Molecular aspects of tibial dyschondoplasia in the chicken: I. Expression of calbindin-D 28k gene

Abstract

Avian tibial dyschondroplasia (TD) is a skeletal disorder characterized by a cartilage plug in the proximal metaphysis of the tibiotarsus. Experiments were carried out to investigate whether the expression of calbindin-D 28k gene is altered in this disease or in the presence of vitamin D metabolites. The intestinal mRNA levels for calbindin-D 28k in normal and TD chicks were determined by northern blot analysis, and the distribution of calbindin-D 28k in the normal growth plate (LTD) and tibial dyschondroplastic cartilage of chicks were examined immunocytochemically. There were no differences in the intestinal calbindin-D 28k mRNA levels between LTD and TD chicks fed diets sufficient in vitamin D 3. However, reduced calbindin-D 28k mRNA levels were found in TD chicks fed a diet supplemented with 10 μg/kg 1,25 (OH) 2D 3 as compared to LTD chicks. Calbindin-D 28k was distributed throughout the growth plate, but concentrated in the hypertrophic zones. Depletion of vitamin D resulted in the absence of calbindin-D 28k in rachitic growth plates. These findings suggest that calbindin-D 28k is vitamin D dependent in this tissue. This protein was also found to be present in the TD- associated epiphyseal growth plate, but appeared to be less intensely concentrated than that in LTD growth plate. The proximal part of the dyschondroplastic cartilage was lightly stained, and no evidence of calbindin was found in the middle and distal parts of the lesion. These results suggest that decreased calbindin-D 28k gene expression is observed in the TD lesion.