A functional SNP in CILP, encoding cartilage intermediate layer protein, is associated with susceptibility to lumbar disc disease.

Lumbar disc disease (LDD) is caused by degeneration of intervertebral discs of the lumbar spine. One of the most common musculoskeletal disorders, LDD has strong genetic determinants. Using a case-control association study, we identified a functional SNP (1184T --> C, resulting in the amino acid substitution I395T) in CILP, which encodes the cartilage intermediate layer protein, that acts as a modulator of LDD susceptibility. CILP was expressed abundantly in intervertebral discs, and its expression increased as disc degeneration progressed. CILP colocalized with TGF-beta1 in clustering chondrocytes and their territorial matrices in intervertebral discs. CILP inhibited TGF-beta1-mediated induction of cartilage matrix genes through direct interaction with TGF-beta1 and inhibition of TGF-beta1 signaling. The susceptibility-associated 1184C allele showed increased binding and inhibition of TGF-beta1. Therefore, we conclude that the extracellular matrix protein CILP regulates TGF-beta signaling and that this regulation has a crucial role in the etiology and pathogenesis of LDD. Our study also adds to the list of connective tissue diseases that are associated with TGF-beta.

Parallel regulation of extracellular ATP and inorganic pyrophosphate: roles of growth factors, transduction modulators, and ANK.

OBJECTIVE: Extracellular inorganic pyrophosphate (ePPi) is a key regulator of pathologic mineralization in articular cartilage. Articular chondrocytes generate ePPi by the transportation of intracellular PPi (iPPi) through transport mechanisms such as ANK or by the degradation of extracellular adenosine triphosphate (eATP) by ectoenzymes. Although numerous modulators of ePPi have been characterized, little is known about eATP elaboration in cartilage. We sought to determine (1) whether eATP is coordinately regulated with ePPi and (2) whether ANK transports ATP. METHODS: Primary articular chondrocytes were treated with factors known to modulate ePPi levels including growth factors (TGFß1 and IGF-1), anion channel inhibitors, and chemicals that alter adenylyl cyclase and protein kinase C activities. Additional chondrocyte monolayers were infected with adenovirus containing functional (Ad-ANK) or mutated (Ad-ANK mutant) ANK sequences. eATP levels were measured with a bioluminescent assay. RESULTS: TGFß1 enhanced eATP accumulation by 33%, whereas IGF-1 decreased eATP accumulation by 63% and attenuated TGFß1-induced eATP release by 72%. Forskolin and probenecid diminished eATP accumulation by 55% and 89%. Phorbol-12-myristate-13-acetate increased eATP by 29%. Transfection of chondrocytes with Ad-ANK caused a 10-fold increase in eATP compared with control values. CONCLUSION: Modulation of eATP by various factors paralleled their effects on ePPi production, suggesting a shared pathway of ePPi and eATP production and implicating ANK in eATP transport. As eATP directly contributes to pathologic mineralization in articular cartilage, understanding eATP regulation may lead to effective therapies for crystal-associated arthritis.

Prosthetic joint infection after total hip or knee arthroplasty in rheumatoid arthritis patients treated with nonbiologic and biologic disease-modifying antirheumatic drugs.

The aim of this study was to identify risk factors for acute surgical-site infection (SSI) after total joint arthroplasty in rheumatoid arthritis (RA) patients treated with nonbiologic and biologic disease-modifying antirheumatic drugs (DMARDs). We performed a retrospective study of all consecutive total hip (THA) and total knee (TKA) arthroplasties performed during a 5-year period (THA 81; TKA 339). Multivariate logistic regression analysis was performed to identify SSI risk factors. Of the patients undergoing THA or TKA, 24 cases (5.7%) developed a superficial incisional SSI requiring the use of antibiotics and three cases (0.7%) developed an organ/space SSI necessitating surgical treatment to remove the artificial joint prosthesis. Multivariate logistic regression analysis revealed that the use of biologic DMARDs [P = 0.0007, odds ratio (OR) = 5.69; 95% confidence interval (CI) 2.07-15.61] and longer RA duration (P = 0.0003, OR = 1.09; 95% CI 1.04-1.14) were the only significant risk factors for acute SSI. Furthermore, an analysis that individually evaluated major agents (n > 10) adjusted for disease duration indicated that tumor necrosis factor alpha blockers increased the risk of SSI (infliximab P = 0.001, OR = 9.80, 95% CI 2.41-39.82; etanercept P = 0.0003, OR = 9.16, 95% CI 2.77-30.25). We found that the use of infliximab or etanercept and longer disease duration were associated with an increased risk of acute SSI in RA patients. Prospective studies are thus needed to determine the safety of biologic DMARDs in the perioperative period.

