Abnormalities of respiratory gases in synovial fluid of patients with juvenile rheumatoid arthritis

pH-responsive size-adjustable liposomes induce apoptosis of fibroblasts and macrophages for rheumatoid arthritis treatment

In rheumatoid arthritis (RA), macrophages infiltrate joints, while fibroblast-like synovial cells proliferate abnormally, forming a barrier against drug delivery, which hinders effective drug delivery to joint focus. Here we firstly designed a pH-responsive size-adjustable nanoparticle, composed by methotrexate (MTX)-human serum albumin (HSA) complex coating with pH-responsive liposome (Lipo/MTX-HSA) for delivering drugs specifically to inflamed joints in acidic environments. We showed in vitro that the nanoparticles can induce mitochondrial dysfunction, promote apoptosis of fibroblast-like synoviocytes and macrophages, further reduce the secretion of inflammatory factors (TNF-α, IL-1β, MMP-9), and regulate the inflammatory microenvironment. We also demonstrated similar effects in a rat model of arthritis, in which Lipo/MTX-HSA accumulated in arthritic joints, and at low pH, liposome phospholipid bilayer cleavage released small-sized MTX-HSA, which effectively reduced the number of fibroblast-synoviocytes and macrophages in joints, alleviated joint inflammation, and repaired bone erosion. These findings suggest that microenvironment-responsive size-adjustable nanoparticles show promise as a treatment against rheumatoid arthritis. STATEMENT OF SIGNIFICANCE: Abnormal proliferation of fibroblast synoviocytes poses a physical barrier to effective nanoparticle delivery. We designed size-adjustable nano-delivery systems by preparing liposomes with cholesterol hemisuccinate (CHEM), which were subsequently loaded with small-sized albumin nanoparticles encapsulating the cytotoxic drug MTX (MTX-HSA), termed Lipo/MTX-HSA. Upon tail vein injection, Lipo/MTX-HSA could be aggregated at the site of inflammation via the ELVIS effect in the inflamed joint microenvironment. Specifically, intracellular acidic pH-triggered dissociation of liposomes promoted the release of MTX-HSA, which was further targeted to fibroblasts or across fibroblasts to macrophages to exert anti-inflammatory effects. The results showed that liposomes with adjustable particle size achieved efficient drug delivery, penetration and retention in joint sites; the strategy exerted significant anti-inflammatory effects in the treatment of rheumatoid arthritis by inducing mitochondrial dysfunction to promote apoptosis in fibrosynoviocytes and macrophages.

Current status and prospects of metal-organic frameworks for bone therapy and bone repair

With the development of society, traumatic bone defects caused by accidents, diseases and surgeries have become common, eventually resulting in an increase in bone defects. The treatment of bone defects is characterized by a long period of treatment, high cost and uncontrollable outcomes. Also, it results in complications such as infection and bone discontinuity. Hence, due to this situation, the physical, mental and financial aspects of the patient are severely affected. What's more, such outcomes pose a challenge to orthopaedic surgeons. As a result, bone therapy and bone repair have become a hot topic of interest. In repairing bone defects, materials other than autogenous bone are still unable to provide good biocompatibility, osteogenesis, osteoconductivity and osteoinduction properties at the same time. In addition, the scarcity of autologous bone sources has forced the search for new autologous bone replacement materials. Metal organic frameworks (MOFs) are a new class of developed functional materials that have been widely used in the biomedical field during the recent years due to their porous nature, large specific surface area and diverse structures. With the progress in the investigation into bone treatment and repair, more and more investigators are using MOFs in bone therapy and bone repair. With these viewpoints, in the present perspective, the use of MOFs in bone therapy and bone repair has been summarized, and an insight into the future of MOFs in bone therapy and bone repair has been provided.

Recent Advances in Nano-Therapeutic Strategies for Osteoarthritis

Osteoarthritis (OA) is the most common type of arthritis and the leading cause of disability globally. It tends to occur in middle age or due to an injury or obesity. OA occurs with the onset of symptoms, including joint swelling, joint effusion, and limited movement at a late stage of the disease, which leads to teratogenesis and loss of joint function. During the pathogenesis of this degenerative joint lesion, several local inflammatory responses are activated, resulting in synovial proliferation and pannus formation that facilitates the destruction of the bone and the articular cartilage. The commonly used drugs for the clinical diagnosis and treatment of OA have limitations such as low bioavailability, short half-life, poor targeting, and high systemic toxicity. With the application of nanomaterials and intelligent nanomedicines, novel nanotherapeutic strategies have shown more specific targeting, prolonged half-life, refined bioavailability, and reduced systemic toxicity, compared to the existing medications. In this review, we summarized the recent advancements in new nanotherapeutic strategies for OA and provided suggestions for improving the treatment of OA.

