1. What are the cumulus cells and what is their function?
2. What is the difference between "culture" and "Co-Culture"?
3. What is CAT (Cumulus-aided Embryo Transfer)
4. What are the different cells that can be used for co-culture?
5. Why is cumulus co-culture better than the other techniques of co-culture?

1.  What are the cumulus cells and what is their function?

Cumulus cells surround the oocyte (egg) during maturation of the egg in the women’s ovary. They continue to surround the egg at the time of ovulation. They are embedded in a matrix, which contains hyaluronic acid. Cumulus cells nurture the egg prior to and after ovulation.

2. What is the difference between "culture" and "Co-Culture"?

In IVF, the term "culture" means to grow or incubate embryos in a defined nutrient medium. In the technique of "Co-Culture", embryos are grown in a culture medium on top of a proliferating monolayer of cells called "Feeder" or "Helper" cells. The feeder cells assist in the growth and development of the embryo.

3.  What is CAT (Cumulus-aided Embryo Transfer)

When a few of the feeder cells on which the embryo is being cultured are transferred along with the embryo into the uterus, the technique is referred to as cumulus-aided embryo transfer. At Jaslok Hospital, we use the patient's own cumulus cells as the feeder layer over which her embryos are cultured. These cumulus cells are rich in growth factors such as Insulin-like Growth Factor and Vascular Endothelial Growth Factor. These ensure the proper growth of the developing embryos. In order to improve the technique we go a step further. At the time of embryo transfer we add 30 microlitres of the cumulus cells to the embryos so that the nutrients continued to be provided in vivo thereby enhancing the pregnancy rates.

4.  What are the different cells that can be used for co-culture?

In IVF, various cell types have been used for co-culture of human embryos in an attempt to improve embryo quality, implantation and pregnancy rates.

Fallopian tube cells from human or animal origin.

Endometrial cells from the lining of the uterus.

Vero cells which are derived from the African Green Monkey

Human cumulus cells

5.  Why is cumulus co-culture better than the other techniques of co-culture?

We have developed a co-culture system which uses the patient's own cumulus cells. These would otherwise have been discarded. We remove them from the oocyte and make them into a layer of feeder cells for the embryos to develop on. When non-human cells are used for co-culture, there is a possibility of disease transmission to the embryo and the mother from contaminants such as bacteria and viruses contained within the feeder cells. Since the use of patient's own cumulus cells overcomes this problem and are more easily available unlike other cells like tubal or uterine cells they are ideal for use as feeder cells in a co-culture system.