Enhanced levels of non-enzymatic glycation and pentosidine crosslinking in spontaneous osteoarthritis progression

More than Just Type 1 or Type 2: Radiologically and Anatomically Refined Lunate Classification Correlating Ulnar Carpal Alignment and Hamate-Lunate Osteoarthrosis

Background: Hamate-lunate impingement or osteoarthritis can be a cause of ulnar-sided wrist pain. In the literature, the lunate has commonly been classified according to the configuration of its distal articular surface into type 1 and type 2, as described by Viegas. A type 1 lunate possesses only a distal articular surface for the capitate, while a type 2 lunate shows an additional medial facet articulating directly with the hamate. Type 2 lunates have been identified as a risk factor for ulnar-sided wrist pain and the development of osteoarthritis in the midcarpal wrist. However, this does not sufficiently explain all arthritic changes between the hamate and lunate. Methods: In this prospective anatomical-radiological cadaver study, 60 wrists were examined. The midcarpal articulation was documented using conventional X-ray, CT arthrography, and anatomical dissection. The study specifically analyzed the positioning of the lunate relative to the hamate apex and its association with the development of hamate-lunate osteoarthritis. For this purpose, the classification by Viegas was refined. Based on posterior-anterior (p.a.) X-ray examinations of the wrist lunates were divided into type 1a, type 1b, and type 2. The type 1a lunate articulates only with the capitate in the midcarpal joint. The type 1b lunate also articulates only with the capitate; however, medially, the apex of the hamate protrudes beyond a Differentiation Line (D-line), which extends from the radial border of the trapezium or the ulnar border of the lunotriquetral (LT) space, without forming a facet with the lunate. A type 2 lunate articulates distally with the capitate and has an additional medial facet with the hamate. Results: Osteoarthritis between the hamate and lunate was observed in both Viegas type 1 and type 2 lunates. According to our refined lunate classification, both in situ and radiologically, type 1b and type 2 lunates showed a substantially higher prevalence and severity of hamate-lunate osteoarthritis compared to type 1a lunates. However, there was no significant difference in the prevalence of hamate-lunate osteoarthritis between type 1b and type 2 lunates. Conclusions: Assessing lunate type and signs of osteoarthritis is essential when evaluating patients with ulnar-sided wrist pain. Our study demonstrates that osteoarthritis in Viegas type 1 lunate is influenced by the position of the hamate apex relative to the D-line. The refined lunate classification, based on correlated radiological and anatomical studies of the wrist, provides a straightforward method for identifying a potential cause of ulnar-sided wrist pain on p.a. X-rays. This classification can help guide further diagnostic and therapeutic decisions, such as wrist arthroscopy with possible resection of the hamate apex.

Exogenous Collagen Crosslinking is Highly Detrimental to Articular Cartilage Lubrication

Healthy articular cartilage is a remarkable bearing material optimized for near-frictionless joint articulation. Because its limited self-repair capacity renders it susceptible to osteoarthritis (OA), approaches to reinforce or rebuild degenerative cartilage are of significant interest. While exogenous collagen crosslinking (CXL) treatments improve cartilage's mechanical properties and increase its resistance to enzymatic degradation, their effects on cartilage lubrication remain less clear. Here, we examined how the collagen crosslinking agents genipin (GP) and glutaraldehyde (GTA) impact cartilage lubrication using the convergent stationary contact area (cSCA) configuration. Unlike classical configurations, the cSCA sustains biofidelic kinetic friction coefficients (μk) via superposition of interstitial and hydrodynamic pressurization (i.e., tribological rehydration). As expected, glutaraldehyde- and genipin-mediated CXL increased cartilage's tensile and compressive moduli. Although net tribological rehydration was retained after CXL, GP or GTA treatment drastically elevated μk. Both healthy and "OA-like" cartilage (generated via enzymatic digestion) sustained remarkably low μk in saline- (≤0.02) and synovial fluid-lubricated contacts (≤0.006). After CXL, μk increased up to 30-fold, reaching values associated with marked chondrocyte death in vitro. These results demonstrate that mechanical properties (i.e., stiffness) are necessary, but not sufficient, metrics of cartilage function. Furthermore, the marked impairment in lubrication suggests that CXL-mediated stiffening is ill-suited to cartilage preservation or joint resurfacing.

Biochemical and morpho-mechanical properties, and structural organization of rat tail tendon collagen in diet-induced obesity model

We have investigated the impact of obesity on the structural organization, morpho-mechanical properties of collagen fibers from rat tail tendon fascicles (RTTFs). Polarized Raman microspectroscopy showed that the collagen bands 855, 875, 938, and 960 cm-1 as well as those 1631 and 1660 cm-1 were affected by diet. Mechanical properties exhibited an increase in the yield strength from control (CTRL) to high fat (HF) diet (9.60 ± 1.71 and 13.09 ± 1.81 MPa) (p < 0.01) and ultimate tensile strength (13.12 ± 2.37 and 18.32 ± 2.83 MPa) (p < 0.05) with no significant change in the Young's Modulus. During mechanical, the band at 875 cm-1 exhibited the most relevant frequency shift (2 cm-1). The intensity of those at 855, 875, and 938 cm-1 in HF collagen displayed a comparable response to mechanical stress as compared to CTRL collagen with no significant diet-related changes in the Full Width at Half Maximum. Second harmonic generation technique revealed i) similar fiber straightness (0.963 ± 0.004 and 0.965 ± 0.003) and ii) significant changes in fibers diameter (1.48 ± 0.07 and 1.52 ± 0.08 μm) (p < 0.05) and length (22.06 ± 2.38 and 29.00 ± 3.76 μm) (p < 0.001) between CTRL and HF diet, respectively. The quantification of advanced glycation end products (AGEs) revealed an increase in both carboxymethyl-lysine and total fluorescence AGEs from CTRL to HF RTTFs.

