Toyokawa K, Harayama H, Miyake M
Department of Life Science, Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Hyogo, Japan.
Theriogenology. 2005 Jul 15;64(2):378-92. doi: 10.1016/j.theriogenology.2004.12.005. Epub 2005 Jan 11.
Exogenous hyaluronic acid (HA) has been reported to improve early embryo development in vitro in pigs and cows. Although early embryo development in vitro is improved by exogenous HA, the mechanism mediating the action of HA is not clearly defined. In the present study, two possible HA actions on early embryo development were proposed to understand interactions between HA and the embryos using porcine parthenotes. We hypothesized that improvement of early embryo development mediated by HA would be caused by embryo-derived growth factors due to the high molecular weight of HA or cellular response through its receptor (CD44). We examined the effects of HA molecular weight on parthenogenetic embryo development, permeability of HA into the zona pellucida, expression of CD44 in porcine parthenotes at various stages, and blocking interactions between HA and CD44 by monoclonal anti-CD44 antibody (mCD44Ab). As a result, although development of porcine parthenotes to the blastocyst stage was significantly enhanced by exogenous HA with various molecular weights, there was no difference in blastocyst formation among the various molecular weights (P < 0.05). Immunofluorescence revealed that exogenous HA was accessible to CD44 through the zona pellucida, irrespective of the oocyte activation and that CD44 was also expressed in both oocytes and parthenotes at all developmental stages. In addition, development of parthenotes was partially blocked by mCD44Ab. In conclusion, we demonstrated that exogenous HA enhanced development of porcine parthenotes in vitro. This improvement mediated by exogenous HA on parthenogenetic embryo development was possibly caused by cellular response via CD44.
据报道，外源性透明质酸（HA）可改善猪和牛体外早期胚胎发育。尽管外源性HA可改善体外早期胚胎发育，但其介导HA作用的机制尚不清楚。在本研究中，提出了HA对早期胚胎发育的两种可能作用，以利用猪孤雌胚胎了解HA与胚胎之间的相互作用。我们假设，HA介导的早期胚胎发育改善是由于HA的高分子量导致胚胎衍生生长因子引起的，或者是通过其受体（CD44）引起的细胞反应。我们研究了HA分子量对孤雌胚胎发育的影响、HA进入透明带的通透性、不同阶段猪孤雌胚胎中CD44的表达，以及通过单克隆抗CD44抗体（mCD44Ab）阻断HA与CD44之间的相互作用。结果，尽管不同分子量的外源性HA均显著提高了猪孤雌胚胎发育至囊胚阶段的比例，但不同分子量之间的囊胚形成率并无差异（P<0.05）。免疫荧光显示，无论卵母细胞激活情况如何，外源性HA均可通过透明带与CD44结合，并且CD44在所有发育阶段的卵母细胞和孤雌胚胎中均有表达。此外，mCD44Ab部分阻断了孤雌胚胎的发育。总之，我们证明了外源性HA可增强猪孤雌胚胎的体外发育。外源性HA介导的孤雌胚胎发育改善可能是通过CD44引起的细胞反应所致。
