Combined effects of TNF-α, IL-1β, and HIF-1α on MMP-2 production in ACL fibroblasts under mechanical stretch: an in vitro study

TGF-β1 and Mechanical-Stretch Induction of Lysyl-Oxidase and Matrix-Metalloproteinase Expression in Synovial Fibroblasts Requires NF-κB Pathways

The imbalance in the expression of matrix metalloproteinases (MMPs) and lysyl oxidases (LOXs) in synovial fibroblasts (SFs) caused by mechanical injury and inflammatory response prevents injured anterior cruciate ligaments (ACLs) from self-healing. However, research on the effect of growth factors on SFs on regulating the microenvironment is limited. In this study, mechanical injury and exogenous transform growth factor-β1 (TGF-β1) were employed to mimic a joint-cavity microenvironment with ACL trauma. The function of the NF-κB transcription factor was further studied. The study found that the gene expression of LOXs (except LOXL-1), MMP-1, -2, and -3 in SFs was promoted by the combination of injurious mechanical stretching and TGF-β1 and that the upregulation of MMPs was higher than that of LOXs. In addition, MMP-2 activity induced by the combination of injurious stretch and TGF-β1 was inhibited by NF-κB inhibitors such as Bay11-7082 and Bay11-7085. The findings concluded that the synovium was an important regulator of the knee joint-cavity microenvironment after ACL injury and that the NF-κB pathway mediated the regulation of MMP-2 in SFs via mechanical factors and TGF-β1.

Mechano Growth Factor Accelerates ACL Repair and Improves Cell Mobility of Mechanically Injured Human ACL Fibroblasts by Targeting Rac1-PAK1/2 and RhoA-ROCK1 Pathways

Exceeded mechanical stress leads to a sublethal injury to anterior cruciate ligament (ACL) fibroblasts, and it will hinder cell mobility and ACL regeneration, and even induce osteoarthritis. The mechano growth factor (MGF) could be responsible for mechanical stress and weakening its negative effects on cell physiological behaviors. In this study, effects of MGF on cell mobility and relevant molecules expression in injured ACL fibroblasts were detected. After an injurious mechanical stretch, the analysis carried out, at 0 and 24 h, respectively, showed that the cell area, roundness, migration, and adhesion of ACL fibroblasts were reduced. MGF (10, 100 ng/mL) treatment could improve cell area, roundness and promote cell migration and adhesion capacity compared with the injured group without MGF. Further study indicated that cell mobility-relevant molecules (PAK1/2, Cdc42, Rac1, RhoA, and ROCK1) expression in ACL fibroblasts was down-regulated at 0 or 24 h after injurious stretch (except Rac1 and RhoA at 0 h). Similarly, MGF improved cell mobility-relevant molecule expression, especially the ROCK1 expression level in ACL fibroblasts at 0 or 24 h after injurious stretch. Protein expression of ROCK1 in injured ACL fibroblasts was also reduced and could be recovered by MGF treatment. In a rabbit partial ACL transection (ACLT) model, ACL exhibited poor regenerative capacity in collagen and extracellular matrix (ECM) synthesis after partial ACLT for 2 or 4 weeks, and MGF remarkably accelerated ACL regeneration and restored its mechanical loading capacity after partial ACLT for four weeks. Our findings suggest that MGF weakens the effects of pathological stress on cell mobility of ACL fibroblasts and accelerates ACL repair, and might be applied as a future treatment approach to ACL rupture in the clinic.

Acute promyelocytic leukemia drug - arsenic trioxide in the presence of eugenol shows differential action on leukemia cells (HL-60) and cardiomyocytes (H9c2) - inference from NMR study

The increased concern of cardiovascular dysfunction by cancer therapeutics has led to more effective treatment strategies. Arsenic trioxide (As₂O₃) is a potential chemotherapeutic agent for acute promyelocytic leukemia (APL), but the effectiveness is affected by potential cardiotoxicity. Researchers have been trying to find out novel modalities to manage the adverse effects of As₂O₃. In our study, the antioxidant molecule eugenol showed protective action against the destructive impact of As₂O₃ on cardiomyocytes (H9c2) without compromising the anti-cancer property As₂O₃ on leukemia cells (HL-60). We have studied the interaction between arsenic and eugenol in physiological and acidic pH to understand the molecular mechanism of differential action of As₂O₃ in the presence of eugenol using NMR spectroscopy. The study observed that at physiological pH, arsenic and eugenol interact to form an inactive product, positively affecting H9c2 cardiomyocytes. Still, there is no such interaction in acidic pH evidenced by the useful anti-cancer property of As₂O₃. The result concludes that the antioxidant molecule eugenol is an efficient protective agent against the adverse effect of As₂O₃ on cardiomyocytes.