Advanced glycation end-product accumulation differs by location and sex in aged osteoarthritic human menisci

OBJECTIVE

There is a clear link between increasing age and meniscus degeneration, leading to increased injury, osteoarthritis (OA) progression, and often total knee replacement. Advanced glycation end-products (AGEs) are non-enzymatic crosslinks and adducts that accumulate in collagen with age, altering tissue mechanics and cell function, ultimately leading to increased injury and inflammation. AGEs, both fluorescent and non-fluorescent, play a central role in age-related degradation of tissues throughout the body; however, little is known about their role in meniscus degeneration. The objective of this study was to characterize changes in aged OA menisci, specifically evaluating zonal AGE accumulation, to gain a better understanding of changes that may lead to age-related meniscal degeneration.

METHOD

Deidentified human menisci (N = 48, 52-84 years old) were obtained from subjects undergoing total knee replacement. Changes in extracellular matrix (ECM) were assessed by gross morphology, confocal analysis, and biochemical assays. Deoxyribonucleic acid (DNA), glycosaminoglycan (GAG), collagen, and AGE accumulation were compared with patient age, zonal region, and patient sex.

RESULTS

There were minimal changes in DNA, GAG, and collagen concentration with age or zone. However, collagen fraying and AGEs increased with age, with more AGEs accumulating in the meniscal horns compared to the central body and in male menisci compared to females.

CONCLUSIONS

Overall, this work provides greater insights into regional changes that occur in human menisci with age and OA. These results suggest AGEs may play a role in the degeneration of the meniscus, with AGEs being a possible target to reduce age-related tears, degeneration, and OA progression.

Role of Advanced Glycation End Products in Intervertebral Disc Degeneration: Mechanism and Therapeutic Potential

The incidence of low back pain caused by lumbar disc degeneration is high, and it can lead to loss of work ability and impose heavy social and economic burdens. The pathogenesis of low back pain is unclear, and there are no effective treatments. With age, the deposition of advanced glycation end products (AGEs) in intervertebral disc (IVD) gradually increases and is accelerated by diabetes and a high-AGEs diet, leading to destruction of the annulus fibrosus (AF), nucleus pulposus (NP), and cartilage endplate (CEP) and finally intervertebral disc degeneration (IDD). Reducing the accumulation of AGEs in IVD and blocking the transmission of downstream signals caused by AGEs have a significant effect on alleviating IDD. In this review, we summarize the mechanism by which AGEs induce IDD and potential treatment strategies.

Ribose Intake as Food Integrator: Is It a Really Convenient Practice?

Reports concerning the beneficial effects of D-ribose administration in cardiovascular and muscle stressful conditions has led to suggestions for the use of ribose as an energizing food supplement for healthy people. However, this practice still presents too many critical issues, suggesting that caution is needed. In fact, there are many possible negative effects of this sugar that we believe are underestimated, if not neglected, by the literature supporting the presentation of the product to the market. Here, the risks deriving from the use of free ribose as ATP source, forcing ribose-5-phosphate to enter into the pentose phosphate pathway, is emphasized. On the basis of the remarkable glycation capacity of ribose, the easily predictable cytotoxic effect of the molecule is also highlighted.

Ligament Alteration in Diabetes Mellitus

Connective tissue ageing is accelerated by the progressive accumulation of advanced glycation end products (AGEs). The formation of AGEs is characteristic for diabetes mellitus (DM) progression and affects only specific proteins with relatively long half-lives. This is the case of fibrillar collagens that are highly susceptible to glycation. While collagen provides a framework for plenty of organs, the local homeostasis of specific tissues is indirectly affected by glycation. Among the many age- and diabetes-related morphological changes affecting human connective tissues, there is concurrently reduced healing capacity, flexibility, and quality among ligaments, tendons, bones, and skin. Although DM provokes a wide range of known clinical disorders, the exact mechanisms of connective tissue alteration are still being investigated. Most of them rely on animal models in order to conclude the patterns of damage. Further research and more well-designed large-cohort studies need to be conducted in order to answer the issue concerning the involvement of ligaments in diabetes-related complications. In the following manuscript, we present the results from experiments discovering specific molecules that are engaged in the degenerative process of connective tissue alteration. This review is intended to provide the report and sum up the investigations described in the literature concerning the topic of ligament alteration in DM, which, even though significantly decreasing the quality of life, do not play a major role in research.

An inducible model for unraveling the effects of advanced glycation end-product accumulation in aging connective tissues

PURPOSE

In connective tissues there is a clear link between increasing age and degeneration. Advanced glycation end-products (AGEs) are believed to play a central role. AGEs are sugar-induced non-enzymatic crosslinks which accumulate in collagen with age and diabetes, altering tissue mechanics and cellular function. Despite ample correlative evidence linking collagen glycation to tissue degeneration, little is known how AGEs impact cell-matrix interactions, limiting therapeutic options. One reason for this limited understanding is that AGEs are typically induced using high concentrations of ribose which decrease cell viability, making it impossible to investigate cell-matrix interactions. The objective of this study was to develop a system to trigger AGE accumulation while maintaining cell viability.

MATERIALS AND METHODS

Using cell-seeded high density collagen gels, we investigated the effect of two systems for AGE induction, ribose at low concentrations (30, 100, and 200 mM) over 15 days of culture and riboflavin (0.25 and 0.75 mM) induced with blue light for 40 seconds (riboflavin-465 nm).

RESULTS

We found ribose and riboflavin-465 nm treatment produces fluorescent AGE quantities which match and/or exceed human fluorescent AGE levels for various tissues, ages, and diseases, without affecting cell viability or metabolism. Interestingly, a 40 second treatment of riboflavin-465 nm produced similar levels of fluorescent AGEs as 3 days of 100 mM ribose treatment.

