Objectives. In this study, we compared the pain behaviour and osteoarthritis (OA) progression between anterior cruciate ligament transection (ACLT) and osteochondral injury in surgically-induced OA rat models. Methods. OA was induced in the knee joints of male Wistar rats using transection of the ACL or induction of osteochondral injury. Changes in the percentage of high limb weight distribution (%HLWD) on the operated hind limb were used to determine the pain behaviour in these models. The development of OA was assessed and compared using a histological evaluation based on the Osteoarthritis Research Society International (OARSI) cartilage OA histopathology score. Results. Both models showed an increase in joint pain as indicated by a significant (p < 0.05) decrease in the values of %HLWD at one week post-surgery. In the osteochondral injury model, the %HLWD returned to normal within three weeks, while in the ACLT model, a significant decrease in the %HLWD was persistent over an eight-week period. In addition, OA progression was more advanced in the ACLT model than in the osteochondral injury model. Furthermore, the ACLT model exhibited a higher mean OA score than that of the osteochondral injury model at 12 weeks. Conclusion. The development of pain patterns in the ACLT and osteochondral injury models is different in that the OA progression was significant in the ACLT model. Although both can be used as models for a post-traumatic injury of the knee, the selection of appropriate models for OA in preclinical studies should be specified and relevant to the clinical scenario. Cite this article: T. Tawonsawatruk, O. Sriwatananukulkit, W. Himakhun, W. Hemstapat. Comparison of pain behaviour and osteoarthritis progression between anterior cruciate ligament transection and osteochondral injury in rat models. Bone Joint Res 2018;7:244–251. DOI: 10.1302/2046-3758.73.BJR-2017-0121.R2

Osteoarthritis (OA) affects bone cartilage and underlying bone. Mechanically, the underlying bone provides support to the healthy growth of the overlying cartilage. However, with the progress of OA, bone losses and cysts occur in the bone and these would alter the biomechanical behaviour of the joint, and further leading to bone remodelling adversely affect the overlying cartilage.

Human femoral head and femoral condyle were collected during hip or knee replacement operation due to the end stage of osteoarthritis (age 50–70), and the cartilage patches were graded and marked. A volunteer patient, with minor cartilage injury in his left knee while the right knee is intact, was used as control. Peripheral quantitative computed tomography (pQCT) was used to scan the bone and to determine the volumetric bone mineral density (vBMD) distribution.

The examination of retrieved tissue explants from osteoarthritic patients revealed that patches of cartilage were worn away from the articular surface, and patches of intact cartilage were left. The cysts, ranging from 1 to 10mm were existed in all osteoarthritic bones, and were located close to cartilage defects in the weight-bearing regions, and closely associated with the grade of cartilage defect as measured by pQCT. The bone mineral density (vBMD) distribution demonstrated that the bones around cysts had much higher vBMD than the trabecular bone away from the cysts. Compared to the subchondral bone under thicker cartilage, subchondral bone within cartilage defect has higher vBMD. This may result from the mechanical stimulation as a result of bone-bone direct contact with less protection of cartilage in cartilage defect regions.

This study showed an association between cartilage defect and subchondral bone mineral density distribution. Cysts were observed in all osteoarthritic samples and they are located close to cartilage defects in the weight-bearing regions. Cartilage defect altered the loading pattern of the joints, this leading to the bone remodelling and resultant bone structural changes as compared to the normal bone tissues.

This work was financially supported by The ARUK Proof of Concept Award (grant no: 21160).

Cartilage neoangiogenesis holds a key role in the development of osteoarthritis (OA) by promoting cartilage degradation with proteoglycan loss, subchondral bone sclerosis, osteophyte formation and synovial hyperplasia. This study aimed to assess the in vivo efficacy of bevacizumab, an antibody against vascular endothelial growth factor (VEGF) in an OA animal model.

