The scoring paradigm described here has been found to be sufficiently sensitive to discriminate between treatments and to have high reproducibility. Therefore we recommend its use for evaluation of different rat OA models as well as assessment of disease-modifying effects of treatments in these models.

Murine γδ T cell subsets, defined by their Vγ chain usage, have been shown in various disease models to have distinct functional roles. In this study, we examined the responses of the two main peripheral γδ T cell subsets, Vγ1+ and Vγ4+ cells, during collagen-induced arthritis (CIA), a mouse model that shares many hallmarks with human rheumatoid arthritis. We found that whereas both subsets increased in number, only the Vγ4+ cells became activated. Surprisingly, these Vγ4+ cells appeared to be Ag selected, based on preferential Vγ4/Vδ4 pairing and very limited TCR junctions. Furthermore, in both the draining lymph node and the joints, the vast majority of the Vγ4/Vδ4+ cells produced IL-17, a cytokine that appears to be key in the development of CIA. In fact, the number of IL-17-producing Vγ4+ γδ T cells in the draining lymph nodes was found to be equivalent to the number of CD4+αβ+ Th-17 cells. When mice were depleted of Vγ4+ cells, clinical disease scores were significantly reduced and the incidence of disease was lowered. A decrease in total IgG and IgG2a anti-collagen Abs was also seen. These results suggest that Vγ4/Vδ4+ γδ T cells exacerbate CIA through their production of IL-17.

Objective This review focuses on the criteria for assessing osteoarthritis (OA) in the guinea pig at the macroscopic and microscopic levels, and recommends particular assessment criteria to assist standardization in the conduct and reporting of preclinical trails in guinea pig models of OA. Methods A review was conducted of all OA studies from 1958 until the present that utilized the guinea pig. The PubMed database was originally searched August 1, 2006 using the following search terms: guinea pig and osteoarthritis. We continued to check the database periodically throughout the process of preparing this chapter and the final search was conducted January 7, 2009. Additional studies were found in a review of abstracts from the OsteoArthritis Research Society International (OARSI) conferences, Orthopaedic Research Society (ORS) conferences, and literature related to histology in other preclinical models of OA reviewed for relevant references. Studies that described or used systems for guinea pig joint scoring on a macroscopic, microscopic, or ultrastructural basis were included in the final comprehensive summary and review. General recommendations regarding methods of OA assessment in the guinea pig were derived on the basis of a comparison across studies and an inter-rater reliability assessment of the recommended scoring system. Results A histochemical-histological scoring system (based on one first introduced by H. Mankin) is recommended for semi-quantitative histological assessment of OA in the guinea pig, due to its already widespread adoption, ease of use, similarity to scoring systems used for OA in humans, its achievable high inter-rater reliability, and its demonstrated correlation with synovial fluid biomarker concentrations. Specific recommendations are also provided for histological scoring of synovitis and scoring of macroscopic lesions of OA. Conclusions As summarized herein, a wealth of tools exist to aid both in the semi-quantitative and quantitative assessment of OA in the guinea pig and provide a means of comprehensively characterizing the whole joint organ. In an ongoing effort at standardization, we recommend specific criteria for assessing the guinea pig model of OA as part of an OARSI initiative, termed herein the OARSI-HISTOgp recommendations.

The results of this study demonstrate that FGF18 can stimulate repair of damaged cartilage in a setting of rapidly progressive OA in rats.

ABSTRACT

These results demonstrate that MMP inhibition is effective in reducing the joint damage that occurs in the meniscal tear model of OA and support a potential therapeutic role for MMP inhibition in the treatment of human OA.