CONCLUSIONS

Riboflavin-465 nm is a promising method to trigger AGEs on demand in vivo or in vitro without impacting cell viability and offers potential for unraveling the mechanism of AGEs in age and diabetes related tissue damage.

Advanced glycation end products and their adverse effects: The role of autophagy

The critical roles played by advanced glycation endproducts (AGEs) accumulation in diabetes and diabetic complications have gained intense recognition. AGEs interfere with the normal functioning of almost every organ with multiple actions like apoptosis, inflammation, protein dysfunction, mitochondrial dysfunction, and oxidative stress. However, the development of a potential treatment strategy is yet to be established. Autophagy is an evolutionarily conserved cellular process that maintains cellular homeostasis with the degradation and recycling systems. AGEs can activate autophagy signaling, which could be targeted as a therapeutic strategy against AGEs induced problems. In this review, we have provided an overview of the adverse effects of AGEs, and we put forth the notion that autophagy could be a promising targetable strategy against AGEs.

Collagen: quantification, biomechanics, and role of minor subtypes in cartilage

Collagen is a ubiquitous biomaterial in vertebrate animals. Although each of its 28 subtypes contributes to the functions of many different tissues in the body, most studies on collagen or collagenous tissues have focussed on only one or two subtypes. With recent developments in analytical chemistry, especially mass spectrometry, significant advances have been made toward quantifying the different collagen subtypes in various tissues; however, high-throughput and low-cost methods for collagen subtype quantification do not yet exist. In this Review, we introduce the roles of collagen subtypes and crosslinks, and describe modern assays that enable a deep understanding of tissue physiology and disease states. Using cartilage as a model tissue, we describe the roles of major and minor collagen subtypes in detail; discuss known and unknown structure-function relationships; and show how tissue engineers may harness the functional characteristics of collagen to engineer robust neotissues.

Linagliptin protects human chondrogenic ATDC5 cells against advanced glycation end products (AGEs)-induced apoptosis via a mitochondria-dependent pathway

Chondrocytes in joints are responsible for the formation and remodeling of articular cartilage. The accumulation of advanced glycation end products (AGEs) in cartilage is detrimental to the survival of chondrocytes. Linagliptin is one of the most commonly used anti-diabetes agents, and recent work indicates that it exerts an anti-inflammatory effect in different cell types. In this study, we showed that Linagliptin had a protective role in AGEs-induced chondrocyte injury. The presence of Linagliptin ameliorated AGEs-induced reactive oxygen species (ROS) induction and reduced cellular protein carboxyl content. Linagliptin mitigated AGEs-induced mitochondrial membrane potential (_ΔΨm) reduction and NAPDH oxidase subunit NOX-4 induction, indicating that Linagliptin is a potent anti-ROS agent in chondrocytes. Additionally, Linagliptin inhibited AGEs-induced production of high mobility group box chromosomal protein 1 (HMGB-1), and the expression of matrix metalloproteases (MMPs)-2 and -9. Flow cytometry experimentation showed that Linagliptin inhibited AGEs-induced apoptotic subpopulation. Moreover, Linagliptin inhibited the AGEs-induced increased ratio of Bax to Bcl-2, translocation of cytochrome C from mitochondria to the cytoplasm, and release of cleaved caspase-3. Collectively, our data indicate that the anti-diabetes drug Linagliptin has a new role in rescuing chondrocyte from insult by AGEs, and may, therefore, have the potential to treat joint disorders.

Effect of Hyperglycemia to The mRNA Level and Protein Expression of Perlecan at Rat Model of Osteoarthritis with Diabetes Mellitus Type 1

INTRODUCTION

Previous research found that diabetes mellitus capable to aggravate osteoarthritis disease. In brief, the hyperglycemia condition in diabetes mellitus has an impact on protein glycation of all joint components, including molecule, such as perlecan. The protein expression of perlecan reflects the presence amount of perlecan in the matrix of articular cartilage. However, the impact of hyperglycemia on articular perlecan has not been explained. Moreover, the role of perlecan as a mechanotransducer for chondrocytes in type 1 Diabetes mellitus remains unclear.

AIM

This research aims to analyze the effect of hyperglycemia in type 1 Diabetes mellitus to the mRNA level and protein expression of perlecan.

METHODS

Thirty-five adult male rats were divided into seven groups, such as three groups of rat model with anterior cruciate ligament transection (ACLT) at right knee (ACLT1, ACLT2, ACLT3); three groups of rats with ACLT at right knee which followed by Streptozotocin injection for diabetic mice model (DM1, DM2, DM3); and control group (N). Rat sacrificed at the third week, fourth week, and sixth week after two months of maintenance. The mRNA level and protein expression were analyzed by using PCR and Western blot. All of data was analyzed by ANOVA.

RESULTS

Protein expression of perlecan in ACLT mice with diabetes mellitus (DM1, DM2, DM3 group) was gradually decreased according to the increased hyperglycemia duration. Whilst, protein expression of perlecan within ACLT mice without diabetes mellitus (ACLT1, ACLT2, ACLT3 group) was increased. The similar result also demonstrated by the mRNA level of perlecan. Group of DM1, DM2, DM3 exhibited decreased mRNA level of perlecan over the hyperglycemia duration. While, ACLT1, ACLT2, and ACLT3 group had a gradually increased of perlecan mRNA level.

CONCLUSION

Hyperglycemia on osteoarthritic condition decreased mRNA level and protein expression of perlecan which increased the severity of osteoarthritis disease.

Chondrocyte Intracellular Matrix Strain Fields of Articular Cartilage Surface in Hyperglycemia Model of Rat: Cellular Morphological Study

Introduction:

Chondrocyte is one cell in articular cartilage was products many proteins, molecules, and other factors. The external influence of cartilage, such as: hyperglycemia was entering joint capsule and impact to the chondrocytes and the cartilage. Hyperglycemia caused modification of heparan sulfate proteoglycan 2 (perlecan) proteins through glycation process.

