Onset Of OA Research Articles

ROS-induced imbalance of the miR-34a-5p/SIRT1/p53 axis triggers chronic chondrocyte injury and inflammation

Osteoarthritis is a chronic degenerative disease based on the degeneration and loss of articular cartilage. Inflammation and aging play an important role in the destruction of the extracellular matrix, in which microRNA (miRNA) is a key point, such as miRNA-34a-5p. Upregulation of miRNA-34a-5p was previously reported in a rat OA model, and its inhibition significantly suppressed interleukin (IL)-1β-induced apoptosis in rat chondrocytes. However, Oxidative stress caused by reactive oxygen species (ROS) can exacerbate the progression of miRNA regulated OA by mediating inflammatory processes. Thus, oxidative stress effects induced via tert-butyl hydroperoxide (tBHP) in human chondrocytes were assessed in the current research by evaluating mitochondrial ROS production, mitochondrial cyclooxygenase (COX) activity, and cell apoptosis. We also analyzed the activities of antioxidant enzymes including glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD). Additionally, inflammatory factors, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, and IL-24, which contribute to OA development, were detected by enzyme-linked immunosorbent assay (ELISA). The results of this study indicated that miR-34a-5p/silent information regulator 1 (SIRT1)/p53 axis was involved in the ROS-induced injury of human chondrocytes. Moreover, dual-luciferase assay revealed that SIRT1 expression was directly regulated by miR-34a-5p, indicating the presence of a positive feedback loop in the miR-34a-5p/SIRT1/p53 axis that plays an important role in cell survival. However, ROS disrupted the miR-34a-5p/SIRT1/p53 axis, leading to the development of OA, and articular injection of SIRT1 agonist, SRT1720, in a rat model of OA effectively ameliorated OA progression in a dose-dependent manner. Our study confirms that miRNA-34a-5p could participate in oxidative stress responses caused by ROS and further regulate the inflammatory process via the SIRT1/p53 signaling axis, ultimately affecting the onset of OA, thus providing a new treatment strategy for clinical treatment of OA.

Is muscle activation diverse in females with isolated patellofemoral osteoarthritis contrasted with age-matched healthy controls during stair descent task?

Background: Patellofemoral osteoarthritis (PF OA) is exceptionally predominant and limiting. However, little is known about the risk factors that contribute to its onset and progression. Purpose: The aim of this study was to decide if women with PF OA descend stairs using different muscular activation strategies compared to similarly aged healthy controls. Methods: Thirty-one women with isolated PF OA and 11 similarly aged healthy women took part in this study. The activation onset and duration of PF OA in vastus medialis oblique (VMO), vastus lateralis (VL), gluteus medius (GM), transversus abdominis (TrA), and multifidus muscles were evaluated during the stair descent task using surface electromyography (EMG). Results: There was a non-significant difference between women with PF OA and healthy controls regarding all tested variables, except for the GM activation onset that was significantly delayed in women with PF OA, with the p-value of 0.011. Conclusion: The causes of PF OA differ and might not always be due to a lack of quadriceps strength or VMO activation deficiency, and prospective longitudinal studies are required to confirm this assumption.

Evidence-Based Approach to Orthobiologics for Osteoarthritis and Other Joint Disorders.

Osteoarthritis and cartilage lesions are a major cause of functional limitations which is why the goal of biological treatment is to preserve the native joint to delay the onset of OA. As a result of improvements in surgical techniques and technology, treatment options are more and more available, allowing the treatment of a whole range of injuries, from minor to extensive lesions both acute and chronic. In chondral lesion treatment, restoring hyaline-like cartilage provides improved durability of repaired tissue and desirable wear characteristics. Biological cell-based cartilage restoration treatment was developed to address the need for the long-term viability of repaired tissue. These procedures provide a reliable source of chondrocytes, whether directly or through the differentiation of multipotent precursor cells, capable of producing hyaline-like cartilage, with the minimal formation of fibrocartilage tissue. However, if arthritic changes begin biological therapies offer possibilities to delay. This chapter aims to discuss and give insights into these regenerative, joint preservation techniques for cartilage treatment and possible biological treatment in OA.

