Histopathological and ultrastructural studies of synovium in Milwaukee shoulder syndrome--a basic calcium phosphate crystal arthropathy

Biological effects and osteoarthritic disease-modifying activity of small molecule CM-01

Phosphocitrate inhibits cartilage degeneration, however, the prospect of phosphocitrate as an oral disease modifying drug might be limited. The purpose of this study was to investigate the biological effects and disease-modifying activity of a phosphocitrate "analog," CM-01 (Carolinas Molecule-01), and test the hypothesis that CM-01 is a disease modifying drug for osteoarthritis therapy. The effects of CM-01 on calcium crystal-induced expression of matrix metalloproteinase-1 and interleukin-1 beta, cell-mediated calcification and production of proteoglycan by chondrocytes were examined in cell cultures. Disease-modifying activity was examined using Hartley guinea pig model of posttraumatic osteoarthritis. Cartilage degeneration in untreated and CM-01 treated guinea pigs was examined with Indian ink and Safranin-O-fast green. Levels of matrix metalloproteinase-13, ADAM metallopeptidase with thrombospondin type 1 motif 5, chemokine (C-C motif) ligand 5, and cyclooxygenase 2 were examined with immunostaining. CM-01 inhibited crystal-induced expression of matrix metalloproteinase-1 and interleukin-1β, reduced cell-mediated calcification, and stimulated the production of proteoglycan by chondrocytes. In Hartley guinea pigs, CM-01 not only reduced damages in articular surface but also reduced resorption of calcified zone cartilage. The reduction in cartilage degeneration was accompanied by decreased levels of matrix metalloproteinase-13, ADAM metallopeptidase with thrombospondin type 1 motif 5, chemokine (C-C motif) ligand 5 and cyclooxygenase 2. These findings confirmed that CM-01 is a promising candidate to be tested as an oral drug for human OA therapy. CM-01 exerted its disease-modifying activity on osteoarthritis, in part, by inhibiting the production of matrix-degrading enzymes and a molecular program resembling the endochondral pathway of ossification. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:309-317, 2018.

Disease-modifying effects of phosphocitrate and phosphocitrate-β-ethyl ester on partial meniscectomy-induced osteoarthritis

Background

It is believed that phosphocitrate (PC) exerts its disease-modifying effects on osteoarthritis (OA) by inhibiting the formation of crystals. However, recent findings suggest that PC exerts its disease-modifying effect, at least in part, through a crystal-independent action. This study sought to examine the disease-modifying effects of PC and its analogue PC-β-ethyl ester (PC-E) on partial meniscectomy-induced OA and the structure-activity relationship.

Methods

Calcification- and proliferation-inhibitory activities were examined in OA fibroblast-like synoviocytes (FLSs) culture. Disease-modifying effects were examined using Hartley guinea pigs undergoing partial meniscectomy. Cartilage degeneration was examined with Indian ink, safranin-O, and picrosirius red. Levels of matrix metalloproteinase-13 (MMP-13), ADAM metallopeptidase with thrombospondin type 1 motif 5 (ADAMTS5), chemokine (C-C motif) ligand 5 (CCL5), and cyclooxygenase-2 (Cox-2) were examined with immunostaining. The effects of PC-E and PC on gene expressions in OA FLSs were examined with microarray. Results are expressed as mean ± standard deviation and analyzed using Student’s t test or Wilcoxon rank sum test.

Results

PC-E was slightly less powerful than PC as a calcification inhibitor but as powerful as PC in the inhibition of OA FLSs proliferation. PC significantly inhibited cartilage degeneration in the partial meniscectomied right knee. PC-E was less powerful than PC as a disease-modifying drug, especially in the inhibition of cartilage degeneration in the non-operated left knee. PC significantly reduced the levels of ADAMTS5, MMP-13 and CCL5, whereas PC-E reduced the levels of ADAMTS5 and CCL5. Microarray analyses revealed that PC-E failed to downregulate the expression of many PC-downregulated genes classified in angiogenesis and inflammatory response.

Conclusions

PC is a disease-modifying drug for posttraumatic OA therapy. PC exerts its disease-modifying effect through two independent actions: inhibiting pathological calcification and modulating the expression of many genes implicated in OA. The β-carboxyl group of PC plays an important role in the inhibition of cartilage degeneration, little role in the inhibition of FLSs proliferation, and a moderate role in the inhibition of FLSs-mediated calcification.