Tripterine and all-trans retinoic acid (ATRA) - loaded lipid-polymer hybrid nanoparticles for synergistic anti-arthritic therapy against inflammatory arthritis

Arthritis of joints remains a hard-to-treat disease due to the low drug exposure to the articular cavity. Present study was intended to develop a Tripterine (TRI) and all-trans retinoic acid (ATRA)-loaded lipid-polymer hybrid nanoparticles (ATLP) for enhanced antiarthritic efficacy in arthritis conditions. We have showed that two drugs could be loaded with high loading capacity and control the release kinetics in a pH-responsive manner. The ATLP showed strong inhibitory effects on the expressions of TNF-α, IL-6 and IL-1β in lipopolysaccharide (LPS)-stimulated RAW264.7 cells at the in vitro conditions. Compared to individual drugs (TRI and ATRA), ATLP significantly reduced the paw thickness exhibiting potent inhibition of inflammation. Consistently, ATLP resulted in lowest clinical score compared to that of individual drug indicating the remarkable improvement in the recession of inflammation. We have clearly demonstrated that the nanoparticulate based co-delivery of drugs could abolish the adverse effects of free drug as indicated by the body weight changes. Importantly, ATLP resulted in significant reduction of mRNA of TNF-α, IL-6, IFN-ϒ and IL-17 compared to either free drugs or CIA mice. Overall, ATLP represent a promising therapeutic strategy for the treatment of arthritis conditions.

A pH-responsive mesoporous silica nanoparticles-based drug delivery system with controlled release of andrographolide for OA treatment

Andrographolide (AG) has favorable anti-inflammatory and antioxidative capacity. However, it has low bioavailability due to high lipophilicity and can be easily cleared by the synovial fluid after intra-articular injection, leading to low therapeutic efficiency in osteoarthritis (OA). Herein, we designed a nano-sized pH-responsive drug delivery system (DDS) for OA treatment by using modified mesoporous silica nanoparticles (MSNs) with pH-responsive polyacrylic acid (PAA) for loading of AG to form AG@MSNs-PAA nanoplatform. The nanoparticles have uniform size (∼120 nm), high drug loading efficiency (22.38 ± 0.71%) and pH-responsive properties, beneficial to sustained release in OA environment. Compared with AG, AG@MSNs-PAA showed enhanced antiarthritic efficacy and chondro-protective capacity based on IL-1β-stimulated chondrocytes and anterior cruciate ligament transection-induced rat OA model, as demonstrated by lower expression of inflammatory factors and better prevention of proteoglycan loss. Therefore, the AG@MSNs-PAA nanoplatform may be developed as a promising OA-specific and on-demand DDS.

pH-responsive and hyaluronic acid-functionalized metal-organic frameworks for therapy of osteoarthritis

Drug therapy of osteoarthritis (OA) is limited by the short retention and lacking of stimulus-responsiveness after intra-articular (IA) injection. The weak acid microenvironment in joint provides a potential trigger for controlled drug release systems in the treatment of OA. Herein, we developed an pH-responsive metal − organic frameworks (MOFs) system modified by hyaluronic acid (HA) and loaded with an anti-inflammatory protocatechuic acid (PCA), designated as MOF@HA@PCA, for the therapy of OA. Results demonstrated that MOF@HA@PCA could smartly respond to acidic conditions in OA microenvironment and gradually release PCA, which could remarkably reduce synovial inflammation in both IL-1β induced chondrocytes and the OA joints. MOF@HA@PCA also down-regulated the expression of inflammatory markers of OA and promoted the expression of cartilage-specific makers. This work may provide a new insight for the design of efficient nanoprobes for precision theranostics of OA.

