Calcitonin attenuates cartilage degeneration and nociception in an experimental rat model of osteoarthritis: role of TGF-β in chondrocytes

Intra-Articular Lactate Dehydrogenase A Inhibitor Oxamate Reduces Experimental Osteoarthritis and Nociception in Rats via Possible Alteration of Glycolysis-Related Protein Expression in Cartilage Tissue

Osteoarthritis (OA) is the most common form of arthritis and joint disorder worldwide. Metabolic reprogramming of osteoarthritic chondrocytes from oxidative phosphorylation to glycolysis results in the accumulation of lactate from glycolytic metabolite pyruvate by lactate dehydrogenase A (LDHA), leading to cartilage degeneration. In the present study, we investigated the protective effects of the intra-articular administration of oxamate (LDHA inhibitor) against OA development and glycolysis-related protein expression in experimental OA rats. The animals were randomly allocated into four groups: Sham, anterior cruciate ligament transection (ACLT), ACLT + oxamate (0.25 and 2.5 mg/kg). Oxamate-treated groups received an intra-articular injection of oxamate once a week for 5 weeks. Intra-articular oxamate significantly reduced the weight-bearing defects and knee width in ACLT rats. Histopathological analyses showed that oxamate caused significantly less cartilage degeneration in the ACLT rats. Oxamate exerts hypertrophic effects in articular cartilage chondrocytes by inhibiting glucose transporter 1, glucose transporter 3, hexokinase II, pyruvate kinase M2, pyruvate dehydrogenase kinases 1 and 2, pyruvate dehydrogenase kinase 2, and LHDA. Further analysis revealed that oxamate significantly reduced chondrocyte apoptosis in articular cartilage. Oxamate attenuates nociception, inflammation, cartilage degradation, and chondrocyte apoptosis and possibly attenuates glycolysis-related protein expression in ACLT-induced OA rats. The present findings will facilitate future research on LDHA inhibitors in prevention strategies for OA progression.

Bone marrow lesions in osteoarthritis: From basic science to clinical implications

Osteoarthritis (OA) is the most prevalent musculoskeletal disease characterized by multiple joint structure damages, including articular cartilage, subchondral bone and synovium, resulting in disability and economic burden. Bone marrow lesions (BMLs) are common and important magnetic resonance imaging (MRI) features in OA patients. Basic and clinical research on subchondral BMLs in the pathogenesis of OA has been a hotspot. New evidence shows that subchondral bone degeneration, including BML and angiogenesis, occurs not only at or after cartilage degeneration, but even earlier than cartilage degeneration. Although BMLs are recognized as important biomarkers for OA, their exact roles in the pathogenesis of OA are still unclear, and disputes about the clinical impact and treatment of BMLs remain. This review summarizes the current basic and clinical research progress of BMLs. We particularly focus on molecular pathways, cellular abnormalities and microenvironmental changes of subchondral bone that contributed to the formation of BMLs, and emphasize the crosstalk between subchondral bone and cartilage in OA development. Finally, potential therapeutic strategies targeting BMLs in OA are discussed, which provides novel strategies for OA treatment.

Inactivation of the gene encoding procalcitonin prevents antibody-mediated arthritis

BACKGROUND

Procalcitonin (PCT) is applied as a sensitive biomarker to exclude bacterial infections in patients with rheumatoid arthritis (RA) flare-ups. Beyond its diagnostic value, little is known about the pathophysiological role of PCT in RA.

METHODS

Collagen antibody-induced arthritis (CAIA) was induced in Calca-deficient mice (Calca^-/-), lacking PCT (n = 15), and wild-type (WT) mice (n = 13), while control (CTRL) animals (n = 8 for each genotype) received phosphate-buffered saline. Arthritis severity and grip strength were assessed daily for 10 or 48 days. Articular inflammation, cartilage degradation, and bone lesions were assessed by histology, gene expression analysis, and µ-computed tomography.

RESULTS

Serum PCT levels and intra-articular PCT expression increased following CAIA induction. While WT animals developed a full arthritic phenotype, Calca-deficient mice were protected from clinical and histological signs of arthritis and grip strength was preserved. Cartilage turnover markers and Tnfa were exclusively elevated in WT mice. Calca-deficient animals expressed increased levels of Il1b. Decreased bone surface and increased subchondral bone porosity were observed in WT mice, while Calca-deficiency preserved bone integrity.

CONCLUSION

The inactivation of Calca and thereby PCT provided full protection from joint inflammation and arthritic bone loss in mice exposed to CAIA. Together with our previous findings on the pathophysiological function of Calca-derived peptides, these data indicate an independent pro-inflammatory role of PCT in RA.

Efficacy of Intramuscular Injection of Calcitonin on Pain Functional Status of Patients with Knee Osteoarthritis

Background

Recently, increased attention has been paid to calcitonin for the management of osteoarthritis (OA) regarding its metabolic properties for bone turnover and cartilage.

Objectives

This study was designed to assess the efficacy of intramuscular calcitonin injection in the functional status of individuals suffering from knee OA.

Methods

A total of 40 eligible cases with OA were randomly assigned into intervention and control groups. At baseline, pain intensity and functional ability were evaluated based on the Numeric Rating scale (NRS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaires. Both groups were prescribed with AcetaGel (500 mg) and piroxicam (0.5% topical gel) every 8 hours as needed, and the patients were instructed about conservative treatments and lifestyle modifications. In the case group, the patients received calcitonin (50 IU/mL solution for injection; Aburaihan Pharmaceutical Co., Iran) intramuscularly (gluteal muscle) once a week for 4 consecutive weeks. One month after the last dose, the patients were evaluated based on NRS and WOMAC questionnaires.

