Joint Hypermobility Syndrome and Membrane Proteins: A Comprehensive Review

Ehlers-Danlos syndromes (EDSs) constitute a heterogeneous group of connective tissue disorders characterized by joint hypermobility, skin hyperextensibility, and tissue fragility. Asymptomatic EDSs, joint hypermobility without associated syndromes, EDSs, and hypermobility spectrum disorders are the commonest phenotypes associated with joint hypermobility. Joint hypermobility syndrome (JHS) is a connective tissue disorder characterized by extreme flexibility of the joints, along with pain and other symptoms. JHS can be a sign of a more serious underlying genetic condition, such as EDS, which affects the cartilage, bone, fat, and blood. The exact cause of JHS could be related to genetic changes in the proteins that add flexibility and strength to the joints, ligaments, and tendons, such as collagen. Membrane proteins are a class of proteins embedded in the cell membrane and play a crucial role in cell signaling, transport, and adhesion. Dysregulated membrane proteins have been implicated in a variety of diseases, including cancer, cardiovascular disease, and neurological disorders; recent studies have suggested that membrane proteins may also play a role in the pathogenesis of JHS. This article presents an exploration of the causative factors contributing to musculoskeletal pain in individuals with hypermobility, based on research findings. It aims to provide an understanding of JHS and its association with membrane proteins, addressing the clinical manifestations, pathogenesis, diagnosis, and management of JHS.

Apoptosis Occurs in the Anterior Talofibular Ligament of Patients With Chronic Lateral Ankle Instability: An In Vitro Study

BACKGROUND

Chronic lateral ankle instability is treated operatively, whereas most acute ankle sprains associated with acute anterior talofibular ligament injury are usually treated nonoperatively. This treatment strategy is widely accepted and has been validated using a variety of clinical or radiological methods. We suspected that there may be biological differences between chronic and acutely injured ligaments, particularly with respect to apoptosis. Apoptosis is known to cause ligament degeneration. If it could be demonstrated that apoptosis occurs more in the anterior talofibular ligament tissues of patients with chronic lateral ankle instability compared with patients with acute anterior talofibular ligament injury, biological evidence could be supported.

QUESTIONS/PURPOSES

We sought to (1) elucidate the difference in the extent of apoptosis between patients with chronic lateral ankle instability and those with acute anterior talofibular ligament injury. In addition, we asked: (2) What is the expression level of apoptotic enzymes such as caspases 3, 7, 8, and 9 and cytochrome c in each patient group? (3) Is there a correlation between apoptotic activities and the symptom duration period of chronic lateral ankle instability?

METHODS

Between March 2019 and February 2021, 50 patients were prospectively enrolled in this study. Anterior talofibular ligament tissues were harvested from patients who were divided into two groups: the chronic lateral ankle instability group and the acute anterior talofibular ligament injury group. Patients with insufficient remaining ligaments were excluded from the chronic lateral ankle instability group, and cases in which the tissue was severely damaged or the quality of collected tissue was insufficient because of severe impingement into the fracture site were excluded from the acute anterior talofibular ligament injury group. Tissues were collected from 21 patients (11 males and 10 females) in the chronic lateral ankle instability group with a mean age of 37 ± 14 years and from 17 patients (6 males and 11 females) in the acute anterior talofibular ligament injury group with a mean age of 49 ± 17 years. To investigate our first purpose, apoptotic cells were counted using a TUNEL assay. To answer our second question, Western blotting for apoptotic enzymes such as caspases 3, 7, 8, and 9 and cytochrome c was performed to investigate apoptotic activity. Immunohistochemistry was also used to detect apoptotic enzymes. To answer our third question, the time elapsed after the first symptom related to chronic lateral ankle instability occurred and the expression level of each enzyme was investigated.

RESULTS

More apoptotic cells were observed in the chronic lateral ankle instability group than in the acute anterior talofibular ligament injury group in the TUNEL assay. Western blotting revealed that the apoptotic activities of the chronic lateral ankle instability group were higher than those of the acute anterior talofibular ligament injury group: caspase 3 was 117 in the chronic lateral ankle instability group and 59 in the acute anterior talofibular ligament injury group (mean difference 58 [95% confidence interval (CI) 31 to 86]; p < 0.001), caspase 7 was 138 in the chronic lateral ankle instability group and 45 in the acute anterior talofibular ligament injury group (mean difference 93 [95% CI 58 to 128]; p < 0.001), caspase 8 was 126 in the chronic lateral ankle instability group and 68 in the acute anterior talofibular ligament injury group (mean difference 58 [95% CI 29 to 89]; p < 0.001), caspase 9 was 128 in the chronic lateral ankle instability group and 54 in the acute anterior talofibular ligament injury group (mean difference 74 [95% CI 44 to 104]; p < 0.001), and cytochrome c was 139 in the chronic lateral ankle instability group and 51 in the acute anterior talofibular ligament injury group (mean difference 88 [95% CI 46 to 129]; p < 0.001). Immunohistochemistry revealed higher expression of caspases 3, 7, 8, and 9 and cytochrome c in the chronic lateral ankle instability group compared with those in the acute anterior talofibular ligament injury group. Caspases 3, 7, and 9 showed no correlation with duration of chronic lateral ankle instability symptoms: the Pearson correlation coefficient was 0.22 [95% CI -0.25 to 0.69] for caspase 3 (p = 0.36), 0.29 [95% CI -0.16 to 0.74] for caspase 7 (p = 0.23), and 0.29 [95% CI -0.16 to 0.74] for caspase 9 (p = 0.23).

CONCLUSION

In chronic lateral ankle instability, apoptotic activity in the anterior talofibular ligament was higher than in acute anterior talofibular ligament injury.