Cartilage-targeting and dual MMP-13/pH responsive theranostic nanoprobes for osteoarthritis imaging and precision therapy

Osteoarthritis (OA) microenvironment is marked by matrix metalloproteinases-13 (MMP-13) overexpression and weak acidity, making it possible to develop dual-stimuli responsive theranostic nanoprobes for OA diagnosis and therapy. However, current MMP/pH-responsive systems are not suitable for OA because of their poor biocompatibility, poor degradation and non-cartilage-targeting of the responsive probes. Here we designed a novel biocompatible cartilage-targeting and MMP-13/pH-responsive ferritin nanocages (CMFn) loaded with an anti-inflammatory drug (Hydroxychloroquine, HCQ), termed CMFn@HCQ, for OA imaging and therapy. We found that CMFn could be smartly "turned on" to emit light for OA imaging in response to the level of overexpressed MMP-13 in OA microenvironment, corresponding to the degree of OA severity. Thus the light intensity detected reflected the degree of OA severity, enabling the precise disease classification by our CMFn. CMFn could be "turned off" to stop emitting light in the normal joint. CMFn@HCQ nanocages could target the cartilage and release HCQ in the OA joint specifically under acidic pH conditions in a sustained manner, prolonging the drug retention time to 14 days to remarkably reduce synovial inflammation in the OA joints. The CMFn@HCQ nanocages represent a smart dual-stimuli responsive and cartilage-targeting nanoprobes, and hold promise for imaging-guided precision therapy for OA.

Novel dexamethasone-HPMA copolymer conjugate and its potential application in treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease of unknown etiology. Effective treatment of this disorder has been hampered by the lack of availability of agents that selectively target affected joint tissue. We developed a novel pH-sensitive drug delivery system of dexamethasone (Dex) based on an N-(2-hydroxypropyl)methacrylamide copolymer (P-Dex) and have shown that the delivery system specifically accumulates in inflamed joints in an animal model of arthritis. We hypothesize that the arthrotropism of the delivery system and the local acidosis-mediated drug release provide superior therapeutic efficacy and potentially reduced side effects in RA treatment. The initial in vitro drug-release study confirmed that the Dex release is indeed dependent upon the environmental pH. At pH 5, 37°C, the conjugate shows the highest level of drug release. When administered systemically in an adjuvant-induced arthritis rat model, P-Dex offers superior and longer-lasting anti-inflammatory effects compared with systemically administered free Dex. In addition, greater bone and cartilage preservation was observed with the P-Dex treatment compared with free Dex treatment. Our data indicate that the differential effect of the conjugate is related to its selective accumulation, potential macrophage-mediated retention, and pH-sensitive drug release (extracellular and intracellular) in arthritic joints. This newly developed drug delivery system provides a unique method for selective targeting of glucocorticoids to inflamed joints which may potentially reduce systemic side effects.

Direct assessment of synovial blood flow and its relation to induced hydrostatic pressure changes

A method for measuring synovial blood flow changes using the laser Doppler technique is described. Mean blood flow and mean pulse amplitude decreased by 50-70% in relation to the reference level when the intra-articular hydrostatic pressure in effusive knee joints of patients with rheumatoid arthritis was increased. As an increase of intra-articular pressure of as little as 20 mmHg decreased synovial blood flow significantly it is suggested that hypoxia may occur in vivo during joint use in the presence of an effusion. This may be of aetiopathogenetic importance for tissue destruction and the persistence of chronic synovitis.

Measurement of oxygen and carbon dioxide partial pressures in synovial fluid after tonometry

A commercially available gas analyser was used to measure tension of oxygen (PO2) and carbon dioxide (PCO2) in synovial fluid samples after tonometry. Measured values of PCO2 were close to the expected (median difference 0.2 kPa, range -0.4 to 0.4) within the analysed concentration range of 4-10 kPa. No consistent difference between measured and expected values of PO2 were found for oxygen in the range 3-11 kPa (median difference 0.1 kPa, range -0.3 to 1.2). For oxygen tensions below 3 kPa, however, the measured values invariably overestimated the actual PO2, the errors ranging from 0.3 to 1.9 kPa, median 1.1. The importance of proper handling of samples was investigated and storage for 1 h at 0 degrees C in plastic syringes resulted in elevation of the PO2 levels measured (range of elevation 0.2 to 3.6 kPa, median 1.15), whilst no significant differences were found when stored in glass syringes. Within the limits stated, commercially available gas analysers may thus be used to investigate these parameters related to local tissue metabolism in effusive joint conditions.