Aim:

The aim of this study was to analyze morphological changing of chondrocytes pericellular matrix by the influence of hyperglycemia.

Material and Methods:

Eighteen adult male rats were divided into six groups: control, rat treated with sugar intake was 0.5 mg/kg, 0.75 mg/ kg, 1mg/kg, 1.5 g/kg and 2 mg/kg of body weight. The animal model was dislocated and left knee was taken to observe changing of chondrocytes pericellular matrix strain fields by Scanning Electron Microscope (SEM) from perpendicular to femoral condylus cartilage.

Results:

Changing of chondrocytes intracellular matrix strain fields as changing of cell diameters and cell distances at group control and group I to group V, which cell diameters was lower level and cell distances was the highest level at over diet 2. This changing of intracellular matrix strain fields was corresponding to changing chondrocytes morphology in hyperglycemia condition, due to hypertrophic stage as adaptive responses. This research as based on next research for accomplish of hyperglycemia influence to morphology articular cartilage changing to prevent degeneration of cartilage towards osteoarthritis.

Conclusions:

Present study concludes that hyperglycemia influence to chondrocyte intracellular matrix strain fields changing.

Development of a microcomputed tomography scoring system to characterize disease progression in the Hartley guinea pig model of spontaneous osteoarthritis

AIM

There is potential discrepancy between human and laboratory animal studies of osteoarthritis (OA), as radiographic assessment is the hallmark of the former and histopathology the standard for the latter. This suggests a need to evaluate OA in animal models in a manner similar to that utilized in people. Our study aimed to develop a whole joint grading scheme for microcomputed tomography (microCT) images in Hartley guinea pigs, a strain that recapitulates joint changes highlighted in human spontaneous OA.

MATERIALS AND METHODS

Knees from animals aged 2, 3, 5, 9, and 15 months were evaluated via whole joint microCT and standard histologic scoring. Quantitative microCT parameters, such as bone volume/total volume were also collected.

RESULTS

Both whole joint microCT and histologic scores increased with advancing age and showed strong correlation (r = 0.89. p < 0.0001). Histologic scores, which focus on cartilage changes, increased progressively with age. Whole joint microCT scores, which characterize bony changes, followed a stepwise pattern: scores increased between 3 and 5 months of age, stayed consistent between 5 and 9 months, and worsened again between 9 and 15 months.

CONCLUSIONS

This work provides data that advocates the use of a whole joint microCT scoring system in guinea pig studies of OA, as it provides important information regarding bony changes that occur at a different rate than articular cartilage changes. This grading scheme, in conjunction with histology and quantitative microCT measurements, may enhance the translational value of this animal model as it pertains to human work.

Pioglitazone inhibits advanced glycation end product-induced matrix metalloproteinases and apoptosis by suppressing the activation of MAPK and NF-κB

Apoptosis and degeneration coming mainly from chondrocytes are important mechanisms in the onset and progression of osteoarthritis. Specifically, advanced glycation end products (AGEs) play an important role in the pathogenesis of osteoarthritis. Pioglitazone, a peroxisome proliferator-activated receptor γ (PPARγ) agonist has a protective effect on cartilage. This study aims to evaluate the effect of pioglitazone on AGEs-induced chondrocyte apoptosis and degeneration and their underlying mechanism. The in vitro study shows that AGEs induce cleavage of caspase-3 and PARP, up-regulate MMP-13 expression, enhance chondrocyte apoptosis and down-regulate PPARγ expression in human primary chondrocytes, which is reversed by pioglitazone. Furthermore, AGEs activate phosphorylation of Erk, JNK, and p38, and pioglitazone reverses AGEs-induced phosphorylation of Erk and p38. AGEs-induced degradation of IκBα and translocation of nuclear NF-κB p65 is reversed by pioglitazone. Pretreatment of chondrocytes with SB202190 (p38 inhibitor), SP600125 (JNK inhibitor) and BAY-11-7082 (NF-κB inhibitor) inhibit AGEs-induced apoptosis and degeneration. In vivo experiments suggest that pioglitazone reverses AGEs-induced cartilage degeneration and apoptosis in a mouse model, as demonstrated by HE and Safranin O staining, immunohistochemical analyses of Type II collagen (Col II), metalloproteinases (MMPs) and caspase-3. These findings suggest that pioglitazone, a PPARγ agonist, inhibits AGEs-induced chondrocytes apoptosis and degeneration via suppressing the activation of MAPK and NF-κB.

Mechanical stiffness of TMJ condylar cartilage increases after artificial aging by ribose

OBJECTIVE

Aging is accompanied by a series of changes in mature tissues that influence their properties and functions. Collagen, as one of the main extracellular components of cartilage, becomes highly crosslinked during aging. In this study, the aim was to examine whether a correlation exists between collagen crosslinking induced by artificial aging and mechanical properties of the temporomandibular joint (TMJ) condyle. To evaluate this hypothesis, collagen crosslinks were induced using ribose incubation.

METHODS

Porcine TMJ condyles were incubated for 7 days with different concentrations of ribose. The compressive modulus and stiffness ratio (incubated versus control) was determined after loading. Glycosaminoglycan and collagen content, and the number of crosslinks were analyzed. Tissue structure was visualized by microscopy using different staining methods.

RESULTS

Concomitant with an increasing concentration of ribose, an increase of collagen crosslinks was found. The number of crosslinks increased almost 50 fold after incubation with the highest concentration of ribose. Simultaneously, the stiffness ratio of the samples showed a significant increase after incubation with the ribose. Pearson correlation analyses showed a significant positive correlation between the overall stiffness ratio and the crosslink level; the higher the number of crosslinks the higher the stiffness.

CONCLUSION

The present model, in which ribose was used to mimic certain aspects of age-related changes, can be employed as an in vitro model to study age-related mechanical changes in the TMJ condyle.

