Acute Cartilage Injury Research Articles

Omega-3 fatty acids protect cartilage from acute injurie by reducing the mechanical sensitivity of chondrocytes

Acute cartilage injuries, such as intra-articular fractures and blunt impacts, frequently result in chondrocyte death and extracellular matrix (ECM) degradation, significantly elevating the risk of post-traumatic osteoarthritis (PTOA). Despite advances in treatment, no effective therapies currently exist to fully cure PTOA or halt its progression. This study explores the protective effects of the dietary fatty acid eicosapentaenoic acid (EPA) on human primary chondrocytes (HPCs) and cartilage explants exposed to mechanical overload and blunt trauma. HPCs were isolated and subjected to mechanical stretching using BioFlex six-well culture plates, while cartilage explants were subjected to impact loading via a customized drop tower. EPA was incorporated into the culture medium, followed by assays to evaluate cell viability, calcium (Ca²⁺) influx, apoptosis, reactive oxygen species (ROS) levels, and collagen type II alpha (Col-2a) expression. EPA treatment markedly decreased chondrocyte mechanical sensitivity, as demonstrated by enhanced cell viability and reduced lactate dehydrogenase (LDH) release. Furthermore, EPA inhibited Piezo1 activation, leading to lower intracellular Ca²⁺ concentrations, decreased apoptosis, and diminished ROS levels. In cartilage explants, EPA improved chondrocyte viability, minimized structural damage, and sustained higher Col-2a expression compared to the blunt trauma group. These results indicate that EPA effectively shields chondrocytes and cartilage explants from mechanical overload-induced damage by inhibiting Piezo1 activation and mitigating Ca²⁺ influx, apoptosis, and oxidative stress. The findings suggest that EPA supplementation could offer a promising strategy for preventing PTOA progression following acute cartilage injuries. Further research is warranted to assess the clinical applications of EPA and confirm its efficacy in larger animal models and human trials.

Reliability and validity of the Lever Sign Test in suspected ligament and/or meniscus injuries of the knee: a comparison between an orthopaedist and a physical therapist

The purpose of this study was to investigate the intertester reliability and validity of the Lever Sign Test. Intertester reliability has received little attention in previous studies. In order to make comparisons with other studies, the intertester reliability and validity of the Lachman and Anterior Drawer Tests were also calculated. Patients between 18 and 50 years of age with suspected ligament and/or meniscus injuries were included. Exclusion criteria were suspected malignant, systemic, or central neurologic disease, acute cartilage injury, suspected fracture, or knowledge of the participant's knee findings. Testing was randomized and blinded by an experienced orthopaedic surgeon and a physical therapist. Cohen's kappa was calculated for intertester reliability. Sensitivity and specificity, positive and negative predictive value, and positive and negative likelihood ratio were calculated. MRI findings were used as the gold standard. Thirty-six patients were enrolled in the study, 27 male (75%) and 9 female (25%). The prevalence of anterior cruciate ligament lesions was 44.4%. Cohen's kappa (κ) was κ=0.6 (CI 95% [0.29, 0.91]) for the Lever Sign Test, κ=0.64 (CI 95% [0.35, 0.93]) for the Lachman test, and κ=0.63 (CI 95% [0.3, 0.95]) for the Anterior Drawer Test. The sensitivity of the Lever Sign Test was 0.53 and 0.40 for the orthopaedic surgeon and physical therapist, respectively, specificity was 0.89 and 0.79, the positive predictive value was 0.80 and 0.60, the negative predictive value was 0.70 and 0.62, the positive likelihood ratio was 4.80 and 1.90, respectively, and the negative likelihood ratio was 0.76 and 0.53. The estimated intertester reliability of the Lever Sign Test was good. The Lever Sign Test is suitable as a complement to the Lachman Test, which is considered the most valid test in the literature. The weaknesses and ambiguities of the operating mechanism of the Lever Sign Test should not be ignored and should be further explored.

Decreased Synovial Fluid Ghrelin Level Is Associated With Acute Cartilage Injury in Patients With Anterior Cruciate Ligament Tear.

