Scientists Transform Granulosa Cells into Functional Oocytes That Produced Healthy Offspring in Mice

Main image courtesy of Wikimedia Commons.

In the process of in-vitro fertilization, granulosa cells in follicles are discarded following egg retrieval. A recent study investigated their plasticity, and the potential they have to produce offspring. In this article, we’ll break this research down and answer the following questions:

• What are granulosa cells?
• How can granulosa cells produce healthy offspring?
• What future implications does this research have?

What Are Granulosa Cells?

Granulosa cells are structural units that surround the immature egg, termed the oocyte, during the development of the ovarian follicle. The layers of granulosa cells that surround the oocyte are crucial to the proper development of the follicle. However, studies have shown that aside from this function, granulosa cells demonstrate plasticity properties that give them the capability to act as stem cells. Stem cells are a type of cell that has the ability to develop into different cell types, meaning that granulosa cells could possibly differentiate into something else that is functional. During in-vitro fertilization, the layers of granulosa cells are disposed of once the egg is retrieved, and then tend to undergo cell death after this removal.

How Can Granulosa Cells Produce Healthy Offspring?

In a recent study, researchers decided to investigate what might happen if instead of getting rid of the granulosa cells in mice, they attempted to use their plasticity properties to turn them into oocytes. Because there are thousands of granulosa cells surrounding an egg, great benefits could result from recycling these cells into something useful for fertility. These researchers created a “chemical cocktail,” which essentially contained substances that would promote the proper growth of these cells rather than allowing them to differentiate or undergo cell death as usual. 

By utilizing Rock inhibitor, crotonic acid, and other smaller substances, the researchers allowed the granulosa cells to develop into germline-competent pluripotent stem cells that act similarly to embryonic stem cells. They used another chemical cocktail that included vitamin C to promote follicle development and meiosis, the process a cell undergoes to create sex cells. 

Once the cells were fertilized, the newly made oocytes were able to produce offspring that were healthy. These offspring showed no differences from naturally bred mice. 

What Future Implications Does This Research Have?

It is thought that this type of chemical treatment allows for higher controllability, which may minimize genetic instability risks. This study is the first instance of granulosa cells being turned into oocytes, but it is important to remember that it is in mice. In terms of applying this research to human embryology, the researchers believe that it may have more utility in preserving fertility rather than treating infertility.