Efficacy of total joint arthroplasty in patients with established rheumatoid arthritis: improved longitudinal effects on disease activity but not on health-related quality of life.

Though excellent clinical results have been reported for total joint arthroplasty (TJA) in rheumatoid arthritis (RA) patients, the longitudinal effects of TJA on pain, physical function, and health-related quality of life in RA patients remain unknown. This study aimed to assess changes in disease activity and health-related quality of life after TJA in patients with established RA. We analyzed the effect of total knee arthroplasty (TKA) and total hip arthroplasty (THA) on RA disease activity in an observational cohort of RA patients. Of the registered RA patients, 333 TKA and 77 THA patients were followed for 5 years after surgery. RA disease activity and health-related quality of life were measured using the Disease Activity Score 28 (DAS28) and a Japanese version of the Stanford health assessment questionnaire (J-HAQ). The mean DAS28 in TKA patients decreased from 4.66 (preoperatively) to 4.02 (3 years postoperatively) and to 3.94 (5 years postoperatively); the mean DAS28 in THA patients decreased from 4.41 (preoperatively) to 3.99 (3 years postoperatively) and to 3.92 (5 years postoperatively). The mean J-HAQ for TKA remained essentially unchanged, ranging from 1.48 (preoperatively) to 1.45 (3 years postoperatively) and to 1.47 (5 years postoperatively); the mean J-HAQ for THA also remained unchanged, ranging from 1.74 (preoperatively) to 1.74 (3 years postoperatively) and to 1.73 (5 years postoperatively). Of the total J-HAQ score, the lower limb score improved while the upper limb score worsened. Although TKA and THA improve clinical outcomes in damaged knees and hips and have a positive secondary systemic effect on RA disease activity, they have not had a continuously good effect on the measures of health-related quality of life. We conclude that tight control of RA disease activity is indicated for those patients with TKA and/or THA.

Increased ferritin predicts development and severity of acute interstitial lung disease as a complication of dermatomyositis.

OBJECTIVES: Acute/subacute interstitial pneumonia (A/SIP) is an intractable and fatal complication of DM. Since a useful indicator predicting the complication of A/SIP has not been found, the aim of this study was to determine whether serum ferritin is a potential predictive indicator of the occurrence of A/SIP in 64 patients with DM. METHODS: Of the total patients enrolled, 19 had A/SIP, 24 had chronic interstitial pneumonia and 21 were without interstitial lung disease (ILD). Clinical manifestations and laboratory data were obtained from medical records on admission. RESULTS: Serum ferritin levels were extremely high in patients with DM with A/SIP. It was significantly higher in DM with A/SIP than that in DM without A/SIP (median 790 vs 186 ng/ml; P < 0.0001). The cumulative survival rate for 6 months was 62.7% in patients with DM with A/SIP. Moreover, the cumulative survival rate was significantly (P = 0.016) lower in the group with ferritin levels > or =1500 ng/ml than the rate in the group with ferritin levels <1500 ng/ml. CONCLUSIONS: Serum ferritin can be useful as a predictor of the occurrence of A/SIP and correlates with the prognosis of A/SIP in DM. The intensive treatment using combination therapy with various immunosuppressant agents should be chosen for patients with ILD with DM showing hyperferritinaemia, especially levels >1500 ng/ml.