Ghrelin, an amino acid hormone secreted primarily from the stomach, can regulate bone metabolism, regulate inflammation via suppressing proinflammatory cytokines, and suppress expression of matrix metalloproteinases (MMPs). To measure synovial fluid levels of ghrelin in young patients with anterior cruciate ligament (ACL) tear to assess the role of ghrelin as a potential biomarker for cartilage injury. Controlled laboratory study. This study included 120 patients who underwent ACL reconstructionbetween January 1, 2016, and May 31, 2021. We categorized 60 patients with acute cartilage injury (International Cartilage Regeneration & Joint Preservation Society grade 2 or 3) as the acute group and 60 patients with no acute cartilage injury as the nonacute group, with the healthy contralateral knee of each patient acting as the control group (n = 120). Synovial fluid samples were collected from the knees in the operating room before ACL reconstruction. We assessed the inflammatory biomarkers interleukin (IL)-6, MMP-1, MMP-9, and MMP-13, as well as serum ghrelin level and Mankin score, and results were compared between the 3 study groups with the Mann-Whitney U test. Lower serum ghrelin levels in the synovial fluid were found in the acute group compared with the nonacute group and healthy controls (232.4 vs 434.4 vs 421.5 pg/mL, respectively; P < .001). Ghrelin level in the synovial fluid was significantly and positively correlated with IL-6 (r = 0.4223; P < .0001), MMP-13 (r = 0.3402; P < .0001), and Mankin score (r = 0.1453; P = .0244). In patients with ACL injury, ghrelin synovial fluid was significantly differently expressed in patients with cartilage injury and no cartilage injury. Ghrelin synovial fluid has the potential to be a biomarker to predict acute cartilage injury in patients with ACL injury.

A Mouse Model of Acute Cartilage Injury and Repair.

Chondral defects are common and disabling. The development of pharmacological approaches for cartilage repair requires the availability of in vivo models which are amenable for gain and loss of function and ideally to genetic modification. In this chapter, we describe a method to induce full-thickness cartilage defects which, in young DBA/1 mice, heal spontaneously, but fail to heal in C57BL/6 mice of the same age or in aged DBA/1 mice. This model (or variants) has been used for genetic screenings to identify genes associated to repair capacity, to study stem cells involved in cartilage repair, and to study the function of molecules involved in repair mechanisms.

Urocortin-1 Is Chondroprotective in Response to Acute Cartilage Injury via Modulation of Piezo1.

Post-traumatic OA (PTOA) is often triggered by injurious, high-impact loading events which result in rapid, excessive chondrocyte cell death and a phenotypic shift in residual cells toward a more catabolic state. As such, the identification of a disease-modifying OA drug (DMOAD) that can protect chondrocytes from death following impact injury, and thereby prevent cartilage degradation and progression to PTOA, would offer a novel intervention. We have previously shown that urocortin-1 (Ucn) is an essential endogenous pro-survival factor that protects chondrocytes from OA-associated pro-apoptotic stimuli. Here, using a drop tower PTOA-induction model, we demonstrate the extent of Ucn’s chondroprotective role in cartilage explants exposed to excessive impact load. Using pathway-specific agonists and antagonists, we show that Ucn acts to block load-induced intracellular calcium accumulation through blockade of the non-selective cation channel Piezo1 rather than TRPV4. This protective effect is mediated primarily through the Ucn receptor CRF-R1 rather than CRF-R2. Crucially, we demonstrate that the chondroprotective effect of Ucn is maintained whether it is applied pre-impact or post-impact, highlighting the potential of Ucn as a novel DMOAD for the prevention of injurious impact overload-induced PTOA.

Acute Cartilage Injury Induced by Trans-Articular Sutures.