Results

Demographic data did not show any statistically significant difference. A total of 40 cases (male and female) with mean age values of 53.10 ± 5.28 and 54.55 ± 5.26 years were included in the case and control groups, respectively. The mean body mass index values of the case and control groups were 27.45 ± 1.57 and 27.15 ± 1.53 kg/m2, respectively. After 1 month of treatment with calcitonin, significant improvements were observed in NRS outcomes (P < 0.001). The total WOMAC score was also statistically improved (P < 0.001).

Conclusions

The findings of the present study revealed that the weekly administration of 50 IU calcitonin for 28 days could significantly improve physical ability and pain intensity in OA patients.

Protective effects of equol on the cartilage and subchondral bone in ovariectomized rats with osteoarthritis

Objectives

This study aimed to determine the therapeutic effect of equol (EQ) on osteoporotic osteoarthritis (OP OA).

Materials and Methods

Thirty-six 12-week-old female Sprague-Dawley rats were randomly divided into sham group, OP OA group, and EQ group (n=12). OP OA was induced by anterior cruciate ligament transection (ACLT) combined with ovariectomy (OVX). EQ was orally administrated (10 μg/g/day) after the operation for 12 weeks. The efficacy was evaluated by gross pathology and histopathologic evaluation. The underlying mechanism was investigated by immunohistochemical analysis, micro-computed tomography (micro-CT) scanning, and tartrate-resistant acid phosphatase (TRAP) staining.

Results

EQ effectively retarded cartilage degeneration, decreased the levels of matrix metalloproteinases-13 (MMP-13), a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5), nuclear factor-kappa B P65 (NF-κB P65) and caspase-3, and increased the levels of collagen type II (Col-II), Col-I, aggrecan (AGG), and inhibitor of NF-κB α (IκBα) in the cartilage. In addition, EQ increased bone mineral density, improved the microstructural parameters of the subchondral bone (SB), and decreased the number of osteoclasts.

Conclusion

EQ exerted a chondroprotective effect on OP OA in rats, associated with inhibition of the NF-κB signaling pathway and chondrocyte apoptosis. Furthermore, EQ showed an osteoprotective effect on SB via inhibiting osteoclastic activities.

Assessment of osteoarthritis functional outcomes and intra-articular injection volume in the rat anterior cruciate ligament transection model

The rat surgical anterior cruciate ligament transection (ACLT) model is commonly used to investigate intra-articular osteoarthritis (OA) therapies, and histological assessment is often the primary outcome measure. However, histological changes do not always correlate well with clinical outcomes. Therefore, this study evaluated functional outcomes in the rat surgical ACLT model and compared intra-articular injection volumes ranging from 20 to 50 μl. Unilateral ACLT was surgically induced and static weight-bearing, mechanical allodynia, motor function, and gait were assessed in four groups of male, Sprague-Dawley rats (n = 6 per group). Intra-articular injections of 20 µl Dulbecco's phosphate-buffered saline (DPBS), 50 µl DPBS, or 50 µl of synthetic biomimetic boundary lubricant were administered once weekly for 3 weeks postoperatively. Structural changes were evaluated histologically at 20 weeks. Rat cadaver knees were injected with 20, 30, 40, or 50 µl of gadolinium solutions and were imaged using magnetic resonance imaging (MRI). Static weight-bearing, mechanical allodynia, and gait parameters in ACLT groups revealed differences from baseline and naïve controls for 4 weeks post-ACLT; however, these differences did not persist beyond 6 weeks. Different intra-articular DPBS injection volumes did not result in functional or histological changes; however, peri-articular leakage was documented via MRI following 50, 40, and 30 µl but not 20 µl gadolinium injections. Statement of clinical significance: Differences in functional parameters were predominantly restricted to early, postoperative changes in the rat surgical ACLT model despite evidence of moderate histologic OA at 20 weeks. Injection volumes of 20-30 µl are more appropriate for investigating intra-articular therapies in the rat knee.

Ketogenic diet ameliorates inflammation by inhibiting the NLRP3 inflammasome in osteoarthritis

BACKGROUND

The nucleotide-binding domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome has been reported to be involved in the pathological process of osteoarthritis (OA) inflammation. Here, we investigated the ketogenic diet (KD), which has been previously demonstrated to inhibit NLRP3 inflammasome activation, to elucidate its protective mechanism against OA in rats.

METHODS

Anterior cruciate ligament transaction (ACLT) together with partial medial meniscectomy was used to create a rat knee joint OA model. After treatment with KD or standard diet (SD) for 8 weeks, the knee specimens were obtained for testing.

RESULTS

The KD significantly increased the content of β-hydroxybutyrate (βOHB) in rats. Compared to the SD group, the KD significantly reduced the damage caused by OA in the articular cartilage and subchondral bone. The NLRP3 inflammasome and inflammatory cytokines interleukin-1 β (IL-1β) and IL-18 were significantly increased in the SD group compared with the sham group, while their expression was significantly decreased in rats treated with the KD. In addition, MMP13 was significantly decreased in the KD group compared to that in the SD group, while COL2 was significantly increased.

CONCLUSIONS

KD can protect the articular cartilage and subchondral bone in a rat OA model by inhibiting NLRP3 inflammasome activation and reducing the OA inflammatory response.