Clinical manifestation and prognostic factor in anti-melanoma differentiation-associated gene 5 antibody-associated interstitial lung disease as a complication of dermatomyositis.

OBJECTIVE: The aim of this study is to evaluate the clinical manifestation and prognostic factors of anti-melanoma differentiation-associated gene 5 (MDA5) antibody-associated interstitial lung disease (ILD) with DM. METHODS: Fourteen patients who presented with anti-MDA5 antibody and 10 patients with anti-aminoacyl-tRNA synthetase (ARS) antibody were enrolled. All patients were diagnosed as having DM with ILD. Clinical manifestations in the patients with anti-MDA5 antibody were compared with those in the patients with anti-ARS antibody. RESULTS: The frequencies of acute/subacute interstitial pneumonia (A/SIP) and fatal outcome were significantly higher in the subset with anti-MDA5 antibody. The creatine kinase (CK) value was significantly lower and the gamma-glutamyl transpeptidase and ferritin values were significantly higher in the subset with anti-MDA5 antibody. Significant correlations were found between PaO(2)/F(i)O(2) and ferritin (r(s) = -0.59, P = 0.035), alveolar-arterial oxygen difference (A-aDO(2)) and KL-6 (r(s) = 0.73, P = 0.016) and A-aDO(2) and ferritin (r(s) = 0.66, P = 0.013) in the subset with anti-MDA5 antibody. The most significant prognostic factor was ferritin. The cumulative survival rate was significantly lower (P < 0.0001) in the subset with ferritin >or=1600 ng/ml than that in the subset with ferritin <1600 ng/ml in anti-MDA5 antibody-associated ILD. CONCLUSION: Both serum ferritin and anti-MDA5 antibody are powerful indicators for the early diagnosis of A/SIP with DM. Ferritin also predicts disease severity and prognosis for patients with anti-MDA5 antibody. Intensive treatment should be administered to cases that have anti-MDA5 antibody-associated ILD with DM showing hyperferritinaemia, especially if the ferritin level is >or=1600 ng/ml.

Single nucleotide polymorphisms of CD244 gene predispose to renal and neuropsychiatric manifestations with systemic lupus erythematosus.

The objective of this study was to explore the association of single nucleotide polymorphisms (SNPs) of the CD244 gene with several clinical features of systemic lupus erythematosus (SLE). Two hundred and forty-three patients with SLE and 369 healthy controls were enrolled. Two SNPs (rs6682654 and rs3766379) in the CD244 gene were determined by allelic discrimination using a specific TaqMan probe. Only SNP rs3766379 was significantly associated with susceptibility to SLE [P = 0.009; odds ratio (OR) 1.28; 95% confidence interval (CI) 1.04-1.57]. The association was preferentially observed in subsets of SLE patients with nephritis and neuropsychiatric lupus. The frequency of the rs6682654 C allele was strongly associated with nephritis and neuropsychiatric lupus (P = 0.00065; OR 1.99; 95% CI 1.34-2.95, and P = 1.6 × 10(-7); OR 3.47; 95% CI 2.12-5.70, respectively), as was the frequency of the rs3766379 T allele (P = 0.0014; OR 1.86; 95% CI 1.27-2.71, and P = 2.6 × 10(-7); OR 3.15; 95% CI 2.00-4.96, respectively). In this study, an SNP of the CD244 gene was associated with susceptibility to SLE. There was a strikingly strong association in SLE patients with nephritis and neuropsychiatric lupus, suggesting that this genetic marker could predict involvement of those severe complications.

Antifibrotic effects of 2-carba cyclic phosphatidic acid (2ccPA) in systemic sclerosis: contribution to the novel treatment.

