Hyaluronic acid, cell-free synthesis

Scheme 18. Cell-Free Synthesis of Hyaluronic Acid.

A5. Altshuler, C. H., Kinsman, G., and Bareta, J., Connective tissue metabolism I. Hyaluronic acid synthesis by cell-free extracts of human tissues. Arch. Pathol. 75, 206-211 (1963). 

The function of hyaluronic acid was initially confined to the maintenance and sta-bihty of the ECM (96). However, the action of hyaluronic acid varies with its size, which determines its function in a cell-type specific manner (97-101). Hyaluronic acid represents more than 50% of the ECM in the skin. High molecular weight hyaluronic acid (>1,000 kDa) controls tissue water content, ECM lubrication, structural integrity, free oxygen radicals, and distribution of plasma proteins (96,100,101). The synthesis of hyaluronic acid is achieved by hyaluronan synthase-1 to -3 (102,103). The stability of hyaluronic acid varies with its microenvironment, as its half-life is less than 10 min in blood, up to 12 h in the skin, and extends to months in the vitreous gel of the eye (100,101). Hyaluronic acid is the only GAG with a function of its breakdown molecules, as small hyaluronic acid molecules and fragments stimulated the maturation of dentritic cells and the synthesis of proinflammatory IL-lp, IL-12, and TNF-a (103-105). The latter effect seems to be restricted to an interaction of hyaluronic acid fragments with the Toll-like receptor 4 (104,105). The observation that bacterial spreading in the... 

---