Therapeutic Applications of Type 2 Diabetes Mellitus Drug Metformin in Patients with Osteoarthritis

Type 2 diabetes mellitus (T2DM) and osteoarthritis (OA) are common chronic diseases that frequently co-exist. The link between OA and T2DM is attributed to common risk factors, including age and obesity. Several reports suggest that hyperglycemia and accumulated advanced glycosylation end-products might regulate cartilage homeostasis and contribute to the development and progression of OA. Metformin is used widely as the first-line treatment for T2DM. The drug acts by regulating glucose levels and improving insulin sensitivity. The anti-diabetic effects of metformin are mediated mainly via activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), which is an energy sensing enzyme activated directly by an increase in the AMP/ATP ratio under conditions of metabolic stress. Dysregulation of AMPK is strongly associated with development of T2DM and metabolic syndrome. In this review, we discuss common risk factors, the association between OA and T2DM, and the role of AMPK. We also address the adaptive use of metformin, a known AMPK activator, as a new drug for treatment of patients with OA and T2DM.

Effect of mechanical injury and IL-1β on the expression of LOXs and MMP-1, 2, 3 in PCL fibroblasts after co-culture with synoviocytes

BACKGROUND

Crosstalk between posterior cruciate ligament fibroblasts (PCLfs) and synoviocytes (SCs) significantly modifies the homeostatic balance of the extracellular matrix (ECM) and appears to post a prominent affection for wound healing of PCL. Interleukin-1β (IL-1β) is regarded as a critical factor in acute inflammatory events during ligament injury.

METHODS

In order to confirm the capability of SCs the response of lysyl oxidases (LOXs) and matrix metalloproteinases (MMPs) to IL-1β, the complex cues of the joint cavity following PCL injury were simulated and the effect of IL-1β on the expression of LOXs and MMPs in PCLfs were investigated. PCLfs in both the mono- and co-culture conditions were treated with IL-1β. Cell lysates were collected from the PCLfs and LOXs and MMP-1, 2, 3 expression quantified using quantitative real-time PCR and western bolting.

RESULTS

The results indicated that injury alone elevated the expression of LOXs and MMP-1, 2 and 3. But IL-1β significantly decreased the LOX, LOXL1, and LOXL3 expression, and simultaneously increased MMP-1, 2 and 3 expressions in injured PCLfs. Furthermore, co-culture further suppressed LOXs, but stimulated MMP-1, 2 and 3 expressions when subjected to both mechanical injury and IL-1β treatment. This possibly suggests that a number of soluble factors are secreted that act as mediators that amplify the response of SCs.

CONCLUSION

The results indicated that the SCs could affect the IL-1β-induction of LOXs inhibition and MMPs accumulation, which may be the underlying mechanism of the the poor healing response following PCL injury.

Novel glucosamine-loaded thermosensitive hydrogels based on poloxamers for osteoarthritis therapy by intra-articular injection

Glucosamine (GlcN) is a common drug used to treat osteoarthritis (OA). To prolong the action time of glucosamine on OA and improve its therapeutic effect, this research explored the potential application of GlcN-loaded thermosensitive hydrogels based on poloxamer 407 and poloxamer 188 for OA therapy by intra-articular injection. The thermosensitive hydrogels were prepared by cold method, and the effects of P407, P188, and GlcN on sol-gel transition temperature (T_sol-gel) were compared. After screening was performed, the optimized formulation showed good temperature sensitivity, and T_sol-gel was approximately 35 °C. In vitro release tests showed that GlcN was slowly released from the thermosensitive hydrogels. After the gels were intra-articularly administered to treat OA in rabbits, the degree of swelling and inflammatory factors were significantly decreased in the hydrogel group compared with those in the OA model group (P < 0.05). Histological results showed that the GlcN-administered group had a good repair effect on damaged cartilage. At the same dose, the effect of the thermosensitive hydrogels was better than that of the aqueous solution. Therefore, GlcN-loaded thermosensitive hydrogels based on poloxamers are promising sustainable delivery systems for OA therapy by intra-articular injection.

