In contrast to the abundant researchs as to the aging symptoms of skin, very little is known about those of nails, beyond the decline in the rate of growth and the appearance of vertical lines. However, many women want their nails to be kept in a healthy and fresh condition, as well as their skin, particularly facial skin. To satisfy this demand, it is necessary to understand various symptoms of nail which appear with aging and elucidate the mechanisms of the changes.
A study was conducted, therefore, in which the changes in nail caused by aging were investigated using SEM. The lipid content in nail was measured by GC, GC-MS, or HPLC, and the moisture content absorbed, the water holding capacity and the strength of nail were determined.
It was found that the nails of people over about ten years showed an increase in the desquamation of corneocytes on the nail surface, a reduction in the content of intercellular lipids such as cholesterol and cholesteryl sulfate, and a decrease in moisture absorption and water holding capacity. Nails in which the lipids was removed using acetone showed a decrease in strength against breaking. The structure and moisture absorption function of such nails were similar to those of aged nails. A correlation was also observed between the content of cholesterol in nail and the moisture absorption function.
From the above findings, it is shown that the decrease in the content of intercellular lipids affects the changes in the morphology and properties of nails seen with aging. Consequently, as in skin care, the healthy condition of nails is considered to be maintained by the supply of moisturizing substances, particularly intercellular lipids.