In the clinic. Rotator cuff disease

Shoulder pain is a common musculoskeletal disorder and has a substantial negative effect on quality of life. Its monthly prevalence in the general population is reported to be between 18% and 31%, whereas lifetime prevalence ranges between 6.7% and 66.7%. Shoulder pain is the third most frequent musculoskeletal reason to present to primary care and accounts for up to 10% of all referrals to physical therapists. Although the natural history of shoulder pain varies and is often self-limiting,up to half of persons who present for care, particularly the elderly, might continue to have pain and/or functional disturbance for up to 2 years after presentation.

Fibroblast-like synoviocytes induce calcium mineral formation and deposition

Calcium crystals are present in the synovial fluid of 65%–100% patients with osteoarthritis (OA) and 20%–39% patients with rheumatoid arthritis (RA). This study sought to investigate the role of fibroblast-like synoviocytes (FLSs) in calcium mineral formation. We found that numerous genes classified in the biomineral formation process, including bone gamma-carboxyglutamate (gla) protein/osteocalcin, runt-related transcription factor 2, ankylosis progressive homolog, and parathyroid hormone-like hormone, were differentially expressed in the OA and RA FLSs. Calcium deposits were detected in FLSs cultured in regular medium in the presence of ATP and FLSs cultured in chondrogenesis medium in the absence of ATP. More calcium minerals were deposited in the cultures of OA FLSs than in the cultures of RA FLSs. Examination of the micromass stained with nonaqueous alcoholic eosin indicated the presence of birefringent crystals. Phosphocitrate inhibited the OA FLSs-mediated calcium mineral deposition. These findings together suggest that OA FLSs are not passive bystanders but are active players in the pathological calcification process occurring in OA and that potential calcification stimuli for OA FLSs-mediated calcium deposition include ATP and certain unidentified differentiation-inducing factor(s). The OA FLSs-mediated pathological calcification process is a valid target for the development of disease-modifying drug for OA therapy.

Pathogenic role of basic calcium phosphate crystals in destructive arthropathies

BACKGROUND

basic calcium phosphate (BCP) crystals are commonly found in osteoarthritis (OA) and are associated with cartilage destruction. BCP crystals induce in vitro catabolic responses with the production of metalloproteases and inflammatory cytokines such as interleukin-1 (IL-1). In vivo, IL-1 production induced by BCP crystals is both dependant and independent of NLRP3 inflammasome. We aimed to clarify 1/ the role of BCP crystals in cartilage destruction and 2/ the role of IL-1 and NLRP3 inflammasome in cartilage degradation related to BCP crystals.

METHODOLOGY PRINCIPAL FINDINGS

synovial membranes isolated from OA knees were analysed by alizarin Red and FTIR. Pyrogen free BCP crystals were injected into right knees of WT, NLRP3 -/-, ASC -/-, IL-1α -/- and IL-1β-/- mice and PBS was injected into left knees. To assess the role of IL-1, WT mice were treated by intra-peritoneal injections of anakinra, the IL-1Ra recombinant protein, or PBS. Articular destruction was studied at d4, d17 and d30 assessing synovial inflammation, proteoglycan loss and chondrocyte apoptosis. BCP crystals were frequently found in OA synovial membranes including low grade OA. BCP crystals injected into murine knee joints provoked synovial inflammation characterized by synovial macrophage infiltration that persisted at day 30, cartilage degradation as evidenced by loss of proteoglycan staining by Safranin-O and concomitant expression of VDIPEN epitopes, and increased chondrocyte apoptosis. BCP crystal-induced synovitis was totally independent of IL-1α and IL-1β signalling and no alterations of inflammation were observed in mice deficient for components of the NLRP3-inflammasome, IL-1α or IL-1β. Similarly, treatment with anakinra did not prevent BCP crystal effects. In vitro, BCP crystals elicited enhanced transcription of matrix degrading and pro-inflammatory genes in macrophages.

CONCLUSIONS SIGNIFICANCE

intra-articular BCP crystals can elicit synovial inflammation and cartilage degradation suggesting that BCP crystals have a direct pathogenic role in OA. The effects are independent of IL-1 and NLRP3 inflammasome.

Tumors and diseases of the joint

A variety of different diseases affect the synovium, including infection, noninfectious immunologic inflammatory conditions, degenerative arthroses, crystal deposits, trauma, and tumors. Tumors of the synovium are relatively uncommon. Any mesenchymal tumor may arise in the synovium, but most recapitulate its normal counterpart including synoviocytes, blood vessels, fat, and fibrous tissue. These tumors can arise in any synovial lined structures both within joints and in extraarticular locations. Most synovial tumors are benign. Malignant tumors are rare but important to recognize because many are aggressive and must be treated appropriately. Among common nonneoplastic conditions that affect the synovium and surrounding structures are crystal deposits such as monosodium urate crystals, calcium pyrophosphate dihydrate crystals, and hydroxyapatite crystals. These crystal deposits may be asymptomatic or cause severe pain or chronic joint destruction. Their accurate identification is important to guide appropriate therapy.

