Targeted designed variants of alpha-2-macroglobulin (A2M) attenuate cartilage degeneration in a rat model of osteoarthritis induced by anterior cruciate ligament transection

α2-Macroglobulin Promotes Chondrocyte Proliferation and Cartilage Matrix Synthesis via Inducing PCNA

Objectivesα2-Macroglobulin (A2M) can prevent cartilage degeneration by blocking many types of cartilage-degrading enzymes, but the mechanism remains to be clarified. This study aimed to test that A2M protects against cartilage degeneration by promoting chondrocyte proliferation and cartilage matrix synthesis via inducing proliferating cell nuclear antigen (PCNA).DesignThe cartilage degeneration of the anterior cruciate ligament transection (ACLT) model was evaluated by Safranin O-fast green staining, and articular cartilage degeneration was graded using the Osteoarthritis Research Society International (OARSI)-modified Mankin criteria. The chondrocyte proliferation was detected by 5-Bromodeoxyuridinc (BrdU), MTT, and Cell Counting Kit-8 (CCK8) methods. The chondrocyte apoptosis was detected by lactate dehydrogenase (LDH) assay and Annexin PI staining with the flow cytometer. The glycosaminoglycan (sGAG) and aggrecan in culture supernatant were measured by enzyme-linked immunosorbent assay (ELISA). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to analyze the type II collagen and aggrecan mRNA expression. The PCNA protein expression was analyzed by western blot and immunofluorescent staining.ResultsA2M can attenuate cartilage degeneration in ACLT rats. The OARSI scores for cartilage degeneration in the A2M group were lower than those in the phosphate-buffered saline (PBS) group. A2M can promote chondrocyte proliferation and inhibit chondrocyte apoptosis, promote the cartilage matrix synthesis in chondrocytes (type II collagen and aggrecan), and culture supernatant (sGAG and aggrecan). At the same time, it also up-regulated the PCNA protein expression in chondrocytes.ConclusionsA2M can promote chondrocyte proliferation and cartilage matrix synthesis via inducing PCNA expression.

Clinical-grade extracellular vesicles derived from umbilical cord mesenchymal stromal cells: preclinical development and first-in-human intra-articular validation as therapeutics for knee osteoarthritis

Osteoarthritis (OA) is a joint disease characterized by articular cartilage degradation. Persistent low-grade inflammation defines OA pathogenesis, with crucial involvement of pro-inflammatory M1-like macrophages. While mesenchymal stromal cells (MSC) and their small extracellular vesicles (sEV) hold promise for OA treatment, achieving consistent clinical-grade sEV products remains a significant challenge. This study aims to develop fully characterized, reproducible, clinical-grade batches of sEV derived from umbilical cord (UC)-MSC for the treatment of OA while assessing its efficacy and safety. Initially, a standardized, research-grade manufacturing protocol was established to ensure consistent sEV production. UC-MSC-sEV characterization under non-cGMP conditions showed consistent miRNA and protein profiles, suggesting their potential for standardized manufacturing. In vitro studies evaluated the efficacy, safety, and potency of sEV; animal studies confirmed their effectiveness and safety. In vitro, UC-MSC-sEV polarized macrophages to an anti-inflammatory M2b-like phenotype, through STAT1 modulation, indicating their potential to create an anti-inflammatory environment in the affected joints. In silico studies confirmed sEV's immunosuppressive signature through miRNA and proteome analysis. In an OA mouse model, sEV injected intra-articularly (IA) induced hyaline cartilage regeneration, validated by histological and μCT analyses. The unique detection of sEV signals within the knee joint over time highlights its safety profile by confirming the retention of sEV in the joint. The product development of UC-MSC-sEV involved refining, standardizing, and validating processes in compliance with GMP standards. The initial assessment of the safety of the clinical-grade product via IA administration in a first-in-human study showed no adverse effects after a 12 month follow-up period. These results support the progress of this sEV-based therapy in an early-phase clinical trial, the details of which are presented and discussed in this work. This study provides data on using UC-MSC-sEV as local therapy for OA, highlighting their regenerative and anti-inflammatory properties and safety in preclinical and a proof-of-principle clinical application.

Alpha-2-Macroglobulin Attenuates Posttraumatic Osteoarthritis Cartilage Damage by Inhibiting Inflammatory Pathways With Modified Intra-articular Drilling in a Yucatan Minipig Model

BACKGROUND

Posttraumatic osteoarthritis (PTOA) arises secondarily to joint trauma and is driven by catabolic inflammatory pathways. Alpha-2-macroglobulin (α2M) is a naturally occurring proteinase inhibitor found in human serum and synovial fluid that binds proteases as well as proinflammatory cytokines involved in the pathogenesis of PTOA.

PURPOSE

(1) To investigate the therapeutic potential of intra-articular α2M injections during the acute stages of PTOA by inhibiting inflammatory pathways driven by the cytokines expressed by the synovium in a large preclinical Yucatan minipig model and (2) to determine if 3 intra-articular α2M injections have greater chondroprotective effects compared with 1 intra-articular injection.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 48 Yucatan minipigs were randomized into 4 groups (n = 12 each): (1) modified intra-articular drilling (mIAD) and saline (mIAD + saline), (2) mIAD and 1 intra-articular α2M injection (mIAD +α2M-1), (3) mIAD and 3 α2M injections (mIAD +α2M-3), and (4) sham control. Surgical hindlimbs were harvested at 15 weeks after surgery. Cartilage degeneration, synovial changes, inflammatory gene expression, and matrix metalloproteinase levels were evaluated. Gait asymmetry was measured before and after surgery using a pressure-sensing walkway system.

RESULTS

Macroscopic lesion areas and microscopic cartilage degeneration scores were lower in the mIAD +α2M-1 and mIAD +α2M-3 groups compared with the mIAD + saline group (P < .05) and similar to those in the sham group (P > .05). Synovial membrane scores of the mIAD +α2M-1 and mIAD +α2M-3 groups were lower than that of the mIAD + saline group (P < .05) and higher than that of the sham group (P < .05). Interleukin-1 beta, nuclear factor kappa B, and tumor necrosis factor alpha mRNA expression in the synovium and matrix metalloproteinase-1 levels in synovial fluid were significantly lower in the mIAD +α2M-1 and mIAD +α2M-3 groups compared with the mIAD + saline group (P < .05). No significant differences were observed between the mIAD +α2M-1 and mIAD +α2M-3 groups for all measured outcomes. There were early changes in gait (P < .05) between preoperative and postoperative time points for the mIAD + saline, mIAD +α2M-1, and mIAD +α2M-3 groups that normalized by 15 weeks.

CONCLUSION

Animals receiving early α2M treatment exhibited less cartilage damage, milder synovitis, and lower inflammation compared with animals with no α2M treatment. These results exemplify the early anti-inflammatory effects of α2M and provide evidence that intra-articular α2M injections may slow the progression of PTOA.

CLINICAL RELEVANCE

In patients presenting with an acute joint injury, an early intervention with α2M may have the potential to reduce cartilage degeneration from catabolic pathways and delay the development of PTOA.

The Nrf2/HO-1 pathway participates in the antiapoptotic and anti-inflammatory effects of platelet-rich plasma in the treatment of osteoarthritis

INTRODUCTION

We aimed to explore the molecular mechanisms through which platelet-rich plasma (PRP) attenuates osteoarthritis (OA)-induced pain, apoptosis, and inflammation.

METHODS

An in vivo model of OA was established by injuring rats using the anterior cruciate ligament transection method, whereas an in vitro model was generated by exposing chondrocytes to interleukin (IL)-1β. Both models were then treated with PRP.

RESULTS

In both the in vivo and in vitro models, OA led to the suppression of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway, whereas treatment with PRP reactivated this molecular axis. Inhibition of the Nrf2/HO-1 pathway using the Nrf2 inhibitor brusatol or through Nrf2 gene silencing counteracted the effects of PRP in reducing the tenderness and thermal pain thresholds of OA rats. Additionally, PRP reduced the mRNA expression of IL-1β, IL-6, tumor necrosis factor-alpha (TNF-α), and matrix metallopeptidase 13 (MMP-13) and the protein expression of B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X-protein (Bax), and caspase-3. Furthermore, inflammation and apoptosis were induced by brusatol treatment or Nrf2 silencing. Additionally, in the in vitro model, PRP treatment increased the proliferation of chondrocytes and attenuated their inflammatory response and apoptosis, effects that were abrogated by Nrf2 depletion.