ObjectiveTo determine the extent of acute cartilage injury by using trans-articular sutures.MethodsFive different absorbable sutures, monofilament polydioxanone (PDS) and braided polyglactin (Vicryl), were compared on viable human osteochondral explants. An atraumatic needle with 30 cm of thread was advanced through the cartilage with the final thread left in the tissue. A representative 300 μm transversal slice from the cartilage midportion was stained with Live/Dead probes, scanned under the confocal laser microscope, and analyzed for the diameters of (a) central “Black zone” without any cells, representing in situ thread thickness and (b) “Green zone,” including the closest Live cells, representing the maximum injury to the tissue. The exact diameters of suture needles and threads were separately measured under an optical microscope.ResultsThe diameters of the Black (from 144 to 219 µm) and the Green zones (from 282 to 487 µm) varied between the different sutures (P < 0.001). The Green/Black zone ratio remained relatively constant (from 1.9 to 2.2; P = 0.767). A positive correlation between thread diameters and PDS suturing material, toward the Black and Green zone, was established, but needle diameters did not reveal any influence on the zones.ConclusionsThe width of acute cartilage injury induced by the trans-articular sutures is about twice the thread thickness inside of the tissue. Less compressible monofilament PDS induced wider tissue injury in comparison to a softer braided Vicryl. Needle diameter did not correlate to the extent of acute cartilage injury.

Mitoprotective therapy reduces inflammation and prevents cartilage turnover in an in vivo model of posttraumatic osteoarthritis

Mitoprotective therapy reduces inflammation and prevents cartilage turnover in an in vivo model of posttraumatic osteoarthritis

Regulation of Gdf5 expression in joint remodelling, repair and osteoarthritis

Growth and Differentiation Factor 5 (GDF5) is a key risk locus for osteoarthritis (OA). However, little is known regarding regulation of Gdf5 expression following joint tissue damage. Here, we employed Gdf5-LacZ reporter mouse lines to assess the spatiotemporal activity of Gdf5 regulatory sequences in experimental OA following destabilisation of the medial meniscus (DMM) and after acute cartilage injury and repair. Gdf5 expression was upregulated in articular cartilage post-DMM, and was increased in human OA cartilage as determined by immunohistochemistry and microarray analysis. Gdf5 expression was also upregulated during cartilage repair in mice and was switched on in injured synovium in prospective areas of cartilage formation, where it inversely correlated with expression of the transcriptional co-factor Yes-associated protein (Yap). Indeed, overexpression of Yap suppressed Gdf5 expression in chondroprogenitors in vitro. Gdf5 expression in both mouse injury models required regulatory sequence downstream of Gdf5 coding exons. Our findings suggest that Gdf5 upregulation in articular cartilage and synovium is a generic response to knee injury that is dependent on downstream regulatory sequence and in progenitors is associated with chondrogenic specification. We propose a role for Gdf5 in tissue remodelling and repair after injury, which may partly underpin its association with OA risk.

Simultaneous Quantitation of Cationic and Non-ionic Contrast Agents in Articular Cartilage Using Synchrotron MicroCT Imaging

Early diagnosis of acute cartilage injuries enables monitoring of disease progression and improved treatment option planning to prevent post-traumatic osteoarthritis. In contrast-enhanced computed tomography (CECT), the changes in cationic agent diffusion within the tissue reflect cartilage degeneration. The diffusion in degenerated cartilage depends on proteoglycan (PG) content and water content, but each having an opposite effect on diffusion, thus compromising the diagnostic sensitivity. To overcome this limitation, we propose the simultaneous imaging of cationic (sensitive to PG and water contents) and non-ionic (sensitive to water content) agents. In this study, quantitative dual-energy CT (QDECT) imaging of two agents is reported for the first time at clinically feasible imaging time points. Furthermore, this is the first time synchrotron microCT with monochromatic X-rays is employed in cartilage CECT. Imaging was conducted at 1 and 2 h post contrast agent immersion. Intact, PG-depleted, and mechanically injured + PG-depleted cartilage samples (n = 33) were imaged in a mixture of cationic (iodine-based CA4+) and non-ionic (gadolinium-based gadoteridol) agents. Concurrent evaluation of CA4+ and gadoteridol partitions in cartilage is accomplished using QDECT. Subsequent normalization of the CA4+ partition with that of the gadoteridol affords CA4+ attenuations that significantly correlate with PG content – a key marker of OA.