BACKGROUND: Cyclic phosphatidic acid (cPA) has an inhibitory effect on the autotaxin (ATX)/lysophosphatidic acid (LPA) axis, which has been implicated to play an important role in the progression of fibrosis in systemic sclerosis (SSc). The purpose of this study is to assess the antifibrotic activity of cPA for the treatment of SSc using SSc skin fibroblasts and an animal model of bleomycin-induced skin fibrosis. METHODS: We used a chemically stable derivative of cPA (2ccPA). First, we investigated the effect of 2ccPA on extracellular matrix (ECM) expression in skin fibroblasts. Next, the effect of 2ccPA on the intracellular cAMP levels was determined to investigate the mechanisms of the antifibrotic activity of 2ccPA. Finally, we administered 2ccPA to bleomycin-induced SSc model mice to evaluate whether 2ccPA prevented the progression of skin fibrosis. RESULTS: 2ccPA decreased ECM expression in SSc skin fibroblasts and TGF-ß1-treated healthy skin fibroblasts without LPA stimulation. 2ccPA increased the intracellular cAMP levels in skin fibroblasts, suggesting that the antifibrotic effect of 2ccPA was the consequence of the increase in the intracellular cAMP levels. Administration of 2ccPA also ameliorated the progression of bleomycin-induced skin fibrosis in mice. CONCLUSIONS: Our data indicated that 2ccPA had inhibitory effects on the progression of skin fibrosis by abrogating ECM production from activated skin fibroblasts. These cells were repressed, at least in part, by increased intracellular cAMP levels. 2ccPA may be able to be used to treat fibrotic lesions in SSc.

Osteopontin promotes pathologic mineralization in articular cartilage.

Calcium pyrophosphate dihydrate (CPPD) crystals are commonly found in osteoarthritic joint tissues, where they predict severe disease. Unlike other types of calcium phosphate crystals, CPPD crystals form almost exclusively in the pericellular matrix of damaged articular cartilage, suggesting a key role for the extracellular matrix milieu in their development. Osteopontin is a matricellular protein found in increased quantities in the pericellular matrix of osteoarthritic cartilage. Osteopontin modulates the formation of calcium-containing crystals in many settings. We show here that osteopontin stimulates ATP-induced CPPD crystal formation by chondrocytes in vitro. This effect is augmented by osteopontin's incorporation into extracellular matrix by transglutaminase enzymes, is only modestly affected by its phosphorylation state, and is inhibited by integrin blockers. Surprisingly, osteopontin stimulates transglutaminase activity in cultured chondrocytes in a dose-responsive manner. As elevated levels of transglutaminase activity promote extracellular matrix changes that permit CPPD crystal formation, this is one possible mechanism of action. We demonstrate the presence of osteopontin in the pericellular matrix of chondrocytes adjacent to CPPD deposits and near active transglutaminases. Thus, osteopontin may play an important role in facilitating CPPD crystal formation in articular cartilage.

Tissue-specific and time-dependent clonal expansion of ENU-induced mutant cells in gpt delta mice.

DNA mutations play a crucial role in the origins of cancer, and the clonal expansion of mutant cells is one of the fundamental steps in multistage carcinogenesis. In this study, we correlated tumor incidence in B6C3F1 mice during the period after exposure to N-ethyl-N-nitrosourea (ENU) with the persistence of ENU-induced mutant clones in transgenic gpt delta B6C3F1 mice. The induced gpt mutations afforded no selective advantage in the mouse cells and could be distinguished by a mutational spectrum that is characteristic of ENU treatment. The gpt mutations were passengers of the mutant cell of origin and its daughter cells and thus could be used as neutral markers of clones that arose and persisted in the tissues. Female B6C3F1 mice exposed for 1 month to 200 ppm ENU in the drinking water developed early thymic lymphomas and late liver and lung tumors. To assay gpt mutations, we sampled the thymus, liver, lung, and small intestine of female gpt delta mice at 3 days, 4 weeks, and 8 weeks after the end of ENU exposure. Our results reveal that, in all four tissues, the ENU-induced gpt mutations persisted for weeks after the end of mutagen exposure. Clonal expansion of mutant cells was observed in the thymus and small intestine, with the thymus showing larger clone sizes. These results indicate that the clearance of mutant cells and the potential for clonal expansion during normal tissue growth depends on tissue type and that these factors may affect the sensitivity of different tissues to carcinogenesis. Environ. Mol. Mutagen. 58:592-606, 2017. © 2017 Wiley Periodicals, Inc.

