Hyaluronan exists in the normal stratum corneum

Hyaluronan is well known to exist as a water-sorbed macromolecule in the ex tracellular matrix. We here examined whether hyaluronan exists in the norma l stratum corneum. High performance liquid chromatography was used to quant ify hyaluronan content in the stratum corneum, epidermis (including stratum corneum), and dermis of mice, with the resulting dry weights being 22.3 +/ - 2.9, 15.1 +/- 1.5, and 738.6 +/- 31.6 mu g per g, respectively. Normal mo use skin was then labeled with [H-3]-glucosamine in an organ culture, and a ccumulation of [H-3]-labeled hyaluronan and its molecular mass were determi ned separately for the stratum corneum, epidermis, and dermis. In the strat um corneum, [H-3]-labeled hyaluronan was accumulated linearly over the 3-d culture period. After the 3-d culture period, the epidermis synthesized twi ce the amount (expressed as dpm per mg dry weight) of [H-3]-labeled hyaluro nan as the dermis, whereas the stratum corneum and dermis showed nearly the same content of [H-3]-labeled hyaluronan. The molecular mass of [H-3]-labe led hyaluronan was highest (> 1.0 x 10(6)) in the dermis and clearly lower (< 6.0 x 10(4)) in the stratum corneum. Based on these results, we here con firm that hyaluronan is supplied from keratinocytes beneath the stratum cor neum layer, and is present in the normal stratum corneum. We speculate that hyaluronan may play a role in moisturizing the stratum corneum and/or regu lating its mechanical properties.