CLINICAL RELEVANCE

Apoptosis occurs more in chronic injured ligaments than in acutely injured ligaments. Although urgent surgical repair is not required for acute anterior talofibular ligament injury, chronic lateral ankle instability may progress if the nonoperative treatment is not successful. Further research should focus not only on timing of apoptotic progression, but also on biological augmentation to reverse or prevent apoptosis within the anterior talofibular ligament.

Hypermobile Ehlers-Danlos syndromes: Complex phenotypes, challenging diagnoses, and poorly understood causes

The Ehlers-Danlos syndromes (EDS) are a group of heritable, connective tissue disorders characterized by joint hypermobility, skin hyperextensibility, and tissue fragility. There is phenotypic and genetic variation among the 13 subtypes. The initial genetic findings on EDS were related to alterations in fibrillar collagen, but the elucidation of the molecular basis of many of the subtypes revealed several genes not involved in collagen biosynthesis or structure. However, the genetic basis of the hypermobile type of EDS (hEDS) is still unknown. hEDS is the most common type of EDS and involves generalized joint hypermobility, musculoskeletal manifestations, and mild skin involvement along with the presence of several comorbid conditions. Variability in the spectrum and severity of symptoms and progression of patient phenotype likely depend on age, gender, lifestyle, and expression domains of the EDS genes during development and postnatal life. In this review, we summarize the current molecular, genetic, epidemiologic, and pathogenetic findings related to EDS with a focus on the hypermobile type.

Multifaced Roles of the αvβ3 Integrin in Ehlers-Danlos and Arterial Tortuosity Syndromes' Dermal Fibroblasts

The αvβ3 integrin, an endothelial cells’ receptor-binding fibronectin (FN) in the extracellular matrix (ECM) of blood vessels, regulates ECM remodeling during migration, invasion, angiogenesis, wound healing and inflammation, and is also involved in the epithelial mesenchymal transition. In vitro-grown human control fibroblasts organize a fibrillar network of FN, which is preferentially bound on the entire cell surface to its canonical α5β1 integrin receptor, whereas the αvβ3 integrin is present only in rare patches in focal contacts. We report on the preferential recruitment of the αvβ3 integrin, due to the lack of FN–ECM and its canonical integrin receptor, in dermal fibroblasts from Ehlers–Danlos syndromes (EDS) and arterial tortuosity syndrome (ATS), which are rare multisystem connective tissue disorders. We review our previous findings that unraveled different biological mechanisms elicited by the αvβ3 integrin in fibroblasts derived from patients affected with classical (cEDS), vascular (vEDS), hypermobile EDS (hEDS), hypermobility spectrum disorders (HSD), and ATS. In cEDS and vEDS, respectively, due to defective type V and type III collagens, αvβ3 rescues patients’ fibroblasts from anoikis through a paxillin-p60Src-mediated cross-talk with the EGF receptor. In hEDS and HSD, without a defined molecular basis, the αvβ3 integrin transduces to the ILK-Snail1-axis inducing a fibroblast-to-myofibroblast-transition. In ATS cells, the deficiency of the dehydroascorbic acid transporter GLUT10 leads to redox imbalance, ECM disarray together with the activation of a non-canonical αvβ3 integrin-TGFBRII signaling, involving p125FAK/p60Src/p38MAPK. The characterization of these different biological functions triggered by αvβ3 provides insights into the multifaced nature of this integrin, at least in cultured dermal fibroblasts, offering future perspectives for research in this field.

Molecular pathology of total knee arthroplasty instability defined by RNA-seq

Total knee arthroplasty (TKA) is a durable and reliable procedure to alleviate pain and improve joint function. However, failures related to flexion instability sometimes occur. The goal of this study was to define biological differences between tissues from patients with and without flexion instability of the knee after TKA. Human knee joint capsule tissues were collected at the time of primary or revision TKAs and analyzed by RT-qPCR and RNA-seq, revealing novel patterns of differential gene expression between the two groups. Interestingly, genes related to collagen production and extracellular matrix (ECM) degradation were higher in samples from patients with flexion instability. Partitioned clustering analyses further emphasized differential gene expression patterns between sample types that may help guide clinical interpretations of this complication. Future efforts to disentangle the effects of physical and biological (e.g., transcriptomic modifications) risk factors will aid in further characterizing and avoiding flexion instability after TKA.

Fibulin-4 is essential for maintaining arterial wall integrity in conduit but not muscular arteries

Homozygous or compound heterozygous mutations in fibulin-4 (FBLN4) lead to autosomal recessive cutis laxa type 1B (ARCL1B), a multisystem disorder characterized by significant cardiovascular abnormalities, including abnormal elastin assembly, arterial tortuosity, and aortic aneurysms. We sought to determine the consequences of a human disease-causing mutation in FBLN4 (E57K) on the cardiovascular system and vascular elastic fibers in a mouse model of ARCL1B. Fbln4E57K/E57K mice were hypertensive and developed arterial elongation, tortuosity, and ascending aortic aneurysms. Smooth muscle cell organization within the arterial wall of large conducting vessels was abnormal, and elastic fibers were fragmented and had a moth-eaten appearance. In contrast, vessel wall structure and elastic fiber integrity were normal in resistance/muscular arteries (renal, mesenteric, and saphenous). Elastin cross-linking and total elastin content were unchanged in large or small arteries, whereas elastic fiber architecture was abnormal in large vessels. While the E57K mutation did not affect Fbln4 mRNA levels, FBLN4 protein was lower in the ascending aorta of mutant animals compared to wild-type arteries but equivalent in mesenteric arteries. We found a differential role of FBLN4 in elastic fiber assembly, where it functions mainly in large conduit arteries. These results suggest that elastin assembly has different requirements depending on vessel type. Normal levels of elastin cross-links in mutant tissue call into question FBLN4's suggested role in mediating lysyl oxidase-elastin interactions. Future studies investigating tissue-specific elastic fiber assembly may lead to novel therapeutic interventions for ARCL1B and other disorders of elastic fiber assembly.

