title: Matrix disruptions, growth, and degradation of cartilage with impaired sulfation.
abstract: Diastrophic dysplasia (DTD) is an incurable recessive chondrodysplasia caused by mutations in the SLC26A2 transporter responsible for sulfate uptake by chondrocytes. The mutations cause undersulfation of glycosaminoglycans in cartilage. Studies of dtd mice with a knock-in Slc26a2 mutation showed an unusual progression of the disorder: net undersulfation is mild and normalizing with age, but the articular cartilage degrades with age and bones develop abnormally. To understand underlying mechanisms, we studied newborn dtd mice. We developed, verified and used high-definition infrared hyperspectral imaging of cartilage sections at physiological conditions, to quantify collagen and its orientation, noncollagenous proteins, and chondroitin chains, and their sulfation with 6-μm spatial resolution and without labeling. We found that chondroitin sulfation across the proximal femur cartilage varied dramatically in dtd, but not in the wild type. Corresponding undersulfation of dtd was mild in most regions, but strong in narrow articular and growth plate regions crucial for bone development. This undersulfation correlated with the chondroitin synthesis rate measured via radioactive sulfate incorporation, explaining the sulfation normalization with age. Collagen orientation was reduced, and the reduction correlated with chondroitin undersulfation. Such disorientation involved the layer of collagen covering the articular surface and protecting cartilage from degradation. Malformation of this layer may contribute to the degradation progression with age and to collagen and proteoglycan depletion from the articular region, which we observed in mice already at birth. The results provide clues to in vivo sulfation, DTD treatment, and cartilage growth.
authors.affiliation: Section on Physical Biochemistry, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA. mertze@mail.nih.gov
authors.forename: Edward L
authors.initials: EL
authors.lastname: Mertz
authors.forename: Marcella
authors.initials: M
authors.lastname: Facchini
authors.forename: Anna T
authors.initials: AT
authors.lastname: Pham
authors.forename: Benedetta
authors.initials: B
authors.lastname: Gualeni
authors.forename: Fabio
authors.initials: F
authors.lastname: De Leonardis
authors.forename: Antonio
authors.initials: A
authors.lastname: Rossi
authors.forename: Antonella
authors.initials: A
authors.lastname: Forlino
mesh_terms: D000818:Animals; D027321:Anion Transport Proteins / Q000235:genetics; D002356:Cartilage / Q000378:metabolism*; D019902:Chondrocytes / Q000166:cytology*; D003094:Collagen / Q000737:chemistry; D005109:Extracellular Matrix / Q000378:metabolism; D005269:Femur / Q000473:pathology; D006025:Glycosaminoglycans / Q000378:metabolism; D006132:Growth Plate / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry*; D051379:Mice; D008822:Mice, Transgenic; D015233:Models, Statistical; D009154:Mutation; D010641:Phenotype; D013055:Spectrophotometry, Infrared / Q000379:methods; D000076988:Sulfate Transporters; D013431:Sulfates / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry*
chemical_list: D027321:Anion Transport Proteins; D006025:Glycosaminoglycans; D026901:Membrane Transport Proteins; C513264:Slc26a2 protein, mouse; D000076988:Sulfate Transporters; D013431:Sulfates; D013455:Sulfur; D003094:Collagen