The calcitonin receptor protects against bone loss and excessive inflammation in collagen antibody-induced arthritis

Pharmacological application of teleost calcitonin (CT) has been shown to exert chondroprotective and anti-resorptive effects in patients with rheumatoid arthritis (RA). However, the role of endogenous CT that signals through the calcitonin receptor (CTR) remains elusive. Collagen II antibody-induced arthritis (CAIA) was stimulated in wild type (WT) and CTR-deficient (Calcr^−/−) mice. Animals were monitored over 10 or 48 days. Joint inflammation, cartilage degradation, and bone erosions were assessed by clinical arthritis score, histology, histomorphometry, gene expression analysis, and μ-computed tomography. CAIA was accompanied by elevated systemic CT levels and CTR expression in the articular cartilage. Inflammation, cartilage degradation, and systemic bone loss were more pronounced in Calcr^−/− CAIA mice. Expression of various pro-inflammatory, bone resorption, and catabolic cartilage markers were exclusively increased in Calcr^−/− CAIA mice. Endogenous CT signaling through the mammalian CTR has the potential to protect against joint inflammation, cartilage degradation, and excessive bone remodeling in experimental RA.

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CT levels are increased systemically during acute experimental RA

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CTR is primarily expressed in the superficial articular cartilage layer in CAIA

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In CAIA CTR-deficiency is associated with increased inflammation marker expression

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Bone architecture is impaired in experimental RA when CTR signaling is disrupted

Dcx expression defines a subpopulation of Gdf5 + cells with chondrogenic potentials in E12.5 mouse embryonic limbs

Growth differentiation factor 5 (Gdf5) and doublecortin (Dcx) genes are both expressed in joint interzone cells during synovial joint development. In this study, we re-analyzed the single cell RNA-sequencing data (Gene Expression Omnibus GSE151985) generated from Gdf5 ⁺ cells of mouse knee joints at embryonic stages of E12.5, E13.5, E14.5, and E15.5, with a new focus on Dcx. We found that Dcx expression was enriched in clusters of Gdf5 ⁺ cells, with high expression levels of pro-chondrogenic genes including sex determining region Y-box transcription factor 5 (Sox5), Sox6, Sox9, Gdf5, versican, matrilin 4, collagen type II α 1 chain (Col2a1), Col9a1, Col9a2, and Col9a3 at E12.5. Dcx ⁺ and Dcx ^- cells had differential gene expression profiles. The up-regulated genes in Dcx ⁺ vs. Dcx ^- cells at E12.5 and E13.5 were enriched in chondrocyte differentiation and cartilage development, whereas those genes up-regulated at E14.5 and E15.5 were enriched in RNA splicing, protein stability, cell proliferation, and cell growth. Gene expression profiles in Dcx ⁺ cells showed rapid daily changes from E12.5 to E15.5, with limited number of genes shared across the time period. Expression of Gdf5, Sox5, Sox6, melanoma inhibitory activity, noggin, odd-skipped related transcription factor 2, matrilin 4, and versican was positively correlated with Dcx expression. Our results demonstrate that Dcx expression defines a subpopulation of Gdf5 ⁺ cells with chondrogenic potentials in E12.5 mouse embryonic limbs.

Intra-articular treatment with hyaluronic acid associated with gold nanoparticles in a mechanical osteoarthritis model in Wistar rats

This study aimed to evaluate the effects of intra-articular treatment with hyaluronic acid (HA) associated with GNPs in a mechanical model of osteoarthritis induced by median meniscectomy (MM). Fifty Wistar rats (2 months weighing between 250 and 300 g) were used, divided into five groups of 10 animals each: Sham, osteoarthritis (OA), OA + HA, OA + gold nanoparticles (GNPs), and OA + HA + GNPs. Intra-articular treatment was started 30 days after the model was induced, with a frequency of 2 weeks for 60 days. Fifteen days after the last application, the animals were euthanized with the removal of the joint tissue for biochemical and histological analysis. The model used was able to mimic osteoarthritis, characterized by the presence of high levels of proinflammatory cytokines, oxidative stress, and degeneration of joint surfaces (Grade III, according to SCORE OARSI). The isolated use of HA or GNPs provided beneficial results to the joint; however, only the group subjected to the association between HA and GNPs showed the attenuation of oxidative stress and reduced proinflammatory markers, with a simultaneous increase in levels of anti-inflammatory cytokines and growth factors. Upon histological analysis, only the OA + HA + GNPs group achieved the restoration of the thickness of the joint cartilage with reduced damage and return to the intact joint surface. The results found demonstrated that the association of GNPs with HA was able to reverse the deleterious effects caused by the model by inhibiting the progressive degeneration of joint surfaces, representing a promising treatment for osteoarthritis.