Oxidative Stress-induced DNA Damage in the Synovial Cells of the Temporomandibular Joint in the Rat

Synovial hyperplasia is a feature of degenerative temporomandibular joint (TMJ) disease. However, the mechanism by which hyperplasia progresses in the TMJ is unknown. Based on the hypothesis that the oxidative stress generated by mechanical loading causes degenerative changes in the TMJ synovium, we investigated the generation of the highly reactive species, peroxynitrite, and the occurrence of DNA damage in the synovium. After condylar hypermobility of rat TMJs, a marker of peroxynitrite, nitrotyrosine, was localized to the nuclei and cytoplasm of the synovial lining cells and fibroblasts in synovitis-induced TMJ. DNA single-strand breaks were found in the nuclei of the synovial cells only after enzyme treatment, whereas DNA double-strand breaks were not detected. These findings indicate that condylar hypermovement induces the proliferation of synovial cells, and suggest that oxidative stress leads to the progression of synovial hyperplasia via DNA damage of the synovial cells in TMJs after mechanical loading.

Elk3 deficiency causes transient impairment in post-natal retinal vascular development and formation of tortuous arteries in adult murine retinae

Serum Response Factor (SRF) fulfills essential roles in post-natal retinal angiogenesis and adult neovascularization. These functions have been attributed to the recruitment by SRF of the cofactors Myocardin-Related Transcription Factors MRTF-A and -B, but not the Ternary Complex Factors (TCFs) Elk1 and Elk4. The role of the third TCF, Elk3, remained unknown. We generated a new Elk3 knockout mouse line and showed that Elk3 had specific, non-redundant functions in the retinal vasculature. In Elk3(−/−) mice, post-natal retinal angiogenesis was transiently delayed until P8, after which it proceeded normally. Interestingly, tortuous arteries developed in Elk3(−/−) mice from the age of four weeks, and persisted into late adulthood. Tortuous vessels have been observed in human pathologies, e.g. in ROP and FEVR. These human disorders were linked to altered activities of vascular endothelial growth factor (VEGF) in the affected eyes. However, in Elk3(−/−) mice, we did not observe any changes in VEGF or several other potential confounding factors, including mural cell coverage and blood pressure. Instead, concurrent with the post-natal transient delay of radial outgrowth and the formation of adult tortuous arteries, Elk3-dependent effects on the expression of Angiopoietin/Tie-signalling components were observed. Moreover, in vitro microvessel sprouting and microtube formation from P10 and adult aortic ring explants were reduced. Collectively, these results indicate that Elk3 has distinct roles in maintaining retinal artery integrity. The Elk3 knockout mouse is presented as a new animal model to study retinal artery tortuousity in mice and human patients.

Interleukin-6 in serum and in synovial fluid enhances the differentiation between periprosthetic joint infection and aseptic loosening

The preoperative differentiation between septic and aseptic loosening after total hip or knee arthroplasty is essential for successful therapy and relies in part on biomarkers. The objective of this study was to assess synovial and serum levels of inflammatory proteins as diagnostic tool for periprosthetic joint infection and compare their accuracy with standard tests. 120 patients presenting with a painful knee or hip endoprosthesis for surgical revision were included in this prospective trial. Blood samples and samples of intraoperatively acquired joint fluid aspirate were collected. White blood cell count, C-reactive protein, procalcitonin and interleukin-6 were determined. The joint aspirate was analyzed for total leukocyte count and IL-6. The definite diagnosis of PJI was determined on the basis of purulent synovial fluid, histopathology and microbiology. IL-6 in serum showed significantly higher values in the PJI group as compared to aseptic loosening and control, with specificity at 58.3% and a sensitivity of 79.5% at a cut-off value of 2.6 pg/ml. With a cut-off >6.6 pg/ml, the specificity increased to 88.3%. IL-6 in joint aspirate had, at a cut-off of >2100 pg/ml, a specificity of 85.7% and sensitivity of 59.4%. At levels >9000 pg/ml, specificity was almost at 100% with sensitivity just below 50%, so PJI could be considered proven with IL-6 levels above this threshold. Our data supports the published results on IL-6 as a biomarker in PJI. In our large prospective cohort of revision arthroplasty patients, the use of IL-6 in synovial fluid appears to be a more accurate marker than either the white blood cell count or the C-reactive protein level in serum for the detection of periprosthetic joint infection. On the basis of the results we recommend the use of the synovial fluid biomarker IL-6 for the diagnosis of periprosthetic joint infection following total hip and knee arthroplasty.

Further delineation of CANT1 phenotypic spectrum and demonstration of its role in proteoglycan synthesis

Desbuquois dysplasia (DD) is characterized by antenatal and postnatal short stature, multiple dislocations, and advanced carpal ossification. Two forms have been distinguished on the basis of the presence (type 1) or the absence (type 2) of characteristic hand anomalies. We have identified mutations in calcium activated nucleotidase 1 gene (CANT1) in DD type 1. Recently, CANT1 mutations have been reported in the Kim variant of DD, characterized by short metacarpals and elongated phalanges. DD has overlapping features with spondyloepiphyseal dysplasia with congenital joint dislocations (SDCD) due to Carbohydrate (chondroitin 6) Sulfotransferase 3 (CHST3) mutations. We screened CANT1 and CHST3 in 38 DD cases (6 type 1 patients, 1 Kim variant, and 31 type 2 patients) and found CANT1 mutations in all DD type 1 cases, the Kim variant and in one atypical DD type 2 expanding the clinical spectrum of hand anomalies observed with CANT1 mutations. We also identified in one DD type 2 case CHST3 mutation supporting the phenotype overlap with SDCD. To further define function of CANT1, we studied proteoglycan synthesis in CANT1 mutated patient fibroblasts, and found significant reduced GAG synthesis in presence of β-D-xyloside, suggesting that CANT1 plays a role in proteoglycan metabolism.

