Morphologic and biochemical study of sternal cartilage autografts for resurfacing induced osteochondral defects in horses.

This study explores the potential of using sternal cartilage autografts as a substitute for articular cartilage when treating osteochondral defects in horses, demonstrating through morphologic and biochemical analyses that the repair tissue in grafted defects closely resembles hyaline-like cartilage.

Research Implementation and Method

• Scientists undertook the study by using biodegradable pins to fix sternal cartilage autografts into osteochondral defects of the distal radial carpal bone in ten horses aged between 2 to 3 years. The defects, for the purposes of the experiment, measured 1 cm2 on the surface and were 4 mm in depth.
• In order to create a control group, corresponding defects in contralateral carpi (the opposite joint in the other forelimb) were induced but not grafted.
• The horses were confined for 7 weeks, with a daily 1-hour walk for an additional 9 weeks, before euthanization at 16 weeks.

Evaluation: Histologic and Biochemical Analyses

• The scientists analysed the repair tissue using histologic/histochemical (H&E and safranin-O fast green) examinations, which highlight and differentiate between different types of tissues in a sample. They also conducted biochemical analyses to determine the collagen (type-I and type-II) contents, measure total glycosaminoglycan content (an important component of cartilage), and calculate the galactosamine-to-glucosamine ratio.
• On the basis of these examinations, repair tissue in the grafted defects demonstrated a composition akin to hyaline-like cartilage. In contrast, the repair tissue in the non-grafted defects consisted of fibrocartilaginous tissue, with a surface layer of fibrous tissue.

Biochemical Analysis Results

• The researchers found that the repair tissue of grafted defects was predominantly composed of type-II collagen, a protein found in hyaline cartilage, while the repair tissue of non-grafted defects contained mostly type-I collagen.
• When observing glycosaminoglycan content, the repair tissue of grafted defects was found to be similar to that of normal articular cartilage. On the other hand, the total glycosaminoglycan content of the non-grafted defects was only 62% of that of normal articular cartilage.
• All repair tissues had a higher galactosamine-to-glucosamine ratio than that of normal articular cartilage, demonstrating differences in the extracellular matrix component of the repair tissue compared to normal cartilage.
• The researchers concluded that, given the positive results at 16 weeks post-grafting, sternal cartilage could potentially serve as a suitable substitute for articular cartilage in major osteochondral defects of horses.