Osteophytes: relevance and biology

Involvement of Heat Shock Protein 47 in Osteophyte Formation of Knee Joint Osteoarthritis

Osteophytes contribute to the development and progression of knee osteoarthritis (OA). Although transforming growth factor-β (TGF-β) and bone morphogenic protein-2 (BMP2) are known to induce osteophytes, regulators of osteophyte formation remain elusive. This study aimed to search for molecules that modulate osteophytosis in a mouse knee OA model. Proteomic analysis, followed by immunohistochemistry of osteophyte and articular cartilage, identified heat shock protein 47 (HSP47), a molecular chaperone for procollagens, as a molecule selectively overexpressed by osteophyte fibrocartilaginous cells. The treatment of TGF-β3 and BMP2 to a three-dimensional pellet culture of mouse mesenchymal stem cells caused their differentiation into osteophyte-like cells accompanied with the up-regulation of HSP47. The pellet sizes of stimulated three-dimensional-cultured mesenchymal stem cells were significantly reduced by knockdown of HSP47 or treatment with AK778 (HSP47 inhibitor), because of increased apoptosis. Furthermore, intra-articular AK778 injections suppressed osteophyte formation in a mouse OA model. Importantly, the studies with human samples demonstrated HSP47 overexpression by osteophyte fibrocartilaginous cells in human OA knee joints. Similarly, the overexpression of HSP47 was observed in the TGF-β3- and BMP2-treated human osteophytic cell spheroids as well as the size reduction of spheroids by AK778 treatment. These findings highlight the promoting function of HSP47 in osteophyte formation in OA knee joints and suggest that therapeutic interventions targeting HSP47 may be of clinical value.

Bionic bearing-inspired lubricating microspheres with Immunomodulatory effects for osteoarthritis therapy

Inflammatory infiltration and inappropriate friction remain the two main challenges in treating osteoarthritis (OA). An effective treatment platform is anticipated to lubricate the cartilage and ameliorate intra-articular inflammation. Herein, injectable hydrogel microspheres with chondroitin sulfate (Chs)/sericin methacryloyl (SerMA) designed as the core and grafted with folic acid (FA)- and 78c-modified liposomes (78c@Lipo-FA) by DSPE-PEG2k-GPLGLAGQC (DPG) peptides, namely LFDCS, was formed by thin-film hydration and microfluidic methods. Physically, LFDCS exhibited cartilage lubrication and adhesion capability as the bionic bearings. Meanwhile, with the degradation of LFDCS, Chs were set out to promote chondrocyte function. Physiologically, 78c@Lipo-FA were released from LFDCS enzymatically responsible to matrix metalloprotein-9 (MMP9) due to the split of DPG motif, which specifically bound to classical-activated macrophages (M1) by ligating to FA receptor through FA and inhibit M1 function by 78c, consequently rescued cartilage from degradation by inflammation. Mechanically, an RNA sequencing analysis revealed that the LFDCS could ameliorate chondrocyte dysfunction by down-regulating PI3K/AKT signaling and inflammation response. LFDCS greatly reduced friction on articular surfaces, suppressed M1-induced inflammation and attenuated chondrocyte dysfunction in OA rats. In conclusion, the bionic bearing-inspired lubricating microspheres characterized by M1-phenotype macrophage-targeted addresses the unfavorable factors of both the physical and physiological microenvironments in macrophage-mediated diseases.

Long-Term Impact of Intralesional Bony Overgrowth on Opposing Cartilage Integrity: Five-Year Results Following Cartilage Repair

ObjectivesThis study aimed to assess the impact of intralesional bony overgrowth (ILBO) after cartilage repair on the integrity of opposing articulating cartilage (OpAC) using T2 mapping and to correlate these findings with clinical outcomes.MethodsIn this multicenter study, magnetic resonance imaging (MRI) examinations were performed in the follow-up after cartilage repair (Microfracturing (MFX) and Matrix-Induced Autologous Chondrocyte Implantation (MACI)) in 45 patients up to 5 years after surgery. T2 values of the OpAC after 3, 12, and 60 months in patients with and without ILBO after 60 months were conducted along with clinical assessments (International Knee Documentation Committee (IKDC) and Knee injury and Osteoarthritis Outcome Score (KOOS)).ResultsAt 60 months post-surgery, 44.4% of patients presented with ILBO, which was associated with significantly higher T2 values in OpAC (P = 0.004). A tendency toward increased T2 values was observed after 12 months, although this did not reach statistical significance (P = 0.06). However, no significant differences were found in clinical outcomes between patients with or without ILBO, nor between those with or without T2 values comparable to reference cartilage.ConclusionILBO significantly affects the biophysical MRI properties of OpAC as indicated by higher T2 values after 60 months. These alterations, though not reflected in any clinical score, can suggest potential long-term implications for cartilage degeneration and may inform future monitoring strategies for cartilage repair. Further research is required to evaluate the long-term effects of these altered mechanical impacts on articulating cartilage and their clinical implications.

Intelligent Manufacturing for Osteoarthritis Organoids

Osteoarthritis (OA) is the most prevalent degenerative joint disease worldwide, imposing a substantial global disease burden. However, its pathogenesis remains incompletely understood, and effective treatment strategies are still lacking. Organoid technology, in which stem cells or progenitor cells self-organise into miniature tissue structures under three-dimensional (3D) culture conditions, provides a promising in vitro platform for simulating the pathological microenvironment of OA. This approach can be employed to investigate disease mechanisms, carry out high-throughput drug screening and facilitate personalised therapies. This review summarises joint structure, OA pathogenesis and pathological manifestations, thereby establishing the disease context for the application of organoid technology. It then examines the components of the arthrosis organoid system, specifically addressing cartilage, subchondral bone, synovium, skeletal muscle and ligament organoids. Furthermore, it details various strategies for constructing OA organoids, including considerations of cell selection, pathological classification and fabrication techniques. Notably, this review introduces the concept of intelligent manufacturing of OA organoids by incorporating emerging engineering technologies such as artificial intelligence (AI) into the organoid fabrication process, thereby forming an innovative software and hardware cluster. Lastly, this review discusses the challenges currently facing intelligent OA organoid manufacturing and highlights future directions for this rapidly evolving field. By offering a comprehensive overview of state-of-the-art methodologies and challenges, this review anticipates that intelligent, automated fabrication of OA organoids will expedite fundamental research, drug discovery and personalised translational applications in the orthopaedic field.

Association Between Cumulative G-force Exposure and Cervical Spine Degenerative Changes

INTRODUCTION

Fighter pilots work in a unique environment and are subject to high G-force loads under simultaneous head movements. Neck pain is reported to be a common health problem among fighter pilots leading to time lost flying and flight duty limitations. The present study aimed to find out if differences in early military flight career G-force exposure levels could increase the risk for degenerative changes in the cervical spine.

MATERIALS AND METHODS

The study population consisted of 56 20-year-old Finnish Air Force male fighter pilot cadets, who underwent MRI of the cervical spine at baseline and after 5 years. During follow-up, the G-force exposure was measured using the individual Fatigue Index (FI) recordings. The FI data were collected from each flight with BAE Hawks and is determined by the number of times certain levels of G-forces are exceeded during the flights. The incidence or progression of each degenerative change was compared to individual FI values using Pearson correlation coefficients.

RESULTS

The pilots flew on average 220 (±21) hours with high performance aircraft during follow-up, resulting in an average FI of 1.98 (±0.47). A statistically significant progression was found in intervertebral disc (IVD) degeneration sum score with no correlation to corresponding FI values. A statistically significant increase was also found in the prevalence of IVD herniations with a negative correlation with FI values. Other degenerative cervical spine changes did not progress or did not correlate with corresponding FI values.

CONCLUSIONS

The prevalence of IVD degeneration and IVD herniations increases in the early phases of fighter pilots' career. Only the incidence of IVD herniations correlated with FI values and the correlation was negative. The negative correlation may be attributed to avoidance behavior due to neck pain, which was not measured in our study, or other unmeasured confounding factors. This was the first study to compare individual G-force exposure levels to high-quality MRI data over a follow-up of several years. Finnish fighter pilots are known to report increasing cervical symptoms during the Hawk training phase, but longer follow-up periods are likely needed to determine the association between G-force exposure levels and cervical degenerative changes.

Cartilage thickness distribution and its dependence on demographic, radiographic, and MRI structural pathology in knee osteoarthritis-data from the IMI-APPROACH cohort

OBJECTIVE

Cartilage surface mapping is a technique that can visualize 3D cartilage thickness variation throughout a joint without a need for arbitrary regional definitions. The objective of this cross-sectional study was to utilize this technique to evaluate the cartilage thickness distribution in knee osteoarthritis patients and to analyze to what extent it depends on demographic, radiographic, and MRI structural pathology strata.

METHODS

Patients of the IMI-APPROACH cohort were included, with MRIs obtained at 1.5 T or 3 T. Tibial and femoral cartilage segmentation and registration with a canonical surface were performed semi-automatically. Kellgren-Lawrence and OARSI grading were performed on knee radiographs; MOAKS scoring was performed on MRI scans. The association of demographics and radiographic and MRI scorings with cartilage thickness distribution was analyzed with general linear models using statistical parametric mapping.

RESULTS

Two hundred eighty-seven patients were included. Male sex and height were positively associated with cartilage thickness particularly in the trochlea and medial femur, respectively, with differences up to 0.5 mm (male vs female), while radiographic joint space narrowing and bone marrow lesions showed region-specific negative associations (up to 0.14-0.5 mm per grade). Kellgren-Lawrence grade, MOAKS meniscal extrusion, and osteophytes showed patterns of positive and negative associations, with increasing grades showing reduced local tibiofemoral cartilage thickness, but greater thickness in the trochlea (both up to 0.2-0.3 mm per grade).