PREDICTING MECHANICAL LEG ALIGNMENT FROM KNEE X-RAY IMAGES BY UTILIZING DEEP-LEARNING NEURAL NETWORKS

Several studies have linked leg malalignment to early onset and progression of knee OA. Detecting abnormalities in mechanical alignment before radiographic evidence of knee OA is present, might increase the rate of early detection. Hence, conservative joint preserving interventions or even osteotomies could reduce the need or delay full joint replacement. In addition, medical trials often face high dropout rates, consequently, AI based support could improve the recruitment process. Detecting mechanical leg malalignment: 1) before the malalignment is immediately obvious to the clinician and 2) excluding/including patients recruited for medical trials. This study utilized a dataset of 8,878 digital radiographs ((I) 6,181 AP/PA full-leg x-rays, (II) 2,292 AP/PA knee x-rays with SynaFlexer positioning frame, (III) 405 AP/PA knee x-rays captured without SynaFlexer). The images were obtained from a diverse range of sources, including the OAI study, the University for Continuing Education Krems (AT), and five additional sites in Austria and the US. All knee images in the dataset were accompanied by their corresponding full-leg images, obtained on the same day. To determine the ground-truth hip-knee-ankle angle (HKA), the full-leg images were processed using IB Lab LAMA (ImageBiopsyB Lab, Vienna, Austria), a commercial software that automatically determines clinical measurements from full-leg radiographs. These images were used to train the AI algorithm. The algorithm produced binary outputs for HKA threshold values of 5° (clinically relevant) and 7.5° (clinical trial relevant). The algorithm reached MAE rates of 0.98° (cropped full-leg), 1.56° (SynaFlexer knee) and 2.10° (non-SynaFlexer knee). Summarizing all image modalities, the overall performance for the 5° threshold was 74-86% Sensitivity and 79-90% Specificity. Following, 7.5° threshold performance reached 81-92% Sensitivity and 85-92% Specificity. While this study primarily focused on absolute HKA threshold values of 5° and 7.5° for varus/valgus classification, this threshold determination process is highly adaptable to accommodate specific use cases, such as the desired angle threshold for classification or the preferred balance between sensitivity and specificity. In addition, overestimated HKA have an elevated angle above the normal range and could proceed towards or above mentioned thresholds. Chen K. PhD funding “LowerAustria Society for Scientific Research” (LSC20-020). Salzlechner C. and Lepenik C. are employees of ImageBiopsy Lab. Ljuhar R. is a shareholder of ImageBiopsy Lab. This manuscript was prepared using an OAI public use data set and does not necessarily reflect the opinions or views of the OAI investigators or the NIH. Lepenik C. thanks Avelar C. for comments on an early version of this article. CORRESPONDENCE ADDRESS: [email protected]

Low-intensity pulsed ultrasound irradiation attenuates collagen degradation of articular cartilage in early osteoarthritis-like model mice

PurposeOsteoarthritis (OA) is a combination of degeneration and destruction of articular cartilage due to mechanical stress, secondary synovitis, and bone remodelling. In recent years, early knee OA, a preliminary stage of structural failure in OA, has attracted attention as a potential target for therapy to prevent the onset of OA. Intra-articular administration of monoiodoacetic acid (MIA) induces OA-like symptoms, and low doses of MIA induce early OA like symptoms. In this experiment, a low-dose of MIA was induced to early OA model mice, which were then irradiated with low-intensity pulsed ultrasound (LIPUS) to examine whether LIPUS improves symptoms of early OA.MethodsAfter 4 weeks of LIPUS irradiation, articular cartilage was observed at 1 and 4 weeks. The Osteoarthritis Research Society International (OARSI) scores were calculated using Safranin-O staining results. Cartilage degeneration was detected using Denatured Collagen Detection Reagent (DCDR).ResultsWe observed a significant decrease in OARSI scores in the LIPUS irradiated group at week 4. The non-LIPUS group showed widespread areas of double positivity for Type II collagen and DCDR, whereas the LIPUS group showed only a small number of DCDR-positive areas. In addition, macrophage numbers counted in the articular capsule at week 1 showed a significant decrease in the LIPUS irradiated group. Lubricin detection showed that lubricin positive cell number was significantly increased by LIPUS irradiation at week 4.ConclusionsThese results suggest that LIPUS attenuates cartilage degeneration in early OA by relieving inflammation and enhancing the inhibitory effect of lubricin on cartilage degeneration.

Anatomical Imaging Study on Uneven Settlement of the Proximal Tibia.

