Linher Katja, Wu De, Li Julang
Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada.
Endocrinology. 2007 Sep;148(9):4292-301. doi: 10.1210/en.2007-0021. Epub 2007 May 31.
The success of early embryonic development depends on oocyte nuclear and cytoplasmic maturation. We have investigated whether glial cell line-derived neurotrophic factor (GDNF) affects the in vitro maturation (IVM) of porcine oocytes and their subsequent ability to sustain preimplantation embryo development. GDNF and both its coreceptors, GDNF family receptor alpha-1 (GFR alpha-1) and the rearranged during transformation (RET) receptor, were expressed in oocytes and their surrounding cumulus cells derived from small and large follicles. When included in IVM medium, GDNF significantly enhanced cumulus cell expansion of both small and large cumulus-oocyte complexes and increased the percentage of small follicle-derived oocytes maturing to the metaphase II stage, although nuclear maturation of large oocytes was not significantly affected. Examination of cyclin B1 protein expression as a measure of cytoplasmic maturation revealed that in the presence of GDNF, cyclin B1 levels were significantly increased in large follicle-derived oocytes, as well as in oocytes from small follicles to a level comparable to the untreated large group. After activation, a significantly higher percentage of both small and large oocytes that were matured in the presence of GDNF developed to the blastocyst stage compared with untreated controls. Indeed, GDNF enhanced the blastocyst rate of small oocytes to levels comparable to those obtained for large oocytes matured without GDNF. The effect of GDNF was specific; this was evident because its enhancement of nuclear maturation and embryo developmental potential was blocked by an antibody against GFR alpha-1. Our study provides the first functional evidence that GDNF affects oocyte maturation and preimplantation embryo developmental competence in a follicular stage-dependent manner. This finding may provide insights for improving the formulation of IVM culture systems, especially for oocytes from small follicles.
早期胚胎发育的成功取决于卵母细胞核成熟和细胞质成熟。我们研究了胶质细胞源性神经营养因子（GDNF）是否影响猪卵母细胞的体外成熟（IVM）及其随后维持植入前胚胎发育的能力。GDNF及其两种共受体，即GDNF家族受体α-1（GFRα-1）和转化过程中重排（RET）受体，在来自小卵泡和大卵泡的卵母细胞及其周围的卵丘细胞中均有表达。当添加到IVM培养基中时，GDNF显著增强了小卵丘-卵母细胞复合体和大卵丘-卵母细胞复合体的卵丘细胞扩展，并增加了来自小卵泡的卵母细胞成熟到中期II期的百分比，尽管大卵母细胞的核成熟没有受到显著影响。作为细胞质成熟指标的细胞周期蛋白B1蛋白表达检测显示，在GDNF存在的情况下，大卵泡来源的卵母细胞以及小卵泡来源的卵母细胞中的细胞周期蛋白B1水平显著升高，达到与未处理的大卵泡组相当的水平。激活后，与未处理的对照组相比，在GDNF存在下成熟的小卵母细胞和大卵母细胞发育到囊胚阶段的百分比显著更高。事实上，GDNF将小卵母细胞的囊胚率提高到了与未添加GDNF成熟的大卵母细胞相当的水平。GDNF的作用是特异性的；这很明显，因为其对核成熟和胚胎发育潜能的增强被抗GFRα-1抗体阻断。我们的研究提供了首个功能性证据，表明GDNF以卵泡阶段依赖的方式影响卵母细胞成熟和植入前胚胎发育能力。这一发现可能为改进IVM培养系统的配方提供见解，尤其是对于来自小卵泡的卵母细胞。