24 New Zealand white rabbits underwent anterior cruciate ligament transection in order to spontaneously develop knee OA. Animals were divided into four groups: one receiving a sham intraarticular knee injection (saline) and three groups treated with 5, 10, and 20 mg intraarticular bevacizumab injections. The biological effect of the antibody on cartilage and synovium was evaluated through histology and quantified with the Osteoarthritis Research Society International (OARSI) scores. Immunohistochemical analysis was conducted to investigate type 2 collagen, aggrecan, and matrix metalloproteinase 13 (MMP-13) expression in both cartilage and synovium.

Intraarticular bevacizumab led to a significant reduction of cartilage degeneration and synovial OA alterations. Immunohistochemistry showed a significantly reduced MMP-13 expression in all experimental groups, with the one receiving 20 mg bevacizumab showing the lowest. Furthermore, the antibody showed to increment the production of aggrecan and type 2 collagen after administration of 5, 10, and 20 mg. The group treated with 20 mg showed the highest levels of type 2 collagen expression, while aggrecan content was even higher than in the healthy cartilage.

Intraarticular bevacizumab has demonstrated to effectively arrest OA progression in our model, with 20 mg being the most efficacious dose. By inhibiting cartilage and synovial neoangiogenesis, bevacizumab may serve as a possible disease-modifying osteoarthritis drug (DMOAD) in the next future.

Introduction and Objective

Osteoarthristis (OA) has been associated with many genes and yet the genetic basis for this disease has never formally been established. Recent realization that epigenetic changes could be the underlying pathological mechanisms has helped to explain many complex multifactorial diseases with no clear genetic cause. We therefore asked whether epigenetics could also play a role in OA. We have previously shown that the DNA epigenetic modification, specifically the hydroxymethylation on cytosine (5hmC), undergoes a fivefold increase on OA-associated genes which are activated at OA onset. In this study, we further uncovered a set of 5hmC-mediated gene targets and their mechanistic link to OA progression.

Robotic assistance in knee arthroplasty has become increasingly popular due to improved accuracy of prosthetic implantation. However, literature on the mid-term outcomes is limited especially that of hand-held robotic-assisted devices. We present one of the longest follow-up series to date using this novel technology and discuss the learning curve for introducing robotic technology into our practice. The purpose of this single-surgeon study is to evaluate the survival, patient-reported outcomes and learning curve for handheld boundary-controlled robotic-assisted unicompartmental knee arthroplasties (HBRUKAs) at our hospital. This retrospective study evaluates 100 cases (94 Medial, 6 Lateral) performed by a single surgeon between October 2012 and July 2018. 52% were males, mean age was 64.5y (range 47.3y-85.2y) and mean BMI was 31.3 (range 21.8–43). Both inlay (40%) and onlay (60%) designs were implanted. Patients were followed up routinely at 1 and 5 years with Oxford Knee Scores (OKS) recorded. The learning curve was determined by tourniquet times. At a mean follow-up of 4.3 years (range 1.6y–7.3y), survivorship was 97%. There were three revisions: One case of aseptic loosening (1.5y), one case of deep-infection (3.8y) and one case of contralateral compartment osteoarthritis progression (5y). Mean 5-year OKS was 39.8. A 14.3% reduction in mean tourniquet times between the first 25 cases (105.5minutes) and subsequent cases (90.4minutes) was seen. This single-surgeon study showed good survivorship and patient-reported outcomes for HBRUKAs at our hospital. A learning curve of approximately 25 cases was shown, with significant decreases in tourniquet times with respect to increased surgeon experience