Insulin-like growth factors I and II in the aseptic loosening of total hip implants

Periprosthetic interface tissue and pseudocapsule samples surrounding aseptically loosened hip implants and control knee synovium were studied by reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. Endothelial cells, fibroblasts, and monocyte/macrophages contained bone formation-enhancing insulin-like growth factors (IGFs). In interface tissue we found fewer IGF-I and IGF-II positive cells than in control tissue. In pseudocapsular tissue we found fewer IGF-I positive cells and an equal amount of IGF-II positive cells compared to control tissues. Decreased bone formation may contribute to net loss of bone around aseptically loosened hip implants.

Neural growth factor expression in the lateral retinaculum in painful patellofemoral malalignment

We studied 7 samples of lateral retinaculae excised at the time of surgical realignments. They were obtained from patients with isolated symptomatic patellofemoral malalignment resistant to conservative treatment and were evaluated with immunohistochemistry and immunoblotting. We found that neural growth factor is higher in patients with pain than in those with instability as the main symptom. Neural growth factor is related to neural proliferation in vessels and perivascular tissue and to the release of neuroceptive transmitters, such as substance P. We postulate that both mechanisms are involved in the pathogenesis of pain in isolated symptomatic patellofemoral malalignment.

[Molecular pathways in aseptic loosening of orthopaedic endoprosthesis]

Operative joint replacement to treat disabling joint conditions secondary to degenerative and inflammatory arthritides has become one of the most efficacious and cost-effective procedures to relieve pain and restore joint function. However, prosthetic implants are not built to last forever and osteolysis and aseptic loosening has been associated with prosthetic arthroplasties since their introduction. The functional life of a synthetic joint is influenced by many factors including the material of the implant, operation procedures and the surgeon involved, as well as patient-related factors. Although promising developments have been achieved in this field, more than 10% of all implants still have to undergo operative revision within 15 years after the initial operation. Failure due to sepsis, fractures and dislocations has become rare; premature loosening of implants on the other hand is becoming much more important. Prosthetic loosening without concurrent infection or trauma is called aseptic loosening. It is generally accepted that small particles ("wear debris") and activated macrophages play a key role in aseptic loosening. The pathophysiology of this condition, however, is still not very well characterized. In this article, we review the molecular mechanisms and signal pathways that were unravelled as responsible factors for loosening orthopaedic implants. Finally, we discuss possible novel strategies for future therapeutic approaches.

Over-expression of p53/BAK in aseptic loosening after total hip replacement

Particle-induced osteolysis is a major cause of aseptic loosening after total joint replacement. The possible induction of apoptosis has not been addressed in great detail. Thus far, it has been shown that ceramic and polyethylene particles can induce apoptosis of macrophages in vitro. The purpose of this study was to test the hypothesis that wears debris generated from total hip arthroplasty could induce cellular damage and apoptosis in vivo. We therefore determined by immunohistochemical methods if increased expression of p53, an important transcription factor, and BAK and Bcl-2, two important regulators of apoptosis, can be found in interface membranes and capsules of hips with aseptically loose implants. Strongly positive immunohistochemical staining for p53 and BAK was found in peri-implant tissues from patients with aseptic hip implant loosening. Differentiation of various cell types showed that macrophages stained positive for p53 in all capsule and interface specimens. p53 was frequently detected in giant cells. Positive staining of BAK in macrophages and giant cells was seen in all specimens. Some positive reactions were observed in fibroblasts, only two of 19 cases stained for p53 and three cases for BAK within synovial cells. Positive macrophages and giant cells were localized around polyethylene particles. While T-lymphocytes showed a regular BAK-staining, the other leukocytes were negative. Statistical analyses showed significant positive correlations (p < 0.001) between the presence of polyethylene and metal debris and the expression of BAK and p53. Polyethylene particles were surrounded by more positive macrophages and giant cells than were metal particles, indicating that polyethylene debris may be a stronger inductor of cell cycle arrest and apoptosis than metal debris. In this study apoptosis of macrophages, giant cells and T-lymphocytes in capsules and interface membranes of patients with aseptic hip implant loosening has been demonstrated in vivo. It is possible that the apoptotic cascade could evolve as a novel therapeutic target to prevent particle-induced osteolysis.

Contribution of runt-related transcription factor 2 to the pathogenesis of osteoarthritis in mice after induction of knee joint instability

OBJECTIVE

By producing instability in mouse knee joints, we attempted to determine the involvement of runt-related transcription factor 2 (RUNX-2), which is required for chondrocyte hypertrophy, in the development of osteoarthritis (OA).

METHODS

An experimental mouse OA model was created by surgical transection of the medial collateral ligament and resection of the medial meniscus of the knee joints of heterozygous RUNX-2-deficient (Runx2+/-) mice and wild-type littermates. Cartilage destruction and osteophyte formation in the medial tibial cartilage were compared by histologic and radiographic analyses. Localization of type X collagen and matrix metalloproteinase 13 (MMP-13) was examined by immunohistochemistry. Localization of RUNX-2 was determined by X-Gal staining in heterozygous RUNX-2-deficient mice with the lacZ gene insertion at the Runx2-deletion site (Runx2+/lacZ). Messenger RNA levels of type X collagen, MMP-13, and RUNX-2 were examined by real-time reverse transcriptase-polymerase chain reaction analysis.

RESULTS

RUNX-2 was induced in the articular cartilage of wild-type mice at the early stage of OA, almost simultaneously with type X collagen but earlier than MMP-13. Runx2+/- and Runx2+/lacZ mice showed normal skeletal development and articular cartilage; however, after induction of knee joint instability, they exhibited decreased cartilage destruction and osteophyte formation, along with reduced type X collagen and MMP-13 expression, as compared with wild-type mice.