CONCLUSIONS

Decreased height, female sex, and increasing tibiofemoral pathology were associated with thinner tibiofemoral cartilage. Unexpected results such as consistently thicker cartilage in the anterior femur with increasing disease or osteophytosis states provide opportunities for future research.

The comparative efficacy of L-glutamine, celecoxib, and glucosamine sulfate in osteoarthritis management

To explore the therapeutic efficacy of L-glutamine (L-Gln) on pathological progression and clinical symptoms of osteoarthritis (OA), and compare with glucosamine sulfate (GS), and celecoxib (CXB). Rats were administered sodium chloride, L-Gln, GS, or CXB via gavage for eight weeks starting from the fifth week after sham operation or Anterior Cruciate Ligament Transection (ACLT) + Medial Meniscectomy (MMx). Then the severity of knee OA in rats was evaluated by serological analysis, histological examination and imaging examination. In addition, patients with mild primary OA were administered L-Gln, GS, or CXB orally for 12 weeks in accordance with the randomization principle. The efficacy end points were the change from baseline to week 24 in the pain and physical function subscale scores of the Western Ontario and McMaster Universities OA Index (WOMAC), and Lequesne score. Treatment with L-Gln alleviated the increased concentration of serum cartilage degradation markers caused by OA in rats. Histological tests showed improvement in knee joint cartilage destruction after treatment. Three-dimensional CT scans and reconstructions revealed a reduction in osteophyte formation and subchondral bone loss. L-glutamine performed as well as or better than glucosamine sulfate and celecoxib in all comparative measures among the three treatment groups. In clinical trials, the WOMAC pain and physical function subscale scores, as well as the Lequesne score, decreased from baseline in all three patient groups during follow-up, with no significant differences observed between the groups. Our research indicates that L-Gln is comparable to GS and CXB in improving the pathological progression and clinical efficacy of OA, which makes it a promising drug for the treatment of osteoarthritis.

A review of methods of age estimation based on postmortem computed tomography

Age at death is one of the key elements of the "biological profile" prepared when analysing unidentified human remains. Biological age is determined according to physiological indicators and developmental stage, which can be determined by bone assessment. It is worth remembering that the researcher must interpret each case individually and in accordance with the current state of knowledge. One of the most developed tools for analysing human remains is postmortem computed tomography. This allows for the visualization not only of bones without maceration but also of the entire body under various altered states, including corpses in advanced stages of decomposition and burnt bodies. The aim of this review is to present the current methods for age estimation based on postmortem computed tomography evaluation, comparing the results presented in 18 research projects published between 2013 and 2023 on foetuses, children, and adults from contemporary populations. Recent literature includes assessment of bones and characteristics such as skulls, teeth, vertebrae, pelvises, and long bones to estimate age at death. We cover the methods used in this recent literature, including machine learning, and discuss the advantages and disadvantages of them.

Key points

Postmortem computed tomography allows the analysis of several areas of the body at the same time, which may not be possible in the case of clinical trials (where the examination area should be limited).Postmortem computed tomography may enable the collection of data from people whose clinical examinations are relatively rare (e.g., pregnant women, children).Artificial intelligence should increasingly be used in studies on age estimation.Further research on modern populations is necessary to verify and refine the methods used to estimate age at death.

Exploring the Potential of Non-Cellular Orthobiologic Products in Regenerative Therapies for Stifle Joint Diseases in Companion Animals

Stifle joint diseases present a significant challenge in companion animals that often lead to hind limb lameness, with osteoarthritis being a prevalent degenerative condition causing pain and reduced mobility. Regenerative medicine offers a promising avenue for improving treatment outcomes, with a range of emerging therapies showing potential to alleviate symptoms and promote joint health. Among these, hyaluronic acid and platelet-rich plasma have been widely used as intra-articular treatments to enhance joint lubrication, reduce inflammation, and provide symptomatic relief. Interleukin-1 receptor antagonist protein, autologous conditioned serum, and autologous protein solution represent the next generation of regenerative therapies, offering more disease-modifying effects by inhibiting key mediators of joint inflammation. More recently, the MSC-derived secretome has emerged as an innovative, cell-free approach that leverages the diverse bioactive factors secreted by MSCs to support tissue repair and modulate inflammation. This review highlights the evidence base behind these non-cellular orthobiologic treatments for stifle joint disease, aiming to inform veterinary practitioners and owners about available options and their efficacy in supporting conventional treatments.

Short-term prediction of clinical and radiographic contralateral hip osteoarthritis after index total hip arthroplasty

INTRODUCTION

Patients with primary hip osteoarthritis undergoing unilateral total hip arthroplasty (THA) often face uncertainty about the future need for arthroplasty in the contralateral hip. We aimed to identify parameters that have predictive value with regard to the necessity for contralateral THA or the development of contralateral radiographic osteoarthritis (OA) phenotypes following index surgery.

MATERIALS AND METHODS

In this retrospective study, we analyzed 220 patients undergoing THA. Of these, 24.1% required contralateral THA at a mean follow-up of 18.3months. Our assessments included preoperative and follow-up pelvis radiographs as well as bone mineral density (BMD) measurement by dual-energy X-ray absorptiometry prior to index THA. Comprehensive radiological measurements such as the Kellgren-Lawrence OA grade, osteophyte evaluation as well as joint shape and alignment (including alpha and CE angles) were performed.

RESULTS

We identified three indicators at the initial assessment for predicting the need for contralateral THA: higher BMI (odds ratio (OR) 1.1 [95%-CI 1.0-1.2], p = 0.033), higher alpha angles (> 61.5°) (OR 2.5 [95%-CI 1.0-6.3], p = 0.045) and the presence of multiple osteophytes (OR 2.6 [95%-CI 1.4-4.9], p = 0.004). Moreover, higher alpha angles were linked to more severe radiographic OA, especially osteophytosis. Higher BMD T-scores were also associated with progressive formation of multiple and large osteophytes but not joint space narrowing.

CONCLUSION

Three factors - BMI, alpha angle, and osteophyte number - are key short-term predictors for contralateral THA after index THA. We also identified BMD as a surrogate for osteophyte formation. These findings provide novel and valuable insights for patients and surgeons regarding risks and counseling for contralateral OA and THA.

Empirical Modelling Workflow for Resolution Invariant Assessment of Osteophytes

OBJECTIVE

Traditional quantitative analysis of bone microstructure in micro-computed tomography (microCT) is dependent on animal scale and requires parametric tuning in new implementations. This study aims to develop an automated and resolution-invariant 3D image processing workflow for quantitative assessment of osteophytes.

METHODS

In this workflow, cortical bone was segmented from microCT scans, and a 3D sphere-fitting transform was performed to obtain a thickness map, for which each voxel is assigned a thickness value corresponding to the size of the largest sphere containing the voxel that fits entirely within the cortical bone. From the thickness map, a 1-voxel thick outer surface was extracted to model surface roughness. The thickness values of the outer surface were empirically estimated by a series of known statistical distributions. Resulting parameters describing best-fit distributions, along with other cortical bone metrics, were analysed to determine sensitivity to osteoarthritis and the presence of osteophytes.

RESULTS

The workflow was validated using microCT scans and histological gradings of rabbit and rat tibiofemoral joints. Visual inspection shows that samples with osteoarthritis and the presence of osteophytes have more surface voxels assigned small thickness values. The distribution of surface thickness values for each animal is best described by Gamma distributions, whose shape parameter is consistently sensitive to osteoarthritis and the presence of osteophytes.

CONCLUSION

Combining traditional image processing with empirical distribution fitting provides an automated, objective, and resolution-invariant workflow for osteophyte assessment.

SIGNIFICANCE

The proposed method is simple, yet elegant in its implementation, and can be readily used in new implementations.

Sex differences in patellar facet shape among healthy and osteoarthritic cohorts

OBJECTIVE

Patellofemoral osteoarthritis (OA) may be more common in females than males. Reasons for this are not fully understood, but sex differences in patellar morphology may help explain this phenomenon. We quantified differences in patellar morphology between males and females in healthy and patellofemoral OA populations.

DESIGN

A total of 97 (50F, 47M) healthy and 67 (40F, 27M) OA knees were scanned via computed tomography. OA individuals were on a waitlist for total knee replacement. Patella 3D models were segmented and 2D measurements were recorded: patellar width and height, lateral and medial facet width, and surface area. Medial and lateral facet surface topography was mapped using 81 points to describe 3D articular surface shape. Sex and group differences were assessed using Procrustes analysis of variance (ANOVA). Data were ordinated using Principal Component Analysis.

RESULTS

Differences in patellar 2D measurements between healthy and OA individuals were smaller than were differences between males and females from healthy and OA groups. Sex and healthy/OA differences were most pronounced for medial facet shape, which featured a posteriorly-curving facet and taller, narrower facet shape in males compared to females. Lateral facet shape variance was higher in OA cohorts compared to healthy groups.

CONCLUSIONS

Medial and lateral facet shapes showed different patterning of variation by sex and healthy/OA status. Lateral facet shape may be of interest in future models of OA risk in the patellofemoral joint, here showing increased magnitudes of variance associated with increased severity of disease (patellofemoral Kellgren and Lawrence score).