Introduction. Cartilage damage is a critical aspect of osteoarthritis progression, but effective imaging strategies remain limited. Consequently, multimodal imaging approaches are receiving increased attention. Gold nanomaterials, renowned for their therapeutic and imaging capabilities, hold promise in drug development. However, their potential for cartilage imaging is rarely discussed. Here, we developed a versatile nanomaterial, AuNC@BSA-Gd-I, for cartilage detection. By leveraging electrostatic interactions with sulfated glycosaminoglycans (sGAG), the AuNC@BSA-Gd-I can effectively penetrate damaged cartilage while accumulating minimally in healthy cartilage. This probe can be visualized or detected using CT, MRI, IVIS, and a gamma counter, providing a comprehensive approach to cartilage imaging. Additionally, we compared the imaging abilities, cartilage visualization capacities, and versatility of currently disclosed multimodal gold nanomaterials with those of AuNC@BSA-Gd-I. Method. The physicochemical properties of nanomaterials were measured. The potential for cartilage visualization of these nanomaterials was assessed using an in vitro porcine model. The sGAG content in cartilage was determined using the dimethylmethylene blue (DMMB) assay to establish the correlation between sGAG concentration and imaging intensity acquired at each modality. Results. The cartilage imaging abilities of AuNC@BSA-Gd-I for CT, MRI, and optical imaging were verified, with each imaging intensity demonstrating a strong correlation with the sGAG content (MRI; R2=0.93, CT; R2=0.83, IVIS; R2=0.79). Furthermore, AuNC@BSA-Gd-. 131. I effectively accumulated in defective cartilage tissue compared to healthy cartilage (23755.38 ± 5993.61 CPM/mg vs. 11699.97 ± 794.93 CPM/mg). Additionally, current gold nanomaterials excelled in individual imaging modalities but lacked effective multimodal imaging ability. Conclusion. Compared to current multimodal gold nanomaterials, AuNC@BSA-Gd-I demonstrates the potential to image cartilage across multiple medical instruments, providing investigators with a more powerful, visible, and convenient approach to detect cartilage defects. Acknowledgements. This work was financially supported by the National Health Research Institute, Taiwan (NHRI-EX112-11029SI), the National Science and Technology Council (NSTC 112-2314-B-182A-105-MY3), and Chang Gung Memorial Hospital, Taiwan (CMRPG8N0781 and CMRPG8M1281-3)

Objectives. This study aimed to examine the effects of SRT1720, a potent SIRT1 activator, on osteoarthritis (OA) progression using an experimental OA model. Methods. Osteoarthritis was surgically induced by destabilization of the medial meniscus in eight-week-old C57BL/6 male mice. SRT1720 was administered intraperitoneally twice a week after surgery. Osteoarthritis progression was evaluated histologically using the Osteoarthritis Research Society International (OARSI) score at four, eight, 12 and 16 weeks. The expression of SIRT1, matrix metalloproteinase 13 (MMP-13), a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5), cleaved caspase-3, PARP p85, and acetylated nuclear factor (NF)-κB p65 in cartilage was examined by immunohistochemistry. Synovitis was also evaluated histologically. Primary mouse epiphyseal chondrocytes were treated with SRT1720 in the presence or absence of interleukin 1 beta (IL-1β), and gene expression changes were examined by real-time polymerase chain reaction (PCR). Results. The OARSI score was significantly lower in mice treated with SRT1720 than in control mice at eight and 12 weeks associated with the decreased size of osteophytes at four and eight weeks. The delayed OA progression in the mice treated with SRT1720 was also associated with increased SIRT1-positive chondrocytes and decreased MMP-13-, ADAMTS-5-, cleaved caspase-3-, PARP p85-, and acetylated NF-κB p65-positive chondrocytes and decreased synovitis at four and eight weeks. SRT1720 treatment partially rescued the decreases in collagen type II alpha 1 (COL2A1) and aggrecan caused by IL-1β, while also reducing the induction of MMP-13 by IL-1β in vitro. Conclusion. The intraperitoneal injection of SRT1720 attenuated experimental OA progression in mice, indicating that SRT1720 could be a new therapeutic approach for OA. Cite this article: K. Nishida, T. Matsushita, K. Takayama, T. Tanaka, N. Miyaji, K. Ibaraki, D. Araki, N. Kanzaki, T. Matsumoto, R. Kuroda. Intraperitoneal injection of the SIRT1 activator SRT1720 attenuates the progression of experimental osteoarthritis in mice. Bone Joint Res 2018;7:252–262. DOI: 10.1302/2046-3758.73.BJR-2017-0227.R1