Uneven settlement of the proximal tibia significantly contributes to the onset and progression of medial compartment knee OA; however, the specific location and variations of proximal tibial deformity remain unclear. Therefore, this study aimed to explore the effects of the anatomic morphology of different tibial regions on proximal tibial vara and proximal tibial microstructural changes with age in both sexes to reveal the pattern of uneven settlement of the proximal tibia. In this retrospective study, we reviewed the radiographs of 414 patients (789 legs) between May and September 2021. The medial proximal tibial angle (MPTA) and four anatomic angles of the tibia (i.e., the tibial plateau-epiphyseal line [PT-EL] angle, epiphyseal line-tibial platform [EL-PF] angle, epiphyseal axis inclination angle [EAIA], and subepiphyseal axis inclination angle [SAIA]) were measured. The effect of each angle on MPTA and their changes with age in both sexes were investigated using Pearson's correlation coefficient and multiple linear regression. In females, PT-EL angle, EL-PF angle, and SAIA negatively correlated with MPTA (r=-0.325, -0.246, and -0.502; p < 0.05), and EAIA positively correlated with MPTA (r=0.099, p < 0.05). Regression analysis showed that the correlations between MPTA and PT-EL angle, EL-PF angle, and SAIA were significant (β=-1.003, -0.013, and -0.971; adjusted R2 =0.979). Furthermore, MPTA negatively correlated with age (r=-0.202, p < 0.05); PT-EL angle and EAIA positively correlated with age (r=0.237 and 0.142, p < 0.05). Regression analysis showed that only the correlation between PT-EL angle and age was significant (β=5.635, p < 0.05). In males, PT-EL angle, EL-PF angle, and SAIA negatively correlated with MPTA (r=-0.270, -0.267, and -0.533; p < 0.05), and EAIA positively correlated with MPTA (r=0.135, p < 0.05). Regression analysis showed that the correlations between MPTA and PT-EL angle, EL-PF angle, and SAIA were significant (β=-0.992, -0.017, and -0.958; adjusted R2 =0.970). However, there was no significant correlation between age and any of the measured angles (p > 0.05). Proximal tibial vara is affected by the anatomic morphology of the epiphyseal and subepiphyseal regions. In females, the uneven settlement of the epiphysis progresses with age and may be responsible for dynamic varus deformity of the proximal tibia.

TLR-8, TNF-α, and ESR-1α Gene Polymorphism Susceptibility in Onset of Arthritis.

Arthritis is a genetic disorder characterized by bones and joint degradation assisted by severe pain and inflammation. It is evident by the studies that 0 candidate genes variations play vital role in its development and progression. Therefore, we investigated the genetic variation of TLR-8, TNF, and ESR-1α genes in the Pakistani population. A case-control study comprising 300 RA, 316 OA, and 412 control subjects was conducted. PCR-RFLP and direct sequencing methods were used for determining genetic variations. Analysis was performed by using PLINK and MEGA 6.0 software. Allelic and genetic frequencies of polymorphisms identified on rs3764879 (TLR-8), rs3764880 (TLR-8), rs5744080 (TLR-8), rs1800629 (TNF), rs2228480 (ESR-1α), and rs1451501590 (ESR-1α) were significantly varied among RA, OA, and controls. Novel functional mutations SCV000844945 and SCV000844946 on TLR-8 as well as a non-functional SCV000804801 and functional variation SCV000804802 on ESR-1α were also identified and reported for the first time in the studied population. Multiple site analyses indicated that polymorphisms on TLR-8 and ESR-1α genes were significant risk factors in disease onset to the next generation. In conclusion, TLR-08 and ESR-1α were significant in the onset of arthritis whereas the TNF was not found as a significant risk factor in the onset of RA and OA.

ACL Research Retreat IX Summary Statement: The Pediatric Athlete, March 17-19, 2022; High Point, North Carolina.

ACL Research Retreat IX Summary Statement: The Pediatric Athlete, March 17-19, 2022; High Point, North Carolina.

