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ObjectiveTo elucidate the role of decorin, a small leucine‐rich proteoglycan, in the degradation of cartilage matrix during the progression of post‐traumatic osteoarthritis (OA). MethodsThree‐month–old decorin‐null (Dcn−/−) and inducible decorin‐knockout (DcniKO) mice were subjected to surgical destabilization of the medial meniscus (DMM) to induce post‐traumaticOA. TheOAphenotype that resulted was evaluated by assessing joint morphology and sulfated glycosaminoglycan (sGAG) staining via histological analysis (n = 6 mice per group), surface collagen fibril nanostructure via scanning electron microscopy (n = 4 mice per group), tissue modulus via atomic force microscopy–nanoindentation (n = 5 or more mice per group) and subchondral bone structure via micro–computed tomography (n = 5 mice per group). Femoral head cartilage explants from wild‐type and Dcn−/−mice were stimulated with the inflammatory cytokine interleukin‐1β (IL‐1β) in vitro (n = 6 mice per group). The resulting chondrocyte response toIL‐1β and release ofsGAGs were quantified. ResultsIn both Dcn−/−and DcniKOmice, the absence of decorin resulted in acceleratedsGAGloss and formation of highly aligned collagen fibrils on the cartilage surface relative to the control (P< 0.05). Also, Dcn−/−mice developed more salient osteophytes, illustrating more severeOA. In cartilage explants treated withIL‐1β, loss of decorin did not alter the expression of either anabolic or catabolic genes. However, a greater proportion ofsGAGs was released to the media from Dcn−/−mouse explants, in both live and devitalized conditions (P< 0.05). ConclusionIn post‐traumaticOA, decorin delays the loss of fragmented aggrecan and fibrillation of cartilage surface, and thus, plays a protective role in ameliorating cartilage degeneration.
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Diversity of extracellular matrix morphology in vertebrate skeletal muscle
Abstract Existing data suggest the extracellular matrix (ECM) of vertebrate skeletal muscle consists of several morphologically distinct layers: an endomysium, perimysium, and epimysium surrounding muscle fibers, fascicles, and whole muscles, respectively. These ECM layers are hypothesized to serve important functional roles within muscle, influencing passive mechanics, providing avenues for force transmission, and influencing dynamic shape changes during contraction. The morphology of the skeletal muscle ECM is well described in mammals and birds; however, ECM morphology in other vertebrate groups including amphibians, fish, and reptiles remains largely unexamined. It remains unclear whether a multilayered ECM is a common feature of vertebrate skeletal muscle, and whether functional roles attributed to the ECM should be considered in mechanical analyses of non‐mammalian and non‐avian muscle. To explore the prevalence of a multilayered ECM, we used a cell maceration and scanning electron microscopy technique to visualize the organization of ECM collagen in muscle from six vertebrates: bullfrogs (Lithobates catesbeianus), turkeys (Meleagris gallopavo), alligators (Alligator mississippiensis), cane toads (Rhinella marina), laboratory mice (Mus musculus), and carp (Cyprinus carpio). All muscles studied contained a collagen‐reinforced ECM with multiple morphologically distinct layers. An endomysium surrounding muscle fibers was apparent in all samples. A perimysium surrounding groups of muscle fibers was apparent in all but carp epaxial muscle; a muscle anatomically, functionally, and phylogenetically distinct from the others studied. An epimysium was apparent in all samples taken at the muscle periphery. These findings show that a multilayered ECM is a common feature of vertebrate muscle and suggest that a functionally relevant ECM should be considered in mechanical models of vertebrate muscle generally. It remains unclear whether cross‐species variations in ECM architecture are the result of phylogenetic, anatomical, or functional differences, but understanding the influence of such variation on muscle mechanics may prove a fruitful area for future research.
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- Award ID(s):
- 1832795
- PAR ID:
- 10458763
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Morphology
- Volume:
- 281
- Issue:
- 2
- ISSN:
- 0362-2525
- Page Range / eLocation ID:
- p. 160-169
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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