A hypothesis on the pathogenesis of rheumatoid and other non-specific synovitides. IV A. The possible intermediate role of local hypoxia and metabolic alterations

According to the original hypothesis, synovial tissue (ST) oedema and synovial fluid (SF) volume increase contribute to local hypoxia and metabolic alterations and to inflammation (A 1). Studies on biochemical mechanisms (A 2) in synovitides show that the SF volume correlates to SF hypoxia that correlates to lactate increase, acidosis and to some decrease in glucose. Normal ST produces lactate by glycolytic and pentose phosphate pathway activity, both, as well as the normally low oxygen utilization, being increased in synovitides . In ST very little carbohydrate seems to pass directly into the citric acid cycle and oxidation of fat may be involved, but it is not known if the fat is carried to ST by the blood or if it is synthetized locally (B). ST oedema and effusions may be most important as causes of local hypoxia (C). Acidosis alters physico-chemical properties of proteins, possibly changing their chemotactic and antigenic qualities, etc. Hypoxia and fuel supply might be related to fibroblast, macrophage and neutrophil reactions, and, in view of the high metabolic demands of villi, they may contribute to, e.g., ST necroses, and to erosions (D). I shall summarize some essentials of my present views on the pathogenesis (E 1 a) and causes in single cases (E 3 b) of synovitis, and comment on two other new hypotheses on rheumatoid arthritis (E 2) and on therapeutic (E 4) and other implications of this concept (E).

Synovial fluid lactic acid in septic and nonseptic arthritis

We determined lactic acid levels by the lactic dehydrogenase method in synovial fluid of 41 patients with various rheumatic diseases, to test the concept that significantly elevated values were diagnostic of septic arthritis. Nine patients had septic arthritis, 15 rheumatoid arthritis (RA), and the remainder miscellaneous conditions. In another 9 patients with different rheumatic diseases, including 1 with septic arthritis, synovial fluid lactic acid was determined by both the lactic dehydrogenase and gas-liquid chromatography methods. There was a wide scatter of values among patients with septic and nonseptic inflammatory arthritis, and much overlap occurred. We could not differentiate septic arthritis from RA on the basis of synovial fluid lactic acid levels. Results were similar with both procedures for determining lactic acid levels.

Synovial fluid lactic acid. A diagnostic aid in septic arthritis

Lactic acid concentrations in the synovial fluid of 84 patients with acute monoarticular arthritis were determined by gas liquid chromatography. Lactic acid values in 27 cases of nongonococcal septic arthritis were strikingly higher (mean 1170 mg/100ml) than in 45 cases of inflammatory or degenerative arthritis (mean 34 mg/100 ml), as well as in 12 cases of gonococcal arthritis (mean 27 mg/100 ml). With the proper equipment, determination of lactic acid can be a relatively rapid, reliable procedure. Synovial fluid lactic acid concentrations therefore can be used as a rapid, supplemental diagnostic aid in differentiating nongonococcal septic arthritis from both gonococcal and nonseptic acute arthritis.

Postoperative synovial fluid. Metabolic response to meniscectomy or synovectomy

The metabolic response of synovial tissue to surgery was investigated by synovial fluid analysis after two types of operations, medial meniscectomy and synovectomy. Analyses of intra-articular fluid were also performed in non-operated patients with traumatic effusion or chronic synovitis in the knee. It was found that the knee joint metabolism in chronic synovitis is shifted towards anaerobic glycolysis in both operated and non-operated patients whereas meniscectomized and traumatized knees are more capable of maintaining oxidative metabolism. The data also demonstrate that one of the main reasons for decreased oxygen supply on the articular surface after meniscectomies or synovectomies is excessive intra-articular effusion which, according to earlier investigations, produces pressure in the joint cavity and inhibits local capillary circulation.

Intraarticular activation of the complement system in patients with juvenile rheumatoid arthritis

Analyses of CH50, complement components, properdin factors, and kininogen in synovial fluid of patients with juvenile rheumatoid arthritis revealed evidence of activation of the classic complement pathway in all clinical subgroups. Juveniles with the adult pattern of disease had the greatest incidence of complement abnormalities. Evaluation of individual components by both activity determination and protein measurement showed decreased synovial fluid specific functional activity (activity per microgram protein) to the more marked in synovial fluids with profound depressions of complement activity. These findings provide further evidence that nonfunctional, antigenically intact component protein may remain after complement activation. Radial immunodiffusion measurements of properdin factors and kininogen failed to support their involvement in joint inflammation. Serum complement component measurements by activity but not protein concentration correlated with other parameters or inflammation. Four patients had isolated depressions of serum C2 activity. Immunoglobulin levels, particularly IgA, correlated with some complement measurements and with the sedimentation rate.