title: Femoral epiphyseal cartilage matrix changes at predilection sites of equine osteochondrosis: Quantitative MRI, second-harmonic microscopy, and histological findings.
abstract: Osteochondrosis is an ischemic chondronecrosis of epiphyseal growth cartilage that results in focal failure of endochondral ossification and osteochondritis dissecans at specific sites in the epiphyses of humans and animals, including horses. The upstream events leading to the focal ischemia remain unknown. The epiphyseal growth cartilage matrix is composed of proteoglycan and collagen macromolecules and encases its vascular tree in canals. The matrix undergoes major dynamic changes in early life that could weaken it biomechanically and predispose it to focal trauma and vascular failure. Subregions in neonatal foal femoral epiphyses (n = 10 osteochondrosis predisposed; n = 6 control) were assessed for proteoglycan and collagen structure/content employing 3T quantitative MRI (3T qMRI: T1ρ and T2 maps). Site-matched validations were made with histology, immunohistochemistry, and second-harmonic microscopy. Growth cartilage T1ρ and T2 relaxation times were significantly increased (p < 0.002) within the proximal third of the trochlea, a site predisposed to osteochondrosis, when compared with other regions. However, this was observed in both control and osteochondrosis predisposed specimens. Microscopic evaluation of this region revealed an expansive area with low proteoglycan content and a hypertrophic-like appearance on second-harmonic microscopy. We speculate that this matrix structure and composition, though physiological, may weaken the epiphyseal growth cartilage biomechanically in focal regions and could enhance the risk of vascular failure with trauma leading to osteochondrosis. However, additional investigations are now required to confirm this. 3T qMRI will be useful for future non-invasive longitudinal studies to track the osteochondrosis disease trajectory in animals and humans. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1743-1752, 2016.
authors.affiliation: Comparative Orthopaedic Research Laboratory, Faculté de médecine vétérinaire, Université de Montréal, Québec, Canada.
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Martel
authors.affiliation: INRS-EMT, Université du Québec, Québec, Canada.
authors.forename: Charles-André
authors.initials: CA
authors.lastname: Couture
authors.affiliation: MR Clinical Science, Philips Healthcare, Markham, Ontario, Canada.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Gilbert
authors.affiliation: INRS-EMT, Université du Québec, Québec, Canada.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bancelin
authors.affiliation: Comparative Orthopaedic Research Laboratory, Faculté de médecine vétérinaire, Université de Montréal, Québec, Canada.
authors.forename: Hélène
authors.initials: H
authors.lastname: Richard
authors.affiliation: Department of Radiology, Centre Hospitalier de l'Université de Montréal, Hôpital Notre-Dame, Montréal, Québec, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Moser
authors.affiliation: Department of Radiology, Centre Hospitalier de l'Université de Montréal, Hôpital Notre-Dame, Montréal, Québec, Canada.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Kiss
authors.affiliation: INRS-EMT, Université du Québec, Québec, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Légaré
authors.affiliation: Comparative Orthopaedic Research Laboratory, Faculté de médecine vétérinaire, Université de Montréal, Québec, Canada. sheila.laverty@umontreal.ca.
authors.forename: Sheila
authors.initials: S
authors.lastname: Laverty
mesh_terms: D000818:Animals; D024043:Collagen Type II / Q000378:metabolism; D005260:Female; D005269:Femur; D006132:Growth Plate / Q000378:metabolism / Q000473:pathology*; D006736:Horses; D008279:Magnetic Resonance Imaging; D008297:Male; D055034:Osteochondrosis / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D011509:Proteoglycans / Q000378:metabolism
chemical_list: D024043:Collagen Type II; D011509:Proteoglycans
keywords: collagen; epiphyseal growth cartilage; osteochondrosis; proteoglycan; quantitative MRI