Spatiotemporally controlled calcitonin delivery: Long-term and targeted therapy of skeletal diseases

Bone is a connective tissue that support the entire body and protect the internal organs. However, there are great challenges on curing intractable skeletal diseases such as hypercalcemia, osteoporosis and osteoarthritis. To address these issues, calcitonin (CT) therapy is an effective treatment alternative to regulate calcium metabolism and suppress inflammation response, which are closely related to skeletal diseases. Traditional calcitonin formulation requires frequent administration due to the low bioavailability resulting from the short half-life and abundant calcitonin receptors distributed through the whole body. Therefore, long-term and targeted calcitonin delivery systems (LCDS and TCDS) have been widely explored as the popular strategies to overcome the intrinsic limitations of calcitonin and improve the functions of calcium management and inflammation inhibition in recent years. In this review, we first explain the physiological effects of calcitonin on bone remodeling: (i) inhibitory effects on osteoclasts and (ii) facilitated effects on osteoblasts. Then we summarized four strategies for spatiotemporally controlled delivery of calcitonin: micro-/nanomedicine (e.g. inorganic micro-/nanomedicine, polymeric micro-/nanomedicine and supramolecular assemblies), hydrogels (especially thermosensitive hydrogels), prodrug (PEGylation and targeting design) and hybrid biomaterials. Subsequently, we discussed the application of LCDS and TCDS in treating hypercalcemia, osteoporosis, and arthritis. Understanding and analyzing these advanced calcitonin delivery applications are essential for future development of calcitonin therapies toward skeletal diseases with superior efficacy in clinic.

PARP-1 inhibition attenuates the inflammatory response in the cartilage of a rat model of osteoarthritis

Aims

Poly (ADP-ribose) polymerase (PARP) inhibitor has been reported to attenuate inflammatory response in rat models of inflammation. This study was designed to investigate the effect of PARP signalling in osteoarthritis (OA) cartilage inflammatory response in an OA rat model.

Methods

The OA model was established by anterior cruciate ligament transection with medial meniscectomy in Wistar rats. The poly (ADP-ribose) polymerase 1 (PARP-1) shRNA (short hairpin (sh)-PARP-1) and negative control shRNA (sh-NC) were delivered using a lentiviral vector and were intra-articularly injected into rats after surgery. The weight-bearing distribution of the hind limbs and the knee joint width were measured every two weeks. The expression levels of PARP-1, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) in cartilage were determined using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot. The serum concentrations of inflammatory cytokines were detected using enzyme-linked immunosorbent assay (ELISA).

Results

PARP-1 expression level significantly increased in the cartilage of the established OA rat model. sh-PARP-1 treatment suppressed PARP-1 levels, decreased the Δ Force (the difference between the weight on ipsilateral limb and contralateral limb) and the knee joint width, inhibited cartilage matrix catabolic enzymes, and ameliorated OA cartilage degradation and attenuated inflammatory response.

Conclusion

PARP-1 inhibition attenuates OA cartilage inflammatory response in the OA rat model.

Cite this article: Bone Joint Res 2021;10(7):401–410.

Raloxifene inhibits the overexpression of TGF-β1 in cartilage and regulates the metabolism of subchondral bone in rats with osteoporotic osteoarthritis

Overexpression of transforming growth factor-beta 1 (TGF-β1) and subchondral bone remodelling play key roles in osteoarthritis (OA). Raloxifene (RAL) reduces the serum level of TGF-β1 in postmenopausal women. However, the effect of RAL on TGF-β1 expression in articular cartilage is still unclear. Therefore, we aimed to investigate the protective effect of RAL on osteoporotic osteoarthritis via affecting TGF-β1 expression in cartilage and the metabolism of subchondral bone. Osteoporotic osteoarthritis was induced by a combination of anterior cruciate transection (ACLT) and ovariectomy (OVX). Rats were divided into five groups (n = 12): The sham group, the ACLT group, the OVX group, the ACLT + OVX group, and the RAL group (ACLT + OVX + RAL, 6.25 mg/kg/day for 12 weeks). Assessment was performed by histomorphology, microcomputed tomography (micro-CT) scan, immunohistochemistry, and tartrate-resistant acid phosphatase (TRAP) staining. We found that severe cartilage degeneration was shown in the ACLT + OVX group. The histomorphological scores, the levels of TGF-β1, and its related catabolic enzymes and osteoclasts numbers in the ACLT + OVX group were higher than those in other groups (p < 0.05). Furthermore, structure model index (SMI) and trabecular spacing (Tb.Sp) were decreased (p < 0.05), while bone mineral density (BMD), bone volume fraction (BV/TV), and trabecular number (Tb.N) were increased by RAL compared with the ACLT + OVX group (p < 0.05). Our findings demonstrated that RAL in clinical doses retards the development of osteoporotic osteoarthritis by inhibiting the overexpression of TGF-β1 in cartilage and regulating the metabolism of subchondral bone. These results provide support for RAL in the expansion of clinical indication for prevention and treatment in postmenopausal osteoarthritis.

Subchondral Bone Remodeling: A Therapeutic Target for Osteoarthritis

There is emerging awareness that subchondral bone remodeling plays an important role in the development of osteoarthritis (OA). This review presents recent investigations on the cellular and molecular mechanism of subchondral bone remodeling, and summarizes the current interventions and potential therapeutic targets related to OA subchondral bone remodeling. The first part of this review covers key cells and molecular mediators involved in subchondral bone remodeling (osteoclasts, osteoblasts, osteocytes, bone extracellular matrix, vascularization, nerve innervation, and related signaling pathways). The second part of this review describes candidate treatments for OA subchondral bone remodeling, including the use of bone-acting reagents and the application of regenerative therapies. Currently available clinical OA therapies and known responses in subchondral bone remodeling are summarized as a basis for the investigation of potential therapeutic mediators.