Relationship between plasma glycation with membrane modification, oxidative stress and expression of glucose trasporter-1 in type 2 diabetes patients with vascular complications

BACKGROUND OF STUDY

Enhanced protein glycation in diabetes causes irreversible cellular damage through membrane modifications. Erythrocytes are persistently exposed to plasma glycated proteins; however, little are known about its consequences on membrane. Aim of this study was to examine the relationship between plasma protein glycation with erythrocyte membrane modifications in type 2 diabetes patients with and without vascular complications.

METHOD

We recruited 60 healthy controls, 85 type 2 diabetic mellitus (DM) and 75 type 2 diabetic patients with complications (DMC). Levels of plasma glycation adduct with antioxidants (fructosamine, protein carbonyl, β-amyloids, thiol groups, total antioxidant status), erythrocyte membrane modifications (protein carbonyls, β-amyloids, free amino groups, erythrocyte fragility), antioxidant profile (GSH, catalase, lipid peroxidation) and Glut-1 expression were quantified.

RESULT

Compared with controls, DM and DMC patients had significantly higher level of glycation adducts, erythrocyte fragility, lipid peroxidation and Glut-1 expression whereas declined levels of plasma and cellular antioxidants. Correlation studies revealed positive association of membrane modifications with erythrocyte sedimentation rate, fragility, peroxidation whereas negative association with free amino groups, glutathione and catalase.

CONCLUSION

Our data suggest that plasma glycation is associated with oxidative stress, Glut-1 expression and erythrocyte fragility in DM patients. This may further contribute to progression of vascular complications.

Differential proteomics of the synovial membrane between bilateral and unilateral knee osteoarthritis in surgery‑induced rabbit models

The present study investigated the differential proteomics of synovial membranes between bilateral and unilateral anterior cruciate ligament transection (ACLT) in rabbits with knee osteoarthritis (KOA), in order to elucidate the pathological biomarkers of different degrees of KOA. A total of 6 New Zealand rabbits were randomly divided into groups A and B (three rabbits per group). The two groups were subjected to bilateral and unilateral ACLT, respectively. A total of 6 weeks following surgery, proteins were extracted from the knee joint synovial membranes of KOA rabbits and were separated by two‑dimensional polyacrylamide gel electrophoresis. The differentially expressed proteins in the OA synovial membranes were selected for further analysis by linear ion trap‑Fourier transform ion cyclotron resonance mass spectrometry. Ten protein spots were identified to be different between the synovial membranes of the bilateral and unilateral KOA rabbits. Protein disulfide‑isomerase and creatine kinase M‑type were identified in the unilateral KOA rabbit synovial membranes. Serum albumin (three spots), lumican, α‑2‑HS‑glycoprotein and three uncharacterized proteins were identified in the synovial membranes of the bilateral KOA rabbits. The differential proteomic expression demonstrated the different biomarkers associated with bilateral and unilateral KOA, and indicated that spontaneous and secondary KOA require diverse methods of treatment; thus the underlying mechanism of KOA requires further investigation.

Establishment of a rabbit model to study the influence of advanced glycation end products accumulation on osteoarthritis and the protective effect of pioglitazone

OBJECTIVE

To investigate the role of advanced glycation end products (AGEs) in cartilage degeneration in vivo and determine the influence of the peroxisome proliferator-activated receptor-γ (PPARγ) agonist pioglitazone on AGEs-induced osteoarthritis (OA) in a rabbit model.

DESIGN

Thirty-two rabbits were separated into four groups (n = 8 each) and received 500 μL of 123, 350, or 1000 mmol/L D-ribose or Phosphate buffered saline (PBS) solution administered to the right stifle joint via intra-articular injection twice a week. All the rabbits ran 500 m on treadmills every day. Another 16 rabbits were administered 1000 mmol/L D-ribose and divided into 2 groups (n = 8) that received either placebo or pioglitazone administered orally at 20 mg/kg/day. Eight weeks later, cartilage damage was evaluated macroscopically, histologically, and biochemically.

RESULTS

Artificially increasing the AGEs level and exercise load resulted in cartilage damage and dose-dependent downregulation of PPARγ expression. The efficacy of pioglitazone treatment was tested in a rabbit OA model, and a clear chondroprotective effect was revealed by macro- and microscopic assessments.

CONCLUSION

Elevating AGEs in rabbits can accelerate the articular cartilage degradation that occurs with physical exercise, and pioglitazone can reduce the severity of the AGEs-induced OA in a rabbit model.

Inter-relations between osteoarthritis and metabolic syndrome: A common link?

Osteoarthritis (OA) is a degenerative disorder of the joint, principally occurring during aging, and characterized by a focal degradation of cartilage. It is the most prevalent rheumatic disease in industrialized countries and represents the second cause of disability in France. However, the etiology of OA remains unclear. There is only one cell type found in cartilage, chondrocyte, which is responsible for its repair and the synthesis of the elements of the extra-cellular matrix. A dysfunction of these cells results in an imbalance between repair and degradation in cartilage, leading to its destruction. Recently, a link between OA and metabolic syndrome (MetS) has been suggested, introducing a notion of metabolic OA, and a new vision of the disease. MetS is characterized by a cluster of factors (insulin resistance, hypertension, dyslipidemia, visceral obesity), although there is still no clear definition of it. During the 20th century, MetS dramatically increased with changes in population lifestyle, becoming a major health issue in industrialized countries. MetS concerns 10-30% of the worldwide population, but is prevalent in 59% of OA patients. Patients with both OA and MetS have more severe symptoms, occurring sooner than in the general population. Indeed, OA is generally a disease concerning the population over 65 years old, but with an associated MetS the target population is around 50 years old. In this review, we will focus on common factors in OA and MetS, such as hypertension, obesity, dyslipidemia, mitochondrial dysfunction and hyperglycemia, linking one disease to the other.