CONCLUSIONS

The Nrf2/HO-1 pathway participates in the PRP-mediated attenuation of OA development by suppressing inflammation and apoptosis.

Use of quantitative mass spectrometry-based proteomics and ELISA to compare the alpha 2 macroglobulin concentration in equine blood-based products processed by three different orthobiologic devices

Introduction

Alpha 2 macroglobulin (A2M), a multi-functional protein in the plasma protease inhibitor class, regulates proinflammatory cytokines and the clearance of chondrodestructive enzymes in cases of joint injury and osteoarthritis (OA). The purpose of this study was to compare A2M concentrations in equine plasma samples processed by three commercial devices developed for stall-side regenerative joint therapy.

Methods

Plasma samples were obtained from healthy adult horses (N = 13). Mass spectrometry analysis was used to determine the concentration of protein analytes in each sample. Selected reaction monitoring measured a specific A2M peptide as a surrogate of the whole A2M protein. A2M concentrations produced by each test device were compared for two sample types: a pre-concentrate or platelet-poor (PP) component and a final component for use in the horse.

Results

There was no significant difference (p > 0.05) in the geometric mean (GM) concentration of A2M in the final concentration samples produced by the Alpha2EQ® device (N horses = 13) and the single-centrifugation PP samples produced by the Pro-Stride® APS (autologous protein solution) device (N = 13) and the Restigen® PRP (platelet-rich plasma) device (N = 11). When A2M content in final concentration samples produced by each device was compared, the Pro-Stride APS and Restigen PRP samples had significantly greater GM A2M content (p < 0.0001) compared to the Alpha2EQ samples, and the Pro-Stride APS final concentration samples had significantly greater GM A2M concentration (p < 0.0001) versus that for the Restigen PRP final samples.

Discussion

This comparison demonstrated that the volume and A2M concentration of an Alpha2EQ final concentrate are no different than the volume and concentration of A2M in the PP from Pro-Stride or Restigen devices.

Proteomics Analysis of Knee Subchondral Bone Identifies Differentially Expressed Proteins Associated with Osteoarthritis

Osteoarthritis (OA) is a prevalent debilitating whole-joint disorder. Currently, a growing number of proteomic studies have been performed to evaluate molecular biomarkers in several tissues from OA patients; however, little is known about the protein profiles in subchondral bone of OA. In this study, proteomic analysis was performed on subchondral bone from patients with OA to identify differentially expressed proteins (DEPs). Bioinformatics tools were used to further investigate these DEPs. Thereafter, DEPs were validated in the samples from patients with OA, as well as in bilateral ovariectomy-induced OA (OVX-OA) rats using immunohistochemistry. A comprehensive subchondral bone proteome profile of patients with OA was constructed. Additionally, biological information analysis showed that a majority of DEPs participated in the dysregulation of the complement and coagulation cascades. The validation experiments suggested that SerpinA5, the protein involved in the complement and coagulation cascades, was significantly increased in severely damaged subchondral bone of patients with OA compared to the control group. Furthermore, the increase of SerpinA5 in OVX-OA rats compared to control rats was also confirmed. Our results indicated that the dysregulation of coagulation and complement pathways plays a role in the progression of OA, and it provides a promising therapeutic target of OA.

Engineering New Protease Inhibitors Using α2-Macroglobulin

Protease inhibitors of the alpha-macroglobulin family (αM) have a unique mechanism that allows them to trap proteases that is dependent not on the protease's class, but rather on its cleavage specificity. Proteases trigger a conformational change in the αM protein by cleaving within a "bait region," resulting in the sequestering of the protease inside the αM molecule. This nonspecific inhibitory mechanism appears to have arisen early in the αM family, and the broad protease-trapping capacity that it allows may play a role in pathogen defense.Human α2-macroglobulin (A2M) is a tetrameric αM whose bait region is permissive to cleavage by most proteases, making it a broad-spectrum protease inhibitor. Recent work has demonstrated that the inhibitory capacity of A2M derives directly from its bait region sequence: modifying the bait region sequence to introduce or remove protease cleavage sites will modify A2M's inhibition of the relevant proteases accordingly. Thus, changing the amino acid sequence of the bait region presents an effective avenue for protein engineering of new protease inhibitors if the substrate specificity of the target protease is known. The design of new A2M-based protease inhibitors with tailored inhibitory capacities has potential applications in basic research and the clinic. In this chapter, we describe the general approach and considerations for the bait region engineering of A2M.

Evaluating the causal effect of circulating proteome on the risk of osteoarthritis-related traits

OBJECTIVES

This study aims to identify circulating proteins that are causally associated with osteoarthritis (OA)-related traits through Mendelian randomisation (MR)-based analytical framework.

METHODS

Large-scale two-sample MR was employed to estimate the effects of thousands of plasma proteins on 12 OA-related traits. Additional analyses including Bayesian colocalisation, Steiger filtering analysis, assessment of protein-altering variants and mapping expression quantitative trait loci to protein quantitative trait loci were performed to investigate the reliability of the MR findings; protein-protein interaction, pathway enrichment analysis and evaluation of drug targets were conducted to deepen the understanding and identify potential therapeutic targets of OA.

RESULTS

Dozens of circulating proteins were identified to have putatively causal effects on OA-related traits, and a majority of these proteins were either drug targets or considered druggable.

CONCLUSIONS

Through MR analysis, we have identified numerous plasma proteins associated with OA-related traits, shedding light on protein-mediated mechanisms and offering promising therapeutic targets for OA.

The Effects of an Osteoarthritic Joint Environment on ACL Damage and Degeneration: A Yucatan Miniature Pig Model

Posttraumatic osteoarthritis (PTOA) arises secondary to joint injuries and is characteristically driven by inflammatory mediators. PTOA is often studied in the setting of ACL tears. However, a wide range of other injuries also lead to PTOA pathogenesis. The purpose of this study was to characterize the morphological changes in the uninjured ACL in a PTOA inflammatory environment. We retrospectively reviewed 14 ACLs from 13 Yucatan minipigs, 7 of which had undergone our modified intra-articular drilling (mIAD) procedure, which induced PTOA through inflammatory mediators. Seven ACLs were harvested from mIAD minipigs (PTOA) and seven ACLs from control minipigs with no cartilage degeneration (non-PTOA). ACL degeneration was evaluated using histological scoring systems. IL-1β, NF-κB, and TNF-α mRNA expression in the synovium was measured using qRT-PCR. PTOA minipigs demonstrated significant ACL degeneration, marked by a disorganized extracellular matrix, increased vascularity, and changes in cellular shape, density, and alignment. Furthermore, IL-1β, NF-κB, and TNF-α expression was elevated in the synovium of PTOA minipigs. These findings demonstrate the potential for ACL degeneration in a PTOA environment and emphasize the need for anti-inflammatory disease-modifying therapies following joint injury.

Modulation of miR-146b Expression during Aging and the Impact of Physical Activity on Its Expression and Chondrogenic Progenitors

The finding of molecules associated with aging is important for the prevention of chronic degenerative diseases and for longevity strategies. MicroRNAs (miRNAs) are post-transcriptional regulators involved in many biological processes and miR-146b-5p has been shown to be involved in different degenerative diseases. However, miR-146b-5p modulation has not been evaluated in mesenchymal stem cells (MSCs) commitment or during aging. Therefore, the modulation of miR-146b-5p in the commitment and differentiation of mesenchymal cells as well as during maturation and aging in zebrafish model were analyzed. In addition, circulating miR-146b-5p was evaluated in human subjects at different age ranges. Thus, the role of physical activity in the modulation of miR-146b-5p was also investigated. To achieve these aims, RT (real-time)-PCR, Western blot, cell transfections, and three-dimensional (3D) culture techniques were applied. Our findings show that miR-146b-5p expression drives MSCs to adipogenic differentiation and increases during zebrafish maturation and aging. In addition, miR-146b-5p expression is higher in females compared to males and it is associated with the aging in humans. Interestingly, we also observed that the physical activity of walking downregulates circulating miR-146b-5p levels in human females and increases the number of chondroprogenitors. In conclusion, miR-146b-5p can be considered an age-related marker and can represent a useful marker for identifying strategies, such as physical activity, aimed at counteracting the degenerative processes of aging.