Objective. Lubricin, also referred to as superficial zone protein and PRG4, is a synovial glycoprotein that supplies a friction-resistant, antiadhesive coating to the surfaces of articular cartilage, thereby protecting against arthritis-associated tissue wear and degradation. This study was undertaken to generate and characterize a novel recombinant lubricin protein construct, LUB:1, and to evaluate its therapeutic efficacy following intraarticular delivery in a rat model of osteoarthritis (OA).Methods. Binding and localization of LUB:1 to cartilage surfaces was assessed by immunohistochemistry. The cartilage-lubricating properties of LUB:1 were determined using a custom friction testing apparatus. A cell-binding assay was performed to quantify the ability of LUB:1 to prevent cell adhesion. Efficacy studies were conducted in a rat meniscal tear model of OA. One week after the surgical induction of OA, LUB:1 or phosphate buffered saline vehicle was administered by intraarticular injection for 4 weeks, with dosing intervals of either once per week or 3 times per week. OA pathology scores were determined by histologic analysis.Results. LUB:1 was shown to bind effectively to cartilage surfaces, and facilitated both cartilage boundary lubrication and inhibition of synovial cell adhesion. Treatment of rat knee joints with LUB:1 resulted in significant disease-modifying, chondroprotective effects during the progression of OA, by markedly reducing cartilage degeneration and structural damage.Conclusion. Our findings demonstrate the potential use of recombinant lubricin molecules in novel biotherapeutic approaches to the treatment of OA and associated cartilage abnormalities.Osteoarthritis (OA) severely restricts the daily activities, mobility, and overall quality of life of millions of patients worldwide, imposing a high societal burden that reflects the current lack of effective medical therapies. OA is characterized by escalated degeneration and loss of articular cartilage, the specialized connective tissue covering the ends of interfacing bones within joints. To help withstand formidable biomechanical forces and loads, articular cartilage surfaces possess an inherently low coefficient of friction, which is facilitated in part by localization of the boundary lubricant lubricin (1). Lubricin was originally identified as a lubricating glycoprotein present in synovial fluid (2), and it is now recognized to have a major protective role in preventing cartilage wear and synovial cell adhesion and proliferation (3). Lubricin is encoded by the PRG4 gene, and PRG4-nullifying mutations can cause OA-like symptoms in mice and humans (3,4). Lubricin synthesis/localization (and therefore function) is also down-regulated in sheep (5), guinea pig (6), and rat (7)

During toxicologic evaluation of a dimeric PEG-linked protein, tumor necrosis factor binding protein (TNF-bp), vacuolation of renal cortical tubular epithelium was seen in male and female Sprague-Dawley rats (200-300 g) given i.v. doses of 40, 20, or 10 mg/kg every other day for 3 months. Tubular lesions in rats treated with 20 or 40 mg/kg for 3 months were only partially reversible after a 2-month recovery period. Despite the presence of marked vacuolation, there were no changes in BUN, creatinine, urinalysis parameters, urinary NAG, urinary B2-microglobulin, or fractional sodium excretion. Single i.v. doses > or = 20 mg/kg TNF-bp caused similar but milder changes. However, equivalent doses of PEG alone or the non-PEG-linked TNF-bp did not cause light microscopic evidence of vacuolation. Treatment of rats with another PEG-linked protein of similar molecular weight resulted in similar changes. Immunostaining for TNF-bp revealed positivity in the apical cytoplasm of renal tubular epithelium within 1 h of i.v. dosing. Immunostaining of kidneys from chronically dosed rats indicated that protein was present in some vacuoles as long as dosing continued; however, kidneys from animals on a reversibility study had vacuoles but no immunostaining for TNF-bp. These results, along with a study that showed more severe lesions with PEG-linked proteins of lower molecular weight and minimal if any lesions with PEG-linked proteins > 70 kDa, suggest that TNF-bp is filtered through the glomerulus and that the protein with attached PEG is reabsorbed by the proximal tubules. Vacuolation may be a result of fluid distension of lysosomes due to the hygroscopic nature of PEG. These studies demonstrated that PEG-linked proteins have the capacity to induce renal tubular vacuolation at high doses. However, the change was not associated with alteration of clinical pathology or functional markers.