Advanced Glycation-Modified Human Serum Albumin Evokes Alterations in Membrane and Eryptosis in Erythrocytes

Increased burden of advanced glycation end-products (AGEs) in case of hyperglycemic conditions leads to the development of retinopathy, nephropathy, and cardiovascular and neurological disorders such as Alzheimer's disease. AGEs are considered as pro-oxidants, and their accumulation increases the oxidative stress. The prolonged exposure to these AGEs is the fundamental cause of chronic oxidative stress. Abnormal morphology of red blood cells (RBCs) and excessive eryptosis has been observed in diabetes, glomerulonephritis, dyslipidemia, and obesity, but yet the contribution of extracellular AGEs remains undefined. In this study, we investigated the effect of AGEs on erythrocytes to determine their impact on the occurrence of different pathological forms of these blood cells. Specifically, carboxymethyllysine (CML), carboxyethyllysine (CEL), and Arg-pyrimidine (Arg-P) which have been reported to be the most pre-dominant AGEs formed under in vivo conditions were used in this study. Results suggested the eryptotic properties of CML, CEL, and Arg-P for RBCs, which were evident from the highly damaged cell membrane and occurrence of abnormal morphologies. Methylglyoxal-modified albumin showed more severe effects, which can be attributed to the high reactivity and pro-oxidant nature of glycation end products. These findings suggest the possible role of AGE-modified albumin towards the morphological changes in erythrocyte's membrane associated with diabetic conditions.

Computed tomography analysis of guinea pig bone: architecture, bone thickness and dimensions throughout development

The domestic guinea pig, Cavia aperea f. porcellus, belongs to the Caviidae family of rodents. It is an important species as a pet, a source of food and in medical research. Adult weight is achieved at 8–12 months and life expectancy is ∼5–6 years. Our aim was to map bone local thickness, structure and dimensions across developmental stages in the normal animal. Guinea pigs (n = 23) that had died of natural causes were collected and the bones manually extracted and cleaned. Institutional ethical permission was given under the UK Home Office guidelines and the Veterinary Surgeons Act. X-ray Micro Computed Tomography (microCT) was undertaken on the left and right scapula, humerus and femur from each animal to ascertain bone local thickness. Images were also used to undertake manual and automated bone measurements, volumes and surface areas, identify and describe nutrient, supratrochlear and supracondylar foramina. Statistical analysis between groups was carried out using ANOVA with post-hoc testing. Our data mapped a number of dimensions, and mean and maximum bone thickness of the scapula, humerus and femur in guinea pigs aged 0–1 month, 1–3 months, 3–6 months, 6 months–1 year and 1–4 years. Bone dimensions, growth rates and local bone thicknesses differed between ages and between the scapula, humerus and femur. The microCT and imaging software technology showed very distinct differences between the relative local bone thickness across the structure of the bones. Only one bone showed a singular nutrient foramen, every other bone had between 2 and 5, and every nutrient canal ran in an oblique direction. In contrast to other species, a supratrochlear foramen was observed in every humerus whereas the supracondylar foramen was always absent. Our data showed the bone local thickness, bone structure and measurements of guinea pig bones from birth to 4 years old. Importantly it showed that bone development continued after 1 year, the point at which most guinea pigs have reached full weight. This study is the first to show the high abundance (100% in this study) of the supratrochlear foramen within the guinea pig humerus and the complete absence of a supracondylar foramen, which is different to many other species and may also affect potential fracture points and frequencies. Understanding bone morphology and growth is essential in not only understanding the requirements of the healthy guinea pig, but also necessary in order to investigate disease states.

In vitro glycation of articular cartilage alters the biomechanical response of chondrocytes in a depth-dependent manner

OBJECTIVE

To determine if increasing cartilage cross-links through in vitro glycation of cartilage explants can alter the biomechanical response of chondrocytes to compressive deformation.

METHOD

Bovine osteochondral explants were either incubated with cell culture solution supplemented with (n = 7) or without (n = 7) ribose for 42 h in order to induce glycation. Deformation-induced changes in cell volume, dimensions and local tissue strains were determined through confocal laser scanning microscopy (CLSM) and the use of a custom built micro-compression device. Osteochondral explants were also utilized to demonstrate changes in depth-wise tissue properties, biomechanical tissue properties and cross-links such as pentosidine (Pent), hydroxylysyl pyridinoline (HP) and lysyl pyridinoline (LP).

RESULTS

The ribose treated osteochondral samples experienced reduced cell volume deformation in the upper tissue zone by ∼ 8% (P = 0.005), as compared the control samples, through restricting cell expansion. In the deeper tissue zone, cell volume deformation was increased by ∼ 12% (P < 0.001) via the transmission of mechanical signals further into the tissue depth. Biomechanical testing of the ribose treated osteochondral samples demonstrated an increase in the equilibrium and dynamic strain dependent moduli (P < 0.001 and P = 0.008, respectively). The biochemical analysis revealed an increase in Pent cross-links (P < 0.001). Depth-wise tissue property analyses revealed increased levels of carbohydrate content, greater levels of fixed charge density and an increased carbohydrate to protein ratio from 6 to 16%, 55-100% and 72-79% of the normalized tissue thickness (from the surface), respectively, in the ribose-treated group (P < 0.05).

CONCLUSION

In vitro glycation alters the biomechanical response of chondrocytes in cartilage differently in upper and deeper zones, offering possible insights into how aging could alter cell deformation behavior in cartilage.

Structure, function, aging and turnover of aggrecan in the intervertebral disc

BACKGROUND

Aggrecan is the major non-collagenous component of the intervertebral disc. It is a large proteoglycan possessing numerous glycosaminoglycan chains and the ability to form aggregates in association with hyaluronan. Its abundance and unique molecular features provide the disc with its osmotic properties and ability to withstand compressive loads. Degradation and loss of aggrecan result in impairment of disc function and the onset of degeneration.