Differential effects of alendronate on chondrocytes, cartilage matrix and subchondral bone structure in surgically induced osteoarthritis in mice

Bisphosphonates (BP) are considered a treatment option for osteoarthritis (OA) due to reduction of OA-induced microtrauma in the bone marrow, stabilization of subchondral bone (SB) layer and pain reduction. The effects of high-dose alendronate (ALN) treatment on SB and articular cartilage after destabilization of the medial meniscus (DMM) or Sham surgery of male C57Bl/6J mice were analyzed. We performed serum analysis; histology and immunohistochemistry to assess the severity of OA and a possible pain symptomatology. Subsequently, the ratio of bone volume to total volume (BV/TV), epiphyseal trabecular morphology and the bone mineral density (BMD) was analyzed by nanoCT. Serum analysis revealed a reduction of ADAMTS5 level. The histological evaluation displayed no protective effect of ALN-treatment on cartilage erosion. NanoCT-analysis of the medial epiphysis revealed an increase of BV/TV in ALN-treated mice. Only the DMM group had significantly higher SB volume accompanied by decreased subchondral bone surface. Furthermore Nano-CT analysis revealed an increase in trabecular density and number, a decreased BMD and reduced osteophyte formation in the ALN mice. ALN treatment affected bone micro-architecture by reducing osteophytosis with simultaneous increasing subchondral bone plate thickness, trabecular thickness and BMD. Accordingly, ALN cannot be considered as a potential treatment strategy in general, however in a subgroup of patients with high bone turnover in an early-stage of OA, ALN might be an option when applied during a restricted time frame.

Numerical study of osteophyte effects on preoperative knee functionality in patients undergoing total knee arthroplasty

Osteophytes are routinely removed during total knee arthroplasty, yet the preoperative planning currently relies on preoperative computed tomography (CT) scans of the patient's osteoarthritic knee, typically including osteophytic features. This complicates the surgeon's ability to anticipate the exact biomechanical effects of osteophytes and the consequences of their removal before the operation. The aim of this study was to investigate the effect of osteophytes on ligament strains and kinematics, and ascertain whether the osteophyte volume and location determine the extent of this effect. We segmented preoperative CT scans of 21 patients, featuring different osteophyte severity, using image-based active appearance models trained to identify the osteophytic and preosteophytic bone geometries and estimate the cartilage thickness in the segmented surfaces. The patients' morphologies were used to scale a template musculoskeletal knee model. Osteophytes induced clinically relevant changes to the knee's functional behavior, but these were variable and patient-specific. Generally, severe osteophytic knees significantly strained the oblique popliteal ligament (OPL) and posterior capsule (PC) relative to the preosteophytic state. Furthermore, there was a marked effect on the lateral collateral ligament and anterolateral ligament (ALL) strains compared to mild and moderate osteophytic knees, and concurrent alterations in the tibial lateral-medial translation and external-internal rotation. We found a strong correlation between the OPL, PC, and ALL strains and posterolateral condylar and tibial osteophytes, respectively. Our findings may have implications for the preoperative planning in total knee arthroplasty, toward reproducing the physiological knee biomechanics as close as feasibly possible.

Dissolving magnesium hydroxide implants enhance mainly cancellous bone formation whereas degrading RS66 implants lead to prominent periosteal bone formation in rabbits

Bone fractures often require internal fixation using plates or screws. Normally, these devices are made of permanent metals like titanium providing necessary strength and biocompatibility. However, they can also cause long-term complications and may require removal. An interesting alternative are biocompatible degradable devices, which provide sufficient initial strength and then degrade gradually. Among other materials, biodegradable magnesium alloys have been developed for craniofacial and orthopaedic applications. Previously, we tested implants made of magnesium hydroxide and RS66, a strong and ductile ZK60-based alloy, with respect to biocompatibility and degradation behaviour. Here, we compare the effects of dissolving magnesium hydroxide and RS66 cylinders on bone regeneration and bone growth in rabbit condyles using microtomographical and histological analysis. Both magnesium hydroxide and RS66 induced a considerable osteoblastic activity leading to distinct but different spatio-temporal patterns of cancellous and periosteal bone growth. Dissolving RS66 implants induced a prominent periosteal bone formation on the medial surface of the original condyle whereas dissolving magnesium hydroxide implants enhance mainly cancellous bone formation. Especially periosteal bone formation was completed after 6 and 8 weeks, respectively. The observed bone promoting functions are in line with previous reports of magnesium stimulating cancellous and periosteal bone growth and possible underlying signalling mechanisms are discussed. STATEMENT OF SIGNIFICANCE: Biodegradable magnesium based implants are promising candidates for use in orthopedic and traumatic surgery. Although these implants are in the scientific focus for a long time, comparatively little is known about the interactions between degrading magnesium and the biological environment. In this work, we investigated the effects of two degrading cylindrical magnesium implants (MgOH2 and RS66) both on bone regeneration and on bone growth. Both MgOH2 and RS66 induce remarkable osteoblastic activities, however with different spatio-temporal patterns regarding cancellous and periosteal bone growth. We hypothesize that degradation products do not diffuse directionless away, but are transported by the restored blood flow in specific spatial patterns which is also dependent on the used surgical technique.

Imaging Response to Treatment in Rheumatology

This article highlights the crucial role of various imaging techniques in the diagnosis and monitoring of rheumatologic diseases. It provides an overview of the different modalities available for imaging rheumatic diseases, the disease processes they are able to demonstrate, and their utility in the monitoring response to therapy. It emphasizes the need for a multifaceted approach that combines radiography, ultrasound, MR imaging, and PET imaging to gain a comprehensive understanding of disease progression and treatment response. Standardized grading systems along with quantitative imaging techniques are playing an increasing role in monitoring disease activity and assessing response to therapy.

The Spatial Relationship between Spinal Osteoarthritis and CSF Venous Fistulas in Patients with Spontaneous Intracranial Hypotension

BACKGROUND AND PURPOSE

CSF venous fistula leads to spontaneous intracranial hypotension. The exact mechanisms underlying the development of CSF venous fistula remain unclear: Some researchers have postulated that underlying chronic intracranial hypertension may lead to damage to spinal arachnoid granulations, given that many patients with CSF venous fistulas have an elevated body mass index (BMI). However, individuals with higher BMIs are also more prone to spinal degenerative disease, and individuals with CSF venous fistulas also tend to be older. CSF venous fistula tends to occur in the lower thoracic spine, the most frequent location of thoracic degenerative changes. The current study aimed to examine whether CSF venous fistulas are more likely to occur at spinal levels with degenerative changes.

MATERIALS AND METHODS

Forty-four consecutive patients with CSF venous fistulas localized on dynamic CT myelography were included in analyses. Whole-spine CT was scrutinized for the presence of degenerative changes at each spinal level. The proportion of levels positive for CSF venous fistula containing any degenerative findings was compared to levels without CSF venous fistula using the Fisher exact test. The Pearson correlation coefficient was calculated to explore the association between the burden of degenerative disease and BMI and age and between BMI and opening pressure.

RESULTS

Forty-four patients with 49 total CSF venous fistulas were analyzed (5 patients had 2 CSF venous fistulas). Mean patient age was 62.3 (SD, 9.5) years. Forty-seven CSF venous fistulas were located in the thoracic spine; 1, in the cervical spine; and 1, in the lumbar spine. Within the thoracic spine, 39/49 (79.6%) fistulas were located between levels T7-8 and T12-L1. Forty-four of 49 (89.8%) CSF venous fistulas had degenerative changes at the same level. The levels without CSF venous fistulas demonstrated degenerative changes at 694/1007 (68.9%) total levels. CSF venous fistulas were significantly more likely to be present at spinal levels with associated degenerative changes (OR = 4.03; 95% CI, 1.58-10.27; P = .001). Age demonstrated a positive correlation with the overall burden of degenerative disease (correlation coefficient: 0.573, P < .001), whereas BMI did not (correlation coefficient: 0.076, P = .625). There was a statistically significant positive correlation between BMI and opening pressure (correlation coefficient: 0.321, P = .03).

CONCLUSIONS

Results suggest a potential association between spinal degenerative disease and development of CSF venous fistula.

Diet influences knee osteoarthritis osteophyte formation via gut microbiota and serum metabolites

Osteophyte formation, a key indicator of osteoarthritis (OA) severity, remains poorly understood in its relation to gut microbiota and metabolites in knee osteoarthritis (KOA). We conducted 16S rDNA sequencing and untargeted metabolomics on fecal and serum samples from 20 healthy volunteers, 80 KOA patients in Guangdong, and 100 in Inner Mongolia, respectively. Through bioinformatics analysis, we identified 3 genera and 5 serum metabolites associated with KOA osteophyte formation. Blautia abundance negatively correlated with meat, cheese, and bean consumption. The 5 serum metabolites negatively correlated with dairy, beef, cheese, sugar, and salt intake, yet positively with age and oil consumption. Higher Blautia levels in the gut may contribute to KOA osteophyte formation, with serum metabolites LTB4 and PGD2 potentially serving as biomarkers. KOA patients in Inner Mongolia exhibited lower Blautia levels and reduced expression of 5 serum metabolites, possibly due to cheese consumption habits, resulting in less osteophyte formation.

Development of primary osteoarthritis during aging in genetically diverse UM-HET3 mice

BACKGROUND

Primary osteoarthritis (OA) occurs without identifiable underlying causes such as previous injuries or specific medical conditions. Age is a major contributing factor to OA, and as one ages, various joint tissues undergo gradual change, including degeneration of the articular cartilage, alterations in subchondral bone (SCB) morphology, and inflammation of the synovium.

