Oxidatire Breakdown of Hyaluronic and Chondroitin Sulphuric Acid

Clinical uses of hyaluronan

The availability of elastoviscous solutions of highly purified hyaluronan has created two new therapeutic methods in human and veterinary medicine: viscosurgery and viscosupplementation. Viscosurgical tools and implants are widely used in ophthalmology and have been suggested for use in otology. Visco-supplementation of joint fluid using elastoviscous hyaluronan solutions is widely used in the treatment of equine traumatic arthritis. It was also suggested for use in idiopathic osteoarthritis in humans, but this application has not received wide acceptance. Cross-linked forms of hyaluronan have been developed and given the generic name of hylans. Water-insoluble soft gels of hylans are ideally suitable as viscosurgical implants to prevent postoperative adhesions and to control scar formation. Hylan solutions are being used in arthroscopic viscosurgery. Hylan devices in various forms (gels, tubes, membranes) have been used in animal studies for matrix engineering, the purpose of which is to control and direct tissue regeneration and augmentation.

Inhibition of oxidative degradation of hyaluronic acid by uric acid

It has been postulated that glycosaminoglycans in the trabeculum have an influence on aqueous humor drainage. Ascorbate reduces the viscosity of hyaluronic acid, and also increases outflow facility. Our recent observation of high urate concentrations in some glaucomatous eyes led us to study the influence of urate on oxidative degradation of hyaluronic acid by ascorbate. The viscosity of rooster comb hyaluronic acid was reduced slowly by ascorbate. Cupric sulfate accelerated ascorbate oxidation and also enhanced hyaluronic acid degradation. Urate inhibited ascorbate oxidation and prevented the copper catalyzed oxidative degradation of rooster comb hyaluronic acid. The range of urate concentrations used in this study was within the range of urate concentrations observed in glaucomatous eyes. The partially purified umbilical cord hyaluronic acid had lower viscosity than rooster comb hyaluronic acid, and rapidly degraded in the presence of ascorbate. The ascorbate effect on umbilical cord hyaluronic acid was partially prevented by urate.

The molecular weight of hyaluronate in the aqueous humour and vitreous body of rabbit and cattle eyes

The molecular weight distribution of hyaluronate in the aqueous humour and vitreous body of rabbit and cattle has been determined by gel chromatography. The eluate from the column was monitored by a radioassay, whereby the molecular weight distribution of 15-20 microgram samples could be analysed. Control experiments were carried out with radioactively-labelled hyaluronate added to bovine material to estimate the degradation of the polymer during handling of the ocular fluids. It was shown that in vitro degradation does not appreciably affect the results. The analyses show a considerable polydispersity of the hyaluronate preparations. There is also a marked variation in the degree of polymerization between the two species. Hyaluronate from rabbit vitreous has a weight-average molecular weight (MW) of 2-3 X 10(6) while adult bovine vitreous displays a value of about 5-8 X 10(5). The hyaluronate of bovine vitreous varies with age. In newborn calf, a value of 3 X 10(6) was registered. This value dropped to about 5 X 10(5) in old cattle. The hyaluronate in the aqueous humour of rabbit showed a considerably higher molecular weight than that of the vitreous indicating that part of the hyaluronate in the anterior segment originates elsewhere than the vitreous. The differences between hyaluronate from the aqueous humour of adult cattle and that from the vitreous were more complex. As with the rabbit, a relatively large proportion of hyaluronate in the aqueous humour was of high-molecular weight, but, in contrast, the aqueous humour also contained material which had a lower degree of polymerization than the hyaluronate in the vitreous. The proportion of high-molecular weight material in bovine aqueous humour seemed to be lower in the summer than in the winter.

Pathways to the decisive extension of the human specific lifespan

Three approaches to reversal or removal of gerogenic aggregations of macromolecules have shown promise. Of these the enzyme approach is the most gentle, and can be made specific. Aside from this, the lower the molecular weight of an enzyme, the better chance it will have to be immunologically tolerated as well as replicated synthetically in whole or in part. The chelating approach provides a powerful means for removing a single class of unwanted, random crosslinkages, i.e., those due to extraneous polyvalent metals such as lead, cadmium and aluminum. The free hydroxyl radical approach is the most penetrant and most versatile means for removing otherwise insoluble aggregates, but its very lack of specificity will demand great foresight in control and use. Together, these three methods, when properly applied, might bring some principal objectives of gerontology within closer range.