TLDR PAI-2 helps in the maturation and protection of hair and nail cells.
The study investigated the localization of Plasminogen Activator Inhibitor Type 2 (PAI-2) in hair follicles and nails, revealing its role in terminal differentiation and protection against programmed cell death. PAI-2 was found in differentiating cells of the outer root sheath and medulla during the anagen phase, in the permanent portion of the catagen follicle, and in postmitotic cells adjacent to the club hair during telogen. In nails, PAI-2 was detected in the matrix and nail bed. The consistent presence of PAI-2 in maturing cells before terminal keratinization suggested it could serve as a differentiation marker and protect epithelial cells from premature cell death.
55 citations,
May 1995 in “The journal of investigative dermatology/Journal of investigative dermatology” 
130 citations,
January 1994 in “Differentiation” Mouse hair follicle cells briefly grow during the early hair growth phase, showing that these cells are important for starting the hair cycle.
521 citations,
January 1954 in “Physiological Reviews” Hair growth is cyclic and influenced mainly by local factors.
107 citations,
September 2002 in “Journal of Investigative Dermatology” Researchers found that hair shedding happens mostly when new hair is growing and involves a unique process.
1 citations,
December 2011 Marine-derived ingredients show potential for hair health but need more human trials to confirm effectiveness.
11 citations,
August 2013 in “International Journal of Cosmetic Science” The study suggests that a new protease inhibitor can make hair harder to pull out, potentially reducing hair loss.
81 citations,
April 2009 in “Journal of Investigative Dermatology” Hair shedding is an active process that could be targeted to treat hair loss.
2 citations,
February 2023 in “BMC women's health” Birth control pills change the activity of certain inflammation and blood clotting genes in women with PCOS.