Discovery of potential therapeutics for post-traumatic osteoarthritis using a high throughput mechanical injury platform

Purpose: The aim of this study was to utilize a high throughput cartilage injury platform that can be used as a model of post-traumatic osteoarthritis (PTOA) and rapidly assess a large number of compounds that are relevant to many cell functions after compressive injury. We developed and validated an in vitro high throughput mechanical injury (HiTMI) platform for investigating PTOA using engineered cartilage. The injury response in this model mimics that of native cartilage, and enables screening of chemical libraries for therapeutic discovery in a “high” throughput manner. Here we describe the screening of a number of small molecule compound libraries targeting various pathways using this HiTMI platform. Our goal was to identify ‘hits’ (i.e. significant regulators) that might serve as novel therapeutics for early intervention in PTOA. Six libraries were evaluated, including natural and synthetic compounds with potential to regulate a variety of cell responses, such as apoptosis, cell signaling, and cell proliferation. We probed compounds libraries that contained protease, kinase, and phosphatase inhibitors, all critical to cell function. An additional natural compound library and one focused on anti-apoptosic molecules was also utilized. Rapidly identifying compounds that may affect cell behavior and health in the acute phase post injury could be timely and of significant clinical importance to this growing form of osteoarthritis. Methods: Our model consists of engineered cartilage tissue analogs (CTA), which have been extensively characterized in our laboratory. In this model, chondrocytes are cultured in high density cultures above a hydrogel coating (poly 2-hydroxyethyl methacrylate) to prevent cell attachment. Within 24 hours, chondrocytes coalesce to form a stable construct that remains in suspension and increases in mass with time. Chondrocytes in CTAs possess phenotypic characteristics and deposit ECM that is similar to native cartilage. Since CTA can be generated in large numbers (100’s), each bearing an identical profile, they were used in our screening studies using a multi-platen mechanical injury device we recently fabricated. This device uses an Instron to deliver a single compressive injury, similar to that which occurs in a clinical setting. We have previously shown this to mimic the injury and cell responses in cartilage explants. CTA (4-5 months) were compressed to 75% strain at a rate of 50% strain/sec. Immediately following injury, CTA were treated with library compounds at 10 υM. Since this is a HTS platform, all primary screenings were carried out for 48 hours post injury/treatment. Medium was collected to assess proteoglycan loss (by measuring released or soluble glycosaminoglycans (GAG) using the DMMB assay) and indirectly measure cell stress / death (by measuring LDH using the CytoToxONE Homogenous Membrane Integrity Assay), two hallmarks of acute cartilage injury. Additional secondary screening was performed on positive hits using early (48 h) and late (96 h) time points and extended dose ranges. Results: Using this cartilage analog injury platform, we screened a total of 428 molecules. Primary screening resulted in 5 positive hits in the protease inhibitor, 9 in the apoptosis, 8 in the phosphatase, 10 in the kinase, and lastly 12 in the natural compound library (Figure 1). For example, results from the kinase inhibitor library revealed that there were 10 compounds that met the ‘hit’ criteria based on the released sGAG. These molecules included included PDGFR tyrosine kinase inhibitors. Conversely, for example, one compound, AG-370 resulted in worsening of the response (increased sGAG and LDH). The third phosphatase library screening resulted in identification of potential hits including compounds inhibitors of calcineurin. From 23 compounds screened through secondary screening, and based on a 20% or better threshold, more than 3 of these compounds remain significantly positive with respect to GAG release, relative to the injury-control. The compounds, with activities specific to pan-caspase inhibition, tyrosine phosphatase inhibition, and JNK-pathway signaling activation, resulted in a released-GAG reduction of 43%, 24% and 25%, respectively (Figure 2). Conclusions: Collectively, the results of this study present a promising strategy for identification of potential PTOA related therapeutic targets. This system permits the rapid identification of compounds that may act to interfere with the chondrocyte’s response to injury, both in regard to the early cell death and the later matrix degradation that occurs. With the successful follow up of positive hits with additional molecular pathway assays and an in vivo injury animal model, this new testing platform has the potential to identify new and early therapy for this common clinical problem of trauma-related osteoarthritis,View Large Image Figure ViewerDownload Hi-res image Download (PPT)

