High-resolution microscopy of osteochondral lesions in the distal tarsal joints of young icelandic horses

• Introduction: Distal tarsal joint osteoarthritis (OA) is a common cause of lameness in adult Icelandic horses1 and high-detail radiography and microscopic OA changes are reported in young Icelandic horses suggesting the disease starts when the horses are young and develops slowly2. Thus young Icelandic horses are potentially an excellent natural model for the early stages of osteoarthritis. This study describes and characterises novel mineralised and non-mineralised osteochondral lesion types in left distal tarsal region joint samples from twenty-two 29 to 31 month-old Icelandic horses. Materials and Methods: Combinations of confocal scanning light microscopy, backscattered electron scanning electron microscopy (including novel iodine staining methods) and three-dimensional microcomputed tomography were used on samples obtained with guidance from clinical computed tomography and magnetic resonance imaging equipment. Osteochondral lesion types were described and the frequency of lesion types calculated. Associations and correlations between osteochondral lesion types were investigated for centrodistal joints. Results: Lesion types were identified in hyaline articular cartilage (HAC), articular calcified cartilage (ACC), subchondral bone (SCB) and the joint margin tissues. The highest lesion frequency was in the centrodistal joint where several lesion types including HAC chondrocyte necrosis, HAC fibrillation, HAC central chondrocyte clusters, ACC arrest and ACC advancement had moderate to high frequency, significant associations and strong correlations. Joint margin lesions had high frequency in centrodistal and tarsometatarsal joints but no significant associations with other lesion types. The frequency of SCB lesions in all joints was low. Hypermineralised protrusions and cracks of the ACC were detected. Discussion/Conclusions: Our results provide detailed morphological information about how tissues respond during the early stages of OA and that these changes occur in HAC and ACC, rather than in the SCB. We speculate that chondrocyte death and chondrocyte hyperplasia in the HAC result in the ACC arrest and ACC advancement respectively. Thinning or loss of the ACC resulting from ACC arrest may have a key role in the development and perpetuation of OA since this likely results in areas in the ACC that allow increased transfer of substances between the SCB and the intra-articular compartments. Young Icelandic horses offer a promising model for the study of ACC behaviour in early OA, a morphological region that we believe is crucial in the early stages of OA development.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Ortopedi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Orthopaedics (hsv//eng)

Publikations- och innehållstyp

vet (ämneskategori)

kon (ämneskategori)