Effects of Streptococcus thermophilus on anterior cruciate ligament transection-induced early osteoarthritis in rats

Osteoarthritis (OA) is the most common joint disorder and is classically defined as a progressively degenerative disease of articular cartilage. It manifests as joint pain and disability and currently has no comprehensive treatments. The primary purpose of the present study was to test the effects of probiotics, Streptococcus thermophilus (TCI633), on anterior cruciate ligament transection (ACLT)-induced experimental osteoarthritis (OA) in rats. In the current study, the experimental groups were given TCI633 (5x10⁹, 5x10¹⁰ and 5x10¹¹ CFU/kg/day) and glucosamine sulfate (250 mg/kg) between week 8 and 20 following ACLT. The results showed that oral administration of TCI633 and glucosamine had significant therapeutic effects on pain behaviors and knee swelling. Dose-dependent effects of TCI633 were also observed in ACLT-treated rats. Histopathological analysis demonstrated that ACLT+TCI633 (5x10⁹, 5x10¹⁰ and 5x10¹¹ CFU/kg/day) improved the synovial inflammation and cartilage damage of ACLT rats. Histology evaluation using the Osteoarthritis Research Society International system and synovial inflammatory score analysis showed the dose-dependent inhibition of TCI633 on synovial inflammation and cartilage damage. Immunohistochemical staining and TUNEL apoptosis staining showed that TCI633 could effectively increase the expression of type II collagen and reduce the amount of chondrocyte apoptosis in cartilage. Therefore, the present study demonstrated that oral intake of TCI633 could significantly suppressing pain behavior, reduce joint swelling and synovial tissue inflammation and increase type II collagen expression in cartilage. There was also a reduction in chondrocyte apoptosis and decreased progression of OA in ACLT-treated rats.

Etoricoxib prevents progression of osteolysis in repeated intra-articular monosodium urate-induced gouty arthritis in rats

Deposition of monosodium urate (MSU) crystals in the joint or synovium is the major factor in Gouty arthritis (GA). The clinical features of chronic and recurrent GA include pain and the subsequent development of chronic tophaceous GA with multiple tophi deposits accompanied by osteolysis. The majority of previous animal studies have focused on MSU-induced acute GA without making observations regarding osteolysis. In the study, intra-articular injections of MSU into the knee (2 times/week for 10 weeks) was used to induce chronic and recurrent attacks of GA that in turn induced progressive osteolysis. Moreover, we also evaluated whether the clinical, nonsteroidal anti-inflammatory drug (NSAID) etoricoxib attenuated the osteoclastogenesis of progressive osteolysis. The knee morphometry and the expression of osteoclastogenesis-related proteins (cathepsin K and matrix metalloproteinase-9 and -13) in the knee were examined by micro-CT and immunohistochemistry, respectively. Results showed that oral etoricoxib not only significantly attenuated the nociceptive behaviors of the rats but that it also inhibited the expression of osteoclastogenesis-related proteins in their knee joints in chronic and recurrent attacks of GA. Our findings thus suggest that NSAIDs not only inhibit nociception but also prevent the progression of osteolysis in chronic and repeated attacks of GA.

The COX-2 inhibitor etoricoxib reduces experimental osteoarthritis and nociception in rats: The roles of TGF-β1 and NGF expressions in chondrocytes

BACKGROUND

Osteoarthritis (OA) is the most common joint disease, especially affecting the knee joint. Etoricoxib, a highly selective cyclooxygenase (COX)-2 inhibitor which can reduce postoperative pain after orthopaedic surgery. The aim of this study was to investigate the effects of oral etoricoxib on the development of OA and to examine concomitant changes in the nociceptive behaviour of rats.

METHOD

OA was induced in wistar rats by anterior cruciate ligament transection (ACLT) of the right knee. The ACLT + etoricoxib groups received 6.7 or 33.3 mg/kg of oral etoricoxib three times a week for 12 consecutive weeks, starting at week 8 after ACLT. Nociceptive behaviours and changes in knee joint width during OA development were analyzed. Histopathological studies were then performed on the cartilage. Immunohistochemical analysis was performed to examine the effect of etoricoxib on the expression of transforming growth factor-beta (TGF-β) and nerve growth factor (NGF) in articular cartilage chondrocytes.

RESULTS

OA rats receiving etoricoxib showed a significantly lower degree of cartilage degeneration than the rats receiving placebo. Nociceptive behaviour studies showed significant improvement in the ACLT + etoricoxib groups compared to that in the ACLT group. Moreover, etoricoxib attenuated NGF expression, but increased TGF-β expression, in OA-affected cartilage.

CONCLUSIONS

Oral etoricoxib in a rat OA model (a) attenuates the development of OA, (b) concomitantly reduces nociception, and (c) modulates chondrocyte metabolism, possibly by inhibiting NGF expression and increasing TGF-β expression.

SIGNIFICANCE

Oral administration of etoricoxib can attenuate the development of OA, with an associated attenuation of nociceptive behaviour in an experimental rat OA model. Moreover, etoricoxib attenuated NGF expression, but enhanced TGF-β expression in OA-affected chondrocytes. These findings may pave the way for further investigations of etoricoxib as a potential therapeutic target for the treatment of the inflammatory component in OA.

A dual amylin and calcitonin receptor agonist inhibits pain behavior and reduces cartilage pathology in an osteoarthritis rat model

OBJECTIVES

Pain and disability are the main clinical manifestations of osteoarthritis, for which only symptomatic therapies are available. Hence, there is a need for therapies that can simultaneously alter disease progression and provide pain relief. KBP is a dual amylin- and calcitonin-receptor agonist with antiresorptive and chondroprotective properties. In this study we investigated the effect of KBP in a rat model of osteoarthritis.

