Differential distribution of cathepsins B and L in articular cartilage during skeletal development in the horse.

BACKGROUND

This study was designed to examine a new role for cysteine proteinases in the process of endochondral ossification.

OBJECTIVE

The aim of the present study was to investigate the presence and distribution of cathepsin B and cathepsin L in equine articular cartilage during development.

METHODS

Full-depth cartilage samples from a total of 40 horses (age range: 4 month fetuses to 2 years) were examined and enzymes detected by immunocytochemical localisation.

RESULTS

Observations on the presence of cathepsins B and L revealed significant age-related differences, resulting in clear division of the animals into 2 age groups: i) fetuses and neonates; ii) young growing horses (age 4 weeks to 2 years). Cathepsin B was not detected in cartilage from the majority of fetuses and neonates but was located characteristically in chondrocytes at the articular surface and hypertrophic zone in all growing horses. In contrast, cathepsin L was predominantly present in fetal and neonatal cartilage, located primarily in proliferating chondrocytes.

CONCLUSIONS

This study is the first to demonstrate differential and site-specific roles for cathepsin B and cathepsin L in skeletal development in the horse.

CONCLUSIONS

The demonstrated involvement of cathepsins B and L in endochondral ossification is of relevance to developmental orthopaedic diseases such as osteochondrosis in which there is a focal failure of bone formation.