Regulation of transglutaminase activity in articular chondrocytes through thrombin receptor-mediated factor XIII synthesis.

Transglutaminases are a family of enzymes that catalyze the formation of epsilon-(gamma-glutamyl)lysine isopeptide bonds in proteins, an activity that has been implicated in the pathogenesis of cartilage matrix mineralization in degenerative arthritis. Type II transglutaminase and thrombin-activatable factor XIII have been identified in articular cartilage. Thrombin, a coagulation protease, is found in pathological synovial fluids, and is known to stimulate transglutaminase activity in non-articular tissues. We investigated the effects of thrombin on transglutaminase activity in porcine articular chondrocytes. Direct addition of thrombin to chondrocyte lysates resulted in increased transglutaminase activity due to proteolytic conversion of factor XIII to XIIIa. Thrombin-treated chondrocyte cultures (0.001 to 2.0 U/ml) also showed increased transglutaminase activity. Thrombin treatment of chondrocyte cultures increased transglutaminase activity as early as 15 minutes after addition, an effect that we attributed to factor XIII activation. Additional stimulatory effects of thrombin were observed in cultured chondrocytes at 4 and 24 hours. A thrombin receptor agonist peptide (TRAP) which activates the PAR1 thrombin receptor mimicked these later effects. Thrombin treatment of chondrocyte cultures increased factor XIII mRNA and protein levels, without affecting levels of type II transglutaminase. Thus, thrombin stimulates transglutaminase activity in articular cartilage by directly cleaving factor XIII and by receptor-mediated up-regulation of factor XIII synthesis. Such increases in potential transglutaminase activity may facilitate pathological matrix calcification in degenerative arthritis.

Upregulation of ANK protein expression in joint tissue in calcium pyrophosphate dihydrate crystal deposition disease.

OBJECTIVE: Accumulation of excess extracellular inorganic pyrophosphate leads to calcium pyrophosphate dihydrate (CPPD) crystal formation in articular cartilage. CPPD crystal formation occurs near morphologically abnormal chondrocytes resembling hypertrophic chondrocytes. The ANK protein was recently implicated as an important factor in the transport of intracellular inorganic pyrophosphate across the cell membrane. We characterized ANK in joint tissues from patients with and without CPPD deposition and correlated the presence of ANK with markers of chondrocyte hypertrophy. METHODS: Articular tissues were obtained from 24 patients with CPPD crystal deposition disease, 11 patients with osteoarthritis (OA) without crystals, and 6 controls. We determined the number of ANK-positive cells in joint tissues using immunohistochemistry and in situ hybridization, and correlated ANK positivity with markers of chondrocyte hypertrophy including Runx2, type X collagen, osteopontin (OPN), and osteocalcin (OCN). RESULTS: ANK was detected in synoviocytes, chondrocytes, osteoblasts, and osteocytes. ANK was seen extracellularly only in the matrix of cartilage and meniscus. The number of ANK-positive cells was significantly higher in CPPD than in OA or normal joint tissues. The amount and intensity of ANK immunoreactivity reached maximum levels in the large chondrocytes around crystal deposits. ANK was similarly distributed to and significantly correlated with Runx2, type X collagen, OPN, and OCN. CONCLUSION: ANK levels were higher in articular tissues from patients with CPPD deposition. ANK was concentrated around crystal deposits and correlated with markers of chondrocyte hypertrophy. These findings support a role for ANK in CPPD crystal formation in cartilage.

Clinical utility of computed tomographic scanning for the evaluation of lupus profundus in two patients with systemic lupus erythematosus.