The Role of Ankle Arthroscopy in Ankle Fractures

The purpose of this chapter is to review the available literature and describe the technique when utilizing arthroscopy in the treatment of ankle fractures. The high incidence of acute cartilage injuries and the difficulty diagnosing syndesmotic instability in ankle fractures have led to the adjunctive use of arthroscopy in their treatment since the 1990s. Although this remains a controversial topic, multiple studies have demonstrated the potential of ankle arthroscopy to help confirm anatomic reduction, limit the surgical exposure and soft tissue trauma, and to diagnose and treat associated intra-articular pathology in displaced ankle fractures. Level of Evidence: Diagnostic Level 4. See Instructions for Authors for a complete description of levels of evidence.

Deep Learning Approach for Evaluating Knee MR Images: Achieving High Diagnostic Performance for Cartilage Lesion Detection.

Purpose To determine the feasibility of using a deep learning approach to detect cartilage lesions (including cartilage softening, fibrillation, fissuring, focal defects, diffuse thinning due to cartilage degeneration, and acute cartilage injury) within the knee joint on MR images. Materials and Methods A fully automated deep learning-based cartilage lesion detection system was developed by using segmentation and classification convolutional neural networks (CNNs). Fat-suppressed T2-weighted fast spin-echo MRI data sets of the knee of 175 patients with knee pain were retrospectively analyzed by using the deep learning method. The reference standard for training the CNN classification was the interpretation provided by a fellowship-trained musculoskeletal radiologist of the presence or absence of a cartilage lesion within 17 395 small image patches placed on the articular surfaces of the femur and tibia. Receiver operating curve (ROC) analysis and the κ statistic were used to assess diagnostic performance and intraobserver agreement for detecting cartilage lesions for two individual evaluations performed by the cartilage lesion detection system. Results The sensitivity and specificity of the cartilage lesion detection system at the optimal threshold according to the Youden index were 84.1% and 85.2%, respectively, for evaluation 1 and 80.5% and 87.9%, respectively, for evaluation 2. Areas under the ROC curve were 0.917 and 0.914 for evaluations 1 and 2, respectively, indicating high overall diagnostic accuracy for detecting cartilage lesions. There was good intraobserver agreement between the two individual evaluations, with a κ of 0.76. Conclusion This study demonstrated the feasibility of using a fully automated deep learning-based cartilage lesion detection system to evaluate the articular cartilage of the knee joint with high diagnostic performance and good intraobserver agreement for detecting cartilage degeneration and acute cartilage injury. © RSNA, 2018 Online supplemental material is available for this article .

Engineered cartilage regeneration from adipose tissue derived-mesenchymal stem cells: A morphomolecular study on osteoblast, chondrocyte and apoptosis evaluation

The poor self-repair capacity of cartilage tissue in degenerative conditions, such as osteoarthritis (OA), has prompted the development of a variety of therapeutic approaches, such as cellular therapies and tissue engineering based on the use of mesenchymal stem cells (MSCs). The aim of this study is to demonstrate, for the first time, that the chondrocytes differentiated from rat adipose tissue derived-MSCs (AMSCs), are able to constitute a morphologically and biochemically healthy hyaline cartilage after 6 weeks of culture on a Collagen Cell Carrier (CCC) scaffold. In this study we evaluated the expression of some osteoblasts (Runt-related transcription factor 2 (RUNX2) and osteocalcin), chondrocytes (collagen I, II and lubricin) and apoptosis (caspase-3) biomarkers in undifferentiated AMSCs, differentiated AMSCs in chondrocytes cultured in monolayer and AMSCs-derived chondrocytes seeded on CCC scaffolds, by different techniques such as immunohistochemistry, ELISA, Western blot and gene expression analyses. Our results showed the increased expression of collagen II and lubricin in AMSCs-derived chondrocytes cultured on CCC scaffolds, whereas the expression of collagen I, RUNX2, osteocalcin and caspase-3 resulted decreased, when compared to the controls. In conclusion, this innovative basic study could be a possible key for future therapeutic strategies for articular cartilage restoration through the use of CCC scaffolds, to reduce the morbidity from acute cartilage injuries and degenerative joint diseases.