CONCLUSION

RUNX-2 contributes to the pathogenesis of OA through chondrocyte hypertrophy and matrix breakdown after the induction of joint instability.

Proinflammatory cytokines and metalloproteases are expressed in the subacromial bursa in patients with rotator cuff disease

PURPOSE

The pathophysiology of subacromial impingement syndrome is poorly understood. We investigated the expression of inflammatory cytokines, metalloproteases, and the cyclooxygenases in the subacromial bursa in control patients and in patients with rotator cuff tear.

TYPE OF STUDY

Basic science evaluation.

METHODS

Eighteen patients undergoing shoulder surgery had a subacromial bursa biopsy examination. Patients were divided into 2 groups. Group I (study group) had 10 patients with a full-thickness rotator cuff tear (RCT). Group II (control group) had 8 patients. Seven of 8 underwent shoulder arthroscopy with anterior capsular reconstruction for instability; 1 of 8 underwent open reduction internal fixation for acute proximal humerus fracture. None of the patients in group II had any history of symptoms or signs consistent with subacromial impingement. H&E and immunohistochemical antibody (MMP-1, MMP-9, IL-1, IL-6, TNF-alpha, COX-1, and COX-2) stained specimens were examined by 2 blinded observers using a histologic scale (grade 0 = no staining to grade 4 = intense staining).

RESULTS

Histologic evidence of inflammation was present in all patients with RCT (group I). No or mild inflammation was noted in group II. The average staining grade for inflammatory cytokines (IL-1, IL-6, TNF-alpha) and proteinases (MMP-1 and MMP-9) was significantly more pronounced in the RCT group (P < .001). Cyclooxygenase enzymes (COX-1 and COX-2) were also increased in group II (P < .001).

CONCLUSIONS

A high level of expression of inflammatory cytokines, proteinases, and cyclooxygenase enzymes, known to produce a catabolic environment, is present in the subacromial bursa of patients with rotator cuff tear.

CLINICAL RELEVANCE

These findings support the role of nonsteroidal anti-inflammatory drugs and corticosteroids in RCT treatment, and emphasize the importance of subacromial bursectomy to reduce inflammation in RCT surgery.

Nitroxide synthase activity as a marker of early stages of experimental cartilage dysmetabolism

Time course of nitroxide synthase activity in the knee joint cartilage was studied in animals with experimental anterior instability of the knee joint. A significant increase in nitroxide synthase activity in chondrocytes was paralleled by a progressive decrease in glycosaminoglycan content in the cartilaginous matrix and subsequent destruction of the cartilage cytoarchitectonics.

Immunohistochemical analysis of the extracellular matrix in the posterior capsule of the zygapophysial joints in patients with degenerative L4-5 motion segment instability

OBJECT

Although the hypertrophied shape of the zygapophysial joints in degenerative instability of the lumbar spine is well known, its underlying pathophysiological mechanism is unclear. The authors sought to provide evidence that there is increased fibrocartilaginous metaplasia in the posterior joint capsule resulting from greater mechanical loading; the authors suggest that these capsular changes are central to understanding the altered joint shape.

METHODS

The LA-5 posterior articular complex was removed in 14 patients undergoing fusion for degenerative instability. After methanol-assisted fixation, cryosections were immunolabeled for a wide range of extracellular matrix molecules. These were collagens (Types I, II, III, V, and VI), glycosaminoglycans (chondroitin 4 and 6 sulfates; dermatan- and keratan-sulfate), and proteoglycans (versican, tenascin, aggrecan, and its associated link protein). The grade of degeneration of the articular complexes was assessed radiologically and histologically.

CONCLUSIONS

The results of this study provide molecular evidence for an altered loading history on the joint capsule. The pronounced loss of intervertebral disc height that occurred in all patients with severe degeneration of the lumbar motion segment promotes an increased range of axial rotation that places the posterior capsule under greater mechanical load. Compared with normal joints studied previously, the posterior capsules involved in these degenerative joint complexes were hypertrophied and fibrocartilaginous throughout. Cartilaginous metaplasia was especially pronounced at the attachment sites (entheses) where the fibrocartilage now extended beyond the original level of the joint space, and capped the osseous spurs arising from these attachment sites.

Elevation of a collagenase generated type II collagen neoepitope and proteoglycan epitopes in synovial fluid following induction of joint instability in the dog

CLINICAL RELEVANCE

Measurement of markers of cartilage pathology in synovial fluid may provide clinical rheumatologists and osteoarthritis (OA) researchers important information for early diagnosis of OA as well as a method for monitoring disease progression and response to treatment. This study demonstrates the value of this approach in an established model of OA (cranial cruciate ligament rupture) at a point distant enough from the original surgical manipulation so as to have little to no effect on the marker concentrations.

OBJECTIVE

The objective of this study was to determine whether measurement of markers of cartilage collagen cleavage and proteoglycan turnover in synovial fluid from a canine model could be used to detect cartilage changes following the onset of joint instability during the development of OA.

DESIGN

A model of joint instability that develops OA was created in 18 mature dogs using monopolar radiofrequency energy (MRFE). MRFE was arthroscopically applied to one cranial cruciate ligament (CCL) while the contralateral CCL was sham treated. The treated CCLs ruptured approximately 8 weeks (55 +/- 1.6 days) after MRFE treatment. Synovial fluid was collected at time zero prior to MRFE treatment, 4 weeks after MRFE treatment, and at 4, 8, and 16 weeks after CCL rupture. Synovial fluid concentrations of the neoepitope COL2-3/4C long (type II collagen cleavage by collagenase) and epitopes 3B3(-) (proteoglycan aggrecan sulfation) and 846 (associated with aggrecan synthesis) were analyzed.

