The structural consequences of calcium crystal deposition

Amorphous-mediated crystallization of calcium pyrophosphate tetrahydrate: the role of alkaline earth metal ions

Although calcium pyrophosphates are commonly involved in crystal arthropathies, their formation mechanisms remain largely underexplored. Here, we investigated the crystallization pathway of calcium pyrophosphate tetrahydrate in the absence and presence...

Optical Biomarkers for the Diagnosis of Osteoarthritis through Raman Spectroscopy: Radiological and Biochemical Validation Using Ex Vivo Human Cartilage Samples

Osteoarthritis (OA) is the most common rheumatic disease, characterized by progressive articular cartilage degradation. Raman spectroscopy (RS) has been recently proposed as a label-free tool to detect molecular changes in musculoskeletal tissues. We used cartilage samples derived from human femoral heads to perform an ex vivo study of different Raman signals and ratios, related to major and minor molecular components of articular cartilage, hereby proposed as candidate optical biomarkers for OA. Validation was performed against the radiological Kellgren-Lawrence (K-L) grading system, as a gold standard, and cross-validated against sulfated glycosaminoglycans (sGAGs) and total collagens (Hyp) biochemical contents. Our results showed a significant decrease in sGAGs (SGAGs, A1063 cm^-1/A1004 cm^-1) and proteoglycans (PGs, A1375 cm^-1/A1004 cm^-1) and a significant increase in collagen disorganization (ColD/F, A1245 cm^-1/A1270 cm^-1), with OA severity. These were correlated with sGAGs or Hyp contents, respectively. Moreover, the SGAGs/HA ratio (A1063 cm^-1/A960 cm^-1), representing a functional matrix, rich in proteoglycans, to a mineralized matrix-hydroxyapatite (HA), was significantly lower in OA cartilage (K-L I vs. III-IV, p < 0.05), whilst the mineralized to collagenous matrix ratio (HA/Col, A960 cm^-1/A920 cm^-1) increased, being correlated with K-L. OA samples showed signs of tissue mineralization, supported by the presence of calcium crystals-related signals, such as phosphate, carbonate, and calcium pyrophosphate dihydrate (MGP, A960 cm^-1/A1004 cm^-1, MGC, A1070 cm^-1/A1004 cm^-1 and A1050 cm^-1/A1004 cm^-1). Finally, we observed an increase in lipids ratio (IL, A1450 cm^-1/A1670 cm^-1) with OA severity. As a conclusion, we have described the molecular fingerprint of hip cartilage, validating a panel of optical biomarkers and the potential of RS as a complementary diagnostic tool for OA.

Imaging of crystalline arthropathy in 2020

Crystal-related arthropathies are the result of crystal deposition in joint and periarticular soft tissues. Identification of urate crystals is mandatory to distinguish gout from other crystalline arthropathies, including calcium pyrophosphate dihydrate and basic calcium phosphate crystal deposition diseases. ACR/EULAR classification criteria for gout included dual-energy computed tomography and ultrasound with equal impact to the final score. Different diagnostic strengths of these imaging modalities depend on disease duration and scanned anatomic site. While ultrasound has been indicated as the first-choice imaging technique, especially in the early stages of the disease, dual-energy computed tomography has shown to be highly specific, allowing the detection of crystal deposits in anatomic sites not accessible by ultrasound, such as the spine. At the spinal level, MRI findings are usually nonspecific. Finally, there is preliminary evidence that at the knee, dual-energy computed tomography may discriminate calcium pyrophosphate dihydrate from basic calcium phosphate crystal deposits.

Calcium crystal deposition diseases - beyond gout

The most common types of calcium-containing crystals that are associated with joint and periarticular disorders are calcium pyrophosphate dihydrate (CPP) and basic calcium phosphate (BCP) crystals. Several diverse but difficult-to-treat acute and chronic arthropathies and other clinical syndromes are associated with the deposition of these crystals. Although the pathogenic mechanism of calcium crystal deposition is partially understood, much remains to be investigated, as no drug is available to prevent crystal deposition, permit crystal dissolution or specifically target the pathogenic effects that result in the clinical manifestations. In this Review, the main clinical manifestations of CPP and BCP crystal deposition are discussed, along with the biological effects of these crystals, current therapeutic approaches and future directions in therapy.