Abstract. INTRODUCTION. Knee tactile afferents act as synovial joint limit detectors, eliciting signalling upon excessive fibrous tissue strain but play little role in joint function as disruption of their activity does not induce impairments in movement or sensation. In contrast, knee nociceptive afferents gain activity upon inflammation producing painful sensation in pathology such as osteoarthritis. We hypothesize that similar in origin, fast-conducting tactile afferents become sensitized by inflammatory mediators and gain activity causing proprioceptive sensation impairment in patients with knee pathology, driving gait abnormalities and osteoarthritis progression. To investigate the activity of these neurons, we will produce a co-culture model using our existing 3D bone mimetic and iPSC derived tactile sensory neurons by utilizing the NGN2-BRN3A plasmid produced by Nickolls et al producing a model of these tactile neurons at their position within the joint at the fibrous/bony interface. METHODS. Human Y201 MSC cells embedded in type I collagen gels (0.05 × 106 cell/gel) were differentiated to osteocytes andmechanically loaded in silicone plates (5000 µstrain, 10Hz, 3000 cycles) (n=5). RNA quantified by RNAseq analysis (NovaSeq S1) and neuronal communication pathways identified using DEseq2 analysis. RESULTS. Over 20 genes involved in neural communication were expressed in 100% of bone cultures, and most of these showed regulation under mechanical strain including receptors for Substance P (p= 0.91), CGRP (p=0.05), Norepinepherin (p=0.002), NPY (p=0.0002), Sema3A (p=0.01), Leptin (p=0.00005), Neutrophin3A (p=0.23), BDNF (p=0.5), GDNF (p=0.02), and glutamate(p=0.024) and signalling molecules Neutrophin3 (p=0.73), NGF (p=0.02), Sema3A (p=0.003), BDNF (p=0.02) and GDNF (p=0.006). DISCUSSION. The production of this 3D neural co-culture model is still in its infancy. However, preliminary RNAseq data has shown our Y201 bone model expresses all the signalling pathways known to exert neural regulatory responses and therefore is now ready to move forward to neural inclusion

Summary. The dGEMRIC index correlates more strongly with the pattern of radiographic joint space narrowing in hip osteoarthritis at five year follow-up than morphological measurements of the proximal femur. It therefore offers potential to refine predictive models of hip osteoarthritis progression. Introduction. Longitudinal general population studies have shown that femoroacetabular impingement increases the risk of developing hip osteoarthritis, however, morphological parameters have a low positive predictive value. Arthroscopic debridement of impingement lesions has been proposed as a potential strategy for the prevention of osteoarthritis, however, the development of such strategies requires the identification of individuals at high risk of disease progression. We investigated whether delayed Gadolinium-Enhanced MRI of Cartilage (dGEMRIC) predicts disease progression. This imaging modality is an indirect measure of cartilage glycosaminoglycan content. Patients and Methods. 34 asymptomatic individuals from a longitudinal cohort study (sibkids) were assessed at baseline with the collection of Patient Reported Outcome Measures (PROMs), anteroposterior and cross-table lateral radiographs, 3D morphological MRI, and dGEMRIC at 3T of their index hip. A dGEMRIC index was calculated as a ratio of the anterosuperior acetabular cartilage T1 relaxation time and the total femoral and acetabular cartilage T1 relaxation time. 29 individuals were followed up at 5 years for repeat assessment (average age 51 years and range 36 to 67). Radiological measurements were made by a single observer using in house Hipmorf software. Radiographic disease progression was assessed using minimum joint space width (JSW), lateral sourcil JSW, and medial sourcil JSW. These were measured on baseline and five year follow-up anteroposterior radiographs with an intra-observer ICC of 0.916. Alpha angle measurements were made by the same observer on radiographs and MRI radial slices with an intra-observer ICC of 0.926. Results. Mean minimum JSW for the cohort fell by 0.16mm over five years (p=0.024). Baseline dGEMRIC index did not correlate with change in minimum JSW (r=0.031 p=0.873). There was a moderate correlation between baseline dGEMRIC and the direction of JSW loss (change in JSW at the lateral sourcil minus change in JSW at the medial sourcil) (r=0.561 p=0.002). There was a weak correlation between the change in Non-Arthritic Hip Score and baseline dGEMRIC (r=0.256 P=0.180). Maximum alpha angle measured on baseline MRI radial slices did not correlate with change in minimum JSW and weakly correlated with the direction of JSW narrowing (r=0.273 p=0.160). Conclusion. A low dGEMRIC index indicates reduced glycosaminoglycan concentration in the anterosuperior acetabular cartilage compared with the total femoral and acetabular cartilage. This correlates with lateral JSW narrowing relative to medial JSW narrowing as osteoarthritis progresses. The dGEMRIC index correlates better with osteoarthritis progression than alpha angle measurements and offers the potential to refine a predictive model for osteoarthritis progression to aid patient selection for clinical trials

