Biochemical analysis of normal articular cartilage in horses.

The study conducts a biochemical analysis of normal articular cartilage from horses’ radiocarpal bones, assessing the collagen content, specifically types-I and -II, and other components like galactosamine, glucosamine, and glycosaminoglycan content.

Methods

• The analysis involved studying samples of articular cartilage from the radiocarpal bones of 24 horses aged between 2 and 5 years.
• The total collagen content was determined based on the 4-hydroxyproline content, using a colorimetric method.
• A spectrophotometric method was used to estimate the proportions of types-I and -II collagen. This was done by measuring the densities of specific cyanogen bromide peptide bands from mixtures of these collagen types on sodium dodecyl sulfate-polyacrylamide gels.
• The unique signature peptides of both collagen types were identified for comparison and the peptide ratios were computed for standards of type-I and -II mixtures. A standard curve was derived from the correlation between these ratios and the amounts of type-II collagen in standard mixtures.
• The content of galactosamine and glucosamine (hexosamines) were measured by ion chromatography. From these measurements, additional variables such as galactosamine-to-glucosamine ratio, chondroitin sulfate and keratan sulfate values, and total glycosaminoglycan content were derived.

Results and Interpretation

• The average total collagen content was found to be 556 mg/g (55.6 mg/100 mg) of tissue (dry weight).
• Type-II collagen was identified as the majority collagen type in normal articular cartilage specimens.
• An interesting observation was made where the ratio of the alpha 1 (II)CB10 peak area to the area under the alpha 1 (I) CB7,8 + alpha 1(II)CB11 peak was found to be a second-order polynomial function of the proportion of type-II collagen.
• Galactosamine and glucosamine content averaged 20.6 mg/g and 7.9 mg/g (dry weight), respectively, with a mean ratio of galactosamine to glucosamine being 3.74 +/- 0.62.

This study provided valuable data by systematically quantifying the fundamental biochemical components of horse articular cartilage which could be beneficial in understanding cartilage health and pathology in these animals.