Depletion of SNORA33 Abolishes ψ of 28S-U4966 and Affects the Ribosome Translational Apparatus

Eukaryotic ribosomes are complex molecular nanomachines translating genetic information from mRNAs into proteins. There is natural heterogeneity in ribosome composition. The pseudouridylation (ψ) of ribosomal RNAs (rRNAs) is one of the key sources of ribosome heterogeneity. Nevertheless, the functional consequences of ψ-based ribosome heterogeneity and its relevance for human disease are yet to be understood. Using HydraPsiSeq and a chronic disease model of non-osteoarthritic primary human articular chondrocytes exposed to osteoarthritic synovial fluid, we demonstrated that the disease microenvironment is capable of instigating site-specific changes in rRNA ψ profiles. To investigate one of the identified differential rRNA ψ sites (28S-ψ4966), we generated SNORA22 and SNORA33 KO SW1353 cell pools using LentiCRISPRv2/Cas9 and evaluated the ribosome translational capacity by 35S-Met/Cys incorporation, assessed the mode of translation initiation and ribosomal fidelity using dual luciferase reporters, and assessed cellular and ribosomal proteomes by LC-MS/MS. We uncovered that the depletion of SNORA33, but not SNORA22, reduced 28S-ψ4966 levels. The resulting loss of 28S-ψ4966 affected ribosomal protein composition and function and led to specific changes in the cellular proteome. Overall, our pioneering findings demonstrate that cells dynamically respond to disease-relevant changes in their environment by altering their rRNA pseudouridylation profiles, with consequences for ribosome function and the cellular proteome relevant to human disease.

A2M inhibits inflammatory mediators of chondrocytes by blocking IL-1β/NF-κB pathway

A hallmark of osteoarthritis (OA) is cartilage degeneration, which has been previously correlated with dramatic increases in inflammatory enzymes. Specifically, interleukin-1β (IL-1β) and subsequent upregulation of nuclear factor kappa B (NF-κB) is implicated as an important player in the development of posttraumatic osteoarthritis (PTOA). Alpha 2-macroglobulin (A2M) can inhibit this inflammatory pathway, making it a promising therapy for PTOA. Herein, we demonstrate that A2M binds and neutralizes IL-1β, blocking downstream NF-κB-induced catabolism seen in in vitro. Human chondrocytes (cell line C28) were incubated with A2M protein and then treated with IL-1β. A2M was labeled with VivoTag™ 680 to localize the protein postincubation. The degree of binding between A2M and IL-1β was evaluated through immunoprecipitation (IP). Catabolic proteins, including IL-1β and NF-kB, were detected by Western blot. Pro-inflammatory and chondrocyte-related gene expression was examined by qRT-PCR. VivoTag™ 680-labeled A2M was observed in the cytoplasm of C28 human chondrocytes by fluorescence microscopy. IP experiments demonstrated that A2M could bind IL-1β. Additionally, western blot analysis revealed that A2M neutralized IL-1β and NF-κB in a dose-dependent manner. Moreover, A2M decreased levels of MMPs and TNF-α and increased the expression of cartilage protective genes Col2, Type2, Smad4, and aggrecan. Mostly importantly, A2M was shown to directly neutralize IL-1β to downregulate the pro-inflammatory responses mediated by the NF-kB pathway. These results demonstrate a mechanism by which A2M reduces inflammatory catabolic activity and protects cartilage after joint injury. Further in vivo studies are needed to fully understand the potential of A2M as a novel PTOA therapy.

The current state of the osteoarthritis drug development pipeline: a comprehensive narrative review of the present challenges and future opportunities

In this narrative review article, we critically assess the current state of the osteoarthritis (OA) drug development pipeline. We discuss the current state-of-the-art in relation to the development and evaluation of candidate disease-modifying OA drugs (DMOADs) and the limitations associated with the tools and methodologies that are used to assess outcomes in OA clinical trials. We focus on the definition of DMOADs, highlight the need for an updated definition in the form of a consensus statement from all the major stakeholders, including academia, industry, regulatory agencies, and patient organizations, and provide a summary of the results of recent clinical trials of novel DMOAD candidates. We propose that DMOADs should be more appropriately targeted and investigated according to the emerging clinical phenotypes and molecular endotypes of OA. Based on the findings from recent clinical trials, we propose key topics and directions for the development of future DMOADs.

Peptide location fingerprinting identifies species- and tissue-conserved structural remodelling of proteins as a consequence of ageing and disease

Extracellular matrices (ECMs) in the intervertebral disc (IVD), lung and artery are thought to undergo age-dependant accumulation of damage by chronic exposure to mechanisms such as reactive oxygen species, proteases and glycation. It is unknown whether this damage accumulation is species-dependant (via differing lifespans and hence cumulative exposures) or whether it can influence the progression of age-related diseases such as atherosclerosis. Peptide location fingerprinting (PLF) is a new proteomic analysis method, capable of the non-targeted identification of structure-associated changes within proteins. Here we applied PLF to publicly available ageing human IVD (outer annulus fibrosus), ageing mouse lung and human arterial atherosclerosis datasets and bioinformatically identified novel target proteins alongside common age-associated differences within protein structures which were conserved between three ECM-rich organs, two species, three IVD tissue regions, sexes and in an age-related disease. We identify peptide yield differences across protein structures which coincide with biological regions, potentially reflecting the functional consequences of ageing or atherosclerosis for macromolecular assemblies (collagen VI), enzyme/inhibitor activity (alpha-2 macroglobulin), activation states (complement C3) and interaction states (laminins, perlecan, fibronectin, filamin-A, collagen XIV and apolipoprotein-B). Furthermore, we show that alpha-2 macroglobulin and collagen XIV exhibit possible shared structural consequences in IVD ageing and arterial atherosclerosis, providing novel links between an age-related disease and intrinsic ageing. Crucially, we also demonstrate that fibronectin, laminin beta chains and filamin-A all exhibit conserved age-associated structural differences between mouse lung and human IVD, providing evidence that ECM, and their associating proteins, may be subjected to potentially similar mechanisms or consequences of ageing across both species, irrespective of differences in lifespan and tissue function.

Cathepsin S (CTSS) activity in health and disease - A treasure trove of untapped clinical potential

Amongst the lysosomal cysteine cathepsin family of proteases, cathepsin S (CTSS) holds particular interest due to distinctive properties including a normal restricted expression profile, inducible upregulation and activity at a broad pH range. Consequently, while CTSS is well-established as a member of the proteolytic cocktail within the lysosome, degrading unwanted and damaged proteins, it has increasingly been shown to mediate a number of distinct, more selective roles including antigen processing and antigen presentation, and cleavage of substrates both intra and extracellularly. Increasingly, aberrant CTSS expression has been demonstrated in a variety of conditions and disease states, marking it out as both a biomarker and potential therapeutic target. This review seeks to contextualise CTSS within the cysteine cathepsin family before providing an overview of the broad range of pathologies in which roles for CTSS have been identified. Additionally, current clinical progress towards specific inhibitors is detailed, updating the position of the field in exploiting this most unique of proteases.

Improving the symptoms of post-traumatic osteoarthritis by α2-macroglobulin-rich serum

PURPOSE

Altered joint loading by trauma induces joint degeneration, eventually leading to the generation of post-traumatic osteoarthritis (PTOA). Recent studies have shown that α2-macroglobulin (A2M) inhibits PTOA, induced by anterior cruciate ligament transection (ACLT), pathogenesis by regulating proinflammatory cytokines and matrix metalloproteinases. However, the application of A2M is limited due to high prices. Therefore, the aim of this study is to explore the novel preparation of A2M.