Cuff tear arthropathy: current trends in diagnosis and surgical management

Massive tears of the rotator cuff resulting in arthritis of the glenohumeral joint remain a difficult challenge. Although cuff tear arthropathy (CTA) has been recognized for more than 150 years, a treatment strategy with uniformly satisfactory outcomes remains elusive, partly due to the difficulty in defining CTA in the literature. Most studies combine true CTA, rheumatoid arthritis, and massive rotator cuff tears under the CTA diagnosis. Determining outcomes from these studies is difficult. Hemiarthroplasty and total shoulder arthroplasty have led to pain relief, but the high rate of glenoid component loosening after total shoulder arthroplasty is a concern, and active range of motion remains limited after hemiarthroplasty. There is increasing interest in the use of a constrained or reverese total shoulder arthroplasty to treat this complex process, with promising early results. This review article studies current trends in the diagnosis and management of arthritis due to massive cuff tears and CTA.

Radiographic evaluation of osteoarthritis

Osteoarthritis is the most widespread form of arthritis in the United States. Classically, osteoarthritis has been grouped into primary and secondary types. Primary or idiopathic osteoarthritis is believed to be a sequela of altered biomechanical stresses across joints in susceptible individuals. Secondary osteoarthritis is a consequence of underlying cartilage damage, such as from preceding inflammatory arthritis, metabolic abnormality, or injury. The radiographic hallmark of osteoarthritis is asymmetric loss of cartilage space. Osteophytosis bony eburnation, subchondral cysts, and eventual subluxation follow. Osteoporosis and erosions are not usual features of this disease.

Pathology of the synovium

Synovium is specialized mesenchymal tissue that is essential for the appropriate function of the locomotor apparatus. It is the site for a series of pathologic processes that are characteristic, and in some cases specific, to this distinctive tissue. In this article, the normal microscopic anatomy of synovium is briefly reviewed. Synovial proliferative disorders, including pigmented villonodular synovitis, giant cell tumor of tendon sheath, hemosiderotic synovitis, and fatty infiltration of the synovial membrane are discussed. Additionally, the subjects of intrasynovial cartilaginous lesions (primary and secondary synovial chondromatosis) and crystal deposition diseases are reviewed. Finally, the response of synovial tissues to implanted foreign materials that are used in large and small joint arthroplasty are described.

Crystals and arthritis

Monosodium urate, calcium pyrophosphate dihydrate, and basic calcium phosphate (carbonate-substituted hydroxyapatite and octacalcium phosphate) crystal aggregates are associated with gout, pseudogout, and cartilage degeneration (osteoarthritis, Milwaukee Shoulder/Knee Syndrome), respectively. Hyperuricemia is a frequent but nonspecific and inconstant feature of gout just as an elevated synovial fluid inorganic pyrophosphate level is an inconstant feature of pseudogout. Monosodium urate, calcium pyrophosphate dihydrate, or basic calcium phosphate crystals can cause acute inflammation associated with phagocytosis by neutrophilic leukocytes. Each induces neutral protease synthesis and secretion and arachidonic acid metabolism by synoviocytes and macrophages in a dose-dependent fashion, postulated to produce the damage to bone, cartilage, and other joint tissues that is perceived clinically as tophaceous destruction or degenerative joint disease. Crystals containing calcium are potent mitogens. All three types of crystals are more common in older persons and will attract additional attention as the mean age of our population increases. Gout is perhaps the most treatable disease in medicine, although mistakes in diagnosis and in choice of appropriate therapy are very common. Acute pseudogout and acute calcific periarthritis are readily treated medically, but the chronic effects of crystals containing calcium are not. New approaches using drugs derived from scientific study of the biologic effects of these crystals may become useful therapeutically.

