Normalization of essential-fatty-acid-deficient keratinocytes requires palmitic acid

Cultured adult human keratinocytes show accelerated growth rates in medium that is essential fatty acid deficient. The cells also show decreased amounts of the essential fatty acids 18:2, 20:3, and 20:4 and contain increased amounts of the monounsaturated fatty acids 16:1 and 18:1. These lower levels of polyunsaturated fatty acids were only partially restored by supplementing the medium with 18:2 and 20:4 fatty acid. The addition of the non-essential fatty acid 16:0 (5 microM), along with the essential fatty acids, resulted in the successful normalization of the major fatty acids in the deficient keratinocytes. Normalized cells showed a constant total fatty acid/mg of protein in the phospholipid fraction, as the total cell fatty acid content per cell increased with augmenting fatty acid supplementation. Supplementation of the medium with 16:0 and essential fatty acids decreased the growth and passage potential of the cells. Use of 18:1 in lieu of 18:2 fatty acid yielded essential-fatty-acid-deficient keratinocyte growth values. Likewise the least supplemented medium (5 microM 18:2 + 5 microM 16:0) also gave the accelerated cell growth rates. This study shows that manipulation of the essential fatty acid levels, if accompanied by 5 microM 16:0 in the growth medium, alters the growth properties of adult human primary keratinocytes.