METHODS

We investigated the prevalence of primary OA in aged, genetically diverse UM-HET3 mice. Articular cartilage (AC) integrity and SCB morphology were assessed in 182 knee joints of 22-25 months old mice using the Osteoarthritis Research Society International (OARSI) scoring system and micro-CT, respectively. Additionally, we explored the effects of methylene blue (MB) and mitoquinone (MitoQ), two agents that affect mitochondrial function, on the prevalence and progression of OA during aging.

RESULTS

Aged UM-HET3 mice showed a high prevalence of primary OA in both sexes. Significant positive correlations were found between cumulative AC (cAC) scores and synovitis in both sexes, and osteophyte formation in female mice. Ectopic chondrogenesis did not show significant correlations with cAC scores. Significant direct correlations were found between AC scores and inflammatory markers in chondrocytes, including matrix metalloproteinase-13, inducible nitric oxide synthase, and the NLR family pyrin domain containing-3 inflammasome in both sexes, indicating a link between OA severity and inflammation. Additionally, markers of cell cycle arrest, such as p16 and β-galactosidase, also correlated with AC scores. In male mice, no significant correlations were found between SCB morphology traits and cAC scores, while in female mice, significant correlations were found between cAC scores and tibial SCB plate bone mineral density. Notably, MB and MitoQ treatments influenced the disease's progression in a sex-specific manner. MB treatment significantly reduced cAC scores at the medial knee joint, while MitoQ treatment reduced cAC scores, but these did not reach significance.

CONCLUSIONS

Our study provides comprehensive insights into the prevalence and progression of primary OA in aged UM-HET3 mice, highlighting the sex-specific effects of MB and MitoQ treatments. The correlations between AC scores and various pathological factors underscore the multifaceted nature of OA and its association with inflammation and subchondral bone changes.

PTH treatment before cyclic joint loading improves cartilage health and attenuates load-induced osteoarthritis development in mice

Osteoarthritis (OA) treatment is limited by the lack of effective nonsurgical interventions to slow disease progression. Here, we examined the contributions of the subchondral bone properties to OA development. We used parathyroid hormone (PTH) to modulate bone mass before OA initiation and alendronate (ALN) to inhibit bone remodeling during OA progression. We examined the spatiotemporal progression of joint damage by combining histopathological and transcriptomic analyses across joint tissues. The additive effect of PTH pretreatment before OA initiation and ALN treatment during OA progression most effectively attenuated load-induced OA pathology. Individually, PTH directly improved cartilage health and slowed the development of cartilage damage, whereas ALN primarily attenuated subchondral bone changes associated with OA progression. Joint damage reflected early transcriptomic changes. With both treatments, the structural changes were associated with early modulation of immunoregulation and immunoresponse pathways that may contribute to disease mechanisms. Overall, our results demonstrate the potential of subchondral bone-modifying therapies to slow the progression of OA.

Nerve growth factor receptor limits inflammation to promote remodeling and repair of osteoarthritic joints

Osteoarthritis (OA) is a painful, incurable disease affecting over 500 million people. Recent clinical trials of the nerve growth factor (NGF) inhibitors in OA patients have suggested adverse effects of NGF inhibition on joint structure. Here we report that nerve growth factor receptor (NGFR) is upregulated in skeletal cells during OA and plays an essential role in the remodeling and repair of osteoarthritic joints. Specifically, NGFR is expressed in osteochondral cells but not in skeletal progenitor cells and induced by TNFα to attenuate NF-κB activation, maintaining proper BMP-SMAD1 signaling and suppressing RANKL expression in mice. NGFR deficiency hyper-activates NF-κB in murine osteoarthritic joints, which impairs bone formation and enhances bone resorption as exemplified by a reduction in subchondral bone and osteophytes. In human OA cartilage, NGFR is also negatively associated with NF-κB activation. Together, this study suggests a role of NGFR in limiting inflammation for repair of diseased skeletal tissues.

Association of Bone Shape and Alignment Analyzed Using Statistical Shape Modeling With Severity of First Metatarsophalangeal Joint Osteoarthritis

OBJECTIVE

We aimed to explore the relationship between bone shape and radiographic severity in individuals with first metatarsophalangeal joint osteoarthritis (first MTP joint OA).

METHODS

Weightbearing lateral and dorsoplantar radiographs were obtained for the symptomatic foot of 185 participants (105 females, aged 22 to 85 years) with clinically diagnosed first MTP joint OA. Participants were classified into none/mild, moderate, or severe categories using a standardized atlas. An 80-point model for lateral radiographs and 77-point model for dorsoplantar radiographs was used to define independent modes of variation using statistical shape modeling software. Odds ratios adjusted for confounders were calculated using ordinal regression to determine the association between radiographic severity and mode scores.

RESULTS

After assessment and grading of radiographs, 35 participants (18.9%) were included in the none/mild first MTP joint OA severity category, 69 (37.2%) in the moderate severity category, and 81 (43.7%) in the severe category. For lateral-view radiographs, 16 modes of variation were included, which collectively represented 83.2% of total shape variance. Of these, four modes were associated with radiographic severity. For dorsoplantar-view radiographs, 15 modes of variation were included, representing 82.6% of total shape variance. Of these, six modes were associated with radiographic severity.

CONCLUSIONS

Variations in the shape and alignment of the medial cuneiform, first metatarsal, and proximal and distal phalanx of the hallux are significantly associated with radiographic severity of first MTP joint OA. Prospective studies are required to determine whether bone shape characteristics are associated with the development and/or progression of this condition.

Tranexamic Acid Attenuates the Progression of Posttraumatic Osteoarthritis in Mice

BACKGROUND

Posttraumatic osteoarthritis (OA) is a common disorder associated with a high socioeconomic burden, particularly in young, physically active, and working patients. Tranexamic acid (TXA) is commonly used in orthopaedic trauma surgery as an antifibrinolytic agent to control excessive bleeding. Previous studies have reported that TXA modulates inflammation and bone cell function, both of which are dysregulated during posttraumatic OA disease progression.

PURPOSE

To evaluate the therapeutic effects of systemic and topical TXA treatment on the progression of posttraumatic OA in the knee of mice.

STUDY DESIGN

Controlled laboratory study.

METHODS

OA was induced via anterior cruciate ligament (ACL) transection on the right knee of female mice. Mice were treated with TXA or vehicle intraperitoneally daily or intra-articularly weekly for 4 weeks, starting on the day of surgery. Articular cartilage degeneration, synovitis, bone erosion, and osteophyte formation were scored histologically. Micro-computed tomography evaluation was conducted to measure the subchondral bone microstructure and osteophyte volume. Cartilage thickness and bone remodeling were assessed histomorphometrically.

RESULTS

Both systemic and topical TXA treatment significantly reduced cartilage degeneration, synovitis, and bone erosion scores and increased the ratio of hyaline to calcified cartilage thickness in posttraumatic OA. Systemic TXA reversed ACL transection-induced subchondral bone loss and osteophyte formation, whereas topical treatment had no effect. Systemic TXA decreased the number and surface area of osteoclasts, whereas those of osteoblasts were not affected. No effect of topical TXA on osteoblast or osteoclast parameters was observed.

CONCLUSION

Both systemic and topical TXA exerted protective effects on the progression of posttraumatic OA. Drug repurposing of TXA may, therefore, be useful for the prevention or treatment of posttraumatic OA, particularly after ACL surgery.

CLINICAL RELEVANCE

TXA might be beneficial in patients with posttraumatic OA of the knee.

Evaluation of subchondral bone cysts in canine elbows with radiographic osteoarthritis secondary to elbow dysplasia

OBJECTIVE

To investigate whether subchondral bone cysts (SBCs) were present in dogs with radiographic elbow osteoarthritis (OA) and to investigate their relationship with radiographic OA severity.

STUDY DESIGN

Retrospective cross-sectional study.

SAMPLE POPULATION

Thirty-eight Labrador retrievers (total of 76 elbows).

METHODS

Elbow computed tomography (CT) images of 18 young (≤2 years old) and 20 old (>2 years old) Labrador retrievers, which presented for elbow-associated lameness, were reviewed. Radiographic elbow OA was graded into four groups based on the largest osteophyte size on CT. The presence, number, and maximum diameter of SBCs were determined.

RESULTS

Subchondral bone cysts were only identified in elbows with osteophytic new bone formation. The number and size of SBCs were associated with radiographic OA severity (p < .001 and p = .041 respectively). Specifically, the rate at which SBCs were present increased for both moderate and severe OA in comparison with the mild OA (moderate OA RR = 2.46, 95% CI 2.08-2.92, p < .001; severe OA RR = 5.60, 95% CI 4.79-6.55, p < .001). For dogs with severe OA, there was an increased likelihood that their SBCs were larger than SBCs from dogs with mild OA (OR = 1.056, 95% CI 1.012-1.101, p = .012). No SBCs were observed in elbows without radiographic evidence of OA.

CONCLUSION

Subchondral bone cysts were identified as a feature of radiographic elbow osteoarthritis in Labrador retrievers, and their number and size were indicative of the presence and severity of radiographic elbow OA.

CLINICAL SIGNIFICANCE

Subchondral bone cysts are a potential imaging biomarker for quantitative assessment for canine OA.

