用能够通过TrkB受体阻断剂k252a而阻断。体内研究进一步证实,k252a处理后能够抑制囊胚细胞数而明显抑制早期胚胎发育。结论 BDNF/TrkB信号系统可能通过某种自分泌或旁分泌的作用方式促进植入前胚胎的发育,同时也可能参与胚胎的着床过程。

Objective. To investigate the expression and distribution of brain-derived neurotrophic factor（BDNF） in preimplantation embryos and explore the effect of BDNF in early embryo development. Methods. The expression of BDNF and tyrosine kinase receptor B（TrkB）was detected by RT-PCR and immunocytochemical staining. Two-cell embryos were collected and cultured in the medium with different concentration of BDNF, and with or without a pan-specific Trk receptor inhibitor, k252a or k252b. Then the embryo development was observed,and the numbers of inner cell mass and trophectoderm cells in blastoeysts were counted. K252a or k252b was administrated four times（10 μg×4）at 72,76,84 and 88 hours after HCG injection. The numbers of embryos developed to the expanded blastocyst stage and the cells in blastocyst were counted. Results： Both BDNF and TrkB were expressed in all stage of preimplantation embryos. Treatment with BDNF promoted the development of two-cell-stage embryos into blastocysts in vitro, increased the blastocyst formation rate and hatching rate,and the total number of trophectoderm cells. And the effects could be blocked by the Trk receptor inhibitor, K252a. K252a could also suppress early embryo development by inhibiting blastocyst cell numbers in in vivo experiments. Conclusions： BDNF/TrkB signaling system plays an important role during the development of pre- implantation embryos and implantation process in mice by autocrine and paracrine regulation.