Matrix metalloproteinase enzymes (MMPs) play a crucial role in the remodeling of articular cartilage, contributing also to osteoarthritis (OA) progression. The pericellular matrix (PCM) is a specialized space surrounding each chondrocyte, containing collagen type VI and perlecan. It acts as a transducer of biomechanical and biochemical signals for the chondrocyte. This study investigates the impact of MMP-2, -3, and -7 on the integrity and biomechanical characteristics of the PCM. Human articular cartilage explants (n=10 patients, ethical-nr.:674/2016BO2) were incubated with activated MMP-2, -3, or -7 as well as combinations of these enzymes. The structural degradative effect on the PCM was assessed by immunolabelling of the PCM's main components: collagen type VI and perlecan. Biomechanical properties of the PCM in form of the elastic moduli (EM) were determined by means of atomic force microscopy (AFM), using a spherical cantilever tip (2.5µm). MMPs disrupted the PCM-integrity, resulting in altered collagen type VI and perlecan structure and dispersed pericellular arrangement. A total of 3600 AFM-measurements revealed that incubation with single MMPs resulted in decreased PCM stiffness (p<0.001) when compared to the untreated group. The overall EM were reduced by ∼36% for all the 3 individual enzymes. The enzyme combinations altered the biomechanical properties at a comparable level (∼36%, p<0.001), except for MMP-2/-7 (p=0.202). MMP-induced changes in the PCM composition have a significant impact on the biomechanical properties of the PCM, similar to those observed in early OA. Each individual MMP was shown to be highly capable of selectively degrading the PCM microenvironment. The combination of MMP-2 and -7 showed a lower potency in reducing the PCM stiffness, suggesting a possible interplay between the two enzymes. Our study showed that MMP-2, -3, and -7 play a direct role in the functional and structural remodeling of the PCM. Acknowledgements: This work was supported by the Faculty of Medicine of the University of Tübingen (grant number.: 2650-0-0)

