Gene and protein expression of cartilage canal and osteochondral junction chondrocytes and full-thickness cartilage in early equine osteochondrosis.

This study investigates whether certain regulatory factors related to cartilage maturation are expressed differently in horses with early osteochondrosis (OC) compared to normal horses. The results indicate that in early OC, the pathways involving cartilage maturation and ossification display altered expressions of proteins and genes.

Study objective and hypothesis

• The main purpose of this research was to study the expression of several regulatory factors associated with cartilage maturation in horses suffering from early osteochondrosis (OC).
• The researchers hypothesized that the levels of Indian hedgehog (Ihh), parathyroid hormone-related peptide (PTH-rP), vascular endothelial growth factor (VEGF), platelet-derived growth factor-A (PDGF-A), and matrix metalloproteinase-13 and -3 (MMP-13, -3) might be increased in OC.

Methodology

• Articular cartilage and osteochondral samples were collected from the femoropatellar joints of seven horses with OC and eight normal young horses.
• These samples were snap frozen or preserved in paraformaldehyde for further analysis.
• Laser capture microdissection was utilized to isolate cells surrounding the cartilage canals and the osteochondral junction.
• The total RNA was extracted from the whole cartilage and laser-captured cells.
• The expression levels of the equine-specific genes and proteins Ihh, PTH-rP, VEGF, PDGF-A, MMP-13, and MMP-3 were evaluated using real-time (RT)-PCR and immunohistochemistry.

Findings

• The researchers observed a significant increase in PDGF-A and MMP-13 gene expression in chondrocytes close to cartilage canals in OC-affected horses.
• There was also a significant increase in PDGF-A gene expression in osteochondral junction chondrocytes of OC-affected horses.
• In the full-thickness cartilage samples, there was significantly increased Ihh, MMP-3, and MMP-13 gene expression in OC samples.
• PTH-rP protein expression was also significantly higher along the osteochondral junction.

Implications

• The results suggest that the process of cartilage maturation and ossification undergoes significant changes in early OC.
• These changes may play a role in the disease pathogenesis of OC in horses.
• The study provides insight into the molecular mechanisms that are potentially involved in early OC and could guide the development of therapeutic strategies for this condition.