SCOPE OF REVIEW

This review summarizes current knowledge concerning the structure and function of aggrecan in the normal intervertebral disc and how and why these change in aging and degenerative disc disease. It also outlines how supplementation with aggrecan or a biomimetic may be of therapeutic value in treating the degenerate disc.

MAJOR CONCLUSIONS

Aggrecan abundance reaches a plateau in the early twenties, declining thereafter due to proteolysis, mainly by matrix metalloproteinases and aggrecanases, though degradation of hyaluronan and non-enzymic glycation may also participate. Aggrecan loss is an early event in disc degeneration, although it is a lengthy process as degradation products may accumulate in the disc for decades. The low turnover rate of the remaining aggrecan is an additional contributing factor, preventing protein renewal. It may be possible to retard the degenerative process by restoring the aggrecan content of the disc, or by supplementing with a bioimimetic possessing similar osmotic properties.

GENERAL SIGNIFICANCE

This review provides a basis for scientists and clinicians to understand and appreciate the central role of aggrecan in the function, degeneration and repair of the intervertebral disc.

Characterisation of osteoarthritis in a small animal model of type 2 diabetes mellitus

Objectives

Our objective in this article is to test the hypothesis that type 2 diabetes mellitus (T2DM) is a factor in the onset and progression of osteoarthritis, and to characterise the quality of the articular cartilage in an appropriate rat model.

Methods

T2DM rats were obtained from the UC Davis group and compared with control Lewis rats. The diabetic rats were sacrificed at ages from six to 12 months, while control rats were sacrificed at six months only. Osteoarthritis severity was determined via histology in four knee quadrants using the OARSI scoring guide. Immunohistochemical staining was also performed as a secondary form of osteoarthritic analysis.

Results

T2DM rats had higher mean osteoarthritis scores than the control rats in each of the four areas that were analysed. However, only the results at the medial and lateral femur and medial tibia were significant. Cysts were also found in T2DM rats at the junction of the articular cartilage and subchondral bone. Immunohistochemical analysis does not show an increase in collagen II between control and T2DM rats. Mass comparisons also showed a significant relationship between mass and osteoarthritis score.

Conclusions

T2DM was found to cause global degeneration in the UCD rat knee joints, suggesting that diabetes itself is a factor in the onset and progression of osteoarthritis. The immunohistochemistry stains showed little to no change in collagen II degeneration between T2DM and control rats. Overall, it seems that the animal model used is pertinent to future studies of T2DM in the development and progression of osteoarthritis.

Cite this article: Bone Joint Res 2014;3:203–11

Lifestyle and Advanced Glycation End Products (AGEs) Burden: Its Relevance to Healthy Aging

Uncontrolled continued exposure to oxidative stress is a precursor to many chronic diseases including cancer, diabetes, degenerative disorders and cardiovascular diseases. Of the many known mediators of oxidative stress, reactive oxygen species (ROS) and advanced glycation end products (AGEs) are the most studied. In the present review, we have summarized current data on the origin of circulating AGEs, discussed issues associated with reliable assessment of its steady state level, and changes in its level with age and select metabolic diseases. Lastly, we have made recommendations about life style changes that may decrease AGEs burden to promote healthy aging.

The prevalence of osteoarthritis of the atlanto-odontoid joint in adults using multidetector computed tomography

BACKGROUND

The prevalence of osteoarthritis of the atlanto-odontoid joint has been reported by radiology, autopsy, and conventional computed tomography (CT), but the prevalence has not yet been assessed by multidetector computed tomography (MDCT).

PURPOSE

To reveal the prevalence of osteoarthritis of the atlanto-odontoid joint and to analyze the inter-relationships among gender, age, and osteoarthritis with MDCT in adults.

MATERIAL AND METHODS

First, a series of 700 selected domestic patients aged >18 years undergoing an upper cervical MDCT scan were divided equally into seven age groups. Second, using the postprocessing technique of multiplanar reconstruction, osteoarthritis of the atlanto-odontoid joint was viewed from any direction and classified into four grades, which were normal, mild, moderate, and severe. Lastly, the incidence of the different grades of osteoarthritis was assessed, and the reproducibility was tested.

RESULTS

There was no significant difference between gender and osteoarthritis of atlanto-odontoid joint (P > 0.05). The rate of osteoarthritis was 16% in the age group 18-25 years, 23% in the age group 25-30 years, 33% in the age group 30-40 years, 54% in the age group 40-50 years, 70% in the age group 50-60 years, 87% in the age group 60-70 years, and 93% in the age group >70 years. Mild osteoarthritis appeared at the earliest at age 19.6 years, moderate osteoarthritis in at earliest at age 24.2 years, and severe osteoarthritis at the earliest at age 48.5 years. The inter-observer reliability was excellent (k = 0.86).

CONCLUSION

Osteoarthritis of the atlanto-odontoid joint could be detected by MDCT in a young adult. It increased rapidly with increasing age on MDCT.

Non-enzymatic glycation and glycoxidation protein products in foods and diseases: an interconnected, complex scenario fully open to innovative proteomic studies

The Maillard reaction includes a complex network of processes affecting food and biopharmaceutical products; it also occurs in living organisms and has been strictly related to cell aging, to the pathogenesis of several (chronic) diseases, such as diabetes, uremia, cataract, liver cirrhosis and various neurodegenerative pathologies, as well as to peritoneal dialysis treatment. Dozens of compounds are involved in this process, among which a number of protein-adducted derivatives that have been simplistically defined as early, intermediate and advanced glycation end-products. In the last decade, various bottom-up proteomic approaches have been successfully used for the identification of glycation/glycoxidation protein targets as well as for the characterization of the corresponding adducts, including assignment of the modified amino acids. This article provides an updated overview of the mass spectrometry-based procedures developed to this purpose, emphasizing their partial limits with respect to current proteomic approaches for the analysis of other post-translational modifications. These limitations are mainly related to the concomitant sheer diversity, chemical complexity, and variable abundance of the various derivatives to be characterized. Some challenges to scientists are finally proposed for future proteomic investigations to solve main drawbacks in this research field.