Non-invasive assessments of cartilage macromolecular composition in patients with acute cartilage injury

Purpose: Cartilage degeneration or defective repair after an injury is typically associated with changes in the macromolecular composition of cartilage. The major function of large aggregating glycosaminoglycans (GAGs) is hydration of the cellular matrix, ensuring cartilage resiliency through electrostatic repulsion. A decrease in GAGs is likely to expose cartilage to dehydration, predisposing the joint to further degeneration. In parallel, roughening of the articular surface may also occur as a result of cartilage fibrillation, a process involving loosening of the collagen network, denaturation of the collagen and loss of the collagen fiber organization. Such a complex matrix makes any progression or repair of the defect challenging to monitor. New MRI developments allowing for a combined evaluation of both macromolecules are considered as a non-invasive alternative to cartilage biopsies. Thus, recent reports suggest that GAG chemical exchange saturation transfer (gagCEST) and T2 mapping MRI sequences are well suited for the detection of change in GAGs and collagen content and structure, respectively. However, clinical proof is still required to monitor cartilage degeneration after injury using biochemical MRI methods. Therefore, the purpose of this study is to establish sensitivity and reproducibility of quantitative imaging biomarkers, such as gagCEST asymmetry values and T2 relaxation times values of the superficial and deep layers of cartilage. Combined MRI measurements were performed in patients with an acute cartilage injury likely to worsen during the observational period due to several risk factors. Methods: Imaging sessions were performed on 7 patients with cartilage defect(s) in the knee joint (ICRS grade 1 or 2) as well as high risk factors (concomitant meniscus damage and/or ligament instability) for further progression of defect. Cartilage gagCEST and T2 images (Fig.1) were obtained for all patients at 7T using following MRI sequences and acquisition parameters: a 3D RF-spoiled GRE sequence with a resolution of 0.9x0.9x2.2 mm3 for gagCEST imaging, and a 3D-TESS sequence with a resolution of 0.25x0.25x3 mm3 for T2 mapping. For image analysis, regions-of-interest were defined on 2D-TSE morphological images in the suspicious regions for defective and normal appearing cartilage, and transferred to gagCEST and T2 images for quantitative analysis. All MRI measurements were repeated 8 days later for reproducibility assessment Results: The gagCEST asymmetry values (N=5 , preliminary data) were 28% lower in damaged areas as compared to adjacent healthy regions in cartilage (3.06±2.18% vs 4.27±1.61%, p=0.17). Disruption in the zonal organization of collagen fibrils was also observed in the damaged areas. T2 relaxation values becoming more uniform between the superficial and deep cartilage layers in defect region ([superficial/deep]T2 ratio in the defective region: 0.81±0.22 vs in the healthy region: 0.68±0.10, p=0.08). Both, gagCEST and T2 measurements showed high correlation between baseline and day-8 values (r=0.78 and r=0.86 , both p<0.0005, respectively). Conclusions: Both MRI methods, as applied here in combination to patients with low-grade cartilage injury, appear to be reproducible and might be able to detect differences between a defective and healthy region of cartilage. These preliminary results support the use of a comprehensive MRI approach in observational and therapeutic trials to differentiate early formation of hyaline from fibrotic cartilage without resorting to serial biopsies.

Cellular Chondroplasty: A New Technology for Joint Regeneration

Cellular therapy involves the isolation, expansion, and transplantation of human cells for the replacement or regeneration of injured tissues. It is one of the most significant tissue repair strategies in the emerging discipline of regenerative medicine. Cellular strategies have been applied in joint repair for the treatment of acute cartilage injury, meniscal repair, and osteoarthritis (OA). Many of these efforts have been motivated by the apparent incapacity of cartilage to repair itself and the observation that initial trauma is likely to lead to sustained joint degeneration. A particularly important question that arises about cellular therapy in OA relates to the long-term outcome of these procedures. In addition, questions remain about the most suitable cell source, the advantages of allogeneic over autologous therapy, their potential uses in late stage OA, and, not least, the logistics of manufacturing and supply. These topics are discussed in this review, as well as an evaluation of knowledge gaps and technical obstacles that remain to be addressed.