RESULTS

Compared to sham treated joints, the synovial fluid concentrations of COL2-3/4C long and 3B3(-) were significantly increased 2.2 fold and 2.9 fold, respectively, in joints with MRFE treated CCLs following CCL rupture. Concentrations of the 846 epitope in synovial fluid showed a trend toward an increase, which was not significant, after CCL rupture.

CONCLUSIONS

Concentrations of the collagenase-cleaved type II collagen neoepitope and 3B3(-) epitope in synovial fluid were significantly increased by 4 weeks and remained elevated for at least 16 weeks after CCL rupture. This suggests that in dogs the COL2-3/4C long neoepitope and 3B3(-) epitope are sensitive markers for changes in joint cartilage turnover in joints that are developing OA.

High macrophage-colony stimulating factor levels in synovial fluid of loose artificial hip joints

OBJECTIVE

To clarify a macrophage-colony stimulating factor (M-CSF) related mechanism of aseptic loosening of artificial hip joints.

METHODS

Synovium-like interface tissues between bone and prosthesis, regenerated pseudocapsular tissues, and synovial fluid (SF) were collected from 9 patients with loose artificial hip joint at revision surgery. Tissue distribution, production site, and SF level of M-CSF in loose hip joints were investigated by immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR), and ELISA, respectively. For a comparative assessment of the M-CSF level in loose hip joints, SF of active rheumatoid arthritis (RA) and mild osteoarthritis (OA) also were analyzed by ELISA.

RESULTS

Immunohistochemical analysis showed the presence of M-CSF immunoreactive cells mainly in the interface tissues between bone and prosthesis and inner pseudocapsular tissues, both of which were in contact with joint fluid. RT-PCR analysis confirmed the local production of M-CSF in these periprosthetic tissues. Significantly higher M-CSF level in loose hip joint fluid than in active RA and mild OA fluid was revealed by ELISA.

CONCLUSION

High M-CSF level in loose hip joint fluid suggests transportation of M-CSF from production sites to joint fluid. This indicates that not only polyethylene wear particles (reported to induce foreign body reaction at the bone-prosthesis interface), but also M-CSF, abundant in joint fluid, are transported to and affect the interface. Thus, M-CSF is locally produced in periprosthetic tissues of loose hip joints and possibly contributes to periprosthetic weakening and osteolysis via joint fluid, leading to prosthetic loosening.

Increased interleukin-1beta production in the synovium of glenohumeral joints with anterior instability

Macroscopic synovitis of the glenohumeral joint is frequently seen during arthroscopy in patients with anterior instability. Interleukin-1beta is known to be expressed in inflamed tissue, to correlate with the magnitude of inflammation, and to affect articular cartilage in the joint. We hypothesized that chronic synovitis may occur in the glenohumeral joint in patients with anterior instability. The purpose of this study was to examine the expression of interleukin-1beta in the synovium of the glenohumeral joint with anterior instability and to discuss its clinicopathologic significance. Specimens of synovial tissue around the greater tuberosity in the subacromial synovium (as controls) and around the rotator interval in the glenohumeral synovium were obtained from 10 patients who had anterior instability without signs of subacromial impingement. Semiquantitative reverse transcriptase-polymerase chain reaction was used to compare the levels of interleukin-1beta mRNA expression in the glenohumeral joint with those in the subacromial bursa. We also employed immunohistochemistry and in situ reverse transcriptase-polymerase chain reaction to detect the cells producing interleukin-1beta protein and mRNA. The levels of interleukin-1beta mRNA expression were significantly higher in the glenohumeral joint than in the subacromial bursa (p < 0.01). Histology showed nonspecific inflammation in all 10 samples of glenohumeral synovium, whereas no inflammation was seen in seven of 10 samples of subacromial synovium. Immunohistochemistry identified interleukin-1beta protein in the vessels and inflammatory and synovial cells (from lining to sublining layers) in synovium of the glenohumeral joint, whereas immunoreactivity was negative in seven subacromial bursa. The remaining three synovial specimens of subacromial bursa, however, showed positive immunoreactivity that was unremarkable and confined around the vessels. In situ reverse transcriptase-polymerase chain reaction was exclusively performed in the synovial specimens of the glenohumeral joint, which exhibited a positive reaction (in the same kinds of cells as seen with immunohistochemistry) in the lining and sublining layers and to a lesser extent in the stroma. Thus, our data confirmed the increased production of interleukin-1beta in the synovium of the glenohumeral joint in patients with anterior instability, suggesting the presence of chronic inflammation at the site. We conclude that this chronic synovitis may be partly associated with the development of dislocation arthropathy in the long term.

Analysis of collagen and elastic fibers in shoulder capsule in patients with shoulder instability

This study examined collagen cross-links, collagen fibril diameter and density, amino acid composition, and elastic fibers in shoulder capsule and skin in four patient groups: 1) unidirectional anterior instability (N = 8); 2) multidirectional instability/primary surgery (N = 6); 3) multidirectional instability/revision surgery (N = 6); and 4) no history of instability (N = 5). Compared with normal capsule, capsule from groups 1 and 2 had more stable and reducible collagen cross-links, significantly greater mean collagen fibril diameter, more cysteine, and a higher density of elastin staining. Compared with shoulder capsule in groups 1 and 2, shoulder capsule from group 3 contained significantly more reducible cross-links, smaller-diameter collagen fibrils, decreased collagen fibril density, and an increased density of elastin staining. There were no significant differences in any parameters between groups 1 and 2. We hypothesized that repeated capsular deformation in patients with shoulder instability results in changes in the capsule that increase its strength and resistance to stretching. Skin analyses demonstrated a significantly smaller mean collagen fibril diameter in skin from group 2 compared with group 1, suggesting the possibility of an underlying connective tissue abnormality.