MATERIALS AND METHODS

The early change of A2M in synovial fluid and serum was measured by ELISA. Ultra-filtered centrifugation was performed to prepare α2-macroglobulin-rich serum (A2MRS). The bioactivity of A2M in A2MRS was detected by improved Ellis and Gollas-Galvan method. The effects of A2MRS on PTOA were observed using immunohistochemistry, safranine O staining, micro X-ray, fluorescence molecular tomography etc.

RESULTS

The concentration of A2M in PTOA group was significantly higher than that in Sham group in synovial fluid on the third day after ACLT in rat PTOA model. On the contrary, a significant downregulation of A2M levels in PTOA group was observed compared to the Sham group in serum at the seventh day after ACLT. Secondly, A2MRS was prepared successfully, and the concentration and bioactivity of A2M in A2MRS was significantly higher than that in serum. Lastly, A2MRS not only reduced notably the production of secondary cartilage ossification, type 10 collagen and matrix metalloproteinase 13, but also increased profoundly the generation of type 2 collagen, aggrecan, and chondrocytes' number.

CONCLUSION

Our results indicate that A2MRS has protective effects on PTOA.

α2-macroglobulin-rich serum as a master inhibitor of inflammatory factors attenuates cartilage degeneration in a mini pig model of osteoarthritis induced by “idealized” anterior cruciate ligament reconstruction

Post-traumatic osteoarthritis is a special type of osteoarthritis and a common disease, with few effective treatments available. α2-Macroglobulin (α2M) is important to chondral protection in post-traumatic osteoarthritis. However, its injection into xenogeneic joint cavities involves safety hazards, limiting clinical applications. Exploring serum α2M-enriching strategies and the therapeutic effect and mechanism of α2M-rich serum (α2MRS) autologous joint injection to treat post-traumatic osteoarthritis has significant value. In the present study, a unique filtration process was used to obtain α2MRS from human and mini pig serum. We evaluated the potential of α2MRS in protecting against post-surgery cartilage degeneration. We identify the potential of α2MRS in reducing the expression of inflammatory cytokines and factors that hasten cartilage degeneration in post-operative conditions leading to post-traumatic osteoarthritis. The potential of α2MRS was analyzed in interleukin-1β induced human chondrocytes and mini pig models. In the chondrocyte model, α2MRS significantly promoted human chondrocyte proliferation and reduced apoptosis and chondrocyte catabolic cytokine gene transcription and secretion. The anterior cruciate ligament autograft reconstruction model of mini pigs was randomized into groups, operated on, and injected with α2MRS or saline. The results showed that α2MRS injection significantly suppressed the levels of inflammatory factors, improved gait, and showed significantly lower cartilage degeneration than the groups that did not receive α2MRS injections. This study highlights the chondroprotective effects of α2MRS, elucidated its potential applications against cartilage degeneration, and could provide a basis for the clinical translation of α2MRS.

Knockdown of NEK7 alleviates anterior cruciate ligament transection osteoarthritis (ACLT)-induced knee osteoarthritis in mice via inhibiting NLRP3 activation

Osteoarthritis is thought to be a NLRP3-related disease. NEK7 is an essential mediator for NLRP3 inflammasome activation. This study aimed to demonstrate whether NEK7 has regulatory roles in the pathogenesis of osteoarthritis. C57BL/6 mice were subjected to anterior cruciate ligament transection osteoarthritis (ACLT) for constructing animal models of osteoarthritis. Injection of adeno-associated virus (AAV) expressing NEK7-specific shRNA into the knee joints of mice, following of which immunohistochemistry, qRT-PCR, western blotting, Safranin-O Fast Green staining, ELISA, and co-immunoprecipitation were performed to determine the effects of NEK7. NEK7 was highly expressed in the joint tissues of ACLT mice. As compared with shScr, AAV delivery of NEK7 shRNA significantly inhibited cartilage degeneration, OARSI score, and serum CTX-II and COMP levels. AAV delivery of NEK7 shRNA downregulated the expression of matrix-degrading enzymes (ADAMTS-4, MMP3, and MMP13) and upregulated the expression of ECM-related molecules (SOX9, collagen II, and aggrecan). In addition, AAV delivery of NEK7 shRNA alleviated ACLT-induced synovial inflammation, as was evidenced by the decreased levels of TNF-α, IL-6, IL-1β, and IL-18 and increased levels of IL-10. In the joint tissues of ACLT mice, NEK7 interacted with NLRP3 proteins. AAV delivery of NEK7 shRNA inhibited the protein interaction, and thereby inhibited the activation of the NLRP3 inflammasome. AAV delivery of NEK7 shRNA has no significant effects on cartilage degeneration and synovial inflammation in Nlrp3^-/- mice. In conclusion, knockdown of NEK7 exerted anti-osteoarthritic effects, possibly via inhibiting the activation of the NLRP3 inflammasome. This study provided a novel mechanism of NEK7-NLRP3 interaction affecting osteoarthritis.

Orthobiologics for the Management of Early Arthritis in the Middle-Aged Athlete

This article is dedicated to the use of orthobiologic therapies in the management of early osteoarthritis in middle-aged athletes. Understanding a patient's presenting symptoms, physical examination, imaging results, and goals is of critical importance in applying orthobiologic therapies. The field of orthobiologics is expanding at a rapid pace, and the clinical studies examining the utility of each treatment lag behind the direct-to-consumer marketing that leads to these products being used. Here we provide a review of the available treatments, emerging treatments, and the current literature supporting or refuting their use. Currently studied orthobiologics include autologous and allogenic cell therapies, autologous blood products, hyaluronic acid, gene therapies, Wnt inhibitors, and a variety of systemic treatments.

Key Genes Identified in Nonsyndromic Microtia by the Analysis of Transcriptomics and Proteomics

As one of the common birth defects worldwide, nonsyndromic microtia is a complex disease that results from interactions between environmental and genetic factors. However, the underlying causes of nonsyndromic microtia are currently not well understood. The present study determined transcriptomic and proteomic profiles of auricular cartilage tissues in 10 patients with third-degree nonsyndromic microtia and five control subjects by RNA microarray and tandem mass tag-based quantitative proteomics technology. Relative mRNA and protein abundances were compared and evaluated for their function and putative involvement in nonsyndromic microtia. A total of 3971 differentially expressed genes and 256 differentially expressed proteins were identified. Bioinformatics analysis demonstrated that some of these genes and proteins showed potential associations with nonsyndromic microtia. Thirteen proteins with the same trend at the mRNA level obtained by the integrated analysis were validated by parallel reaction monitoring analysis. Several key genes, namely, LAMB2, COMP, APOA2, APOC2, APOC3, and A2M, were found to be dysregulated, which could contribute to nonsyndromic microtia. The present study is the first report on the transcriptomic and proteomic integrated analysis of nonsyndromic microtia using the same auricular cartilage sample. Additional studies are required to clarify the roles of potential key genes in nonsyndromic microtia.

Alpha-2-macroglobulin in hemostasis and thrombosis: An underestimated old double-edged sword

Antiproteinases such as alpha-2-macroglobulin (A2M) play a role in hemostasis. A2M is highly conserved throughout evolution and is a high molecular weight homo-tetrameric glycoprotein. A2M proteinase inhibitor activity is possible via a unique cage structure leading to proteinase entrapment without direct enzymatic activity inhibition. Following this entrapment, proteinase clearance is possible through A2M binding to the low-density lipoprotein receptor-related protein 1. A2M synthesis is regulated by pro-inflammatory cytokines and increases during several chronic or acute inflammatory diseases and varies with age. For instance, A2M plasma levels are known to be increased in patients with diabetes mellitus, nephrotic syndrome, or sepsis. Concerning hemostasis, A2M can trap many proteinases involved in coagulation and fibrinolysis. Because of its pleiotropic effects A2M can be seen as both anti- and pro-hemostatic. A2M can inhibit thrombin, factor Xa, activated protein C, plasmin, tissue-plasminogen activator, and urokinase. Through its many different functions A2M is generally put apart in the balanced regulation of hemostasis. In addition, the fact that A2M plasma levels are differently regulated during inflammatory-related diseases and that A2M can neutralize cytokines that also modify hemostasis could explain why it is difficult to link common proteins and parameters of hemostasis with the mechanisms of thrombosis in such diseases. Thus, we propose in the present review to summarize known functions of A2M, give a brief overview about diseases, and then to focus on the roles of this antiproteinase in hemostasis and thrombosis.

