Diff Quik staining method for detection and identification of monosodium urate and calcium pyrophosphate crystals in synovial fluids

Canine transmissible venereal tumour established in immunodeficient mice reprograms the gene expression profiles associated with a favourable tumour microenvironment to enable cancer malignancy

Background

Canine transmissible venereal tumours (CTVTs) can cross the major histocompatibility complex barrier to spread among dogs. In addition to the transmissibility within canids, CTVTs are also known as a suitable model for investigating the tumour–host immunity interaction because dogs live with humans and experience the same environmental risk factors for tumourigenesis. Moreover, outbred dogs are more appropriate than inbred mice models for simulating the diversity of human cancer development. This study built a new model of CTVTs, known as MCTVTs, to further probe the shaping effects of immune stress on tumour development. For xenotransplantation, CTVTs were first injected and developed in immunodeficient mice (NOD.CB17-Prkdc^scid/NcrCrl), defined as XCTVTs. The XCTVTs harvested from NOD/SCID mice were then inoculated and grown in beagles and named mouse xenotransplantation of CTVTs (MCTVTs).

Results

After the inoculation of CTVTs and MCTVTs into immune-competent beagle dogs separately, MCTVTs grew faster and metastasized more frequently than CTVTs did. Gene expression profiles in CTVTs and MCTVTs were analysed by cDNA microarray to reveal that MCTVTs expressed many tumour-promoting genes involved in chronic inflammation, chemotaxis, extracellular space modification, NF-kappa B pathways, and focal adhesion. Furthermore, several well-known tumour-associated biomarkers which could predict tumour progression were overexpressed in MCTVTs.

Conclusions

This study demonstrated that defective host immunity can result in gene instability and enable transcriptome reprogramming within tumour cells. Fast tumour growth in beagle dogs and overexpression of tumour-associated biomarkers were found in a CTVT strain previously established in immunodeficient mice. In addition, dysregulated interaction of chronic inflammation, chemotaxis, and extracellular space modification were revealed to imply the possibly exacerbating mechanisms in the microenvironments of these tumours. In summary, this study offers a potential method to facilitate tumour progression and provide a niche for discovering tumour-associated biomarkers in cancer research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03093-4.

Correlation between synovial fluid calcium containing crystal estimation and varying grades of osteoarthritis created using a rabbit model: Potential diagnostic tool

OBJECTIVES

Accurate diagnosis of osteoarthritis (OA) is the first important step in ensuring appropriate management of the disease. A multitude of tests involving assessment of biomarkers help in assessment of severity and grading of osteoarthritic damage. However, most tests are time consuming and are limited by the paucity in synovial fluid volume. In majority of OA effusions, calcium containing crystals are found. The aim of our study was to evaluate whether a correlation existed between the amount of calcium containing crystals present in synovial fluid and severity scoring of OA to propose a quick and inexpensive technique for disease assessment.

MATERIALS AND METHODS

Monosodium-iodoacetate was used to induce high- and low-grade knee OA in adult New Zealand white rabbits (n = 6 joint each group). At 16 weeks, synovial fluid and joints were harvested for histopathological analysis. OA grading was established based on OARSI scoring. Synovial fluid calcium crystal count was assessed by light microscopy (Alizarin red) and confirmed by Fluo-4, AM imaging and polarized microscopy. Statistical analysis was performed using unpaired Student t-test and Pearson correlation.

RESULTS AND CONCLUSION

The clumps counted in low-grade OA were significantly lower than high-grade OA, in addition to showing a positive correlation (coefficient: 0.65; P=0.021) between calcium crystal count and the grade of OA created. Fluo-4, AM staining, and polarized microscopy were indicative of calcium pyrophosphate dihydrate crystals. This is the first study to suggest that Alizarin red could serve as an effective and rapid, bed-side method for screening and assessing disease progression.

[Synovial fluid cytodiagnosis]

Synovial fluid samples represent only a very small percentage of routine work in a cytology laboratory. However, its microscopic examination allows us to observe different types of cells, particles and structures that, due to their morphological characteristics, may provide relevant data for cytodiagnosis. We present certain aspects related to arthrocentesis, the relationship between the gross appearance of synovial fluid and certain pathological processes, as well as the different techniques for processing and staining the smears. Furthermore, we describe the main cytological findings in various pathological conditions of the synovial joints, such as infections (bacterial and fungal), non-infectious inflammatory type (osteoarthrosis, rheumatoid arthritis, connective tissue diseases) and tumoral, distinguishing between primary and metastatic, both solid and haematological neoplasms.

The accuracy of methods for urate crystal detection in synovial fluid and the effect of sample handling: a systematic review

This study aims to compare different methods of monosodium urate crystal (MSU) detection in synovial fluid (SF) and the effect of sample storage and handling on crystal detection. A systematic literature search was performed in MEDLINE, EMBASE, the Cochrane Library and the American College of Rheumatology/European League Against Rheumatism conference abstracts of 2010 and 2011. Studies that compared a method for detecting MSU crystals in SF with polarised light microscopy (PLM) or compared various SF storage and handling factors with the detection of MSU crystals as an outcome were included. Twelve studies out of 247 identified references were included in the review. Seven studies compared different methods of MSU crystal detection in SF with PLM. Due to study heterogeneity, methodological limitations and risk of bias, no firm conclusions could be drawn from the available data. Five studies examining SF storage and handling factors were identified. A reduction in MSU crystal concentration was observed over time at room temperature that was not seen in refrigerated samples. The use of anticoagulation as a storage medium provided no benefit. Dried cytospin preparations appeared to be a suitable medium for long-term storage and delayed crystal analysis for at least 12 months. The existing data do not provide a compelling argument for the replacement of PLM as the current standard. SF sample storage and handling have an effect on MSU crystals and may impact on the reliability of analysis.