ENPP1 in Blood and Bone: Skeletal and Soft Tissue Diseases Induced by ENPP1 Deficiency

The enzyme ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) codes for a type 2 transmembrane glycoprotein that hydrolyzes extracellular ATP to generate pyrophosphate (PPi) and adenosine monophosphate, thereby contributing to downstream purinergic signaling pathways. The clinical phenotypes induced by ENPP1 deficiency are seemingly contradictory and include early-onset osteoporosis in middle-aged adults and life-threatening vascular calcifications in the large arteries of infants with generalized arterial calcification of infancy. The progressive overmineralization of soft tissue and concurrent undermineralization of skeleton also occur in the general medical population, where it is referred to as paradoxical mineralization to highlight the confusing pathophysiology. This review summarizes the clinical presentation and pathophysiology of paradoxical mineralization unveiled by ENPP1 deficiency and the bench-to-bedside development of a novel ENPP1 biologics designed to treat mineralization disorders in the rare disease and general medical population.

Development of primary osteoarthritis during aging in genetically diverse UM-HET3 mice

Background

Primary osteoarthritis (OA) occurs without identifiable underlying causes such as previous injuries or specific medical conditions. Age is a major contributing factor to OA, and as one ages, various joint tissues undergo gradual change, including degeneration of the articular cartilage, alterations in subchondral bone (SCB) morphology, and inflammation of the synovium.

Methods

We investigated the prevalence of primary OA in aged, genetically diverse UM-HET3 mice. Articular cartilage (AC) integrity and SCB morphology were assessed in 182 knee joints of 22-25 months old mice using the Osteoarthritis Research Society International (OARSI) scoring system and micro-CT, respectively. Additionally, we explored the effects of methylene blue (MB) and mitoquinone (MitoQ), two agents that affect mitochondrial function, on the prevalence and progression of OA during aging.

Results

Aged UM-HET3 mice showed a high prevalence of primary OA in both sexes. Significant positive correlations were found between cumulative AC (cAC) scores and synovitis in both sexes, and osteophyte formation in female mice. Ectopic chondrogenesis did not show significant correlations with cAC scores. Significant direct correlations were found between AC scores and inflammatory markers in chondrocytes, including matrix metalloproteinase-13, inducible nitric oxide synthase, and the NLR family pyrin domain containing-3 inflammasome in both sexes, indicating a link between OA severity and inflammation. Additionally, markers of cell cycle arrest, such as p16 and β-galactosidase, also correlated with AC scores. In male mice, no significant correlations were found between SCB morphology traits and cAC scores, while in female mice, significant correlations were found between cAC scores and tibial SCB plate bone mineral density. Notably, MB and MitoQ treatments influenced the disease's progression in a sex-specific manner. MB treatment significantly reduced cAC scores at the medial knee joint, while MitoQ treatment reduced cAC scores, but these did not reach significance.

Conclusions

Our study provides comprehensive insights into the prevalence and progression of primary OA in aged UM-HET3 mice, highlighting the sex-specific effects of MB and MitoQ treatments. The correlations between AC scores and various pathological factors underscore the multifaceted nature of OA and its association with inflammation and subchondral bone changes.

Development of primary osteoarthritis during aging in genetically diverse UM-HET3 mice

This study investigated the prevalence and progression of primary osteoarthritis (OA) in aged UM-HET3 mice. Using the Osteoarthritis Research Society International (OARSI) scoring system, we assessed articular cartilage (AC) integrity in 182 knee joints of 22-25 months old mice. Aged UM-HET3 mice showed a high prevalence of primary OA in both sexes. Significant positive correlations were found between cumulative AC (cAC) scores and synovitis in both sexes, and osteophyte formation in female mice. Ectopic chondrogenesis did not show significant correlations with cAC scores. Significant direct correlations were found between AC scores and inflammatory markers in chondrocytes, including matrix metalloproteinase-13 (MMP-13), inducible nitric oxide synthase (iNOS), and the NLR family pyrin domain containing-3 (NLRP3) inflammasome in both sexes, indicating a link between OA severity and inflammation. Additionally, markers of cell cycle arrest, such as p16 and β-galactosidase, also correlated with AC scores. Using micro-CT, we examined the correlations between subchondral bone (SCB) morphology traits and AC scores. In male mice, no significant correlations were found between SCB morphology traits and cAC scores, while in female mice, significant correlations were found between cAC scores and tibial SCB plate bone mineral density. Finally, we explored the effects of methylene blue (MB) and mitoquinone (MitoQ), two agents that affect mitochondrial function, on the prevalence and progression of OA during aging. Notably, MB and MitoQ treatments influenced the disease's progression in a sex-specific manner. MB treatment significantly reduced cAC scores at the medial knee joint, while MitoQ treatment reduced cAC scores, but these did not reach significance. In conclusion, our study provides comprehensive insights into the prevalence and progression of primary OA in aged UM-HET3 mice, highlighting the sex-specific effects of MB and MitoQ treatments. The correlations between AC scores and various pathological factors underscore the multifaceted nature of OA and its association with inflammation and subchondral bone changes.

Characteristics of the synovial microenvironment and synovial mesenchymal stem cells with hip osteoarthritis of different bone morphologies

BACKGROUND

Variations in bone morphology in patients with hip osteoarthritis (HOA) can be broadly categorized into three types: atrophic, normotrophic, and hypertrophic. Despite the investigations examining clinical elements, such as bone morphology, pain, and range of motion, our understanding of the pathogenesis of HOA remains limited. Previous studies have suggested that osteophytes typically originate at the interface of the joint cartilage, periosteum, and synovium, potentially implicating synovial mesenchymal stem cells (SMSCs) in the process. This study aimed to investigate the potential factors that drive the development of bone morphological features in HOA by investigating the characteristics of the synovium, differentiation potential of SMSCs, and composition of synovial fluid in different types of HOA.

METHODS

Synovial tissue and fluid were collected from 30 patients who underwent total hip arthroplasty (THA) with the variable bone morphology of HOA patients. RNA sequencing analysis and quantitative reverse transcription-polymerase chain reaction (RT-qPCR) were performed to analyse the genes in the normotrophic and hypertrophic synovial tissue. SMSCs were isolated and cultured from the normotrophic and hypertrophic synovial tissues of each hip joint in accordance with the variable bone morphology of HOA patients. Cell differentiation potential was compared using differentiation and colony-forming unit assays. Cytokine array was performed to analyse the protein expression in the synovial fluid.

RESULTS

In the RNA sequencing analysis, 103 differentially expressed genes (DEGs) were identified, predominantly related to the interleukin 17 (IL-17) signalling pathway. Using a protein-protein interaction (PPI) network, 20 hub genes were identified, including MYC, CXCL8, ATF3, NR4A1, ZC3H12A, NR4A2, FOSB, and FOSL1. Among these hub genes, four belonged to the AP-1 family. There were no significant differences in the tri-lineage differentiation potential and colony-forming capacity of SMSCs. However, RT-qPCR revealed elevated SOX9 expression levels in synovial tissues from the hypertrophic group. The cytokine array demonstrated significantly higher levels of CXCL8, MMP9, and VEGF in the synovial fluid of the hypertrophic group than in the normotrophic group, with CXCL8 and MMP9 being significantly expressed in the hypertrophic synovium.

CONCLUSION

Upregulation of AP-1 family genes in the synovium and increased concentrations of CXCL8, MMP9, and VEGF were detected in the synovial fluid of the hypertrophic group of HOA patients, potentially stimulating the differentiation of SMSCs towards the cartilage and thereby contributing to severe osteophyte formation.

Enlarged colony housing promotes linear progression of subchondral bone remodeling in joint instability rat models

Objective: Osteoarthritis (OA) is a disease with high prevalence and an unmet medical need for disease modifying treatments. In rat models, OA-like subchondral bone and cartilage changes can be induced by instability surgery with different severity levels. Factors which determine structural changes additionally comprise the study duration and activity-impacted joint loading. Methods: A medial meniscal tear (MMT) or anterior cruciate ligament transection with partial meniscectomy (ACLT+pMx) was induced unilaterally in rats housed in a rat colony cage (RCC), allowing high activity levels including jumping and stair climbing. In parallel, ACLT+pMx rats were housed in Type IV cages. The time course of OA-related changes was investigated at 4, 8, 12, and 16 weeks after surgery by micro-CT, gait analysis and joint diameter measurements. Results: Gait disturbance was observed after 2 weeks and to a similar extend in all models. The increase in ipsilateral joint diameters peaked after 2 weeks and were more pronounced after ACLT+pMx compared to MMT-surgery, but independent of housing. Micro-CT analysis revealed that increases in osseous tibial width were most distinct after ACLT+pMx in RCC and progressed continuously until week sixteen. In contrast, osseous tibial width of ipsilateral joints in MMT RCC and ACLT+pMx Type IV groups did not increase further after week twelve. In contralateral joints, this parameter was not affected, regardless of the model or caging. However, a significant increase in bone volume fraction and trabecular thickness was observed over time in the femur and tibia of both ipsilateral and contralateral knees. Here, the medial tibial compartment of the operated joint was most affected and linear changes were most pronounced in the ACLT+pMx RCC group. Conclusion: Increased movement of animals in colony cages leads to robust structural changes in subchondral bone after surgically induced joint instability over time, while in regular Type IV housing maximal changes are reached in week twelve. The new insights into the differentiation of the models, particularly with respect to the linear progression of bone changes in ACLT+pMx in the RCC, may be useful for the design of chronic OA-studies within a longer lifespan and therefore supporting the development of novel therapies.