Alpha-2-Macroglobulin in Inflammation, Immunity and Infections

Alpha-2-macroglobulin is an extracellular macromolecule mainly known for its role as a broad-spectrum protease inhibitor. By presenting itself as an optimal substrate for endopeptidases of all catalytic types, alpha-2-macroglobulin lures active proteases into its molecular cage and subsequently ‘flags’ their complex for elimination. In addition to its role as a regulator of extracellular proteolysis, alpha-2-macroglobulin also has other functions such as switching proteolysis towards small substrates, facilitating cell migration and the binding of cytokines, growth factors and damaged extracellular proteins. These functions appear particularly important in the context of immune-cell function. In this review manuscript, we provide an overview of all functions of alpha-2-macroglobulin and place these in the context of inflammation, immunity and infections.

Comparison of Curative Effect of Human Umbilical Cord-Derived Mesenchymal Stem Cells and Their Small Extracellular Vesicles in Treating Osteoarthritis

Introduction

Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) and their small extracellular vesicles (hUC-MSC-sEVs) have shown attractive prospects applying in regenerative medicine. This study aimed to compare the therapeutic effects of two agents on osteoarthritis (OA) and investigate underlying mechanism using proteomics.

Methods

In vitro, the proliferation and migration abilities of chondrocytes treated with hUC-MSCs or hUC-MSC-sEVs were detected by Cell Counting Kit-8 assay and scratch wound assay. In vivo, hUC-MSCs (a single dose of 5 × 10⁵) or hUC-MSC-sEVs (30 μg/time) were injected into the knee joints of anterior cruciate ligament transection-induced OA model. Hematoxylin and eosin, Safranin O/Fast Green staining were used to observe cartilage degeneration. The levels of cartilage matrix metabolic molecules (Collagen II, MMP13 and ADAMTS5) and macrophage polarization markers (CD14, IL-1β, IL-10 and CD206) were assessed by immunohistochemistry. Finally, proteomics analysis was performed to characterize the proteinaceous contents of two agents.

Results

In vitro data showed that hUC-MSC-sEVs were taken up by chondrocytes. A total of 15 μg/mL of sEVs show the greatest proliferative and migratory capacities among all groups. In the animal study, hUC-MSCs and hUC-MSC-sEVs alleviated cartilage damage. This effect was mediated via maintaining cartilage homeostasis, as was confirmed by upregulation of the COL II and downregulation of the MMP13 and ADAMTS5. Moreover, the M1 macrophage markers (CD14) were significantly reduced, while the M2 macrophage markers (CD206 and IL-10) were increased in the hUC-MSCs and hUC-MSC-sEVs relative to the untreated group. Mechanistically, we found that many proteins connected to cartilage repair were more abundant in sEVs. Notably, compared to hUC-MSCs, the upregulated proteins in sEVs were mostly involved in the regulation of immune effector process, extracellular matrix organization, PI3K-AKT signaling pathways, and Rap1 signaling pathway.

Conclusion

Our study indicated that hUC-MSC-sEVs protect cartilage from damage and many cartilage repair-related proteins are probably involved in the restoration process. These data suggest the promising potential of hUC-MSC-sEVs as a therapeutic agent for OA.

Platelet-rich plasma treatment alleviates osteoarthritis-related pain, inflammation, and apoptosis by upregulating the expression levels of microRNA-375 and microRNA-337

OBJECTIVE

The present study was designed to determine the molecular mechanism by which platelet-rich plasma (PRP) acts on Osteoarthritis (OA) -related pain, inflammation, and apoptosis in vivo and in vitro.

MATERIALS AND METHODS

An in vivo OA model was established in rats using anterior cruciate ligament transection, and an in vitro OA model was created by treating chondrocytes with IL-1β. Then, the induced rats and chondrocytes were treated with PRP. Real-time PCR were used to examine the expression of micorRNAs (miRs) and mRNAs of inflammatory cytokines. WB were performed to detect the expression of apoptotic factors and Wnt/β-catenin signals. Structural damage of the cartilage and pain in OA rats were analyzed and represented by Mankin Score, OARSIS score, Tender threshold, and Thermal pain threshold. CCK-8 assay and flow cytometry were used to determine cell viability and apoptosis.

RESULTS

The expression levels of miR-337 and miR-375 were downregulated in the in vivo and vitro OA models; however, PRP treatment elevated their levels. miR-337 and miR-375 inhibition reversed the effects of PRP of reducing tenderness and thermal pain thresholds in OA rats. Moreover, PRP decreased the mRNA expression levels of MMP-13, Bax, and inflammatory factors, such as IL-1β, IL-18, and TNF-α, as well as increased the expression levels of collagen II and antiapoptotic Bcl-2. The decrease in inflammation and apoptosis was reversed by miR-337 and miR-375 inhibition, respectively.

DISCUSSION AND CONCLUSIONS

In conclusion, miR-337 and miR-375 are involved in PRP-delayed OA progression by affecting inflammation and apoptosis.

Complement system deregulation in SAPHO syndrome revealed by proteomic profiling

SAPHO syndrome is an inflammatory disease invading the skin and bones, whose diagnosis has been difficult due to its low incidence and diversified manifestation. We investigated the serum proteomic profile of SAPHO patients to identify key proteins associated with SAPHO syndrome, trying to find clinical biomarkers or functional molecules for this rare disease. Blood samples from 8 SAPHO patients and 8 healthy controls were detected and analyzed using data independent acquisition (DIA) method to identify differentially expressed proteins (DEPs) specific to SAPHO. A total of 57 differentially expressed proteins were identified (p < 0.05, fold change >1.2), in which 27 proteins were upregulated and 30 downregulated. DEPs may participate in GO terms such as "lipid particle" and "Notch signaling pathway", as well as KEGG pathways including "complement and coagulation cascades" and "mTOR signaling pathway". The overexpression of inhibitors of the complement system (CFH and C4BP), were verified in a larger cohort (16 SAPHO patients, 8 AS patients and 24 healthy controls) with ELISA, and the combined diagnostic ability of CFH and C4BP was predicted by ROC curve with an AUC of 0.91, which may be molecular candidates for further study on diagnosis and pathology of this rare disease. SIGNIFICANCE: Our research provided the first insight into plasma proteomic profile for SAPHO patients，offering potential biomarkers for disease diagnosis. We found that inhibitors of complement system such as CFH and C4BP were up-regulated in SAPHO syndrome, which may play important roles in the pathogenesis of SAPHO syndrome.

Enhancement of DUSP14 (dual specificity phosphatase 14) limits osteoarthritis progression by alleviating chondrocyte injury, inflammation and metabolic homeostasis

Osteoarthritis (OA) is a proverbial inflammatory degenerative joint disease associated with the acceleration of the aging process and is characterized by chondrocyte injury and articular cartilage degradation. Dual-specificity phosphatase 14 (Dusp14), a common member of the DUSP family, has been implicated in multiple inflammatory diseases and bone loss. Nevertheless, the function of DUSP14 in OA remains unclear. In the present study, down-regulation of DUSP14 was corroborated in anterior cruciate ligament transection (ACLT)-induced OA rats and interleukin-1β (IL-1β)-stimulated chondrocytes. Additionally, the gain of DUSP14 reversed IL-1β-induced inhibition of chondrocyte viability but attenuated cell apoptosis. Concomitantly, DUSP14 overexpression muted IL-1β-induced release of pro-inflammatory mediators NO and prostaglandin E2 (PGE2), as well as pro-inflammatory cytokine levels (IL-6 and TNF-α). Furthermore, up-regulation of DUSP14 overturned the effects of IL-1β on the inhibition of collagen II and aggrecan expression, and enhancement of A Disintegrin and Metalloproteinase with Thrombospondin Motifs 5 (ADAMTS5) and matrix metalloproteinases (MMPs; MMP3 and MMP-13). Mechanistically, DUSP14 elevation increased the p-Adenosine 5ʹ-monophosphate-activated protein activated protein kinase(AMPK), inhibitor of NF-κB (IκB) expression and decreased p-p65 NF-κB expression, indicating that DUSP14 might restore the AMPK-IκB pathway to restrain NF-κB signaling under IL-1β exposure. Notably, blockage of AMPK signaling muted the protective efficacy of DUSP14 elevation against IL-1β-induced inflammatory injury and metabolism disturbance in chondrocytes. Interestingly, histological evaluation substantiated that DUSP14 injection alleviated cartilage degradation in OA rats. Together, DUSP14 may ameliorate OA progression by affecting chondrocyte injury, inflammatory response and cartilage metabolism homeostasis, implying a promising therapeutic strategy against OA.