Dried cytospin preparations of synovial fluid are a stable material for long-time storage and delayed crystal analysis

The aim of this study was to evaluate dried SF cytospin preparations as a suitable medium for long-time storage and delayed crystal analysis. For this purpose, we analyzed ten MSU-positive, ten CPPD-positive and 20 crystal-negative SF at baseline (wet preparation), after 24 h, 1 week, 4 weeks, 6 months and 12 months for the occurrence of crystals. After cytocentrifugation for 10 min at 700 rpm in a Shandon Cytospin 4 cytocentrifuge (Thermo Fisher Scientific, Waltham, USA), the sediments were dried on the slides and examined in blinded fashion at any time point by an experienced analyst using polarized microscopy. The crystal content of the initially MSU- and CPPD-positive samples was positively confirmed at any time point of the study, whereas the controls remained crystal-negative during the whole study period. Thus, compared to the examined wet preparations at baseline, there were no false positive or false negative results observed. In conclusion, dried cytospin preparations were confirmed as a suitable material for long-time storage and delayed crystal identification.

Detection of calcium phosphate crystals in the joint fluid of patients with osteoarthritis - analytical approaches and challenges

Clinically, osteoarthritis (OA) is characterised by joint pain, stiffness after immobility, limitation of movement and, in many cases, the presence of basic calcium phosphate (BCP) crystals in the joint fluid. The detection of BCP crystals in the synovial fluid of patients with OA is fraught with challenges due to the submicroscopic size of BCP, the complex nature of the matrix in which they are found and the fact that other crystals can co-exist with them in cases of mixed pathology. Routine analysis of joint crystals still relies almost exclusively on the use of optical microscopy, which has limited applicability for BCP crystal identification due to limited resolution and the inherent subjectivity of the technique. The purpose of this Critical Review is to present an overview of some of the main analytical tools employed in the detection of BCP to date and the potential of emerging technologies such as atomic force microscopy (AFM) and Raman microspectroscopy for this purpose.

Update on identification of pathogenic crystals in joint fluid

Crystal identification in joint fluid has been an essential part of diagnosis of joint disease. Recent advances have included progress in crystal identification on stained slides, attention to aspiration techniques, and arthrocenteses of asymptomatic joints. Challenges remain to increase use and optimize techniques.

Calcium pyrophosphate dihydrate and hydroxyapatite crystal deposition in the joint: new developments relevant to the clinician

The major types of crystals containing calcium, which causes arthropathy and periarticular disease, are calcium pyrophosphate dihydrate and basic calcium phosphates, including hydroxyapatite. Exciting advances include the identification of mutations in the gene ANKH associated with disordered inorganic pyrophosphate (PPi) transport in some kindred with familial chondrocalcinosis linked to chromosome 5p. In addition, central basic mechanisms governing cartilage calcification and their relationship to aging and osteoarthritis have now been elucidated. These include the role of plasma cell glycoprotein-1, the PPi-generating ecto-enzyme, in chondrocalcinosis and the linkage of low- grade inflammation to expression and activation of two cartilage-expressed transglutaminase isoenzymes with direct calcification-stimulating activity. This review discusses clinically pertinent new information on pathogenesis. The authors also address, in detail, current diagnostic and therapeutic issues pertaining to calcium pyrophosphate dihydrate and hydroxyapatite crystal deposition in the joint, as well as possible therapeutic directions for the future.

Delayed examination of synovial fluid by ordinary and polarised light microscopy to detect and identify crystals

OBJECTIVE

To determine the reliability of a delay in the microscopic examination of synovial fluid (SF) to detect and identify crystals.

METHODS

Ninety one SF samples were examined, 31 with monosodium urate (MSU) crystals, 30 with crystals of calcium pyrophosphate dihydrate (CPPD), and 30 containing no crystals. The specimens were stored with EDTA, sodium heparin, and without anticoagulant at 4 degrees C before examination at 24 and 72 hours with ordinary and polarised light microscopy. Another aliquot of the same samples was stored in a plastic container without anticoagulant at -80 degrees C and examined after two months.

RESULTS

When the samples stored at 4 degrees C were re-examined after 24 hours, intracellular crystals of MSU were seen in 90/93 (97%) cases where they had been identified previously and 89/93 (96%) cases after 72 hours. Similarly, CPPD crystals were identified in 90/90 (100%) and 87/90 (97%) cases after 24 and 72 hours. Examination of the samples stored at -80 degrees C showed intracellular MSU crystals in 25/31 (81%) of cases and CPPD crystals in 25/30 (83%). No crystals were seen in any sample which had previously been diagnosed as crystal-free.

CONCLUSIONS

Deferred microscopic examination of refrigerated or deep frozen SF provides a strong probability of detecting MSU or CPPD crystals if these are present initially.