Lupus profundus is a rare lupus-specific skin lesion with skin biopsies exhibiting lobular lymphocytic infiltration and destruction of subcutaneous fat tissue. In this report, a CT scan was effective in demonstrating both the presence and the extent of inflammation of lupus profundus in two patients with systemic lupus erythematosus (SLE). Case 1 was a 30-year-old woman developing erythema with subcutaneous induration on the upper arms during the quiescent phase of SLE. A skin biopsy confirmed a diagnosis of lupus profundus. A CT scan of the right upper arm demonstrated a high density area (HDA) of the subcutis under the erythema: a finding consistent with lupus profundus. Case 2 was a 28-year-old woman recently diagnosed with SLE. She also developed a skin ulcer on the right hip. A CT scan of the hip revealed an HDA and lipoatrophy of the subcutis around the ulcer: these findings were compatible with lupus profundus. Treatment with high-dose prednisolone improved the illness in the both cases. A CT scan is a useful and convenient imaging modality for confirming the diagnosis of lupus profundus.

Therapeutic efficacy of intravenous cyclophosphamide concomitant with moderate- to high-dose prednisolone in two patients with fasciitis panniculitis syndrome.

Fasciitis panniculitis syndrome (FPS) has been proposed as a new category of 'fasciitis' and includes the well-established eosinophilic fasciitis (EF). Unlike EF, FPS exhibits inconsistent eosinophilia and/or eosinophilic infiltration of the lesions. Principal histological FPS findings include dermal thickening, inflammation and thickening of the subcutaneous fat tissue, fibrous thickening of the fascia and inflammation of the adjacent muscle. FPS is commonly resistant to corticosteroids, and cimetidine is effective in approximately 80% of FPS patients. A new therapy for FPS is required for cases refractory to treatment or intolerant to cimetidine because of adverse drug reaction. In this report, two FPS patients were resistant to corticosteroids. Both received intravenous cyclophosphamide (IVCY) concomitant with moderate- to high-dose prednisolone (PSL), and this effectively treated the induration of the FPS lesions. Patient 1 was a 50-year-old woman who had been diagnosed with fasciitis following en bloc muscle biopsy of the thigh. She had been treated with high-dose PSL for 6 years, but the fasciitis was refractory. Induration of the neck, thorax and thighs resulted in impaired neck rotation, restrictive respiratory failure and impaired walking. A diagnosis of FPS was made by re-assessing the en bloc muscle biopsy. Although PSL (40 mg/day) for 18 days was ineffective, the addition of IVCY (400 mg) dramatically improved the disease manifestations. Patient 2 was a 68-year-old man who was diagnosed with fasciitis based on en bloc muscle biopsy of the left foot. He had been treated with PSL for 16 years, but the fasciitis was refractory. He exhibited lower limb induration and a refractory skin ulcer of the left foot. A diagnosis of FPS was made by re-assessing the en bloc muscle biopsy. Although PSL (40 mg/day) for 2 weeks was ineffective, the addition of IVCY (450 mg) improved both the lower limb induration and the skin ulcer. FPS may cause both entrapment vasculopathy of subcutis and perivasculitis of the subcutaneous fat tissue such that the skin ulcer might be closely related with the ischemic mechanism triggered by FPS. According to the clinical courses of our cases, IVCY combined with moderate- to high-dose PSL may be a new therapeutic choice for corticosteroid-resistant FPS patients.

A case of relapsing polychondritis with bilateral sensorineural hearing loss and perforation of the nasal septum at the onset.

A 33-year-old woman suffered from epistaxis and perforation of the nasal septum. Based on a biopsy of nasal mucosa, Wegener's granulomatosis was suspected initially. Her nasal symptoms improved spontaneously, but tinnitus, hearing loss, and dizziness appeared within 3 months. Laboratory analyses revealed no inflammation, and antineutrophil cytoplasmic antibodies were negative. Audiometry revealed bilateral sensorineural hearing loss. A second biopsy of the nasal septum showed an inflammatory change in the cartilage. Thus we diagnosed early-stage relapsing polychondritis.

The serine protease inhibitor trappin-2 is present in cartilage and synovial fluid in osteoarthritis.

