In a new study, researchers from the New York University Grossman School of Medicine revealed that they have found the mechanism for hair turning grey. They noted that this discovery can help in developing a treatment to alter cells to reverse or halt this process. The study revealed that as hair ages, stem cells become locked and lose their capacity to grow and keep hair colour.

The researchers focused on melanocyte stem cells, or McSCs, which are present in the skin, to better understand the process of hair greying. Melanocytes, or pigment-producing cells, are constantly decaying and renewing. New melanocytes are formed from stem cells, and it is these cells that researchers believe become "stuck" in limbo in people with grey hair.

Hair follicles, which are structures in the skin, create and grow hair. Melanocyte stem cells (McSCs) are responsible for the production of the protein pigments that give hair its colour. Dr. Mayumi Ito, a senior researcher on the study, stated that the loss of chameleon-like function in melanocyte stem cells was responsible for greying and loss of hair colour.

He noted that as hair ages, sheds, and then grows back repeatedly, increasing numbers of McSCs become trapped in the stem cell compartment known as the hair follicle bulge. These trapped McSCs fail to regenerate into pigment-producing cells, which results in hair thinning instead of maturing and returning to their original place.

Concerning hair greying, Dr. Sai Krishna Kotla, Consultant Dermatologist at Yashoda Hospitals in Hyderabad, stated that the underlying cause of this change in hair colour remains unknown, even though we associate it with the natural ageing process. 

(Source: https://indianexpress.com/article/lifestyle/life-style/grey-hair-cause-stuck-cells-scientists-8568711/ )