The role of cyclic-3',5'-adenosine monophosphate in prostaglandin-mediated inhibition of basic calcium phosphate crystal-induced mitogenesis and collagenase induction in cultured human fibroblasts

Synovial fluid basic calcium phosphate (BCP) crystals are associated with severe destructive arthropathies characterised by synovial proliferation and non-inflammatory degradation of intra-articular collagenous structures. BCP crystals stimulate fibroblast and chondrocyte mitogenesis, metalloprotease secretion and prostaglandin production. As a tissue protective effect of prostaglandins has been suggested, we recently studied the effect of PGE1 on BCP crystal-induced mitogenesis and collagenase mRNA accumulation in human fibroblasts (HF). We demonstrated a dose-dependent inhibition of BCP crystal-induced mitogenesis and collagenase mRNA accumulation. The mechanism of PGE1 inhibition of BCP crystal-induced mitogenesis and collagenase mRNA accumulation was therefore explored. PGE1 (100 ng/ml) increased HF intracellular cAMP 40-fold over control. BCP alone caused no such change but inhibited the PGE1-induced increase in intracellular cAMP by at least 60%. The PGE1-induced increase in intracellular cAMP was also blocked by the adenyl cyclase inhibitor, 2',5'-dideoxyadenosine (ddA) (10 microM) and ddA reversed the PGE1-mediated inhibition of BCP crystal-induced mitogenesis. Dibutyryl cAMP also inhibited BCP crystal-induced mitogenesis in a concentration-dependent manner. Agents which increase intracellular cAMP levels such as the adenyl cyclase activator forskolin and the phosphodiesterase, inhibitor 3-isobutyl-1-methylxanthine (IBMX) mimicked the effect of PGE1 on HF collagenase mRNA levels. PGE1 inhibits the biologic effects of BCP crystals through the cAMP signal transduction pathway and such inhibition may have significant therapeutic implications.

The mitogenic response to stimulation with basic calcium phosphate crystals is accompanied by induction and secretion of collagenase in human fibroblasts

Synovial fluid basic calcium phosphate (BCP) crystals are associated with severe destructive arthropathies that are characterized by synovial proliferation and digestion of articular collagenous structures. BCP crystals are potent mitogens, which may account for this proliferation. The role of collagenase in articular degradation is controversial because, despite the massive loss of collagen, no studies have confirmed collagenolytic activity in synovial fluid, as originally reported. We investigated collagenase messenger RNA induction and enzyme activity in human foreskin fibroblasts proliferating in response to stimulation with BCP crystals, and analyzed the associated secreted proteins. Northern blots revealed a dose-dependent accumulation of collagenase message, evident by 4 hours and continuing to at least 36 hours, in BCP-stimulated cultures. One- and 2-dimensional polyacrylamide gel electrophoresis of conditioned media from BCP crystal-stimulated cultures revealed the selective induction of 2 proteins with molecular weight and pI values consistent with those of collagenase. Increased enzyme activity was also found. Thus, the mitogenic response of fibroblasts to BCP crystals is accompanied by collagenase induction and secretion, supporting the hypothesis that they act as a mediator of joint destruction in BCP crystal-associated arthropathies.

Synovial fluid collagenase in patients with destructive arthritis of the shoulder joint

We studied synovial fluid (SF) collagenase in 10 women with severe rheumatoid arthritis (RA), 10 with pyrophosphate arthropathy, and 10 with idiopathic destructive disease of the shoulder conforming to a pattern recently described. SF cell counts were highest in the RA group. Particles were detected by polarized light microscopy and alizarin red staining. Crystals were seen in fluids from all 3 groups; pyrophosphate predominated in the pyrophosphate arthropathy group and alizarin red-positive particles in the idiopathic disease group. Collagenase and tissue inhibitor of metalloproteinase levels were estimated in SF after gel filtration. Tissue inhibitor of metalloproteinase activity was detected in all fluids, but tended to be highest in the RA group. Collagenase activity was detected in 3 RA fluids only. In no sample was collagenase found in an active form. These findings support the clinical concept of an aggressive destructive process which sometimes occurs in the shoulder joints of elderly women. Because we were not able to detect free collagenase in SF from any of the patients with idiopathic shoulder disease, the data suggest that high levels of active collagenase are not characteristic of this group of patients.

Rabbit synoviocyte inositol phospholipid metabolism is stimulated by hydroxyapatite crystals