Centrifugal and biochemical comparison of proteoglycan aggregates from articular cartilage in experimental joint disuse and joint instability

Two models involving altered joint loading were compared with regard to their effects on the biochemical composition and proteoglycan aggregate structure of articular cartilage. Disuse atrophy was created in greyhound dogs by nonrigid immobilization of the right knee in 90 degrees of flexion, and joint instability was created by transection of the anterior cruciate ligament. Similarities and differences between the two experimental groups at two different time periods were examined to investigate why joint instability induces progressive and irreversible changes to the articular cartilage, whereas joint disuse induces changes that may be reversible when the joint is remobilized. The following studies were performed on the cartilage from all experimental and control groups: (a) compositional analyses to determine water, uronate, and hydroxyproline contents; (b) high performance liquid chromatography for detection of hyaluronan and chondroitin sulfates; and (c) centrifugation analyses of nondissociatively extracted and purified proteoglycans to isolate and quantify the populations of monomers and slow and fast-sedimenting families of aggregates. In general, all cartilage was found to have a decreased ratio of proteoglycan to collagen after 4 weeks of disuse, and this ratio returned to control values at 8 weeks. In contrast, cartilage had an elevated ratio of proteoglycan to collagen as well as increased hydration at 12 weeks after transection of the anterior cruciate ligament. The most striking contrast between the two models was the finding of an approximately 80% decrease in the content of hyaluronan at both time periods after transection of the anterior cruciate ligament, with no evidence of a change after disuse. The results of centrifugation analyses indicated a significant decrease in the quantity of proteoglycan aggregates in both models. However, this decrease was associated primarily with a loss of slow-sedimenting aggregates after disuse and a loss of both slow and fast-sedimenting aggregates after transection of the anterior cruciate ligament. Furthermore, the population of fast-sedimenting aggregates was depleted to a greater extent than that of the slow-sedimenting aggregates. The preservation of fast-sedimenting aggregates as well as hyaluronan after periods of joint disuse but not joint instability suggests a possible mechanism for the reversibility of cartilage changes. Although the proteoglycan aggregates were depleted after disuse atrophy, it is possible that an aggregate-depleted matrix could recover when normal proteoglycan synthesis is resumed. In contrast, although synthesis may be maintained or elevated after transection of the anterior cruciate ligament, the matrix may not be repopulated with aggregates because there is an insufficient amount of hyaluronan.

Immunohistochemical analysis of 3-B-(-) and 7-D-4 epitope expression in canine osteoarthritis

OBJECTIVE

To examine the distribution of the 3-B-3(-) and 7-D-4 epitopes in proteoglycans from morphologically normal and osteoarthritic (OA) canine articular cartilage.

METHODS

Cartilage samples from the femurs of stable and destabilized stifle joints of 9 dogs that had undergone transection of the cranial cruciate ligament were examined by immunohistochemistry.

RESULTS

The 3-B-3(-) and 7-D-4 epitopes were expressed in the superficial zone of cartilage from the destabilized femorotibial joints in the early stages of developing OA. The staining patterns with these two antibodies differed, with 3-B-3(-) reactivity confined to the superficial and upper middle zones of the articular cartilage, and 7-D-4 reactivity more prominent in the matrix, extending into the deeper zones and increasing with progression of the lesion. Both epitopes were also expressed in the superficial and upper middle zones of areas peripheral to the lesions and were detectable before the loss of matrix and proteoglycans could be identified by histochemical staining with toluidine blue.

CONCLUSION

In this study, the expression of atypical chondroitin sulfate proteoglycans was demonstrated in osteoarthritic canine cartilage, and the pattern of expression changed as the lesions progressed. The occurrence of 3-B-3(-) and 7-D-4 epitopes appears to be associated with changes in chondrocyte metabolism in the early stages of cartilage degeneration in experimental osteoarthritis.

[Etiological considerations of the loose shoulder from a biochemical point of view--biochemical studies on collagen from deltoid and pectoral muscles and skin]

In order to elucidate the etiology of the loose shoulder, biochemical characteristics of deltoid and major pectoral muscles and skin collagen from patients with loose shoulder have been investigated. Amounts of soluble collagen, reducible cross-links of collagen and their precursors in both muscles and skin from the loose shoulder were found to be higher than those in the control. These data suggest that soft tissues, especially deltoid muscles, of patients with loose shoulder contain relatively immature collagen fibers compared with normal shoulders. In re-operation cases of the loose shoulder, the collagen fibers in skin were more immature, which may reflect the clinical features of the disease.

[On the etiology of the loose shoulder--biochemical studies on collagen from joint capsules]

In order to investigate the etiology of loose shoulder, biochemical characteristics of collagens from four major joint capsules of extremities and from joint capsules of loose shoulder have been investigated. Joint capsules of normal shoulder were found to synthesize less collagen fibers comparing to those of other major joints. Furthermore formation of inter-molecular cross-links of collagen from shoulder joint capsule was relatively lower than that of collagens from other major joints. Noteworthy was the fact that collagen fibers from joint capsules of loose shoulder were more soluble and contain less amount of the reducible cross-links than those from joint capsules of the normal shoulder. These data suggest that collagen synthesis and formation of collagen fibers vary with the differences in joint structures, functions and movements. It may also be implied that the joint capsules of loose shoulder produce immature collagen fibers which may reflect the clinical feature of the disease.

Patient with multiple congenital anomalies and decreased production and processing of procollagen in cultured fibroblasts

We report on a patient with hip and elbow dislocations, joint hyperextensibility, peculiar facial appearance, torticollis, cryptorchidism, unilateral hexadactyly, and other minor anomalies. Cultured cells from this patient produce less type I procollagen and have a slower rate of processing of type I procollagen to collagen in the culture medium. We think that the pattern of clinical anomalies constitutes a previously unreported syndrome with type I procollagen defect as a manifestation of the syndrome.