Osteoarthritis year 2013 in review: biomarkers; reflecting before moving forward, one step at a time

In 2010, in Osteoarthritis and Cartilage, we published a comprehensive systematic review applying the consensus BIPED criteria (Burden of Disease, Investigative, Prognostic, Efficacy of Intervention and Diagnostic) criteria on serum and urinary biochemical markers for knee and hip osteoarthritis (OA) using publications that were available at that time. It appeared that none of the biochemical markers at that time were sufficiently discriminating to allow diagnosis and prognosis of OA in individual or limited numbers of patients, nor performed so consistently that they could function as primary outcome parameters in clinical trials. Also at present, almost 3 years later, this ultimate goal has not been reached (yet). Frankly, it might be questioned whether we are making the most adequate steps ahead and maybe we have to take a step back to reconsider our approaches. Some reflections are made and discussed: A critical review of molecular metabolism in OA and validation of currently investigated marker molecules in this may be vital and may lead to new and better markers. Creating cohorts in which synovial fluid (SF) is obtained in a systematic way, together with serum and urine, may also bring the field a further step ahead. Thirdly, better understanding of different phenotypes (subtypes) of OA may facilitate identification and validation of biochemical markers. Finally, the systems biology approach as discussed in the last years OA in review on biomarkers, although very complex, might provide steps forward. Looking ahead, we are optimistic but realistic in our expectations, we believe that the field can be brought forward by critically and cautiously reconsidering our approaches, and making changes forward, one step at a time.

Autoantibodies to posttranslationally modified type II collagen as potential biomarkers for rheumatoid arthritis

OBJECTIVE

Type II collagen (CII) posttranslationally modified by reactive oxygen species (ROS-CII) that are present in the inflamed joint is an autoantigen in rheumatoid arthritis (RA). The aim of this study was to investigate the potential use of anti-ROS-CII autoantibodies as a biomarker of RA.

METHODS

CII was exposed to oxidants that are present in the rheumatoid joint. Autoreactivity to ROS-CII was assessed by enzyme-linked immunosorbent assays in synovial fluid (SF) and serum samples obtained from patients during various phases of RA. This group included disease-modifying antirheumatic drug (DMARD)-naive patients with early RA (n = 85 serum samples) and patients with established RA (n = 80 serum and 50 SF samples), who were categorized as either DMARD responders or DMARD nonresponders. Control subjects included anti-citrullinated protein antibody (ACPA)-positive patients with arthralgia (n = 58 serum samples), patients with osteoarthritis (OA; n = 49 serum and 52 SF samples), and healthy individuals (n = 51 serum samples).

RESULTS

Reactivity to ROS-CII among DMARD-naive patients with early RA was significantly higher than that among patients with ACPA-positive arthralgia, patients with OA, and healthy control subjects (P < 0.0001), with 92.9% of serum samples from the patients with early RA binding to anti-ROS-II. There was no significant difference in anti-ROS-CII reactivity between ACPA-positive and ACPA-negative patients with RA, with 93.8% and 91.6% of serum samples, respectively, binding to ROS-CII. The sensitivity and specificity of binding to ROS-CII in patients with early RA were 92% and 98%, respectively. Among patients with established RA, serum reactivity in DMARD nonresponders was significantly higher than that in DMARD responders (P < 0.01); 58.3% of serum samples from nonresponders and 7.6% of serum samples from responders bound to HOCl-ROS, while the respective values for SF were 70% and 60%. In patients with longstanding RA, autoreactivity to ROS-CII changed longitudinally.

CONCLUSION

Autoantibodies to ROS-CII have the potential to become diagnostic biomarkers of RA.

Osteoarthritis year 2012 in review: biomarkers

PURPOSE

Biomarkers provide useful diagnostic information by detecting cartilage degradation in osteoarthritis (OA), reflecting disease-relevant biological activity and predicting the course of disease progression. They also serve as surrogate endpoints in the drug discovery process. The aim of this narrative review was to focus on OA biomarker-related papers published between the osteoarthritis research society international (OARSI) 2011 meeting in San Diego and the OARSI 2012 meeting in Barcelona.

METHODS

The PubMed/MEDLINE and SciVerse Scopus bibliographic databases were searched using the keywords: 'biomarker' and 'osteoarthritis' and/or 'biomarker' and 'proteomics'.

RESULTS

Ninety-eight papers were found with the keywords 'biomarker' and 'osteoarthritis'. Fifteen papers were found with the keywords 'biomarker' and 'proteomics'. Review articles were also included. The most relevant published studies focused on extracellular matrix (ECM) molecules in body fluids. Enrichment of the deamidated epitope of cartilage oligomeric matrix protein (D-COMP) suggests that OA disease progression is associated with post-translational modifications that may show specificity for particular joint sites. Fibulin-3 peptides (Fib3-1 and Fib3-2) have been proposed as potential biomarkers of OA along with follistatin-like protein 1 (FSTL1), a new serum biomarker with the capacity to reflect the severity of joint damage. The 'membrane attack complex' (MAC) component of complement has also been implicated in OA.

CONCLUSION

Novel OA biomarkers are needed for sub-clinical disease diagnosis. Proteomic techniques are beginning to yield useful data and deliver new OA biomarkers in serum and urine. Combining biochemical markers with tissue and cell imaging techniques and bioinformatics (i.e., machine learning, clustering, data visualization) may facilitate the development of biomarker combinations enabling earlier detection of OA.