Pathogenesis and Prevention of Posttraumatic Osteoarthritis After Intra-articular Fracture

Posttraumatic osteoarthritis (PTOA) occurs after traumatic injury to the joint. It is most common following injuries that disrupt the articular surface or lead to joint instability. The reported risk of PTOA following significant joint trauma is as high as 75%; articular fractures can increase the risk more than 20-fold. Despite recent advances in surgical management, the incidence of PTOA following intra-articular fractures has remained relatively unchanged over the last few decades. Pathogenesis of PTOA after intra-articular fracture is likely multifactorial and may be associated with acute cartilage injury as well as chronic joint overload secondary to instability, incongruity, and malalignment. Additional studies are needed to better elucidate how these factors contribute to the development of PTOA and to develop advanced treatment algorithms that consist of both acute biologic interventions targeted to decrease inflammation and cellular death in response to injury and improved surgical methods to restore stability, congruity, and alignment.

Subphysiological compressive loading reduces apoptosis following acute impact injury in a porcine cartilage model.

Background:Acute cartilage injuries induce cell death and are associated with an increased incidence of osteoarthritis development later in life. The objective of this study was to investigate the effect of posttraumatic cyclic compressive loading on chondrocyte viability and apoptosis in porcine articular cartilage plugs.Hypothesis:Compressive loading of acutely injured cartilage can maintain chondrocyte viability by reducing apoptosis after a traumatic impact injury.Study Design:In vitro controlled laboratory study.Level of Evidence:Level 5.Methods:Each experiment compared 4 test groups: control, impact, impact with compressive loading (either 0.5 or 0.8 MPa), and no impact but compressive loading (n = 15 per group). Flat, full-thickness articular cartilage plugs were harvested from the trochlear region of porcine knees. A drop tower was utilized to introduce an impact injury. The articular plugs were subjected to two 30-minute cycles of either 0.5 or 0.8 MPa of dynamic loading. Cell viability, apoptosis, and gene expression of samples were evaluated 24 hours postimpaction.Results:Cell viability staining showed that 0.5 MPa of dynamic compressive loading increased cell viability compared with the impact group. Apoptotic analysis revealed a decrease in apoptotic expression in the group with 0.5 MPa of dynamic compressive loading compared with the impact group. Significantly higher caspase 3 and lower collagen II expressions were observed in impacted samples without compressive loading, compared with those with. Compressive loading of nonimpacted samples significantly increased collagen II and decreased caspase 3 expressions.Conclusion:In this porcine in vitro model, dynamic compressive loading at subphysiological levels immediately following impact injury decreases apoptotic expression, thereby maintaining chondrocyte viability.Clinical Relevance:Therapeutic exercises could be designed to deliver subphysiological loading to the injured cartilage, thereby minimizing injury.

Distribution and Progression of Chondrocyte Damage in a Whole-Organ Model of Human Ankle Intra-Articular Fracture

Despite the best current treatments, intra-articular fractures commonly cause posttraumatic osteoarthritis. In this disorder, death and dysfunction of chondrocytes associated with acute cartilage injury presumably plays an important role in triggering the pathomechanical cascade that eventually leads to whole-joint degeneration. Information regarding this cell-level cartilage injury, particularly at the whole-organ level in actual human joints, has been lacking. In this study, the distribution and progression of fracture-associated cell-level cartilage damage were assessed using a novel whole-organ model of human ankle intra-articular fracture. Seven normal human ankles harvested immediately following amputation were subjected to a transarticular compressive impaction insult that mimicked an injury mechanism typical of tibial plafond fractures. For each ankle, site-specific, time-dependent changes in chondrocyte viability in the fractured tibial surface were studied by means of live-dead assay, using a confocal laser-scanning microscope. Fractional chondrocyte death was measured at several time points, in the superficial zone of the cartilage in "fracture-edge" regions within 1 mm of the fracture lines, as well as in "non-fracture" regions more than 3 mm centrally away from the fracture lines. All seven experimental fractures morphologically replicated tibial plafond fractures. Immediately post-fracture, superficial-zone chondrocyte death was significantly greater (p = 0.001) in fracture-edge regions (fractional cell death = 7.6%) than in non-fracture regions (1.6%). Progression of cell death over the next forty-eight hours was significantly faster in fracture-edge regions (p = 0.007), with the fractional cell death reaching 25.9%, which was again significantly higher (p < 0.001) than in non-fracture regions (8.6%). Cell-level cartilage damage in human intra-articular fractures was characterized by acute chondrocyte death that predominated along fracture lines and that spontaneously progressed in the forty-eight hours following injury. Progressive chondrocyte damage along fracture lines appears to be a reasonable target of therapeutic treatment to preserve the whole-joint cartilage metabolism in intra-articular fractures, eventually to mitigate the risk of posttraumatic osteoarthritis.