METHODS

Medial meniscectomy (MNX) was performed in 39 rats, while 10 underwent sham surgery. Rats were treated with KBP and/or naproxen. Nociception was assessed by mechanical and cold allodynia, weight bearing asymmetry, and burrowing behavior. Blood samples were collected for biomarker measurements, and knees for histology. Cartilage histopathology was evaluated according to the advanced Osteoarthritis Research International (OARSI) score and KBPs in vitro antiresorptive effects were assessed using human osteoclasts cultured on bone.

RESULTS

The MNX animals displayed an increased nociceptive behavior. Treatment with KBP attenuated the MNX-induced osteoarthritis-associated joint pain. The cartilage histopathology was significantly lower in rats treated with KBP than in MNX animals. Bone and cartilage degradation, assessed by CTX-I and CTX-II plasma levels, were decreased in all KBP-treated groups and KBP potently inhibited bone resorption in vitro.

CONCLUSIONS

Our study demonstrates the effectiveness of KBP in ameliorating osteoarthritis-associated joint pain and in protecting the articular cartilage, suggesting KBP as a potential drug candidate for osteoarthritis.

Comparative profiling of chondrogenic differentiation of mesenchymal stem cells (MSCs) driven by two different growth factors

This study aimed to investigate the mechanism of nerve growth factor (NGF) from cobra venom and human transforming growth factor-β1 (TGF-β1) on the chondrogenic induction of mesenchymal stem cells (MSCs). NGF and TGF-β1 were used to induce chondrogenesis of MSCs from rabbits for 7 days. Total RNA was extracted for mRNA sequencing. Differentially expressed genes (DEGs), gene ontology (GO), KEGG pathway enrichment, and PPI network analysis were conducted to screen the specific signalling pathways and target genes. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to further confirm the relative target genes. The results showed that NGF could significantly promote the expression of hyaline cartilage specific genes (collagen type II alpha 1 chain, COL2A1) compared with TGF-β1. PI3K-AKT signalling pathway is commonly involved in the chondrogenesis of MSCs induced by NGF and TGF-β1. However, the expression levels of the genes in the PI3K-AKT signalling pathway were significantly higher in NGF group than that in the TGF-β1 group. In the process of chondrogenesis of MSCs induced by NGF and TGF-β1, integrin (ITGAs) were the targeted hub genes to activate the PI3K-AKT signalling pathway. NGF could activate more proliferation and differentiation genes in the process of chondrogenesis of MSCs than TGF-β1. TGF-β1 promoted angiogenesis by targeting the thrombospondin (THBS1) and THBS2 which might contribute to the osteophyte formation. PI3K-AKT was the crucial signalling pathway for chondrogenic differentiation. NGF could activate the PI3K-AKT signalling pathway to a higher level, and NGF had more specificity for promoting expression of specific genes of chondrocyte compared with TGF-β1. SIGNIFICANCE OF THE STUDY: In our study, we compared two different growth factors in promoting cartilage differentiation of MSCs and found some similarities and differences. We revealed that both NGF and TGF-β1 could activate the PI3K-AKT signalling pathway (the expression of it in NGF was higher) by targeting the ITGAs in the process of chondrogenesis from MSCs. However, NGF could activate more proliferation and differentiation genes in the process of chondrogenesis of MSCs, whereas TGF-β1 caused osteophyte formation by activating THBS1 and THBS2. These might be the reason why NGF could promote cartilage differentiation more specifically.

Naproxen attenuates osteoarthritis progression through inhibiting the expression of prostaglandinl-endoperoxide synthase 1

OBJECTIVE

This study aims to test the effect of naproxen treatment and the biological target of naproxen for treating osteoarthritis (OA).

METHODS

Differentially expressed genes (DEGs) in OA synovial tissues and normal counterparts were analyzed by messenger RNA microarray analysis. R package (weighted gene coexpression network analysis) was used to divide DEGs into several modules and determine the hub genes in each module. The expression level of prostaglandin-endoperoxide synthase 1 ( PTGS1) in OA synovial cells and tissues was verified by a quantitative real-time polymerase chain reaction and western blot. Transwell assay evaluated the numbers of cell migration and invasion. Furthermore, Safranin O and fast green staining and hematoxylin and eosin staining were performed on joints from anterior cruciate ligament transection mice.

RESULTS

Microarray analysis determined PTGS1 was the hub gene in the black module, which was overexpressed in OA synovial cells and tissues compared with normal synovial cells. OA synovial cells transfected with sh-PTGS1 showed downregulation of PTGS1. After treatment with naproxen, the expression of PTGS1 sharply decreased in the OA group. The migration and invasion of OA synovial cells increased, whereas the cell apoptosis rate decreased when PTGS1 was overexpressed. However, the cell migration and invasion decreased, whereas cells apoptosis increased when it was treated with naproxen. Naproxen could also influence the expression level of six OA-related genes: LUBRICIN, matrix metalloproteinase 13 (MMP-13), cyclooxygenase-2 (COX-2), ACAN, COL2A1, and COL1A1.

CONCLUSION

We validated that naproxen could suppress the expression of PTGS1 in synovial cells. Moreover, naproxen could inhibit the migration/invasion ability of OA synoviocytes and promote the apoptosis rate OA synoviocytes.

