Influence of vitamin D status on hyaluronan localization in bone

The distribution of hyaluronan was investigated in the proximal tibiotarsal bones of normal (vitamin D-treated) chicks, and chicks with rachitic lesions induced by vitamin D deficiency. Localization studies using a biotinylated hyaluronan-binding probe revealed that in vitamin D-treated chicks, a high level of hyaluronan staining was present in upper proliferative zone cartilage and upper hypertrophic zone cartilage. Hyaluronan staining was greatly reduced in the zone of provisional calcification. In the metaphyses and diaphyses of normal chicks hyaluronan was predominantly localized to the non-bone-forming surfaces of osteoblasts but was also present on the basolateral surfaces of lining cells and osteoclasts. Marked changes in hyaluronan distribution were observed in vitamin D-deficient chicks. The amount of hyaluronan present in proliferative zone growth cartilage was similar to control chicks, although with a more widespread distribution, extending into lower proliferative zone cartilage. In the zone of hypertrophy/calcification, biochemical analyses revealed that hyaluronan levels in rachitic chicks were about 3.6 times greater than in vitamin D-treated chicks; localization studies demonstrated that this increase was associated with the presence of hyaluronan-positive spindle-shaped cells in the metaphyseal vascular spaces. Intense hyaluronan staining was also associated with abundant spindle-shaped cells occupying the marrow spaces of rachitic diaphyseal bone. The distribution of hyaluronan in vitamin D-treated chick bone, and the alterations observed in rachitic tissue suggests a role for hyaluronan in endochondral bone formation.