IL-6 Reduces Spheroid Sizes of Osteophytic Cells Derived from Osteoarthritis Knee Joint via Induction of Apoptosis

Osteophytes in osteoarthritis (OA) joints contribute to restriction of joint movement, joint pain, and OA progression, but little is known about osteophyte regulators. Examination of gene expression related to cartilage extracellular matrix, endochondral ossification, and growth factor signaling in articular cartilage and osteophytes obtained from OA knee joints showed that several genes such as COL1A1, VCAN, BGLAP, BMP8B, RUNX2, and SOST were overexpressed in osteophytes compared with articular cartilage. Ratios of mesenchymal stem/progenitor cells, which were characterized by co-expression of CD105 and CD166, were significantly higher in osteophytic cells than articular cells. A three-dimensional culture method for cartilage and osteophyte cells was developed by modification of cultures of self-assembled spheroid cell organoids (spheroids). These spheroids cultured in the media for mesenchymal stem cells containing transforming growth factor-β3 showed characteristic morphologies and gene expression profiles of articular cartilage and osteophytes, respectively. The effects of IL-1β, tumor necrosis factor-α, and IL-6 on the spheroids of articular and osteophytic cells were studied. To the best of our knowledge, they provide the first evidence that IL-6 suppresses the spheroid size of osteophytic cells by inducing apoptosis and reducing extracellular matrix molecules. These data show that IL-6 is the suppressor of osteophyte growth and suggest that IL-6 expression and/or activity are implicated in the regulation of osteophyte formation in pathologic joints.

Conservative Treatment Using Platelet-Rich Plasma for Acute Anterior Cruciate Ligament Injuries in Highly Active Patients: A Retrospective Survey

Background The recommended treatment for anterior cruciate ligament (ACL) injuries in active, sports-oriented patients is reconstructive surgery in order to regain stability and prevent secondary meniscal injuries. However, ACL reconstruction requires a long recovery period and poses issues such as decreased muscle strength due to tendon harvesting and postoperative osteoarthritis (OA) progression, thereby raising significant expectations for the advancement of conservative treatments. Recent studies have shown that platelet-rich plasma (PRP) therapy, which utilizes the tissue repair-promoting property of platelets, is effective for ACL injuries. Methods We administered PRP therapy within six weeks after ACL injury in patients who expressed the desire for an early return to sports through conservative care. After the treatment, patients wore a simple brace that limited deep flexion but placed no restrictions on weight bearing. Four months was the standard goal established for returning to pre-injury condition, and, depending on the target level, timing, and knee condition, we adjusted the additional PRP treatments and rehabilitation approach, gradually authorizing the patients' return to sport. We assessed the ligament repair status by magnetic resonance imaging (MRI) just before the full return to sports. A retrospective survey was conducted to evaluate the status of ligament repair and the condition of return-to-sport in patients with ACL injuries who underwent conservative treatment using PRP. Results The average patient age was 32.7 years and the average treatment was 2.8 PRP sessions. MRI evaluations confirmed that ligament continuity was regained in all cases. All the patients returned to their pre-injury level (Tegner Activity Scale 7.0) in an average of 139.5 days, but there was one instance of re-rupture following the return to sports. Conclusion All patients with ACL injury who underwent PRP therapy regained ligament continuity and returned to sport successfully with only one case of re-rupture.

Nerve Growth Factor Receptor Limits Inflammation to Promote Remodeling and Repair of Osteoarthritic Joints

Osteoarthritis (OA) is a painful, incurable disease affecting over 500 million people. The need for relieving OA pain is paramount but inadequately addressed, partly due to limited understandings of how pain signaling regulates non-neural tissues. Here we report that nerve growth factor receptor (NGFR) is upregulated in skeletal cells during OA and plays an essential role in the remodeling and repair of osteoarthritic joints. Specifically, NGFR is expressed in osteochondral cells but not in skeletal progenitor cells and induced by TNFα to attenuate NF-κB activation, maintaining proper BMP-SMAD1 signaling and suppressing RANKL expression. NGFR deficiency hyper-activates NF-κB in murine osteoarthritic joints, which impairs bone formation and enhances bone resorption as exemplified by a reduction in subchondral bone and osteophytes. In human OA cartilage, NGFR is also negatively associated with NF-κB activation. Together, this study uncovers a role of NGFR in limiting inflammation for repair of diseased skeletal tissues.

Medial meniscus extrusion is invariably observed and consistent with tibial osteophyte width in elderly populations: The Bunkyo Health Study

We reported that the full-length width of medial tibial osteophytes comprising cartilage and bone parts correlates with medial meniscus extrusion (MME) in early-stage knee osteoarthritis (OA). However, no data exist on the prevalence of MME and its relationship with osteophytes in the elderly population. 1191 elderly individuals (females 57%; 72.9 years old on average) in the Bunkyo Health Study underwent standing plain radiograph and proton density-weighted MRI on knee joints. MRI-detected OA changes were evaluated according to the Whole-Organ Magnetic Resonance Imaging Score. A new method of assessing the cartilage and bone parts of osteophytes was developed using pseudo-coloring images of proton density-weighted fat-suppressed MRI. Most subjects showed Kellgren-Lawrence grade 1 or 2 radiographic medial knee OA (88.1%), MME (98.7%, 3.90 ± 2.01 mm), and medial tibial osteophytes (99.3%, 3.27 ± 1.50 mm). Regarding OA changes, MME was closely associated with the full-length width of medial tibial osteophytes (β = 1.114; 95% CI 1.069-1.159; p < 0.001) in line with osteophyte width (intraclass correlation coefficient, 0.804; 95% CI 0.783-0.823). Our data revealed that MME and medial tibial osteophytes are observed in the elderly and demonstrate that the degree of MME is consistent with the full-length width of medial tibial osteophytes, suggesting that osteophytes might be implicated in MME.

WGA-M001, a Mixture of Total Extracts of Tagetes erecta and Ocimum basilicum, Synergistically Alleviates Cartilage Destruction by Inhibiting ERK and NF-κB Signaling

Tagetes erecta and Ocimum basilicum are medicinal plants that exhibit anti-inflammatory effects against various diseases. However, their individual and combined effects on osteoarthritis (OA) are unknown. Herein, we aimed to demonstrate the effects of T. erecta, O. basilicum, and their mixture, WGA-M001, on OA pathogenesis. The administration of total extracts of T. erecta and O. basilicum reduced cartilage degradation and inflammation without causing cytotoxicity. Although WGA-M001 contained lower concentrations of the individual extracts, it strongly inhibited the expression of pathogenic factors. In vivo OA studies also supported that WGA-M001 had protective effects against cartilage destruction at lower doses than those of T. erecta and O. basilicum. Moreover, its effects were stronger than those observed using Boswellia and Perna canaliculus. WGA-M001 effectively inhibited the interleukin (IL)-1β-induced nuclear factor kappa-light-chain-enhancer of the activated B cell (NF-κB) pathway and ERK phosphorylation. Furthermore, RNA-sequence analysis also showed that WGA-M001 decreased the expression of genes related to the IL-1β-induced NF-κB and ERK signaling pathways. Therefore, WGA-M001 is more effective than the single total extracts of T. erecta and O. basilicum in attenuating OA progression by regulating ERK and NF-κB signaling. Our results open new possibilities for WGA-M001 as a potential therapeutic agent for OA treatment.

Establishment of a uniform histological evaluation method for early stage osteophytes in the destabilization of the medial meniscus mouse model

Background

Osteophyte formation is attracting attention as an early-stage pathology of knee osteoarthritis (OA). Although osteophyte formation is understood as a defense response to joint instability, its role and impact on OA remain largely unknown. Many studies have been conducted using the surgical destabilization of the medial meniscus (DMM) mouse model, but there are few standard evaluation methods, especially in the histological evaluation of early-stage osteophytes. The purpose of this study was to establish a reproducible and uniform method for histological evaluation of characteristics of early osteophyte formation in the DMM mouse model.

Methods

Male mice were operated with DMM at 12 weeks old and histologically evaluated at 4 days and 1, 2 and 4 weeks after DMM. Osteophyte Width, Osteophyte Area, and Original and Modified Maturity Scores were used to evaluate osteophytes for all sections.

Results

Osteophyte Width, Osteophyte Area and Maturity Scores were all greater anteriorly than posteriorly in the knee joint. The Modified Maturity Score was more strongly correlated with position than the Original Maturity Score, and could be used to evaluate early-stage osteophyte formation.

Conclusion

The Modified Maturity Score as well as Osteophyte Width and Area at the section of the anterior cruciate ligament (ACL) attachment site can provide a reproducible evaluation method to histologically assess the early-stage osteophyte formation in the DMM mouse model.

Histopathological Interpretation of TMJ Osteophyte: Report and Review

Introduction

Osteophytes are osseocartilaginous structures which are commonly found in common degenerative joint diseases. It can be free or attached to nature. There is a paucity of information in the literature regarding the histopathological interpretation of osteophytes in Temporomandibular Joint (TMJ).

Purpose

To report the incidental finding of osteophytes in cases of chronic protracted TMJ dislocation.

Material and Method

To present case of an elderly 72-year-old female and a 35-year-old male with chronic protracted TMJ dislocation who were treated surgically for their condition with an incidental finding of an osteophyte in TMJ intraoperatively.

Result

The histopathological examination revealed fibrocartilaginous core tissue surrounded by bone formation due to dystrophic calcification.

Conclusion

The microscopic examination is mandatory in order to study and understand the pathophysiology of an osteophyte. This study presents rare histopathological evidence of an osteophyte. It reflects the process of its formation and the possibilities of fate of an osteophyte in TMJ.

Increased 18F-FAPI uptake in bones and joints of lung cancer patients: characteristics and distributions

OBJECTIVE

This study investigated the distribution and characteristics of various bone and joint lesions on 18F-FAPI PET/CT in lung cancer patients.