Poster 206: TIPE2 Mitigates the Histopathology of Osteoarthritis in An Accelerate Aging Mouse Model

Poster 206: TIPE2 Mitigates the Histopathology of Osteoarthritis in An Accelerate Aging Mouse Model

MEDIAL MENISCUS EXTRUSION (MME) IS A RISK FACTOR FOR PROGRESSION OF EARLY-STAGE KNEE OSTEOARTHRITIS IN MIDDLE-AGED POPULATIONS WITHOUT KNEE OSTEOARTHRITIS -THE DATA FROMOSTEOARTHRITIS INITIATIVE

Purpose: Osteoarthritis of the knee (knee OA) is a major cause of morbidity and disability as well as a burden on health-care resources, especially for the elderly. Knee OA is a slowly but progressive joint disease and is most common form of joint dysfunction and knee pain.The onset of knee OA is defined as having a Kellgren-Lawrence (K/L) classification grade 2 or higher, which is a severity classification of plain radiography. In recent years, attention has been focused on the pre-symptomatic pathology of early-stage knee OA.

Are Psychosocial Factors Determinant in the Pain and Social Participation of Patients with Early Knee Osteoarthritis? A Cross-Sectional Study.

The main objective of this research is to determine the psychosocial differences between patients with knee pain or early osteoarthritis (EOA) and healthy subjects at risk of developing osteoarthritis. The secondary objective is to determine how psychosocial factors might influence pain and social participation in patients with EOA. A cross-sectional study was performed. Participants were divided according to the presence of pain or EOA. Pain intensity both at rest and walking, psychological variables such as anxiety and depression, and social participation were evaluated. A total of 105 participants were included (64 with knee pain and 41 without pain), with a mean age of 51.42 ± 5.92 (35 men and 70 women). Patients with knee pain had higher levels of anxiety (MD = −2.35; p < 0.01; d = 0.66) and depression (MD = −2.45; p < 0.01; d = 0.87), regardless of the presence of EOA. In addition, patients with higher depression levels had lower levels of social participation. The results revealed a relationship between the psychological variables, anxiety and depression, with knee pain and the onset of symptomatic OA, as well as an influence of depression levels on social participation. Improving these psychological characteristics may be useful in delaying the onset of symptomatic OA and enhancing social participation.

Early detection of osteoarthritis in the rat with an antibody specific to type II collagen modified by reactive oxygen species

BackgroundOsteoarthritis (OA) is a disease of the whole joint, with articular cartilage breakdown as a major characteristic. Inflammatory mediators, proteases, and oxidants produced by chondrocytes are known to be responsible for driving cartilage degradation. Nevertheless, the early pathogenic events are still unclear. To investigate this, we employed an antibody that is specific to oxidative post-translationally modified collagen type II (anti-oxPTM-CII) to detect early cartilage pathogenic changes in two rat models of OA.MethodsThe animals underwent surgery for destabilization of the medial meniscus (DMM) and were sacrificed after 3, 5, 7, 14, and 28 days. Alternatively, anterior cruciate ligament transection with partial meniscectomy (ACLT+pMx) was performed and animals were sacrificed after 1, 3, 5, 7, and 14 days. Joints were stained with toluidine blue and saffron du Gatinais for histological scoring, anti-oxPTM-CII, and anti-collagen type X antibodies (anti-CX).ResultsWe observed positive oxPTM-CII staining as early as 1 or 3 days after ACLT+pMx or DMM surgeries, respectively, before overt cartilage lesions were visible. oxPTM-CII was located mostly in the deep zone of the medial tibial cartilage, in the pericellular and territorial matrix of hypertrophic chondrocytes, and co-localized with CX staining. Staining was weak or absent for the lateral compartment or the contralateral knees except at later time points.ConclusionThe results demonstrate that oxidant production and chondrocyte hypertrophy occur very early in the onset of OA, possibly initiating the pathogenic events of OA. We propose to use anti-oxPTM-CII as an early biomarker for OA ahead of radiographic changes.