Detection of mechanical injury of articular cartilage using contrast enhanced computed tomography

Osteoarthritic degeneration may be initiated by mechanical overloading of articular cartilage. Mechanical injury increases the permeability of tissue, thereby probably affecting the diffusion of contrast agents in articular cartilage. We investigated whether it is possible to detect acute cartilage injury by measuring contrast agent diffusion into articular cartilage using contrast enhanced computed tomography (CECT). Osteochondral plugs (Ø=6.0 mm, n=36) were prepared from intact bovine patellae (n=9). Two of the adjacent samples were injured by impact loading, using a drop tower, while the others served as paired controls. The samples were imaged before immersion in contrast agent solution [ioxaglate (Hexabrix™) or sodium iodide (NaI)] and 1, 3, 5, 7, 10, 15, 20 and 25 h after immersion using a MicroCT-instrument. Contrast agent content, diffusion coefficient and diffusion flux were determined for each sample. Already after 1 h the penetration of contrast agents into cartilage was significantly (P<0.05) greater in the injured samples. The diffusion coefficient was not altered by the injury, which suggests that reaching the diffusion equilibrium takes the same time in injured and intact cartilage. However, the diffusion flux of ioxaglate through the articular surface was significantly higher in injured samples at 30-60 min after immersion. To conclude, CECT could diagnose articular cartilage injuries, and determination of the diffusion flux of ioxaglate helped to detect tissue injury without waiting for the diffusion equilibrium. These results are encouraging, however, in vivo application of CECT is challenging and systematic further studies are needed to reveal its clinical potential.

The Effect of Early Hyaluronic Acid Delivery on the Development of an Acute Articular Cartilage Lesion in a Sheep Model

Background Partial-thickness articular cartilage lesions occur with knee trauma and may progress to osteoarthritis. This study evaluates the effectiveness of hyaluronic acid on cartilage healing after acute knee injury in sheep. Hypothesis Early administration of hyaluronic acid to an acute cartilage injury will prevent chondrocyte death and improve cartilage metabolism. Study Design Controlled laboratory study. Methods A 10 × 10 mm partial-thickness articular cartilage lesion was created on the medial condyle of 16 adult sheep stifles (hindlimbs). Eight sheep received intra-articular hyaluronic acid injections at days 0, 8, and 15, and 8 controls received saline. Contralateral stifles were nonoperated controls. All sheep were sacrificed at 12 weeks after surgery. Synovial fluid was drawn before surgery and after euthanasia for collagen II, nitric oxide, and interleukin-1 beta analysis. The medial condyle was analyzed by gross appearance, confocal laser microscopy for cell viability, histologic analysis for cartilage morphology, and dimethylmethylene blue assay for proteoglycan. Results At 12 weeks, histologic analysis revealed that the hyaluronic acid group had significantly better scores than the saline group (P = .001). The hyaluronic acid group had significantly greater glycosaminoglycan content than the saline group (P = .011), and showed a trend of reduced chondrocyte death compared with the saline group (P = .07). Synovial fluid showed no significant differences between the groups in collagen II, nitric oxide, and interleukin-1 beta levels. Conclusion The results demonstrated that early administration of hyaluronic acid shows a significant improvement in cartilage histologic analysis and increased glycosaminoglycan content after acute traumatic cartilage injury. Clinical Relevance Early hyaluronic acid treatment for acute partial-thickness articular cartilage lesions may decrease or delay articular degeneration.