Inhibition of prostaglandin E2 synthesis partially ameliorates some aspects of synovitis, but joint destruction still progresses. Other aspects of phospholipid metabolism may play a role in synovial tissue pathophysiology. Products of phosphatidylinositol metabolism can activate intracellular processes in response to extracellular stimuli. We asked whether this pathway is activated in synoviocytes in monolayer tissue culture by the addition of hydroxyapatite (HA) crystals in medium. These crystals are found in pathological human synovial fluid. These crystals are associated with the secretion of degradative enzymes and with a destructive arthritis in humans. Rabbit synoviocyte cultures, previously incubated with [3H]inositol to label inositol phospholipids, were stimulated with the addition of hydroxyapatite (180 micrograms/ml) to the cultures. There was enhanced intracellular accumulation of [3H]inositol monophosphate (30-100%) after 4 h. This indicated an increased phospholipase C activity. The radioactivity in [3H]inositol bis- and trisphosphates was too low to reliably measure. The use of [32P]Pi allowed detection of these compounds. In the presence of HA, incorporation of [32P]Pi into phosphatidylinositol, phosphatidylinositol monophosphate, and phosphatidylinositol bisphosphate was increased. In addition, cultures exposed to [32P]Pi during stimulation with HA had an increased content of [32P]inositol monophosphate, bisphosphate, and trisphosphate.

Bone resorbing activity in synovial fluids in destructive osteoarthritis and rheumatoid arthritis

The synovial fluids of patients with a destructive form of osteoarthritis (DOA) were shown to contain high levels of bone resorbing activity as judged by the ability of the fluid to stimulate the release of 45Ca from labelled cultured mouse calvariae. The activity was lost on extended storage of the synovial fluids and was dependent for its effect on cellular activity in bone. Bone resorbing activity was present in most synovial fluids from patients with DOA and rheumatoid arthritis (RA) but occurred at higher levels in the former. In contrast, interleukin 1 (IL1) activity, measured by the mouse thymocytes costimulation assay, was higher in RA than DOA synovial fluids. Little or no bone resorbing or IL1 activity was detected in synovial fluids from patients with pseudogout or non-destructive osteoarthritis. These results suggest that most DOA synovial fluids contain a bone resorbing factor other than IL1. It is considered that the factor may be produced by synovial cells stimulated by hydroxyapatite crystals.

Synovial fluid inorganic pyrophosphate concentration and nucleotide pyrophosphohydrolase activity in basic calcium phosphate deposition arthropathy and Milwaukee shoulder syndrome

Synovial fluid (SF) inorganic pyrophosphate (PPi) concentration is elevated in calcium pyrophosphate dihydrate (CPPD) crystal deposition arthropathy. Since CPPD and basic calcium phosphate (BCP) crystals often are present in the same joints, we determined [PPi] and activity of the PPi-generating enzyme, nucleotide pyrophosphohydrolase (NPPH), in SF from the joints of patients with various arthropathies, including those with BCP crystals. We found elevated SF [PPi] in joints with BCP crystals, as well as in joints with CPPD crystals. The presence of BCP crystals in synovial fluids was also predictive of elevated NPPH activity.

Mitogenic activity of hydroxyapatite: requirement for somatomedin C

Synovial hyperplasia is a feature of the chronic synovitis associated with basic calcium phosphate crystals [hydroxyapatite (HA), octacalcium phosphate, tricalcium phosphate] and calcium pyrophosphate. Each of these crystals stimulated mitosis of cultured human skin fibroblasts or canine synovial fibroblasts in a concentration-dependent fashion. We examined the effect of pure somatomedin C (Sm-C) on HA crystal induced mitogenesis. Confluent cultures of human fibroblasts were rendered quiescent by incubation in the presence of 1% platelet-poor-Sm-C free plasma (PPSCFP) for 24 hours. HA crystals stimulated thymidine incorporation 2.3-fold over control value. Addition of Sm-C significantly augmented the effect of HA crystals (P less than 0.01). Nearly identical effects were observed in the presence of 100 micrograms/ml HA crystals or 15 ng/ml PDGF. Monoclonal antibodies against Sm-C had little effect on the basal 3H thymidine uptake by control cells incubated in 1% PPSCFP but blocked over 50% of the HA crystal or PDGF-induced 3H thymidine incorporation both in the presence or absence of Sm-C. The incomplete blocking suggested either the presence of other "progression" factors, such as insulin-like growth factor II in the conditioned media or the possibility that HA or PDGF in high enough dosage enabled cells to escape their dependence on Sm-C for DNA synthesis.

Arthritis associated with crystals containing calcium

Varying combinations of acute inflammatory and/or chronic degenerative arthritis have been found to be associated with crystals of calcium pyrophosphate dihydrate (CPPD) and/or basic calcium phosphates (BCPs). Since the arthropathies associated with CPPDs and/or BCPs occur in older individuals, while diagnosis and treatment for monosodium urate monohydrate crystal deposition disease (gout) have become extremely precise and effective, joint problems associated with calcium crystals have become more common than those associated with monosodium urate monohydrate crystals. The classification, pathogenesis, clinical manifestations, and treatment of CPPD and BCP crystal deposition are discussed.