ARTHRITIS & RHEUMATOLOGY Vol. 68, No. 4, April 2016, pp 868–879 DOI 10.1002/art.39529 V C 2016, American College of Rheumatology Ablation of Perlecan Domain 1 Heparan Sulfate Reduces Progressive Cartilage Degradation, Synovitis, and Osteophyte Size in a Preclinical Model of Posttraumatic Osteoarthritis Cindy C. Shu, 1 Miriam T. Jackson, 1 Margaret M. Smith, 1 Susan M. Smith, 1 Steven Penm, 2 Megan S. Lord, 2 John M. Whitelock, 2 Christopher B. Little, 1 and James Melrose 1 Objective. To investigate the role of the heparan sulfate (HS) proteoglycan perlecan (HSPG-2) in regulat- ing fibroblast growth factor (FGF) activity, bone and joint growth, and the onset and progression of posttraumatic osteoarthritis (OA) in a mouse gene-knockout model. Methods. Maturational changes were evaluated histologically in the knees of 3-, 6-, and 12-week-old wild- type (WT) mice and Hspg2 D32/D32 mice (Hspg2 lacking domain 1 HS, generated by ablation of exon 3 of per- lecan). Cartilage damage, subchondral bone sclerosis, osteophytosis, and synovial inflammation were scored at 4 and 8 weeks after surgical induction of OA in WT and Hspg2 D32/D32 mice. Changes in cartilage expression of FGF-2, FGF-18, HSPG-2, FGF receptor 1 (FGFR-1), and FGFR-3 were examined immunohistochemically. Femoral head cartilage from both mouse genotypes was cultured in the presence or absence of interleukin-1a (IL-1a), FGF-2, and FGF-18, and the content and re- lease of glycosaminoglycan (GAG) and expression of messenger RNA (mRNA) for key matrix molecules, enzymes, and inhibitors were quantified. Results. No effect of perlecan HS ablation on growth plate or joint development was detected. After induction of OA, Hspg2 D32/D32 mice had significantly reduced cartilage erosion, osteophytosis, and synovitis. OA-induced loss of chondrocyte expression of FGF-2, FGF-18, and HSPG-2 occurred in both genotypes. Expression of FGFR-1 after OA induction was main- tained in WT mice, while FGFR-3 loss after OA induc- tion was significantly reduced in Hspg2 D32/D32 mice. There were no genotypic differences in GAG content or release between unstimulated control cartilage and IL- 1a–stimulated cartilage. However, IL-1a–induced carti- lage expression of Mmp3 mRNA was significantly reduced in Hspg2 D32/D32 mice. Cartilage GAG release in either the presence or absence of IL-1a was unal- tered by FGF-2 in both genotypes. In cartilage cultures with FGF-18, IL-1a–stimulated GAG loss was signifi- cantly reduced only in Hspg2 D32/D32 mice, and this was associated with maintained expression of Fgfr3 mRNA and reduced expression of Mmp2/Mmp3 mRNA. Conclusion. Perlecan HS has significant roles in directing the development of posttraumatic OA, poten- tially via the alteration of FGF/HS/FGFR signaling. These data suggest that the chondroprotection conferred by perlecan HS ablation could be attributed, at least in part, to the preservation of FGFR-3 and increased FGF signaling. Perlecan (heparan sulfate proteoglycan 2 [HSPG-2]) is a large proteoglycan found not only in vascularized tissue, but also in the cartilage, meniscus, and interver- tebral disc (1). It is a key component of basement mem- branes and the pericellular matrix surrounding cells in avascular tensional and weight-bearing connective tissue that may serve as an intrinsic basement membrane (2). The pericellular localization of perlecan is consistent with its roles in matrix stabilization, cell binding, and mechano-regulation (3,4). Perlecan is an early marker Supported by the National Health and Medical Research Council of Australia (grant APP512167), Arthritis Australia, and the Northern Sydney Area Grants Scheme. 1 Cindy C. Shu, PhD, Miriam T. Jackson, PhD, Margaret M. Smith, PhD, Susan M. Smith, Biol Tech Cert, Christopher B. Little, BVMS, PhD, James Melrose, PhD: Kolling Institute, Northern Sydney Local Health District, and the University of Sydney at Royal North Shore Hospital, St. Leonards, New South Wales, Australia; 2 Steven Penm, BSc (Hons), Megan S. Lord, PhD, John M. Whitelock, PhD: University of New South Wales, Kensington, New South Wales, Australia. Drs. Little and Melrose contributed equally to this work. Address correspondence to Cindy C. Shu, PhD, Raymond Purves Research Bone and Joint Laboratories, Level 10, Kolling Building B6, Royal North Shore Hospital, St. Leonards, New South Wales 2065, Australia. E-mail: cindy.shu@sydney.edu.au. Submitted for publication June 11, 2015; accepted in revised form November 19, 2015. 868