OBJECTIVE: Trappins are small serine protease inhibitors bound to extracellular matrix (ECM) through the actions of transglutaminase (TGase) enzymes. Trappin-2 is present in many tissues and is upregulated at sites of injury. In osteoarthritis (OA), serine proteases contribute to articular cartilage destruction, and TGase activity is increased. Yet little is known about matrix-bound serine protease inhibitors or TGase substrates in articular cartilage. Our purpose was to determine if trappin-2 was present in OA cartilage and synovial fluid (SF). METHODS: OA knee articular cartilage and SF were assayed for trappin-2 protein by Western blotting, ELISA, and immunohistochemistry. Trappin-2 mRNA was detected with RT-PCR. The ECM components bound to trappin-2 were identified by 2-D gel electrophoresis and peptide fingerprinting. RESULTS: Trappin-2 was detectable in OA articular cartilage extracts, cultured chondrocytes, conditioned media, and SF by Western blotting. OA cartilage protein extracts contained significantly higher quantities of trappin-2 than normal cartilage protein extracts (22.98 +/- 1.28 ng/mg wet weight vs 14.97 +/- 1.92 ng/mg wet weight; p < 0.01). RT-PCR confirmed the presence of trappin-2 mRNA in OA chondrocytes. Immunohistochemical studies of OA cartilage revealed trappin-2 protein in chondrocytes. Peptide mapping of trappin-2 binding partners showed that fibromodulin was bound to trappin-2 in cartilage. CONCLUSION: We confirmed the presence of trappin-2 in OA cartilage and SF. Elevated levels of TGase activity in OA cartilage may increase levels of this serine protease inhibitor in response to injury.

Calcium crystal deposition diseases: lessons from histochemistry.

PURPOSE OF REVIEW: Recent progress in molecular biology and biochemistry has enabled researchers to identify possible key players in physiologic and pathologic calcification. However, important lessons from immunohistochemical studies have contributed greatly to our current understanding of the pathogenesis of calcium crystal deposition disease. RECENT FINDINGS: Histologic findings led to the hypothesis of the important role of hypertrophic differentiation of articular chondrocytes in calcium crystal deposition. In addition, histologic studies have confirmed the importance of individual proteins that may have direct or indirect roles in calcium crystal formation. SUMMARY: Future studies will determine whether in vitro data showing key roles for certain factors in mineralization and calcification in cartilage are relevant to crystal deposition disease in humans.

Animal models of pathologic calcification.

Recent progress in genetics and mouse genomics enables researchers to unveil the molecular basis for mouse phenotypes that express pathologic calcification in soft tissue and/or articular tissues. A newly identified multipass transmembrane protein, ANK, appears to function as an inorganic pyrophosphate (PPi) transporter or regulator of PPi transport. Abnormal extracellular PPi (ePPi) metabolism has been implicated in abnormal calcification, decreased concentrations predisposing to basic calcium phosphate (BCP) deposition, and increased concentrations promoting calcium pyrophosphate dihydrate (CPPD) crystal deposition in articular tissues. The chromosomal location of human ANK overlaps the locus identified in several kindreds affected with familial chondrocalcinosis. Deficient generation of ePPi by the ectoenzyme nucleoside triphosphate pyrophosphohydrolase also results in excessive ossification and ectopic deposition of BCP crystals in tiptoe-walking mice and PC-1 null mice. Recent studies reinforce the important regulatory role of ePPi in pathologic and physiologic calcification.

Up-regulated expression of cartilage intermediate-layer protein and ANK in articular hyaline cartilage from patients with calcium pyrophosphate dihydrate crystal deposition disease.