Discovery and functional analysis of osteoarthritis susceptibility genes using families from a large population-based cohort

Purpose: The main obstacle to the development of disease-modifying therapies for OA is poor understanding of the disease process: we do not know the cell types or molecular pathways that normally function to limit susceptibility to OA. Our goal is to discover molecular pathways that are vulnerability points for the development of OA and generate mouse models using human disease alleles. We discover these pathways by identifying rare gene mutations in coding sequences that have a strong effect on susceptibility to OA in families identified from a unique statewide population-based cohort, the Utah Population Database. From the family studies, we identify gene variants that we view as candidates for having a strong effect on OA susceptibility. To rapidly identify those candidate variants that measurably alter gene function, we quantitatively assay WT and variant gene functions in zebrafish embryos or tissue culture. We then determine whether and how the functionally altered genes confer susceptibility to OA in genetically modified mouse models. Methods: We take an approach used infrequently in the OA field. We study many unrelated families with clear-cut inherited forms of OA to identify susceptibility alleles that have strong determinate effects. To discover pathways that when modified lead to strong and unambiguous susceptibility to OA, we analyzed the exomes of >50 unrelated families from the Utah Population Database that had a significant enrichment of dominantly inherited shoulder OA, distal and proximal interphalangeal joint hand OA, erosive hand OA, and 1st metatarsophalangeal (MTP) joint OA. We use loss- and gain-of-function analyses in zebrafish to rapidly screen for gene variants that have a functional impact on protein activity. Finally, Crispr/Cas9 technology is used to introduce OA-associated disease alleles into the mouse where we analyze the how these mutations affect onset and progression of OA. Results: Our results indicate that we can use families to identify genes and pathways that confer strong susceptibility to the early stages of OA. Our approach has led to the discovery of candidate gene variants in families with different forms of OA that affect common pathways. These pathways include genes that regulate 1) the proinflammatory response, 2) mechanotransduction/mechanosensation, 3) the TGF-b and Notch signaling pathways, 3) transcription modulators, and 4) ECM components and ECM modification. We have discovered variants that are worth pursuing experimentally as they coincide with loci detected in GWAS, affect genes of related biological function, represent multiple alleles of a candidate gene, and identify genes not previously linked to OA. We have identified mutations in the NOD-RIPK2 pathway in families with interphalangeal joint, erosive hand, and 1st MTP joint OA. The NOD-RIPK2 pathway is a central regulator of the proinflammatory response. We have shown the OA-associated variants have increased proinflammatory activity relative to the wildtype protein. Based on these findings, we propose the gene variants act dominantly as a gain-of-function allele to over-stimulate the inflammatory response to naturally occurring joint damage leading to OA. To test this hypothesis we introduced a single amino acid change, encoded by the RIPK2 disease allele, into an isogenic mouse. Current results indicate mice harboring the disease allele exhibit increased severity of OA, an increased systemic inflammatory response, and altered gene expression when compared to controls. We have generated a conditional disease allele to test whether expression of the RIPK2 disease allele in innate immune cells or chondrocytes is sufficient to confer increased susceptibility to experimentally induced or spontaneous OA in the mouse. Erosive hand OA is characterized radiographically by centrally located interphalangeal joint erosions, and clinically by its rapid onset and progression. Genomic analysis of one family identified a rare coding variant in the procollagen galactosyltransferase COLGALT1. Loss- and gain-of-function analyses in the zebrafish indicate that colgalt1a/1b are necessary for cartilage formation. We are also examining if collagen structure is disrupted in articular cartilage of mice with a Colgalt1 mutation and if Colgalt1 mutant mice are more susceptible to injury induced OA. Conclusions: Our studies demonstrate our innovative approach of combining genetic analysis of families with OA and functional variant analysis in the zebrafish to identify well-supported OA-associated alleles and pathways. Our approach has led to the discovery of 1) compelling novel candidate genes, 2) multiple genes that contribute to a common pathway, 3) and identification of common pathways altered in multiple forms of OA, 4) and to the generation of new mouse models of OA. Our genetic studies of families with OA and functional analyses in the mouse support our hypothesis that variation in the inflammatory response may be a key factor in susceptibility to OA. Our work is significant in that we have taken a novel approach to identify genes that when mutated have a significant impact on the onset or progression of OA. Developing new animal models with these susceptibility genes will be useful for discovery of therapeutic drugs.

Evidence of differential metabotypes in synovial fibroblasts and synovial fluid in obese hip osteoarthritis patients

Purpose: Purpose: Synovial inflammation (synovitis) is considered to be an active process in the development and progression of OA joint pathology. Synovitis occurs at the onset of OA and is thought to contribute to the degradation of articular cartilage via the release of pro-inflammatory cytokines from synovial fibroblasts, which can induce the expression and release of cartilage matrixmetalloproteases and aggrecanases that degrade type II collagen and proteoglycans respectively. Importantly, we recently reported that synovial fibroblasts from end-stage obese OA patients display an enhanced inflammatory phenotype, compared to normal-weight OA patients.

