Acquisition of developmental competence and <i>in vitro</i> growth culture of bovine oocytes

Abstract

Recently, the demand of transferable embryos in cattle industry is increasing, and the number of embryos produced in vitro is also increasing in the world. Although oocytes are collected from individual elite cattle by ovum-pick up (OPU) and used for in vitro production (IVP) of embryos, the cattle are mono-ovulatory animal. It means that most of oocytes collected from ovaries are destined to degenerate. To improve the IVP efficiency, we should predict the developmental competence of oocytes correctly and culture them by the suitable way. In addition, in vitro production of bovine oocytes by in vitro growth (IVG) culture system will become a candidate of supply source of oocytes for IVP. If we can produce high competent oocytes by IVG, IVP efficiency will be improved and the genetic improvement of cattle will be dramatically accelerated. In the review, I introduce our researches related to oocyte morphology, the developmental competence, and the production of oocytes having high developmental competence by IVG culture.

Oocyte Selection for <em>in vitro</em> embryo Production in Bovine Species: Non-Invasive Approaches for the New Challenges of Oocyte Competence

“…Taken together, and as stated by the review of Nagano and colleagues [69], a dark ooplasm indicates an accumulation of lipids and good developmental potential, light-colored ooplasm indicates a deficiency of lipid stores and poor developmental potential, and black ooplasm indicates aging and low developmental potential ( Figure 2). Finally, the use of NIC and CARS should be further investigated as a potential non-invasive tool to evaluate the lipid content of single oocytes in livestock species.…”

“…Moreover, brown oocytes with dark edge or with dark spots showed under electron microscopy an organelle arrangement similar to in vivo matured oocytes, and pale or black oocytes appeared to be degenerating and/or aging [67]. The authors concluded that a dark ooplasm is associated with a lipid accumulation and better developmental competence, while a pale ooplasm would indicate fewer amount of organelles and poor developmental potential [69]. Interestingly, a study by Prates et al [70] distinguished fat areas of different color shades using the Nomarski interference differential contrast (NIC) as the fat gray value of porcine oocytes, reflecting alterations in lipid content, and proposing this tool as an appropriate and non-invasive technique to evaluate the lipid content of a single oocyte before or after in vitro maturation.…”

Oocyte Selection for in Vitro Embryo Production in Livestock Species: Non-Invasive Approaches for the New Challenges of Oocyte Competence

“…Taken together, and as stated by the review of Nagano and colleagues [66], a dark ooplasm indicates an accumulation of lipids and good developmental potential, light-colored ooplasm indicates a low density of organelles and poor developmental potential, and black ooplasm indicates aging and low developmental potential. Finally, the use of NIC should be further investigated as a potential non-invasive tool to evaluate the lipid content of single oocytes in other livestock species.…”

MALDI-TOF Mass Spectrometry Revealed Significant Lipid Variations in Follicular Fluid and Somatic Follicular Cells but Not in Enclosed Oocytes between the Large Dominant and Small Subordinate Follicles in Bovine Ovary

“…In bovine reproductive biotechnologies, the oocytes from the large potentially dominant follicles (LFs, >8 mm) are more competent for in vitro embryo development than the oocytes from the smaller ones (<6 mm) [ 23 , 24 ], although the oocytes themselves have similar size. However, accumulation of lipids in the oocytes correlates with their competence to in vitro embryo development [ 25 , 26 ]. In cows, lipid composition of COC environment affected oocyte quality, in vitro and in vivo [ 27 , 28 , 29 ].…”