Regulation of ADAMTS Proteases

A disintegrin and metalloprotease with thrombospondin type I motifs (ADAMTS) proteases are secreted metalloproteinases that play key roles in the formation, homeostasis and remodeling of the extracellular matrix (ECM). The substrate spectrum of ADAMTS proteases can range from individual ECM proteins to entire families of ECM proteins, such as the hyalectans. ADAMTS-mediated substrate cleavage is required for the formation, remodeling and physiological adaptation of the ECM to the needs of individual tissues and organ systems. However, ADAMTS proteases can also be involved in the destruction of tissues, resulting in pathologies such as arthritis. Specifically, ADAMTS4 and ADAMTS5 contribute to irreparable cartilage erosion by degrading aggrecan, which is a major constituent of cartilage. Arthritic joint damage is a major contributor to musculoskeletal morbidity and the most frequent clinical indication for total joint arthroplasty. Due to the high sequence homology of ADAMTS proteases in their catalytically active site, it remains a formidable challenge to design ADAMTS isotype-specific inhibitors that selectively inhibit ADAMTS proteases responsible for tissue destruction without affecting the beneficial functions of other ADAMTS proteases. In vivo, proteolytic activity of ADAMTS proteases is regulated on the transcriptional and posttranslational level. Here, we review the current knowledge of mechanisms that regulate ADAMTS protease activity in tissues including factors that induce ADAMTS gene expression, consequences of posttranslational modifications such as furin processing, the role of endogenous inhibitors and pharmacological approaches to limit ADAMTS protease activity in tissues, which almost exclusively focus on inhibiting the aggrecanase activity of ADAMTS4 and ADAMTS5.

Development of selective protease inhibitors via engineering of the bait region of human α2-macroglobulin

Human α₂-macroglobulin (A2M) is an abundant protease inhibitor in plasma, which regulates many proteolytic processes and is involved in innate immunity. A2M’s unique protease-trapping mechanism of inhibition is initiated when a protease cleaves within the exposed and highly susceptible “bait region.” As the wild-type bait region is permissive to cleavage by most human proteases, A2M is accordingly a broad-spectrum protease inhibitor. In this study, we extensively modified the bait region in order to identify any potential functionally important elements in the bait region sequence and to engineer A2M proteins with restrictive bait regions, which more selectively inhibit a target protease. A2M in which the bait region was entirely replaced by glycine-serine repeats remained fully functional and was not cleaved by any tested protease. Therefore, this bait region was designated as the “tabula rasa” bait region and used as the starting point for further bait region engineering. Cleavage of the tabula rasa bait region by specific proteases was conveyed by the insertion of appropriate substrate sequences, e.g., basic residues for trypsin. Screening and optimization of tabula rasa bait regions incorporating matrix metalloprotease 2 (MMP2) substrate sequences produced an A2M that was specifically cleaved by MMPs and inhibited MMP2 cleavage activity as efficiently as wild-type A2M. We propose that this approach can be used to develop A2M-based protease inhibitors, which selectively inhibit target proteases, which might be applied toward the clinical inhibition of dysregulated proteolysis as occurs in arthritis and many types of cancer.

Platelet-Rich Plasma Combined with Alendronate Reduces Pain and Inflammation in Induced Osteoarthritis in Rats by Inhibiting the Nuclear Factor-Kappa B Signaling Pathway

Purpose

Osteoarthritis (OA) is one of the common degenerative diseases of the joint in the world. This study was designed to explore the effect of platelet-rich plasma (PRP) combined with alendronate (ALN) on OA.

Methods

We induced OA model by anterior cruciate ligament transection (ACLT) method in rats and treating chondrocytes by IL-1β in vitro. PRP and/or ALN were used to treat induced rats and chondrocytes. Hematoxylin and eosin (H&E) and Safranin O staining were used to observe the structures of cartilage. The mRNA expression of Collagen II, MMP-13, and inflammatory factors (IL-18, IL-1β, and TNF-α) in the cartilage and chondrocytes of rats was determined by qRT-PCR. The expression of NF-κB pathway-related proteins (p-p65, p65, IκBα, and p-IκBα) in the cartilage and chondrocytes of rats was determined by Western blot. The proliferation of chondrocytes was detected by MTT assay.

Results

Treatment with PRP, ALN, or PRP combined with ALN decreased the degree of cartilage destruction, the mRNA expression of MMP-13 and inflammatory factors (IL-18, IL-1β, and TNF-α), and the protein expression of p-IκBα/IκBα and p-p65/p65, increased Collagen II expression, and the threshold of tender and thermal pain in OA rats. Meanwhile, ALN, PRP, or ALN combined with PRP reversed the inhibiting effect of phorbol myristate acetate (PMA, an NF-κB agonist) on cell proliferation and cartilage matrix metabolism. Among them, the effects of ALN combined with PRP were most obvious.

Conclusion

PRP combined with ALN delayed OA progression by inhibiting the NF-κB signaling pathway.

In vitro preconditioning of equine adipose mesenchymal stem cells with prostaglandin E2, substance P and their combination changes the cellular protein secretomics and improves their immunomodulatory competence without compromising stemness

Mesenchymal stem cells (MSC) are modern tools in regenerative therapies of humans and animals owed to their immunomodulatory properties, which are activated in a pro-inflammatory environment. Different preconditioning strategies had been devised to enhance the immunomodulatory properties of MSC. In this research, we evaluated the immunological attributes of equine adipose MSC (eAMSC) before and after preconditioning in vitro with prostaglandin E₂ (PGE₂), substance P (SP), their combination and IFNγ. PGE₂/SP was the best combination to keep or enhance the mesodermal lineage differentiation of eAMSC. Alongside with this, preconditioning of eMSC with PGE₂ and SP did not affect expression of stemness MSC surface phenotype: CD90⁺, CD44⁺, MHC class I⁺, MHC class II^- and CD45^-, assessed by cytometry. Both naïve and preconditioned eAMSC expressed genes related with immune properties, such as MHC-I, PTGES, IL6, IL1A, TNFα and IL8 assessed by qPCR. Only TNFα was under expressed in treated cells, while the other markers were either overexpressed or not changed. In no cases MHC-II expression was detected. The antiproliferative effect of preconditioned eAMSC exposed to activated peripheral blood mononuclear cells (PBMC) showed that SP treatment significantly inhibited proliferation of LPS stimulated PBMC. When eAMSC were stimulated with Poly I:C, all the treatments significantly inhibited proliferation of stimulated PBMC (p < 0.05). Direct contact (coculture) between the preconditioned eAMSC and PBMC, induced a shift of significantly more (CD4/CD25/FOXP3)⁺ T-regulatory PBMC than naïve eAMSC. In the experiments of this research, we investigated the secreted proteomic profile of naïve and preconditioned eAMSC, 42 up-regulated and 40 down-regulated proteins were found in the proteomic assay. Our proteomic data revealed profound changes in the secretory pattern of MSC exposed to different treatments, compared to naïve eAMSC as well as among treatments. In overall, compared to naïve cells, the protein profile of preconditioned cells resembled the mesenchymal-epithelial transition (MET). Here we showed that the combined use of PGE₂ and SP provoked in overall the highest expression of anti-inflammatory markers as well as lead to an increased acquisition of a T-regulatory phenotype in preconditioned eAMSC without affecting their "stemness".

