Biochemical Characterization of Normal Navicular Bone Flexor Surface Cartilage

Cartilage tissue specimens were obtained from the flexor surface of the navicular bone and distal radiocarpal bone articular surface (controls) from 8 horses 2 to 5 years old. Water, DNA, total collagen, total glycosaminoglycans, chondroitin sulphate, and keratan sulphate contents were determined. The results from each site were compared and the differences were analyzed by paired t-test (P < 0.05).

Significant differences were determined between the water content of the navicular bone flexor surface cartilage (68.32± 3.46 % ) and the distal radiocarpal bone articular surface cartilage (60.60± 4.09%). The total DNA content, total glycosaminoglycan content, total chondroitin sulphate content, and total keratan sulphate for the flexor surface of the navicular bone was: 524.51± 92.89 ng, 0.1533± 0.0338 mg, 0.1018± 0.0197 mg 0.0800± 0.0176 mg, and 0.0092± 0.0037 mg per mg of dry weight cartilage, respectively. The total DNA content, total glycosaminoglycan content, total chondroitin sulphate content, and total keratan sulphate for the distal radiocarpal articular surface cartilage was: 508.80± 70.16 ng, 0.1686± 0.00838 mg, 0.0919± 0.0191, 0.0615± 0.0109 mg, and 0.0074± 0.0029 mg per mg dry weight cartilage, respectively. Not significant differences were determined between these values.

We concluded that the cartilage of the flexor surface of the navicular bone is biochemically similar to hyaline articular cartilage, but differs from previous descriptions of fibrocartilage. Further studies are needed to determine types and proportions of collagen types of the flexor surface of the normal navicular bone. These findings establish a basis of comparison to assess navicular cartilage in aging, disease, and repair.