TIGAR mediates the inhibitory role of hypoxia on ROS production and apoptosis in rat nucleus pulposus cells

OBJECTIVE

Hypoxia has been shown to inhibit reactive oxygen species (ROS) production in nucleus pulposus (NP) cells. The TP53-induced glycolysis and apoptosis regulator (TIGAR) has been reported to suppress oxidative stress. We sought to explore the role of TIGAR in the effect of hypoxia on ROS production and apoptosis.

METHODS

An intervertebral disc degeneration (IDD) model of Sprague-Dawley (SD) rat caudal spine was established by puncturing the Co_6-7 disc. TIGAR expression was detected by immunohistochemistry and western blotting in human and SD rat NP tissues of degenerated discs. Rat primary NP cells treated with hypoxia and cobalt chloride (CoCl₂) were analyzed by western blotting for TIGAR expression. After TIGAR silence with TIGAR siRNA transfection, apoptosis percentage, mitochondrial and total intracellular ROS levels were measured. H₂O₂ was used to further check the effects of TIGAR on oxidative stress. Finally, NADPH/NADP⁺ and GSH/GSSH ratio were examined after TIGAR silencing under hypoxic conditions and after H₂O₂ treatment.

RESULTS

A degree-dependent increase in TIGAR expression was observed in human and rat degenerated NP tissues. Hypoxia and hypoxia-inducer CoCl₂ enhanced TIGAR and P53 expressions in rat NP cells. TIGAR silence reversed the inhibitory effects of hypoxia on intracellular and mitochondrial ROS production, as well as apoptosis percentage. However, TIGAR silence aggravated H₂O₂-induced ROS production. In addition, TIGAR increased NADPH/NADP⁺ and GSH/GSSH ratio in NP cells.

CONCLUSIONS

These results suggested that TIGAR appears to mediate the protective role of hypoxia on ROS production and apoptosis percentage by enhancing NADPH/NADP⁺ and GSH/GSSH ratio.

MMP-2 as an early synovial biomarker for cranial cruciate ligament disease in dogs

Objectives: To measure the activity of matrix metalloproteinases (MMP)-2 and -9 in synovial fluid from the stifle joints of dogs with cranial cruciate ligament (CrCL) rupture and to compare that to values from contralateral stifle joints and dogs with clinically normal stifle joints. Additionally, the C-reactive protein (CRP) levels were also measured.

Methods: Fourteen large breed dogs with unilateral CrCL rupture and 11 large breed normal dogs were included in this prospective clinical study. Synovial fluid was collected from CrCL-ruptured stifle joints, contralateral clinically normal stifle joints of the same dogs, and stifle joints of normal dogs. Serum was also collected. Synovial fluid activities of MMP-2 and MMP-9 and serum CRP level were measured.

Results: The MMP-2 activity in synovial fluid was significantly higher in CrCL-ruptured joints compared to contralateral joints and to stifles from normal dogs. There was no significant difference in activity of MMP-2 in contralateral joints of CrCL-ruptured dogs compared to normal dogs. Both serum CRP level and MMP-9 activity did not differ significantly between the studied conditions.

Clinical significance: It was confirmed that MMP-2 activity is significantly related to CrCL rupture, but there was a failure to demonstrate any significant increase in the contralateral joints compared to the stifle joints of normal dogs. The MMP-2 involvement in progressing CrCL disease still has to be defined.

Combined effects of tumor necrosis factor-α and interleukin-1β on lysyl oxidase and matrix metalloproteinase expression in human knee synovial fibroblasts in vitro

Previous studies have demonstrated that inflammatory cytokines are associated with matrix metalloproteinases (MMPs) and/or lysyl oxidases (LOXs) produced by anterior cruciate ligament (ACL) fibroblasts, which may contribute to the poor healing ability of the ACL. To evaluate whether the synovium also participates in ACL healing, the inflammatory microenvironment of the knee joint cavity was mimicked following ACL injury, and the combined effects of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) on the expression of MMPs and LOXs in synovial fibroblasts were studied. Cell viability was evaluated using trypan blue staining in the presence of TNF-α and IL-1β, and the expression of LOXs and MMPs was measured by reverse transcription-quantitative polymerase chain reaction. MMP-2 activity was also measured by zymography. The results indicated that the combined effects of TNF-α and IL-1β inhibited LOX expression, while promoting MMP-1, −2 and −3 expression and MMP-2 activity in synovial fibroblasts. These changes may impede healing by altering the balance between the degradative and biosynthetic arms of the ligament tissue remodeling process. Collectively, the present results suggest that the poor healing ability of cruciate ligaments may be due to the sensitivity of the synovium to inflammatory factors. Therefore, the synovium potentially serves a key regulatory role in the joint cavity microenvironment and in the healing process of the ACL, and thus should be considered as a therapeutic target to aid in the treatment of patients with ACL trauma.