OBJECTIVE: Excess accumulation of extracellular inorganic pyrophosphate (ePPi) in aged human cartilage is crucial in calcium pyrophosphate dihydrate (CPPD) crystal formation in cartilage matrix. Two sources of ePPi are ePPi-generating ectoenzymes (NTPPPH) and extracellular transport of intracellular PPi by ANK. This study was undertaken to evaluate the role of NTPPPH and ANK in ePPi elaboration, by investigating expression of NTPPPH enzymes (cartilage intermediate-layer protein [CILP] and plasma cell membrane glycoprotein 1 [PC-1]) and ANK in human chondrocytes from osteoarthritic (OA) articular cartilage containing CPPD crystals and without crystals. METHODS: Chondrocytes were harvested from knee cartilage at the time of arthroplasty (OA with CPPD crystals [CPPD], n = 8; OA without crystals [OA], n = 10). Normal adult human chondrocytes (n = 1) were used as a control. Chondrocytes were cultured with transforming growth factor beta1 (TGFbeta1), which stimulates ePPi elaboration, and/or insulin-like growth factor 1 (IGF-1), which inhibits ePPi elaboration. NTPPPH and ePPi were measured in the media at 48 hours. Media CILP, PC-1, and ANK were determined by dot-immunoblot analysis. Chondrocyte messenger RNA (mRNA) was extracted for reverse transcriptase-polymerase chain reaction to study expression of mRNA for CILP, PC-1, and ANK. NTPPPH and ANK mRNA and protein were also studied in fresh frozen cartilage. RESULTS: Basal ePPi elaboration and NTPPPH activity in conditioned media from CPPD chondrocytes were elevated compared with normal chondrocytes, and tended to be higher compared with OA chondrocytes. Basal expression of mRNA for CILP (chondrocytes) and ANK (cartilage) was higher in both CPPD chondrocytes and CPPD cartilage extract than in OA or normal samples. PC-1 mRNA was less abundant in CPPD chondrocytes and cartilage extract than in OA chondrocytes and extract, although the difference was not significant. CILP, PC-1, and ANK protein levels were similar in CPPD, OA, and normal chondrocytes or cartilage extracts. Both CILP and ANK mRNA expression and ePPi elaboration were stimulated by TGFbeta1 and inhibited by IGF-1 in chondrocytes from all sources. CONCLUSION: CILP and ANK mRNA expression correlates with chondrocyte ePPi accumulation around CPPD and OA chondrocytes, and all respond similarly to growth factor stimulation. These findings suggest that up-regulated CILP and ANK expression contributes to higher ePPi accumulation from CPPD crystal-forming cartilage.

The utility of alizarin red s staining in calcium pyrophosphate dihydrate crystal deposition disease.

OBJECTIVE: To determine the most suitable staining method for preservation and detection of calcium pyrophosphate dihydrate (CPPD) crystals in histological sections of patients with CPPD crystal deposition disease. METHODS: Paraffin sections of CPPD crystal-bearing tissues of 31 patients were stained with hematoxylin and eosin (H&E) and Alizarin red S (ARS). For H&E, the sections were treated with Mayer's hematoxylin (pH 2.3) for 5 min and with eosin alcohol (pH 4.1) for 1 min. For ARS, 1% ARS dissolved in distilled water was adjusted to pH 6.4 by adding 0.1% ammonia solution drop by drop while stirring. As controls, unstained sections were soaked in 1% citric acid monohydrate solution (CAMS, pH 2.3) for 5 or 10 min. The histological preparations were examined under a compensated polarized light using a first-order red compensator. We counted the number of weakly positive birefringent CPPD crystals in 3 high power fields (HPF, 0.272 mm2). RESULTS: CPPD crystals were seen clearly in most specimens stained with ARS, but were markedly reduced in tissue sections stained with H&E or CAMS. The number of CPPD crystals detected in sections stained by ARS (1723 +/- 683 per 3 HPF, mean +/- standard deviation) was significantly higher compared with H&E, CAMS (5 min), and CAMS (10 min) (401 +/- 374, 1022 +/- 616, and 494 +/- 636 per 3 HPF, respectively; p < 0.001, each). CONCLUSION: Standard H&E staining reduces the number of visible CPPD crystals, probably due to the strong acidity of both hematoxylin and eosin solutions, whereas the ARS stain seems to preserve a large number of CPPD crystals. The utility of ARS staining may improve the identification of CPPD crystals and contribute to a correct diagnosis of CPPD crystal deposition.