Characterization of a rat model with temporomandibular joint osteoarthritis following a surgical anterior disc displacement

This study has characterized a rat model with temporomandibular osteoarthritis (TMJ-OA) following a surgical anterior displacement of their articular disc (ADD). The well-established model of OA, induced by an intra-articular injection of complete Freund's adjuvant (CFA) into the TMJ, was used for comparison purposes. Male Wistar rats were assigned into two surgical groups, namely, ADD (anterior disc displacement) and sham-operated (surgical access, without ADD). Additional groups received an intra-articular infiltration of CFA (50 μl/site; 1:1 oil/saline emulsion), or the vehicle (0.9% NaCl). The separate experimental subgroups were euthanized at 15, 30 or 60 days and their left TMJs were collected for histological, immunohistochemistry and micro-CT analyses. The serum levels of IL-1β, IL-6 and TNF were analyzed. The fibrocartilage thicknesses were increased in the ADD groups at all of the analyzed time-points. In the CFA group, fibrocartilage thickenings were seen only in the posterior thirds at 15 days. The ADD group displayed an increase of the proteoglycan contents and ADAMTS5 immunopositivity in the fibrocartilage at 30 and 60 days, without any variations of the collagen contents or the osteoclast activation. Upon the micro-CT evaluation, the ADD group presented increments of their trabecular separations and bone surfaces, with reduced trabecular thicknesses and bone volumes, plus osteophyte formations and condyle flattenings, from 30 to 60 days. The IL-1β, TNF or IL-6 serum levels were undetectable. The surgical ADD in the rats led to long-term OA-like alterations, with typical structural and morphological derangements of the TMJ, representing a reliable experimental model to investigate the TMJ-OA-related mechanisms.

Baicalin Attenuates Joint Pain and Muscle Dysfunction by Inhibiting Muscular Oxidative Stress in an Experimental Osteoarthritis Rat Model

Osteoarthritis (OA) is the most common degenerative joint disease, and causes major pain and disability in adults. It has been reported that muscle weakness and inflammation contribute to osteoarthritis development and progression. Oxidative stress plays important roles in muscle dysfunction and inflammation in osteomyelitis. Baicalin, the major active constituent of the isolated root of Scutellarialateriflora Georgi, has been shown to have anti-oxidative and anti-inflammatory effects. In this study, we evaluated the potential effects of baicalin on osteoarthritis. We established experimental osteoarthritis rat model, applied baicalin to the rats, and then explored the potential protective effect of baicalin on osteoarthritis severity, muscle dysfunction, and oxidative stress. Baicalin alleviated severity of OA in rats. Baicalin application attenuated muscle dysfunction in OA rats by increasing citrate synthase activity, myosin heavy chain IIa expression, and decreasing interleukin 6 production. Baicalin decreased muscular reactive oxygen species generation in OA rats. Baicalin inhibited nuclear factor erythroid-derived 2-like 2 expression in OA rats. Baicalin attenuated osteoarthritis in rat by inhibiting oxidative stress.

Current status and future prospects for disease modification in osteoarthritis

OA is a chronic, progressive and disabling joint disease, leading to a poor quality of life and an enormous social and economic burden. Current therapies for OA patients remain limited, which creates an area of huge unmet medical need. For some time, researchers have been looking for approaches that can inhibit the structural progression of OA. A variety of potential disease-modifying OA drugs have been developed, targeting cartilage, inflammatory pathways or subchondral bone. In addition, non-pharmacological therapies, including joint distraction and weight loss, draw increasing attention, with some showing disease-modifying potential. Thus we performed a comprehensive review to discuss the current status of disease-modifying therapies in OA and appraise the potentials of emerging novel agents.

Isoliquiritigenin blunts osteoarthritis by inhibition of bone resorption and angiogenesis in subchondral bone

Isoliquiritigenin (ISL), a natural flavonoid extracted from licorice, has been demonstrated to exert attenuation of osteoclastogenesis and anti-angiogenesis activity in a wide variety of cells. Here, we first evaluated the effects of ISL on pathogenesis of osteoarthritis in a mouse model of OA. The data showed that ISL blunted progression of OA and lowered the Osteoarthritis Research Society International (OARSI)-Modified Making Score and protected the articular cartilage. The thickness of calcified cartilage zone was significantly decreased in ISL-treated ACLT mice compared with vehicle group. ISL increased expression level of lubricin and decreased collagen X (Col X), matrix metalloproteinase-13 (MMP-13). Moreover, ISL reduced aberrant active subchondral bone remodelling, including lowered trabecular pattern factor (Tb.pf) and increased bone volume/tissue volume (BV/TV, %) and thickness of subchondral bone plate (SBP) compared with vehicle-treated group. The results of immunostaining further revealed that ISL directly reduced RANKL-RANK-TRAF6 singling pathway induced osteoclastogenesis, prevented abnormal bone formation through indirect inhibition of TGF-β release. Additionally, ISL exerts anti-angiogenesis effects in subchondral bone through direct suppression of MMP-2. These results indicated that ISL attenuates progression of OA by inhibition of bone resorption and angiogenesis in subchondral bone, indicating that this may be a potential preventive therapy for OA.