METHODS

Seventy-four lung cancer patients who underwent 18F-FAPI PET/CT were reviewed. Bone and joint lesions with elevated 18F-FAPI uptake were recorded and analyzed. The distribution and maximum uptake value (SUVmax) of different benign lesions or bone metastases were presented. In addition, the SUVmax of bone metastases on 18F-FDG and 18F-FAPI-04 PET/CT were also compared.

RESULTS

In 53 patients, a total of 262 lesions presented 18F-FAPI accumulation. Bone metastases were mainly in vertebrae, pelvis, and ribs, while benign lesions were in vertebral margins, alveolar bone, and shoulder joints. The SUVmax of bone metastases was significantly higher than that of benign lesions ([Formula: see text] vs. [Formula: see text], [Formula: see text]), with NSCLC cases having higher SUVmax values than SCLC cases ([Formula: see text] vs. [Formula: see text], [Formula: see text]). Among benign lesions, arthritis and periodontitis demonstrated higher SUVmax than degenerative lesions (arthritis: [Formula: see text]; periodontitis: [Formula: see text]; degenerative diseases: [Formula: see text]; [Formula: see text] and [Formula: see text], respectively). The SUVmax of bone metastases was comparable between 18F-FDG and 18F-FAPI PET/CT. However, 18F-FAPI PET/CT was found to be superior in identifying cranial metastases compared to 18F-FDG PET/CT (TBRmet/brain: [Formula: see text] vs. [Formula: see text], [Formula: see text]).

CONCLUSION

This study demonstrated that 18F-FAPI PET/CT is a valuable imaging modality for detecting bone and joint lesions in lung cancer patients. The SUVmax of malignant lesions was higher than that of benign lesions, but cannot accurately distinguish benign and malignant lesions. The uptake of FAPI differs among lesions with different pathological types.

Depleting transforming growth factor beta receptor 2 signalling in the cartilage of itga1-null mice attenuates spontaneous knee osteoarthritis

Objectives

Integrin α1β1 protects against osteoarthritis (OA) when it is upregulated in the superficial zone of cartilage in the early stages of disease. However, the mechanism behind this protection is unknown. Integrin α1β1 moderates transforming growth factor β receptor II (TGFBR2) signalling, a critical regulator of chondrocyte anabolic activity. To this end, mice lacking integrin α1β1 have increased baseline activation of TGFBR2 signalling and overall fibrosis. The purpose of this study was to evaluate the interplay between integrin α1β1 and TGFBR2 in the development of spontaneous OA. We hypothesized that dampening TGFBR2 signalling in the cartilage of itga1-null mice would attenuate OA.

Methods

Behavioural and histological manifestations of spontaneous knee OA were measured at 4, 8, 12 and 16 months in mice with and without a ubiquitous itga1 deletion and with and without a tamoxifen-induced cartilage specific TGFBR2 depletion.

Results

Knee cartilage degeneration, collateral ligament ossification and pain responses increased with age. Itga1-null mice with intact TGFBR2 signalling developed earlier and more severe OA compared to controls. In agreement with our hypothesis, depleting TGFBR2 signalling in the cartilage of itga1-null mice attenuated OA progression.

Conclusion

Intact TGFBR2 signalling drives early and worse knee OA in itga1-null mice. This result supports the hypothesis that the increased expression of integrin α1β1 by superficial zone chondrocytes early in OA development dampens TGFBR2 signalling and thus protects against degeneration.

Imaging signs of temporomandibular joint osteoarthritis in an urban population of 65-year-olds: A cone beam computed tomography study

BACKGROUND

Symptoms of osteoarthritis (OA) in the temporomandibular joint (TMJ) may vary and possible causes should be further explored, such as prevalence and characteristics of imaging features.

OBJECTIVES

Investigate prevalence, gender differences and characteristics of imaging signs of TMJ-OA by cone beam computed tomography (CBCT) in a population-based sample of 65-year-old Oslo citizens.

MATERIALS AND METHODS

159 (86 women, 73 men) individuals randomly recruited from a cohort of 460 Oslo citizens were examined with CBCT. The TMJs were categorised as with imaging signs of OA, no OA or indeterminate for OA.

RESULTS

CBCT signs of TMJ-OA were found in 35% of the 159 participants: 47% of the women and 22% of the men. CBCT signs of TMJ-OA were unilateral in two-thirds of the TMJs and characterised by articular surface flattening and condylar osteophytes. In almost all joints with bone erosive findings, bone productive findings were also found. Participants with and without CBCT signs of TMJ-OA showed no significant difference in TMD pain screener. Fourteen of the 159 participants (9%) had pain-related TMD and 12 (8%) had been in contact with health care services due to TMD.

CONCLUSIONS

CBCT signs of TMJ-OA was common in this study group of 65-year-old Oslo citizens, found in every second woman and every fifth man. Articular surface flattening and bone productive changes, in particular condylar osteophytes, were the most frequent imaging features. Despite the high frequency of CBCT signs of TMJ-OA, few of the participants had pain-related TMD.

Identifying Fibroblast Growth Factor Receptor 3 as a Mediator of Periosteal Osteochondral Differentiation through the Construction of microRNA-Based Interaction Networks

Human periosteum-derived progenitor cells (hPDCs) have the ability to differentiate towards both the chondrogenic and osteogenic lineages. This coordinated and complex osteochondrogenic differentiation process permits endochondral ossification and is essential in bone development and repair. We have previously shown that humanised cultures of hPDCs enhance their osteochondrogenic potentials in vitro and in vivo; however, the underlying mechanisms are largely unknown. This study aimed to identify novel regulators of hPDC osteochondrogenic differentiation through the construction of miRNA-mRNA regulatory networks derived from hPDCs cultured in human serum or foetal bovine serum as an alternative in silico strategy to serum characterisation. Sixteen differentially expressed miRNAs (DEMis) were identified in the humanised culture. In silico analysis of the DEMis with TargetScan allowed for the identification of 1503 potential miRNA target genes. Upon comparison with a paired RNAseq dataset, a 4.5% overlap was observed (122 genes). A protein-protein interaction network created with STRING interestingly identified FGFR3 as a key network node, which was further predicted using multiple pathway analyses. Functional analysis revealed that hPDCs with the activating mutation FGFR3N540K displayed increased expressions of chondrogenic gene markers when cultured under chondrogenic conditions in vitro and displayed enhanced endochondral bone formation in vivo. A further histological analysis uncovered known downstream mediators involved in FGFR3 signalling and endochondral ossification to be upregulated in hPDC FGFR3N540K-seeded implants. This combinational approach of miRNA-mRNA-protein network analysis with in vitro and in vivo characterisation has permitted the identification of FGFR3 as a novel mediator of hPDC biology. Furthermore, this miRNA-based workflow may also allow for the identification of drug targets, which may be of relevance in instances of delayed fracture repair.

Long-term results of per-operative knee arthroscopy in confirming suitability for unicompartmental arthroplasty

BACKGROUND

Patient selection is key to the success of medial unicondylar knee arthroplasty (UKA). Progression of arthritis is the most common indication for revision surgery. Per-operative arthroscopy is a means of directly assessing the integrity of the lateral compartment. The aim of the study is to assess the long-term survivorship of UKA performed when per-operative arthroscopy is used as a final means of deciding whether to proceed with UKA.

METHODS

We used per-operative arthroscopy as a means to confirm suitability for UKA in a consecutive series of 279 Oxford medial UKA. Our series of UKA with per-operative arthroscopy (Group 1) was compared to all Oxford UKA (Group 2) and all UKA in the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) (Group 3).

RESULTS

The 14-year cumulative percentage revision (CPR) was 18.5% (95% CI 12.7, 26.4) for group 1, 19.7% (95% CI 18.8, 20.6) for group 2, and 19.2% (95% CI 18.5, 19.8) for group 3. There was no statistically significant difference in the (CPR) for the entire period when group 1 was compared to groups 2 or 3. Progression of arthritis was least in Group 1 compared to groups 2 and 3; 3.6 versus 4.4 and 4.1% respectively. Following per-operative arthroscopy 21.6% (77/356) of knees underwent a change of surgical plan from UKA to TKA.

CONCLUSION

In our practice, which includes per-operative arthroscopy, we have identified a reduced risk of revision due to progression of arthritis but no difference in overall long-term implant survivorship.