Nephronectin Expression is Inhibited by Inorganic Phosphate in Osteoblasts

Nephronectin (Npnt), an extracellular matrix protein, is known to be a ligand of integrin α8β1, and it has also been known to play critical roles as various organs. In the present study, elevated extracellular inorganic phosphate (Pi) strongly inhibited the expression of Npnt in MC3T3-E1 cells, while the existence of extracellular calcium (Ca) was indispensable for its effect. Furthermore, Pi-induced inhibition of Npnt gene expression was recovered by inhibitors of both sodium-dependent Pi transporter (Pit) and fibroblast growth factor receptors (Fgfrs). These results demonstrated that Npnt gene expression is regulated by extracellular Pi via Pit and Fgfrs.

Rapidly Progressive Osteoarthritis: a Review of the Clinical and Radiologic Presentation

PURPOSE OF REVIEW

The purpose of this paper is to review the distinct clinical and radiographic features that may lead to prompt diagnosis of rapidly progressive osteoarthritis (RPOA) and thus obviate unnecessary and costly diagnostic workup.

RECENT FINDINGS

RPOA is uncommon but is more frequently seen in practice because of the aging population. RPOA is a destructive arthropathy that occurs most commonly in elderly women but can also be seen in patients that have sustained trauma. The dramatic radiologic manifestations of RPOA can lead to diagnostic confusion with other arthropathies, infection, and osteonecrosis. RPOA was originally described in the hip but may also involve the shoulder. The etiology of RPOA is not well understood, but subchondral fracture probably plays a role in the development of dramatic destruction of the joint that is seen in affected patients. Early diagnosis may reduce the complexity of surgical management. RPOA is an uncommon condition that occurs most frequently in elderly woman or in patients who have sustained trauma. Prompt recognition of the clinical and radiologic features of this arthropathy can reduce unnecessary diagnostic workup and complexity of surgical intervention.

The association of lumbar intervertebral disc calcification on plain radiographs with the UTE Disc Sign on MRI

PURPOSE

The pathogenesis and the clinical impact of disc calcification are not well known. Utilizing ultra-short time-to-echo (UTE) magnetic resonance imaging, the UTE Disc Sign (UDS) (i.e., hypo/hyper-intense disc band) was developed and found to be more significantly related to pain and disability than the conventional T2-weighted (T2W) MRI. It has been hypothesized that the UDS may represent mineralized deposits in the disc. The following study addressed the relationship between disc calcification on plain radiographs to that of the UDS on MRI.

METHODS

A cross-sectional study was performed on 106 Southern Chinese subjects (50% male; mean age 52.3 years). Standing lateral plain radiographs as well as T2W and UTE MRI of L1-S1 (n = 530 discs) were performed of all subjects. Lateral radiographs were used to localize disc calcification of the lumbar spine, T2W MRI was utilized to assess disc degeneration based on a defined grading scheme, and the UTE MRI was implemented to detect the UDS (hyper- or hypo-intense band across a disc). Disc degeneration and UDS scores were summed to represent cumulative scores. Subject demographics and disability profiles (Oswestry Disability Index: ODI) were obtained.

RESULTS

Disc calcification on plain radiographs was observed in 33.9% of subjects (55.5% males; mean age 54.3 years), whereas UDS was noted in 40.5% of subjects (51.1% males; mean age 55.0 years). Of these subjects, 66.6% calcification and 74.4% UDS occurred at the three lowest lumbar levels, while multilevel calcification and UDS involved 19.4 and 39.5%, respectively. 72.2% of subjects with plain radiographic disc calcification had corresponding UDS on UTE MRI (p < 0.001). Multilevel disc calcification on plain radiographs was associated with multilevel UDS (71.4%, p < 0.001). Both the number of calcified disc levels on plain radiographs and the number of UDS levels were also significantly and positively correlated with each other (r = 0.58, p < 0.001). Subjects with disc calcification and positive UDS as well as individuals with increased disc degeneration scores on T2 W MRI were significantly older (p < 0.05). The cumulative UDS score on UTE MRI significantly correlated with worse ODI scores (r = 0.31; p = 0.001), whereas cumulative disc calcification scores on plain radiographs did not (r = 0.15; p = 0.19).