YAP/TAZ nuclear translocation as a downstream target of mechanical stimuli promotes anabolic activity in human articular chondrocytes and synovial fibroblasts

Purpose: Mechanical loading is considered important to joint health. While physiological loading promotes joint tissue homeostasis and maintains joint function, abnormal or pathophysiological mechanical loading leads to the onset and progression of OA. However, the precise intracellular mechanisms of joint tissue response to external mechanical cues still remains unclear. Yes-associated protein (YAP) together with its transcriptional co-activator with PDZ-binding motif (TAZ) has been widely studied as a mechanotransducer in many cell types.

Elevated levels of TNF-\u03b1, IL-1\u03b2 and IL-6 in the synovial tissue of patients with labral tear: a comparative study with hip osteoarthritis

BackgroundLabral tear can be the initiating factor in the onset of hip osteoarthritis (HOA). However, the physiopathology of labral tear is not fully understood. Our aim was to compare synovial tissue inflammatory cytokine levels between patients with labral tear and late-stage HOA.MethodsSynovial tissue from sites showing the greatest inflammation was harvested from 106 hips from 100 subjects during hip surgery. RNA was extracted, and levels of TNFA, IL1B, IL6 and COX2 mRNA were compared among all patients using real-time PCR. Additionally, we examined whether femoroacetabular impingement (FAI) was associated with elevated levels of inflammatory cytokines in patients with labral tear. To analyze the effects of TNF-α on inflammatory mediators in hip synovial tissue, synovial fibroblasts were extracted from hip synovial tissue of patients with labral tear and late-stage HOA (n = 5 each). Mononuclear cells were extracted from synovial tissue, cultured for 7 days, and stimulated with control or 10 ng/mL human recombinant TNF-α for 1 day. mRNA was extracted from stimulated cells and IL1B, IL6, and COX2 levels were determined using real-time PCR.ResultsTNFA, IL1B, and COX2 expression in synovial tissue were significantly higher in patients with labral tear than late-stage HOA (TNFA, p < 0.001; IL1B, p < 0.001; COX2, p = 0.001). There were no differences in expression between patients with labral tear with and without FAI (TNFA, p = 0.546; IL1B, p = 0.559; IL6, p = 0.599; COX2, p = 0.124). Compared to vehicle control, TNF-α stimulation significantly elevated IL1B, IL6, and COX2 expression in synovial fibroblasts collected from patients with labral tear and late-stage HOA (IL1B, p = 0.043 and p = 0.043; IL6, p = 0.043 and 0.043; COX2, p = 0.043 and p = 0.080, respectively).ConclusionsTNFA, IL1B, and COX2 expression were elevated in the synovial tissue of patients with labral tear. Further investigations are needed to reveal the relationship between inflammatory cytokine levels and various aspects of labral tear pathology, including pain and the onset and progression of OA.

Current Applications of Growth Factors for Knee Cartilage Repair and Osteoarthritis Treatment.

The decreased contact area, edge loading, and increased stress in the adjacent area cartilage resulting from chondral defects are believed to predispose this tissue to degenerative changes that have significant economic implications, especially when considering its progression to osteoarthritis of the knee. Growth factors are considered therapeutic possibilities to enhance healing of chondral injuries and modify the progression to degenerative arthritis. Thus, the purposes of this review are to first to summarize important points for defect preparation and recent advances in techniques for marrow stimulation and second, and to identify specific growth factors and cytokines that have the capacity to advance cartilage regeneration and the treatment of osteoarthritis in light of recent laboratory and clinical studies. TGF-β, BMP-2, BMP-7, IGF-1, as IL-1 receptor antagonist, and recombinant human FGF-18 are some of the promising growth factor/cytokine treatments with pioneering and evolving clinical developments. The bulk of the review describes and discusses these developments in light of fundamental basic science. It is crucial to also understand the other underlying advances made in the surgical management of cartilage defects prior to onset of OA. These advances are in techniques for defect preparation and marrow stimulation, a common cartilage repair procedure used in combination with growth factor/cytokine augmentation. Multiple growth factor/cytokine modulation therapies are currently undergoing clinical trial investigation including Invossa (currently in phase III study), Kineret (currently in phase I study), and Sprifermin (currently in phase II study) for the treatment of symptomatic osteoarthritis.