Molecular and structural imaging in surgically induced murine osteoarthritis

Preclinical imaging in osteoarthritis is a rapidly growing area with three principal objectives: to provide rapid, sensitive tools to monitor the course of experimental OA longitudinally; to describe the temporal relationship between tissue-specific pathologies over the course of disease; and to use molecular probes to measure disease activity in vivo. Research in this area can be broadly divided into those techniques that monitor structural changes in tissues (microCT, microMRI, ultrasound) and those that detect molecular disease activity (positron emission tomography (PET), optical and optoacoustic imaging). The former techniques have largely evolved from experience in human joint imaging and have been refined for small animal use. Some of the latter tools, such as optical imaging, have been developed in preclinical models and may have translational benefit in the future for patient stratification and for monitoring disease progression and response to treatment. In this narrative review we describe these methodologies and discuss the benefits to animal research, understanding OA pathogenesis, and in the development of human biomarkers.

Protective effect of ethyl acetate fraction from Semen sojae germinatum, the processed sprout of Chinese black soybean, on rat experimental osteoarthritis

BACKGROUND

Our previous in vitro study reported that the ethyl acetate fraction (EAF) of Semen sojae germinatum (SSG), the processed sprout of Chinese black soybean, possessed the potent anti-inflammatory and chondroprotective properties. The aim of the present work was to verify the in vivo antiosteoarthritic effect of EAF from SSG on a rat osteoarthritis (OA) model .

METHODS

A classical rat OA model was surgically induced by anterior cruciate ligament transaction (ACLT). The OA rats were intra-articularly administered EAF from SSG for 8 weeks. The cartilage and synovial tissues were stained with hematoxylin and eosin (HE) to observe the histopathological changes. Safranin O/fast green staining was used to assess the glycosaminoglycan content in cartilage tissue sections. The expression of type II collagen and matrix metalloproteinase (MMP)-13 in cartilage was measured by immunohistochemistry. The apoptotic chondrocytes in the cartilage sections were detected using TUNEL assay. The concentrations of interleukin (IL)-1β and tumor necrosis factor (TNF)-ɑ in synovial fluid were determined using ELISA.

RESULTS

Intra-articular administration of EAF from SSG well retained the structure and superficial layer of cartilage tissues, ameliorated cartilage lesion and the degradation of cartilage matrix, including proteoglycan and type II collagen, induced by ACLT operation. The ACLT-induced upregulation of MMP-13 expression in the cartilage tissues was resisted by EAF from SSG. Moreover, EAF from SSG inhibited the ACLT-induced chondrocyte apoptosis. Compared to OA model group, the inflammatory status of synovial membrane was improved, the levels of inflammatory cytokines IL-1β and TNF-ɑ in synovial fluid were decreased in rats administrated with EAF from SSG.

CONCLUSION

These data suggested that EAF from SSG displayed in vivo protective effect on OA development via preventing the degeneration of articular cartilage, inhibiting chondrocyte apoptosis and suppressing synovial inflammation.

Effects of tetrahedral framework nucleic acid/wogonin complexes on osteoarthritis

Osteoarthritis, a disorder characterized by articular cartilage deterioration, varying degrees of inflammation, and chondrocyte apoptosis, is the most common chronic joint disease. To slow or reverse its progression, inflammation should be inhibited, and chondrocyte proliferation should be promoted. Tetrahedral framework nucleic acids can be internalized by chondrocytes (even inflammatory chondrocytes) and can enhance their proliferation and migration. Wogonin, a naturally occurring flavonoid, suppresses oxidative stress and inhibits inflammation. In this study, tetrahedral framework nucleic acids were successfully self-assembled and used to load wogonin. We confirmed the effective formation of tetrahedral framework nucleic acid/wogonin complexes by dynamic light scattering, zeta potential analysis, transmission electron microscopy, and fluorescence spectrophotometry. Tetrahedral framework nucleic acids, wogonin, and especially tetrahedral framework nucleic acid/wogonin complexes effectively alleviated inflammation in vitro and in vivo and prevented cartilage destruction. In addition, these materials remarkably downregulated the expression of inflammatory mediators and matrix metalloproteinases, upregulated chondrogenic markers, and promoted tissue inhibitor of metalloproteinase 1 and B-cell lymphoma 2 expression. In vivo, after treatment with tetrahedral framework nucleic acid/wogonin complexes, the bone mineral density in regenerated tissues was much higher than that found in the untreated groups. Histologically, the complexes enhanced new tissue regeneration, significantly suppressed chondrocyte apoptosis, and promoted chondrogenic marker expression. They also inhibited cell apoptosis, increased chondrogenic marker expression, and suppressed the expression of inflammatory mediators in osteoarthritis. Therefore, we believe that tetrahedral framework nucleic acid/wogonin complexes can be used as an injectable form of therapy for osteoarthritis.

Role of Alpha-2-Microglobulin in the Treatment of Osteoarthritic Knee Pain: a Brief Review of the Literature

PURPOSE OF REVIEW

Chronic knee pain remains a debilitating condition that remains difficult to manage. The purpose of this review, therefore, is to summarize current understanding of alpha-2-microglobulin in the treatment of osteoarthritic knee pain. Furthermore, we investigate its role in the anti-inflammatory properties of platelet-rich plasma (PRP).

RECENT FINDINGS

Alpha-2-microglobulin, a 720-kD protein complex, is an active protease inhibitor with tremendous anti-inflammatory properties in animal models. A growing body of evidence suggests that this complex is the most instrumental factor for cartilage preservation in PRP injections. As an active component of platelet-rich plasma's anti-inflammatory properties, alpha-2-microglobulin has been shown to be an active inhibitor of joint degeneration, cartilage preservation, and improvement in quality of life for patients with knee osteoarthritis compared with a multitude of other modalities.

Involvement of TLR4 in the protective effect of intra-articular administration of curcumin on rat experimental osteoarthritis

PURPOSE

In view of the principal role of Toll-like receptor 4 (TLR4) in mediating sterile inflammatory response contributing to osteoarthritis (OA) pathogenesis, we used lipopolysaccharide (LPS), a known TLR4 activator, to clarify whether modulation of TLR4 contributed to the protective actions of intra-articular administration of curcumin in a classical rat OA model surgically induced by anterior cruciate ligament transection (ACLT).

METHODS

The rats underwent ACLT and received 50μl of curcumin at the concentration of 1 mg mL-1 and 10 μg LPS by intra-articular injection once a week for 8 weeks. Morphological changes of the cartilage and synovial tissues were observed. Apoptotic chondrocytes were detected using TUNEL assay. The concentrations of IL-1β and TNF-ɑ in synovial fluid were determined using ELISA kits. The mRNA and protein expression levels of TLR4 and NF-κB p65 were detected by real-time PCR and Western blotting, respectively.

RESULTS

Intra-articular administration of curcumin significantly improved articular cartilage injury, suppressed synovial inflammation and down-regulated the overexpression of TLR4 and its downstream NF-κB caused by LPS-induced TLR4 activation in rat osteoarthritic knees.

CONCLUSION

The data suggested that the inhibition of TLR4 signal might be an important mechanism underlying a protective effect of local curcumin administration on OA.

MiR-146b accelerates osteoarthritis progression by targeting alpha-2-macroglobulin

Osteoarthritis (OA) is an aging-related chronic degenerative disease characterized by the degradation of chondrocyte extracellular matrix (ECM). Previous studies have suggested that microRNAs (miRNAs) are associated with OA, but the role of miR-146b in OA remains unclear. The aim of this study was to determine the role of miR-146b in OA progression. The effect of miR-146b on ECM degradation were studied in mouse chondrocytes transfected with miRNA and treated with IL-1β. Cell viability and the expression levels of proteolytic enzymes in the transfected cells were assessed by real-time RT-PCR, ELISA and Western blots. We found downregulation of miR-146b expression in chondrocytes dramatically inhibited IL-1β-induced caspase activation and proteolytic enzyme expression via influencing its targeted Alpha-2-macroglobulin (A2M). Luciferase reporter assays confirmed that A2M mRNA was negatively regulated by miR-146b in chondrocytes. Intra-articular injection of antago-miR-146b against miR-146b effectively protected mice from the progression of DMM-induced osteoarthritis by inhibiting cartilage proteoglycan degradation. Our study indicates that miR-146b plays a critical role in the progression of injury-induced osteoarthritis by directly targeting A2M expression to elevate the proteolytic enzyme production and stimulate chondrocytes apoptosis, and miR-146b as well as A2M could be therapeutic targets.