Efficacy and Persistence of Allogeneic Adipose-Derived Mesenchymal Stem Cells Combined with Hyaluronic Acid in Osteoarthritis After Intra-articular Injection in a Sheep Model

Although a number of studies have reported efficacy of autologous adipose-derived mesenchymal stem cells (AD-MSCs) in treating osteoarthritis (OA) no reliable evidences demonstrate whether allogeneic AD-MSCs can efficiently block OA progression in a large animal model. This study explored the efficacy and survival of allogeneic AD-MSCs combined with hyaluronic acid (HA) after intra-articular (IA) injection in a sheep OA model, which were conventionally established by anterior cruciate ligament resection and medial meniscectomy. Allogeneic AD-MSCs from donor sheep at high (5 × 10⁷ cells) and low (1 × 10⁷ cells) doses combined with HA, HA alone, or saline alone were injected into the OA sheep at 3 and 6 weeks after surgery, respectively. Evaluations by magnetic resonance imaging (MRI), macroscopy, micro-computed tomography, and cartilage-specific staining demonstrated that AD-MSCs+HA treated groups preserved typical articular cartilage feature. Inflammatory factors from synovial fluid of AD-MSCs+HA treated groups were significantly lower than those in the HA alone group. Notably, transforming growth factor beta 1 and insulin-like growth factor 1 were detected in the supernatant of cultured AD-MSCs. In addition, labeling signals of allogeneic AD-MSCs could be detected by MRI after 14 weeks of injection and be found in synovium by histology. These results indicated that IA injection of allogeneic AD-MSCs combined with HA could efficiently block OA progression and promote cartilage regeneration and allogeneic AD-MSCs might survive at least 14 weeks after IA injection.

Subchondral mesenchymal stem cells from osteoarthritic knees display high osteogenic differentiation capacity through microRNA-29a regulation of HDAC4

Subchondral bone deterioration and osteophyte formation attributable to excessive mineralization are prominent features of end-stage knee osteoarthritis (OA). The cellular events underlying subchondral integrity diminishment remained elusive. This study was undertaken to characterize subchondral mesenchymal stem cells (SMSCs) isolated from patients with end-stage knee OA who required total knee arthroplasty. The SMSCs expressed surface antigens CD29, CD44, CD73, CD90, CD105, and CD166 and lacked CD31, CD45, and MHCII expression. The cell cultures exhibited higher proliferation and greater osteogenesis and chondrogenesis potencies, whereas their population-doubling time and adipogenic lineage commitment were lower than those of bone marrow MSCs (BMMSCs). They also displayed higher expressions of embryonic stem cell marker OCT3/4 and osteogenic factors Wnt3a, β-catenin, and microRNA-29a (miR-29a), concomitant with lower expressions of joint-deleterious factors HDAC4, TGF-β1, IL-1β, TNF-α, and MMP3, in comparison with those of BMMSCs. Knockdown of miR-29a lowered Wnt3a expression and osteogenic differentiation of the SMSCs through elevating HDAC4 translation, which directly regulated the 3'-untranslated region of HDAC4. Likewise, transgenic mice that overexpressed miR-29a in osteoblasts exhibited a high bone mass in the subchondral region. SMSCs in the transgenic mice showed a higher osteogenic differentiation and lower HDAC4 signaling than those in wild-type mice. Taken together, high osteogenesis potency existed in the SMSCs in the osteoarthritic knee. The miR-29a modulation of HDAC4 and Wnt3a signaling was attributable to the increase in osteogenesis. This study shed an emerging light on the characteristics of SMSCs and highlighted the contribution of SMSCs in the exacerbation of subchondral integrity in end-stage knee OA.

KEY MESSAGES

Subchondral MSCs (SMSCs) from OA knee expressed embryonic stem cell marker Oct3/4. The SMSCs showed high proliferation and osteogenic and chondrogenic potencies. miR-29a regulated osteogenesis of the SMSCs through modulation of HDAC4 and Wnt3a. A high osteogenic potency of the SMSCs existed in mice overexpressing miR-29a in bone. Aberrant osteogenesis in SMSCs provides a new insight to subchondral damage in OA.

Calcitonin protects chondrocytes from lipopolysaccharide-induced apoptosis and inflammatory response through MAPK/Wnt/NF-κB pathways

Calcitonin (CT) is an anti-absorbent, which has long been used for treatment of osteoporosis. However, little information is available about the effects of CT on osteoarthritis (OA). This study was mainly aimed to explore the effects of CT on the treatment of OA, as well as the underlying mechanisms. Chondrocytes were isolated from immature mice and then were incubated with lipopolysaccharide (LPS), CT, small interfering (si) RNA against bone morphogenetic protein (BMP)-2, and/or the inhibitors of MAPK/Wnt/NF-κB pathway. Thereafter, cell viability, apoptosis, nitric oxide (NO) and inflammatory factors productions, and expression levels of cartilage synthesis protein key factors, cartilage-derived morphogenetic protein (CDMP) 1, SRY (sex-determining region Y)-box 9 protein (SOX9), and MAPK/Wnt/NF-κB pathways key factors were determined. CT significantly reversed LPS-induced cell viability decrease, apoptosis increase, the inflammatory factors and NO secretion, the abnormally expression of cartilage synthesis proteins and the activation of MAPK/Wnt/NF-κB pathways (P<0.05). In addition, we observed that administration of the inhibitors of MAPK/Wnt/NF-κB pathways statistically further increased the levels of CDMP1 and SOX9 (P<0.05). Suppression of BMP-2 decreased the levels of CDMP1 and SOX9 and activated MAPK/Wnt/NF-κB pathways, and could partially abolish CT-modulated the expression changes in CDMP1 and SOX9, and MAPK/Wnt/NF-κB pathways key factors (P<0.05). The results showed that CT protects chondrocytes from LPS-induced apoptosis and inflammatory response by regulating BMP-2 and thus blocking MAPK/Wnt/NF-κB pathways.