[Joint hypermobility in Palma school children]

Joint mobility was examined on 1.136 schoolchildren of both sexes at the ages of 11 and 14 years. At the same time, they were asked if they had a history of bone fractures and about their weekly consumption of liver. The results were that 13% of the boys and 21% of the girls had hypermobility of their joints. A description is made of a short test to detect hypermobility. It was found that liver consumption and hypermobility are related, also that only in boys hypermobility is contrarily related with the history of fractures.

Energy cost of walking with hip joint impairment

The energy cost of walking was measured in 12 patients (age 39-73 years) with hip joint impairment and 10 healthy controls during unassisted walking (2-6 km.h-1) on a level treadmill surface and on a 5% incline. The energy cost of locomotion in most patients increased up to 50% and 70% during level-surface and uphill walking, respectively. This difference between patients and controls was probably due to the increased external mechanical work. The energy cost of walking, although related to pain experienced during walking but not to hip joint range of motion or to joint status evaluated radiographically, provides an additional variable when defining the conditions of disability and functional impairment in individuals with this pathological condition. [Gussoni M, Margonato V, Ventura R, et al: Energy cost of walking with hip joint impairment.

Magnetic resonance imaging and spectroscopy of thigh muscles in cruciate ligament insufficiency

In 21 patients with injury-related, chronic, anterior cruciate ligament insufficiency, 1H-magnetic resonance (MR) imaging and 31P-MR spectroscopy of the quadriceps muscles were performed with a systemic superconductive MR apparatus. The quadriceps of the noninjured side was used as the control. The quadriceps had a reduced cross-sectional area, but the knee flexors were not reduced. T2 values were prolonged in the vastus lateralis, medialis, and intermedius, but those of the rectus femoris were not. Phosphocreatine per inorganic phosphate measured with 31P-MR spectroscopy was decreased in the atrophied muscles, which correlated with the muscular cross-section. There was no difference in the muscular pH as recorded by the chemical-shift measurements of phosphocreatine and inorganic phosphate. Serial measurements of muscle cross-sectional area and high-energy phosphate bonds reflect the recovery of muscles.

Mitral valve prolapse, aortic compliance, and skin collagen in joint hypermobility syndrome

Mitral valve prolapse was sought clinically and with phonocardiography and M mode and sector echocardiography in 15 women aged 22-57 years with joint hypermobility syndrome. The type III:III + I collagen ratio was measured in skin biopsy specimens and was found to be raised in seven of 10 patients sampled. Thirteen patients had increased aortic wall compliance measured by the continuous wave Doppler ultrasound technique. Ten (67%) patients had mitral valve prolapse shown by auscultatory signs or echocardiography or both--a prevalence at least three times greater than that in the general adult population. It is concluded that if the abnormality of collagen biosynthesis found in skin biopsy samples in these patients is also present in their mitral valve tissue this may predispose them to prolapse of the valve.

[Collagen volume of the umbilical cord in infants with unstable hip joint]

Collagen amounts in the umbilical cord in infants with unstable hip joint and positive Ortolani 's sign were measured and the results were discussed from pathogenetic viewpoint. Incidence of unstable hip and that of neonatal hip with positive Ortolani 's sign were 0.23% and 0.93% respectively, in 4,824 neonates examined during one year: 1980. Biochemical analysis was carried out in the umbilical cords of 8 female neonates with positive Ortolani 's sign and of 8 female babies who were later diagnosed as having unstable hip joint. A control group consisting of 16 normal babies with similar sex, body weight, period of gestation and birth order, corresponding to the above mentioned 2 groups, was also investigated for the purpose of statistical analysis. The amount of hydroxyproline was examined by a modified Woessner 's method and the amount of collagen was calculated by Fredensborg 's method. No significant statistical difference in collagen amounts was found between these three groups. Relationship between amounts of collagen and 9 obstetrical factors relating to congenital dislocation of the hip joint: mother's height, weight and occupation; neonatal sex, birth order, position in the uterus and weight; weight of placenta and length of the umbilical cord, were studied and statistical analysis was made. Amounts of collagen in the cross section of the umbilical cord were significantly lower in neonates with longer umbilical cords.(ABSTRACT TRUNCATED AT 250 WORDS)

The synovial-like membrane at the bone-cement interface in loose total hip replacements and its proposed role in bone lysis

The membrane present at the bone-cement interface was retrieved from twenty patients with a loose, non-septic failed total hip replacement at a site clearly remote from the pseudocapsule that reformed postoperatively. The orientation of the membrane was carefully marked to identify the surface in contact with cement. The membrane was studied histologically, histochemically, by cell culture, by organ culture, and by assessment of its ability to synthesize prostaglandin E2 and collagenase. This membrane, rather than being a nondescript so-called fibrous membrane, has the histological and histochemical characteristics of a synovial-like lining. The synovial-like cells are adjacent to the cement layer. Deep to them macrophages predominate. Inflammatory cells are absent. Cell cultures of this membrane contain stellate cells similar to those found in cell cultures of normal and rheumatoid synovial tissue. This membrane has the capacity to produce large amounts of prostaglandin E2 and collagenase.

CLINICAL RELEVANCE

This transformation of tissue at the bone-cement interface in patients with a non-septic, loose total hip component to a synovial-like tissue with the capacity to generate prostaglandin E2 and collagenase may explain the progressive lysis of bone that is seen in some patients with loose cemented total joint implants. Loosening of the component may be a stimulus to the synthetic activity of this tissue, which leads to further resorption of bone. Understanding and the possibility of pharmacological control of this membrane may contribute to improved duration of total joint implants.