Embryo Culture in the laboratory has improved greatly in the last five years.
In the earlier, developmental days of in vitro fertilization, various types of media were used without a clear understanding of which essential ingredients were missing from the growth media. In addition, it was unknown as to which elements present in the media were actually detrimental to the early development of embryos. These factors contributed to the slow and incomplete development of the embryos grown in the laboratory at that time. Today, there is a more thorough understanding of the nutrient requirements of embryos in their early stages. Also, there is a more thorough understanding that quality embryo growth in the lab depends on the conditions present in the entire culture system.
The first improvement in embryo culture systems that increased the quality of embryos grown in the IVF lab and led to today’s more complete culture media was the use of a technique known as co-culture. This technique was introduced to human IVF labs in 1985. It involved the growth of human embryos in Petri dishes with a variety of other cell types in order to provide added elements to the simple culture media. It was not fully understood at the time if these cells were actually providing a set of missing ingredients or were simply removing some undesirable waste product of the embryos. Regardless, the outcome was that embryos were growing at a consistently faster rate with a resulting higher pregnancy rate. The more successful and, thus, more popular cell types used with human embryos at that time included fetal calf uterine cells, monkey cells, follicular cells and endometrial cells from the patient and the group culture of several embryos within the same drop of simple media.
The current improvements in culture media used in ivf came as a result of the work of several researchers who analyzed the composition of tissue fluids from the female reproductive tract. They found significant differences in the energy sources available to embryos in the fallopian tubes from those energy sources available to them in the uterus. These differences that they noted in available nutrients in the reproductive tract led to another observation; how animal embryos developed faster and more completely in the lab if the media composition in which they grew changed to more closely resemble what they would be growing in while the fallopian tube and then, in the uterus.
The success of experiments in the growth of animal embryos led to the development of sequential culture media for human embryos. Sequential media are manufactured now by companies that concentrate on the needs for human embryos in all of their stages of growth while they are in the laboratory environment. These sequential media attempt to mimic the changing environment and needs that the human embryo experiences while developing in the fallopian tubes and in the uterus. Further, the use of an entire line of sequential media and their related products from a single manufacturer decreases the stress on embryos growing in a laboratory environment by keeping the pH and osmolarity more constant throughout their time in the laboratory.
In today’s IVF lab, the various elements necessary for successfully culturing human embryos are known as a culture system. This is because the use of each element is only successful if it is paired with other elements that complement the system as a whole. The culture system includes the sequential media, culture oil, the use of Petri dishes and the configuration of the media drops within them, the incubator environment, the environment experienced by the embryos while they are outside of the incubator and the air environment within the laboratory.