Alpha-2-Macroglobulin, a Hypochlorite-Regulated Chaperone and Immune System Modulator

Alpha-macroglobulins are ancient proteins that include monomeric, dimeric, and tetrameric family members. In humans, and many other mammals, the predominant alpha-macroglobulin is alpha-2-macroglobulin (α₂M), a tetrameric protein that is constitutively abundant in biological fluids (e.g., blood plasma, cerebral spinal fluid, synovial fluid, ocular fluid, and interstitial fluid). α₂M is best known for its remarkable ability to inhibit a broad spectrum of proteases, but the full gamut of its activities affects diverse biological processes. For example, α₂M can stabilise and facilitate the clearance of the Alzheimer's disease-associated amyloid beta (Aβ) peptide. Additionally, α₂M can influence the signalling of cytokines and growth factors including neurotrophins. The results of several studies support the idea that the functions of α₂M are uniquely regulated by hypochlorite, an oxidant that is generated during inflammation, which induces the native α₂M tetramer to dissociate into dimers. This review will discuss the evidence for hypochlorite-induced regulation of α₂M and the possible implications of this in neuroinflammation and neurodegeneration.

Early supplemental α2-macroglobulin attenuates cartilage and bone damage by inhibiting inflammation in collagen II-induced arthritis model

OBJECTIVE

To determine if early supplemental intra-articular α2-macroglobulin (A2M) has a chondroprotective effect in a collagen II-induced arthritis (CIA) mice model.

METHODS

DBA/1 mice were randomized into four groups (n = 15/group): (a) CIA + 1.2 μg of A2M; (b) CIA + 0.8 μg of A2M; (c) CIA + 0.4 μg of A2M; (d) vehicle + phosphate-buffered saline (PBS). A2M was injected into right ankles and PBS was injected into the left ankles simultaneously as internal control at days 36, 43 and 50. The CIA inflammation clinical score and ankle thickness were recorded every other day starting on day 21 until sacrifice. Changes in inflammation were monitored by in vivo fluorescence molecular tomography (FMT). Inflammation, cartilage and bone damage were assessed with X-ray, histology and immunohistochemistry. Cartilage and inflammation-related gene expression was quantified by real-time polymerase chain reaction (PCR).

RESULTS

All mice showed ankle inflammation on day 33. After day 43, lower clinical scores, ankle thickness and Sharp/van der Heijde method scores in A2M-treated ankles compared with PBS-treated ankles. FMT data indicated that the inflammation markers MMPSense and ProSense were significantly elevated in the PBS-treated ankles than A2M-treated ankles. Histology and X-ray analyses indicated that A2M administration resulted in lower levels of inflammatory infiltration and synovial hyperplasia, as well as more typical cartilage and bone organization with increased COL II and Aggrecan staining when compared with PBS-treated ankles. In addition, real-time PCR showed that,matrix metalloproteinase-3, -9, -13, COL X and Runx2 were significantly less expressed in A2M-treated groups than PBS-treated animals.

CONCLUSION

Early supplemental intra-articular A2M exerts an anti-inflammatory effect and attenuates cartilage and bone damage in a CIA model.

The Effects of Indian Hedgehog Deletion on Mesenchyme Cells: Inducing Intermediate Cartilage Scaffold Ossification to Cause Growth Plate and Phalange Joint Absence, Short Limb, and Dwarfish Phenotypes

The endochondral ossification plays a critical role in vertebrate limb development and skeletal homeostasis, where limb mesenchyme cells form an intermediate cartilage scaffold that develops into growth plates and then replaced by bone. Although Indian hedgehog (Ihh) is known to control the hypertrophic differentiation process of chondrocytes, its role from the mesenchyme cells to the early stages of chondrogenesis is unclear. To define the function of Ihh in the mesenchymal cell's early stages of chondrogenesis, we specifically delete Ihh in Prx1-expressed mesenchyme cells at E9.5 using Prx1-Cre;Ihh^fl/fl;Rosa26^-ZsGreen1 mice. We found that deleting Ihh in the mesenchyme cells results in an early and quick ossification of the intermediate cartilage scaffold, causing the growth plate and phalange joint absence, short limbs, and dwarfishness. The green fluorescent protein (GFP)-positive cells derived from deleted Ihh mesenchyme cells overlap with von Kossa- and osteocalcin-positive staining area. These deleted Ihh/GFP-positive cells isolated from Prx1-Cre;Ihh^fl/fl;Rosa26^-ZsGreen1 newborn mice had osteogenic differentiation by showing a positive Alizarin red and von Kossa staining, as well as an enhanced Col1a1, osteocalcin, and Runx2 expression. Our findings demonstrate that deleting Ihh in mesenchyme cells during early limb development promotes intermediate cartilage scaffold ossification, which prevents growth plate formation that causes phalange joint absence, short limb, and dwarfish phenotype.

Comparison of phenotypes and transcriptomes of mouse skin-derived precursors and dermal mesenchymal stem cells

Both skin-derived precursors (SKPs) and dermal mesenchymal stem cells (dMSCs) are promising candidates for cellular therapy and regenerative medicine. To date the comparison of phenotypes and transcriptomes of mouse SKPs (mSKPs) and dMSCs has never been reported. Here we characterized and compared the biological properties and transcriptomes of mSKP and dMSCs from the same mouse dermis sample. Firstly, we analyzed mSKPs and dMSCs by use of immunocytochemistry, cell cycle analysis, and CD antigen expression. Then we conducted the osteogenic, adipogenic, and chondrogenic induced differentiation for both cell types. Lastly, we compared their genomic profiles by RNA-sequencing (RNA-Seq), and verified the results of RNA-Seq by quantitative real time reverse transcription PCR (qRT-PCR). The results suggested that mSKPs and dMSCs shared similarities in certain positive stem cells markers expression, but demonstrated difference in Nanog and Oct4 expression. mSKPs and dMSCs demonstrated similar cell cycle distribution and CD antigen expression. Both types of cells could be induced differentiated into osteocytes, adipocytes, and chondrocytes. However, RNA-Seq and qRT-PCR results indicated that mSKPs and dMSCs had distinct transcriptome profiles. The majority of enriched differentially expressed genes (DEGs) from mSKPs was immune-related, while the majority of enriched DEGs from dMSCs was differentiation/development/disease-related. Transcriptome profiles suggested that mSKPs and dMSCs might have potential usage in the relevant morbidity management. These results may indicate a molecular basis for novel stem cell-based therapeutic strategies.

Estrogen Promotes Mandibular Condylar Fibrocartilage Chondrogenesis and Inhibits Degeneration via Estrogen Receptor Alpha in Female Mice

Temporomandibular joint degenerative disease (TMJ-DD) is a chronic form of TMJ disorder that specifically afflicts people over the age of 40 and targets women at a higher rate than men. Prevalence of TMJ-DD in this population suggests that estrogen loss plays a role in the disease pathogenesis. Thus, the goal of the present study was to determine the role of estrogen on chondrogenesis and homeostasis via estrogen receptor alpha (ERα) during growth and maturity of the joint. Young and mature WT and ERαKO female mice were subjected to ovariectomy procedures and then given placebo or estradiol treatment. The effect of estrogen via ERα on fibrocartilage morphology, matrix production, and protease activity was assessed. In the young mice, estrogen via ERα promoted mandibular condylar fibrocartilage chondrogenesis partly by inhibiting the canonical Wnt signaling pathway through upregulation of sclerostin (Sost). In the mature mice, protease activity was partly inhibited with estrogen treatment via the upregulation and activity of protease inhibitor 15 (Pi15) and alpha-2-macroglobulin (A2m). The results from this work provide a mechanistic understanding of estradiol on TMJ growth and homeostasis and can be utilized for development of therapeutic targets to promote regeneration and inhibit degeneration of the mandibular condylar fibrocartilage.