Discovery and functional analysis of osteoarthritis susceptibility genes using pedigrees from a statewide population-based cohort

Purpose: Lack of understanding of the biological processes conferring susceptibility to OA and the paucity of animal models are key limitations to the development of effective therapies. Our goal is to discover molecular pathways that are vulnerability points for the development of OA and generate mouse models using human disease alleles. We discover these pathways by identifying rare gene mutations in coding sequences that have a strong effect on susceptibility to OA in families identified from a unique statewide population-based cohort, the Utah Population Database. From the family studies, we identify gene variants that we view as candidates for having a strong effect on OA susceptibility. To rapidly identify those candidate variants that measurably alter gene function, we quantitatively assay WT and variant gene functions in zebrafish embryos. We then determine whether and how the functionally altered genes confer susceptibility to OA in genetically modified mouse models. Methods: To discover pathways that when modified lead to strong and unambiguous susceptibility to OA, we analyzed the exomes of 50 unrelated families from the Utah Population Database that had a significant enrichment of shoulder OA, distal and proximal interphalangeal joint hand OA, erosive hand OA, and 1st metatarsophalangeal (MTP) joint foot OA. We use loss- and gain-of-function analyses in zebrafish to rapidly screen for gene variants that have a functional impact on protein activity. Finally, Crispr/Cas9 technology is used to introduce OA-associated disease alleles into the mouse where we analyze the how these mutations affect onset and progression of OA. Results: Our results indicate that we can use families to identify genes and pathways that confer strong susceptibility to the early stages of OA. Our approach has led to the discovery of candidate gene variants in families with different forms of OA that affect common pathways. These pathways include genes that regulate i) the proinflammatory response, ii) mechanotransduction/mechanosensation, iii) the TGF-b and Notch signaling pathways, and iv) collagen modification. We have identified mutations in the NOD-RIPK2 pathway in families with interphalangeal joint, erosive hand, and 1st MTP joint OA. The NOD-RIPK2 pathway is a central regulator of the proinflammatory response. We have shown the OA-associated variants have increased proinflammatory activity relative to the wildtype protein. Based on these findings, we propose the gene variants act dominantly as a gain-of-function allele to over-stimulate the inflammatory response to naturally occurring joint damage leading to OA. To test this hypothesis we introduced a single amino acid change, encoded by the RIPK2 disease allele, into an isogenic mouse. Current results indicate mice harboring the disease allele exhibit increased severity of OA when compared to controls. Erosive hand OA is characterized radiographically by centrally located interphalangeal joint erosions, and clinically by its rapid onset and progression. Genomic analysis of one family identified a rare coding variant in the procollagen galactosyltransferase COLGALT1. We are currently analyzing the functional impact of the COLGLAT1 gene variant in zebrafish and examining if collagen structure is disrupted in articular cartilage of mice with a Colgalt1 mutation. Conclusions: Our studies indicate that we can use families to identify genes and pathways that confer strong susceptibility to the early stages of OA. Our approach has led to the discovery of i) compelling novel candidate genes, ii) multiple genes that contribute to a common pathway, iii) and identification of common pathways altered in multiple forms of OA, iv) and to the generation of new mouse models of OA. Our genetic studies of families with OA and functional analyses in the mouse support our hypothesis that variation in the inflammatory response may be a key factor in susceptibility to OA. Our work is significant in that we have taken a novel approach to identify genes that when mutated have a significant impact on the onset or progression of OA. Developing new animal models with these susceptibility genes will be useful for discovery of therapeutic drugs.

The Role of Synovium in the Onset and Progression Of OA

The Role of Synovium in the Onset and Progression Of OA

Diagnostic performance of region- and layer-specific cartilage transverse relaxtion time (T2) in pre-radiographic and radiographic knee osteoarthritis - data from the osteoarthritis initiative

Purpose: Magnetic resonance imaging (MRI) transverse (spin-spin) relaxation time (T2) has been proposed as an imaging biomarker for detecting OA-related alterations in articular cartilage composition before the onset of radiographic knee OA (ROA). A recent meta-analysis reported cartilage T2 to significantly discriminate OA vs. controls, but these analyses have not demonstrated diagnostic sensitivity across pre-radiographic stages of early OA where T2 is thought to be most effective as an “early OA” marker.