CONCLUSIONS

This is the first study to compare the UDS on UTE MRI with disc calcification on plain radiographs. Disc calcification was correlated with the UDS on UTE, suggesting that the UDS may represent disc calcification. However, UTE MRI appears to be a more sensitive imaging modality in identifying subtle and unique disc changes that may not be revealed on plain radiographs or conventional MRI. This disconnect may rationalize the significant correlation of UTE with disability in comparison with the conventional imaging, further stressing its potential clinical importance.

Comparison of outcomes after UKA in patients with and without chondrocalcinosis: a matched cohort study

PURPOSE

Chondrocalcinosis can be associated with an inflammatory arthritis and aggressive joint destruction. There is uncertainty as to whether chondrocalcinosis represents a contraindication to unicompartmental knee arthroplasty (UKA). This study reports the outcome of a consecutive series of patients with chondrocalcinosis and medial compartment osteoarthritis treated with UKA matched to controls.

METHODS

Between 1998 and 2008, 88 patients with radiological chondrocalcinosis (R-CCK) and 67 patients with histological chondrocalcinosis (H-CCK) were treated for end-stage medial compartment arthritis with Oxford UKA. One-to-two matching was performed to controls, treated with UKA, but without evidence of chondrocalcinosis. Functional outcome and implant survival were assessed in each group.

RESULTS

The mean follow-up was 10 years. The mean Oxford Knee Score (OKS) at final follow-up was 43, 41 and 41 in H-CCK, R-CCK and control groups (change from baseline OKS was 21, 18 and 15, respectively). The change was significantly higher in H-CCK than in control but was not significantly different in R-CCK. Ten-year survival was 96 % in R-CCK, 86 % in H-CCK and 98 % in controls. Although the survival in H-CCK was significantly worse than in control, only one failure was due to disease progression.

CONCLUSION

The presence of R-CCK does not influence functional outcome or survival following UKA. Pre-operative radiological evidence of CCK should not be considered to be a contraindication to UKA. H-CCK is associated with significantly improved clinical outcomes but also a higher revision rate compared with controls.

LEVEL OF EVIDENCE

Case control study, Level III.

Basic calcium phosphate crystals and osteoarthritis pathogenesis: novel pathways and potential targets

PURPOSE OF REVIEW

Basic calcium phosphate (BCP) crystals have long been associated with the pathogenesis of osteoarthritis. As our knowledge concerning BCP crystals in osteoarthritis expands, so does the potential to develop targeted therapies. The present review discusses recent advances in this field and attempts to summarize our current understanding regarding the role of BCP crystals in osteoarthritis pathogenesis.

RECENT FINDINGS

BCP crystals injected into the knees of mice induce osteoarthritis-like changes, further evidence of their pathogenic properties. Interleukin-6 has emerged as a key cytokine involved in BCP crystal-induced inflammation that could represent a potential therapeutic target. The role of BCP crystal-induced osteoclastogenesis has also recently been explored and may also hold the key to future targeted therapies. Although tools to detect BCP crystals remain limited, dual energy computerized tomography scanning has emerged as a useful noninvasive means of quantifying intra-articular calcium crystal deposition.

SUMMARY

BCP crystals can activate a number of inflammatory pathways which in turn may lead to cartilage degradation and osteoarthritis. Understanding of these pathways may ultimately yield targeted therapies for osteoarthritis, for which none currently exists.

Unraveling the role of Mg(++) in osteoarthritis

Mg(++) is widely involved in human physiological processes that may play key roles in the generation and progression of diseases. Osteoarthritis (OA) is a complex joint disorder characterized by articular cartilage degradation, abnormal mineralization and inflammation. Magnesium deficiency is considered to be a major risk factor for OA development and progression. Magnesium deficiency is active in several pathways that have been implicated in OA, including increased inflammatory mediators, cartilage damage, defective chondrocyte biosynthesis, aberrant calcification and a weakened effect of analgesics. Abundant in vitro and in vivo evidence in animal models now suggests that the nutritional supplementation or local infiltration of Mg(++) represent effective therapies for OA. The goal of this review is to summarize the current understanding of the role of Mg(++) in OA with particular emphasis on the related molecular mechanisms involved in OA progression.