Introduction. Weight is a modifiable risk factor for osteoarthritis (OA) progression. Despite the emphasis on weight loss, data quantifying the changes seen in joint biomechanics are limited. Bariatric surgery patients experience rapid weight loss. This provides a suitable population to study changes in joint forces and function as weight changes. Method. 10 female patients undergoing gastric bypass or sleeve gastrectomy completed 3D walking gait analysis at a self-selected pace, pre- and 6 months post-surgery. Lower limb and torso kinematic data for 10 walking trials were collected using a Vicon motion capture system and kinetics using a Kistler force plate. An inverse kinematic model in Visual 3D allowed for no translation of the hip joint centre. 6 degrees of freedom were allowed at other joints. Data were analysed using JASP with a paired samples t-test. Result. On average participants lost 28.8±7.60kg. No significant changes were observed in standing knee and hip joint angles. Walking velocity increased from 1.10±0.11 ms. -1. to 1.23±0.17 ms. -1. (t(9)=-3.060, p = 0.014) with no change in step time but a mean increase in stride length of 0.12m (SE: 0.026m; t(9)=-4.476, p = 0.002). A significant decrease of 21.5±4.2% in peak vertical ground reaction forces was observed (t(9)=12.863, p <0.001). Stride width significantly decreased by 0.04m (SE: 0.010m; t(9)=4.316, p = 0.002) along with a decrease in lateral impulse of 21.2Ns (SE: 6.977Ns; t(7), p = 0.019), but no significant difference in knee joint angles were observed. Double limb support time also significantly reduced by 0.02s (SE: 0.006s; t(9) = 3.639, p=0.005). Conclusion. The reduction in stance width and lateral impulse suggests a more sagittal compass-gait walk is being achieved. This would reduce valgus moments on the knee reducing loading in the medial compartment. The reduction in peak ground reaction force would reduce knee contact forces and again potentially slow OA progression

Introduction. During osteoarthritis (OA) progression the articular chondrocyte undergoes a phenotypic switch in which the chondrocyte acquires a catabolic and hypertrophy-like state. Bone morphogenetic protein (BMP)-7 is known for its anti-catabolic and pro-anabolic properties in cartilage repair and in OA chondrocytes. In its anabolic state the chondrocyte”s metabolism and protein synthesis are up-regulated. In order to meet a higher demand of protein synthesis, it is expected that the translational capacity of the chondrocyte is increased after exposure to BMP-7. The cellular availability of maturated ribosomal RNAs (rRNA) is rate-limiting in the assembly of ribosomes and previously it has been shown that BMP-7 treatment resulted in increased expression levels of bagpipe homeobox homolog 1 (BAPX-1/NKX3.2). We therefore hypothesize that BMP-7 enhances the translational capacity of articular chondrocytes via BAPX-1/NKX3.2-dependent synthesis of rRNAs. Methods. OA human articular chondrocytes (HACs) were isolated from OA cartilage from total knee arthroplasty. SW1353 cells and OA HACs were exposed to BMP-7 (1 nM) and expression levels of rRNAs (18S, 5.8S, 28S) rRNA processing snoRNAs (RMRP and U3), a crucial co-factor in rRNA transcription (UBF-1) and BAPX-1/NKX3.2 were determined by RT-qPCR (and immunoblotting for BAPX-1/NKX3.2). BAPX-1/NKX3.2 overexpression and knockdown were achieved via transfection of FLAG-BAPX-1/NKX3.2 or a BAPX-1/NKX3.2 siRNA. For ex vivo confirmation, human OA cartilage explants from total knee arthroplasty were exposed to BMP-7 (1 nM) and gene expression levels of rRNAs were measured via qPCR. Results. BMP-7 treatment resulted in increased 18S and 5.8S rRNA levels, increased UBF-1, RMRP and U3 expression. This correlated with increased BAPX-1/NKX3.2 mRNA and protein expression. Overexpression of BAPX-1/NKX3.2 resulted in increased rRNA expression levels and the reciprocal knockdown of BAPX-1/NKX3.2 resulted in decreased rRNA expression levels. Besides these in vitro data, exposure of OA cartilage explants to BMP-7 confirmed our in vitro data (increase of 18S, 5.8S, UBF-1, RMRP, U3 and BAPX-1 expression levels). Discussion/Conclusion. Here we show that BMP-7 induces increased cellular levels of maturated rRNAs, with concomitant induction of factors involved in the transcription and maturation of rRNAs. This process is directly influenced by BAPX-1/NKX3.2 in similar ways as BMP-7. In future research the transcriptional activity of the 47S pre-rRNA gene will be determined via a luciferase promoter reporter approach and increased translation will be directly determined via puromycilation assays. Our data provide important novel insights into the mechanism behind the anabolic properties of BMP-7 and may even provide a new molecular cue to target the chondrocyte phenotype in OA