Development of Mongolian Gerbil Embryos in Chemically Defined Media: Effects of Osmolarity, Glucose and Phosphate

Special nutrition in mouse developmental oocytes

Investigation of nutrition-related proteins in mouse oocytes and zygotes is crucial for the development of an effective therapy for patients with infertility. Currently, we are concerned with the role of nutrition in the process of oocyte development in order to better reveal the relationship between nutrition and infertility. We collected mouse oocytes at three different developmental stages: germinal vesicle (GV) stage, metaphase II-arrested (MII) stage and fertilized oocytes (zygotes). Semi-quantitative mass spectrometry and GeneMapper software were used to analyze nutrition-related proteins in these oocytes. Various specific proteins were abundantly expressed in the mouse oocytes. These proteins included heat shock proteins and Ybx2. Additional proteins which exist in important meta bolism pathways also demonstrated differential expression among the three stages. We identified additional nutrition elements required for oocyte development and fertilization. The present study contributed to increased understanding of nutrition in the process of oocyte development, which may enhance the efficacy of therapy for patients with infertility.

Effect of relaxin and IGF-I on the pre-implantation development of Mongolian gerbil (Meriones unguiculatus) embryos in vitro

Purpose

Both relaxin and insulin-like growth factor (IGF) are members of the insulin super family. This study aimed to investigate the effect of relaxin and IGF-I on the pre-implantation of Mongolian gerbil of blastocyst development in vitro.

Methods

Blastocysts and eight-cell stage embryos were collected from female gerbils. Eight-cell embryos and blastocysts were cultured in mM16 medium supplemented with or without relaxin or IGF-I for 24 h. Blastocysts were counted for total, inner cell mass (ICM) and trophectoderm (TE) cell numbers, and assessed apoptosis incidence. In addition, to measure incorporation of ³H-methionine, blastocysts were cultured for 3 h with relaxin or IGF-I, washed with trichloroacetic acid and measured by liquid scintiration counter.

Results

Relaxin (200 ng/ml) increased total, TE and ICM cell numbers of blastocyst (P < 0.05) when it was compared with the control. IGF-I (150 ng/ml) also has influence on total and ICM cell numbers of blastocyst when compared with control. Apoptosis incidence was relatively low, and a significant difference was not observed between each group. The effect of relaxin on incorporation of ³H-methionine was higher than the control group (P < 0.05). Relaxin increased the developmental rate from the eight-cell stage to blastocyst (P < 0.05).

Conclusions

In conclusion, relaxin and IGF-I stimulated protein synthesis and increased cell numbers of blastocysts, promoting development of the gerbil embryo in vitro culture.

The beneficial effect of fructose and glucose on in vitro maturation and the fertilization of porcine oocytes

Purpose

This study was conducted to investigate the effects of supplementing fructose in the culture medium on in vitro maturation (IVM), in vitro fertilization (IVF), and metabolism of porcine oocytes.

Methods

Porcine oocytes were matured in vitro in modified North Carolina State University 37 medium (NCSU-37) and then supplemented with either glucose (5.5 mM), fructose (5.5 mM), or glucose (2.75 mM) plus fructose (2.75 mM). The maturation and fertilization of oocytes, and the incorporation and oxidation of ¹⁴C-glucose, ¹⁴C-fructose, and ¹⁴C-methionine in oocytes at different stages of development were examined.

Results

The supplementation of glucose plus fructose significantly promoted (P < 0.05) oocytes germinal vesicle break down (GVBD), maturation to metaphase II (MII), penetration by spermatozoa, and male pronuclear formation compared with glucose. The incorporation and oxidation of ¹⁴C-methionine into the oocyte significantly increased (P < 0.05) with glucose plus fructose supplementation than glucose. A significantly higher (P < 0.05) rate of incorporation and oxidation was achieved with ¹⁴C-fructose compared to ¹⁴C-glucose.

Conclusions

Glucose plus fructose supplementation improved maturation, penetration by spermatozoa, male pronuclear formation, and energy metabolism by porcine oocytes.

Mammalian embryo co-culture: Trials and tribulations of a misunderstood method

Embryo-somatic cell co-culture was devised over 40 years ago in an attempt to improve the development and viability of mammalian preimplantation embryos generated and cultured in vitro. While initial endeavours were successful in this respect, other studies soon highlighted a number of significant long-term detrimental impacts of this approach. Surprisingly little is known about the mechanisms underlying the beneficial effects of co-culture, although the production of embryotrophic compounds, modulation of nutrient profile, protection against culture-induced stress and/or toxin clearance are all contenders. The extent to which the inadvertent exposure of embryos to serum accounts for many of these effects remains open to question. Although the popularity of somatic cell co-culture has recently declined in favour of the use of sequential media due to concerns associated with its risk of disease transmission and long-term sequelae, we argue that complete dismissal of this technique is ill advised, given that our limited understanding of basic somatic cell interactions has prevented us from fully exploiting its potential. In this respect, there is some merit in focussing future research strategies based on reconstructed maternal tract tissue. Although the use of co-culture in clinical practice is unacceptable and its implementation in domestic species for commercial purposes should be viewed with diffidence, this technique can still provide a wealth of information on the development of novel, more physiological embryo in vitro culture systems. The proviso for acquiring such information is to gain a fuller understanding of the culture requirements/biochemistry of somatic cells and their interaction with the early conceptus.