What Happens in an In Vitro Fertilization Procedure?

In Vitro Fertilization or external fertilization refers to the technology of mammalian sperm and eggs to complete the fertilization process in an artificially controlled environment in vitro, referred to as IVF in English. Because it is inseparable from embryo transfer technology (ET), it is also called IVF-ET for short. In biology, an animal obtained by transferring an in vitro fertilized embryo to a mother is called a test-tube animal. This technology succeeded in the 1950s and has developed rapidly in the last 20 years. It has become increasingly mature and has become an important and conventional animal breeding biotechnology.

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In Vitro Fertilization or external fertilization refers to mammalian

In vitro fertilized organisms include fish and amphibians, which means that sperm and eggs

From the early 1960s to the mid-1980s, people used rabbits, mice, and rats as experimental materials.

After the mid-1980s, the IVF technology of cattle, represented by cattle, developed rapidly. In 1987, Parrish et al. Treated the frozen semen of cattle with a heparin-containing medium, and then matured with in vitro matured semen.

Cattle in vitro fertilization technology is not only applied to livestock production, but also has

Status of IVF development

After nearly 20 years of development, in vitro fertilization of livestock has made great progress. Among them, the IVF level of cattle is the highest, and the cleavage rate of incubated oocytes (that is, into mature culture) is 80% to 90%. Seven days after fertilization, The development rate of blastocysts is 40% to 50%, the blastocysts continue to grow at 80% after cryogenic freezing, and the calving rate after transplantation is 30% to 40%. On average, 10 A-grade oocytes can be obtained per ovary. Right and left, 3 to 4 blastocysts can be obtained by in vitro fertilization, and 1 to 2 calves are born after transplantation.

Problems with IVF

Blastocyst development rate is low, the number of cells is small. Developmental blocking of IVF eggs during culture

block), which means that the embryo stops developing and degenerates after it reaches a certain stage. Bovine embryo blockage occurs at the 8-16 cell stage, which results in a blastocyst development rate of in vitro fertilized eggs that is much lower than in vivo fertilization. In addition, compared with in vitro fertilized blastocysts, the total number of cells and the number of inner cell mass cells of in vitro fertilized blastocysts were significantly reduced.

The calving rate is low and the fetal weight is high. After in vitro fertilization of livestock, especially bovine IVF embryos, the calving rate is 15% to 20% lower than that of in vivo fertilization. However, the fetal birth weight is 3 to 4kg higher than that of in vitro fertilized offspring, which results in a high rate of dystocia for recipient mothers.

Development of IVF

In-depth study of the molecular mechanism of oocyte maturation and embryonic development

We don't know enough about the molecular mechanisms of egg development and embryo development. The premise of greatly improving the efficiency of IVF is to find out the molecular regulatory mechanism of oocyte and early embryo development, and then use this theory as a guide to study the ideal culture system to promote stable and orderly expression of the embryo's genome.

Strengthen the research of pre-cavity follicular culture and use the genetic resources of excellent female animals. The current IVF technology uses less than one thousandth of the total oocytes on livestock ovaries. For this reason, on the one hand, the technique of egg retrieval in vivo is improved, and on the other hand, in vitro maturation techniques of preantral follicles and small follicles need to be studied. In order to ensure a stable source of oocytes and conservation of breeding females or endangered animals, the research on the cryopreservation technology of follicles and oocytes must also be strengthened.

(3) Strengthen the combination of in vitro fertilization and other biotechnology. In vitro fertilization is inextricably linked to transgene, cloning, sex control, and embryonic stem cell culture. In vitro fertilization can provide a sufficient source of embryos for the introduction of foreign genes; provide a culture system for mature oocytes and cloned embryos for cloning technology; use in vitro fertilization of isolated X and Y sperm and eggs to sex the mammal control. Similarly, the isolation of embryonic stem cells also requires IVF technology to provide embryos and culture systems. The comprehensive development of these biotechnology will have a significant impact on human life.