Hyaluronic acid biological sources

Because of the great and continuing biological interest in the acid carbohydrates of connective tissue, there has been an intensive effort to locahze by histochemical methods the various carbohydrates that have been characterized by the chemical studies of Meyer and others (see Chapter XII). Although it is not yet settled completely whether hyaluronic acid is stainable by any of the customary methods, most workers have assumed it to be metachromatic with toluidine blue. Hyaluronidases (see Chapter XII) from various sources have been used (50), Much of the earlier work was done with impure preparations and needs verification. Bull-testis hyaluronidase can be obtained in concentrated form and has been most often used. As bull-testis hyaluronidase depolymerizes both hyaluronic acid and chondroitin sulfates of types A and C, metachromasia that is abolished by this enzyme has been considered due to one of these (114)-As the optimal conditions for the histochemical application of bull-testis hyaluronidase have not been systematically explored, technical directions vary greatly and need to be standardized. 

The term hyaluronan was introduced in 1986 to conform to the international nomenclature of polysaccharides and is attributed to Endre Balazs (Balazs E. A, et al., 1986), who coined it to encompass the different forms of the molecule can take, e.g., the acid form, hyaluronic acid, and the salts, such as sodium hyaluronate, which forms at physiological pH [10], HA was subsequently isolated from many other sources and the physicochemical stracture properties, and biological role of this polysaccharide were studied in numerous laboratories [11]. This work has been summarized in a Ciba Foundation Symposium [12] and a recent review [13]. 

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