Biomechanical Impact of Phosphate Wasting on Articular Cartilage Using the Murine Hyp Model of X-linked hypophosphatemia

Degenerative osteoarthritis (OA) is recognized as an early-onset comorbidity of X-linked hypophosphatemia (XLH), contributing to pain and stiffness and limiting range of motion and activities of daily living. Here, we extend prior findings describing biochemical and cellular changes of articular cartilage (AC) in the phosphate-wasting environment of XLH to determine the impact of these changes on the biomechanical properties of AC in compression and potential role in the etiology of OA. We hypothesize that despite increased proteoglycan biosynthesis, disruption of the mineralized zone of AC impacts the mechanical properties of cartilage that function to accommodate loads and that therapeutic restoration of this zone will improve the mechanical properties of AC. Data were compared between three groups: wild type (WT), Hyp, and Hyp mice treated with calcitriol and oral phosphate. EPIC microCT confirmed AC mineral deficits and responsiveness to therapy. MicroCT of the Hyp subchondral bone plate revealed that treatment improved trabecular bone volume (BV/TV) but remained significantly lower than WT mice in other trabecular microstructures (p < 0.05). Microindentation AC studies revealed that, compared with WT mice, the mean stiffness of tibial AC was significantly lower in untreated Hyp mice (2.65 ± 0.95 versus 0.87 ± 0.33 N/mm, p < 0.001) and improved with therapy (2.15 + 0.38 N/mm) to within WT values. Stress relaxation of AC under compressive loading displayed similar biphasic relaxation time constants (Taufast and Tauslow) between controls and Hyp mice, although Tauslow trended toward slowed relaxation times. In addition, Taufast and Tauslow times correlated with peak load in WT mice (r = 0.80; r = 0.78, respectively), whereas correlation coefficient values for Hyp mice (r = 0.46; r = 0.21) improved with treatment (r = 0.71; r = 0.56). These data provide rationale for therapies that both preserve AC stiffness and recovery from compression. The Hyp mouse also provides unique insight into determinants of structural stiffness and the viscoelastic properties of AC in the progression of OA. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Bone Remodeling in Osteoarthritis-Biological and Radiological Aspects

Among available papers published on the given subject over the last century, various terms have been used as synonyms for one, now generally accepted-osteoarthritis, in some countries called "wear and tear" or "overload arthritis". The opsolent terms-hypertrophic arthritis, degenerative arthritis, arthritis deformans and osteoarthrosis-sought to highlight the dominant clinical signs of this ubiquitous, polymorph disease of the whole osteochondral unit, which by incidence and prevalence represents one of the leading chronic conditions that cause long-term pain and incapacity for work. Numerous in vitro and in vivo research resulted in broadened acknowledgments about osteoarthritis pathophysiology and pathology on both histological and cellular levels. However, the cause of osteoarthritis is still unknown and is currently the subject of a hypothesis. In this paper, we provide a review of recent findings on biological phenomena taking place in bone tissue during osteoarthritis to the extent useful for clinical practice. Choosing a proper radiological approach is a conditio sine qua non to the early diagnosis of this entity.

Intra-articular delivery of micronized dehydrated human amnion/chorion membrane reduces degenerative changes after onset of post-traumatic osteoarthritis

Background: Micronized dehydrated human amnion/chorion membrane (mdHACM) has reduced short term post-traumatic osteoarthritis (PTOA) progression in rats when delivered 24 h after medial meniscal transection (MMT) and is being investigated for clinical use as a disease modifying therapy. Much remains to be assessed, including its potential for longer-term therapeutic benefit and treatment effects after onset of joint degeneration. Objectives: Characterize longer-term effects of acute treatment with mdHACM and determine whether treatment administered to joints with established PTOA could slow or reverse degeneration. Hypotheses: Acute treatment effects will be sustained for 6 weeks, and delivery of mdHACM after onset of joint degeneration will attenuate structural osteoarthritic changes. Methods: Rats underwent MMT or sham surgery (left leg). mdHACM was delivered intra-articularly 24 h or 3 weeks post-surgery (n = 5-7 per group). Six weeks post-surgery, animals were euthanized and left tibiae scanned using equilibrium partitioning of an ionic contrast agent microcomputed tomography (EPIC-µCT) to structurally quantify joint degeneration. Histology was performed to examine tibial plateau cartilage. Results: Quantitative 3D µCT showed that cartilage structural metrics (thickness, X-ray attenuation, surface roughness, exposed bone area) for delayed mdHACM treatment limbs were significantly improved over saline treatment and not significantly different from shams. Subchondral bone mineral density and thickness for the delayed treatment group were significantly improved over acute treated, and subchondral bone thickness was not significantly different from sham. Marginal osteophyte degenerative changes were decreased with delayed mdHACM treatment compared to saline. Acute treatment (24 h post-surgery) did not reduce longer-term joint tissue degeneration compared to saline. Histology supported µCT findings and further revealed that while delayed treatment reduced cartilage damage, chondrocytes displayed qualitatively different morphologies and density compared to sham. Conclusion: This study provides insight into effects of intra-articular delivery timing relative to PTOA progression and the duration of therapeutic benefit of mdHACM. Results suggest that mdHACM injection into already osteoarthritic joints can improve joint health, but a single, acute mdHACM injection post-injury does not prevent long term osteoarthritis associated with meniscal instability. Further work is needed to fully characterize the durability of therapeutic benefit in stable osteoarthritic joints and the effects of repeated injections.

Anterior meniscus extrusion is associated with anterior tibial osteophyte width in knee osteoarthritis - The Bunkyo Health Study

Background

In knee osteoarthritis (OA), medial meniscus extrudes both medially and anteriorly. We reported that full-length width of medial tibial osteophyte, which comprises cartilage and bone parts, is directly associated with medial meniscus extrusion in early-stage knee OA and hypothesized that anterior tibial osteophyte (ATO) is also associated with anterior meniscus extrusion (AME). Thus, we aimed to examine their prevalence and relationship.

Methods

Elderly subjects (638 females and 507 males; average 72.9 years old) in the Bunkyo Health Study cohort were enrolled. MRI-detected OA changes were evaluated according to the Whole Organ Magnetic Resonance Imaging Score. ATO was evaluated using the method which can assess both cartilage and bone parts of osteophyte by pseudo-coloring images of proton density-weighted fat-suppressed MRI.

Results

Most subjects showed the Kellgren-Lawrence grade 1/2 of the medial knee OA (88.1%), AME (94.3%, 3.7 ​± ​2.2 ​mm), and ATO (99.6%, 4.2 ​± ​1.5 ​mm). Among the OA changes, AME was most closely associated with full-length width of ATO (multivariable β ​= ​0.877, p ​< ​0.001). The area under the receiver operating characteristic curve for determining the presence of AME as evaluated by ATO width was 0.75 (95% confidence interval 0.60-0.84, p ​< ​0.001). The odds ratio for the presence of AME as evaluated by ATO width at 2.9 ​mm was 7.16 (4.23-12.15, p ​< ​0.001, age, gender, BMI, and K-L adjusted).

Conclusions

AME and ATO were inevitably observed in the elderly subjects and AME was closely associated with full-length width of ATO. Our study provides the first evidence on the close relationship between AME and ATO in knee OA.

Adseverin, an actin-binding protein, modulates hypertrophic chondrocyte differentiation and osteoarthritis progression

In osteoarthritis (OA), a disease characterized by progressive articular cartilage degradation and calcification, the articular chondrocyte phenotype changes and this correlates with actin cytoskeleton alterations suggesting that it regulates gene expression essential for proper phenotype. This study reports that OA is associated with the loss of adseverin, an actin capping and severing protein. Adseverin deletion (Adseverin-/-) in mice compromised articular chondrocyte function, by reducing F-actin and aggrecan expression and increasing apoptosis, Indian hedgehog, Runx2, MMP13, and collagen type X expression, and cell proliferation. This led to stiffer cartilage and decreased hyaline and increased calcified cartilage thickness. Together, these changes predisposed the articular cartilage to enhanced OA severity in Adseverin-/- mice who underwent surgical induction of OA. Adseverin-/- chondrocyte RNA sequencing and in vitro studies together suggests that adseverin modulates cell viability and prevents mineralization. Thus, adseverin maintains articular chondrocyte phenotype and cartilage tissue homeostasis by preventing progression to hypertrophic differentiation in vivo. Adseverin may be chondroprotective and a potential therapeutic target.

Degenerative cervical spine changes among early career fighter pilots: a 5-year follow-up

INTRODUCTION

Degenerative changes of the cervical spine often cause disability and flight duty limitations among Finnish Air Force (FINAF) fighter pilots. We aimed to study the effect of +Gz exposure on degenerative changes in the cervical spine by comparing cervical MRIs of FINAF fighter pilots and controls.

METHODS

At baseline, the volunteer study population consisted of 56 20-year-old FINAF male fighter pilots (exposure group) and 56 21-year-old Army and Navy cadets (control group). Both groups underwent MRI of the cervical spine at the baseline and after 5 years. Degenerative changes evaluated using MRI included intervertebral disc (IVD) degeneration (Pfirrmann classification), disc herniations, uncovertebral arthrosis, Schmorl's nodes, Modic changes, spinal canal stenosis, kyphosis and scoliosis.

RESULTS

The degree of IVD degeneration in the whole cervical spine increased significantly in both populations with no between-group differences. The prevalence of disc herniations also tended to increase in both populations with no difference in the incidence over the follow-up. However, pilots proved to have more disc herniations at the baseline and at the follow-up. There were virtually no between-group differences in other assessed degenerative changes.

DISCUSSION

We found that IVD degeneration and the prevalence of disc herniations increased at a similar rate for fighter pilots and non-flying military students when all cervical levels were summed up. The lack of difference may be explained by the relatively low cumulative +Gz exposure during the first 5 years of a pilots' career.

Genetic models for lineage tracing in musculoskeletal development, injury, and healing

Musculoskeletal development and later post-natal homeostasis are highly dynamic processes, marked by rapid structural and functional changes across very short periods of time. Adult anatomy and physiology are derived from pre-existing cellular and biochemical states. Consequently, these early developmental states guide and predict the future of the system as a whole. Tools have been developed to mark, trace, and follow specific cells and their progeny either from one developmental state to the next or between circumstances of health and disease. There are now many such technologies alongside a library of molecular markers which may be utilized in conjunction to allow for precise development of unique cell 'lineages'. In this review, we first describe the development of the musculoskeletal system beginning as an embryonic germ layer and at each of the key developmental stages that follow. We then discuss these structures in the context of adult tissues during homeostasis, injury, and repair. Special focus is given in each of these sections to the key genes involved which may serve as markers of lineage or later in post-natal tissues. We then finish with a technical assessment of lineage tracing and the techniques and technologies currently used to mark cells, tissues, and structures within the musculoskeletal system.