Therapeutic Effects of Olive and Its Derivatives on Osteoarthritis: From Bench to Bedside

Osteoarthritis is a major cause of morbidity among the elderly worldwide. It is a disease characterized by localized inflammation of the joint and destruction of cartilage, leading to loss of function. Impaired chondrocyte repair mechanisms, due to inflammation, oxidative stress and autophagy, play important roles in the pathogenesis of osteoarthritis. Olive and its derivatives, which possess anti-inflammatory, antioxidant and autophagy-enhancing activities, are suitable candidates for therapeutic interventions for osteoarthritis. This review aimed to summarize the current evidence on the effects of olive and its derivatives, on osteoarthritis and chondrocytes. The literature on animal and human studies has demonstrated a beneficial effect of olive and its derivatives on the progression of osteoarthritis. In vitro studies have suggested that the augmentation of autophagy (though sirtuin-1) and suppression of inflammation by olive polyphenols could contribute to the chondroprotective effects of olive polyphenols. More research and well-planned clinical trials are required to justify the use of olive-based treatment in osteoarthritis.

Mechanical stretch and hypoxia inducible factor-1 alpha affect the vascular endothelial growth factor and the connective tissue growth factor in cultured ACL fibroblasts

PURPOSES

The adult human anterior cruciate ligament (ACL) has poor functional healing response. Hypoxia plays an important role in regulating the microenvironment of the joint cavity after ACL injury, however, its role in mechanical injury is yet to be examined fully in ACL fibroblasts. In this study, we used CoCl₂ to induce Hypoxia-inducible factor-1α (HIF-1α) in our experimental model to study its affect on matrix metalloproteinase-2 (MMP-2), vascular endothelial growth factor (VEGF), and connective tissue growth factor (CTGF) expression in ACL fibroblasts after mechanical stretch.

MATERIALS AND METHODS

Cell treatments were performed in the stretch chamber in all experimental groups. Quantitative real-time PCR was used to check mRNA expression levels of MMP-2, CTGF, VEGF, and HIF-1α. Western blot was used to detect the HIF-1α production. Enzyme-Linked immunosorbent assay was performed to check the VEGF and CTGF protein contents in supernatant. MMP-2 activity was assayed by gelatin zymography.

RESULTS

The real-time PCR results show that mechanical stretch or CoCl₂ treatment increases the expression of MMP-2, VEGF, CTGF, and HIF-1α; however, the combined effects of mechanical stretch and CoCl₂-induced HIF-1α increased MMP-2 production but decreased the VEGF and CTGF expression, compared to the CoCl₂ treatment group alone. Western blot analysis and ELISA also confirmed these results.

CONCLUSIONS

Our results demonstrated that mechanical stretch and CoCl₂-induced HIF-1α together increased the level of MMP-2 and decreased the levels of VEGF and CTGF in cultured ACL fibroblasts. The differential expression and production of HIF-1α, VEGF, MMP-2, and CTGF might help to explain the poor healing ability of ACL.

Tensile strength suppresses the osteogenesis of periodontal ligament cells in inflammatory microenvironments

The present study aimed to investigate the role of orthodontic force in osteogenesis differentiation, matrix deposition and mineralization in periodontal ligament cells (PDLCs) cells in inflammatory microenvironments. The mesenchymal origin of PDLCs was confirmed by vimentin and cytokeratin staining. PDLCs were exposed to inflammatory cytokines (5 ng/ml IL‑1β and 10 ng/ml TNF‑α) and/or tensile strength (0.5 Hz, 12% elongation) for 12, 24 or 48 h. Cell proliferation and tensile strength‑induced cytokine expression were assessed by MTT assay and ELISA, respectively. Runt‑related transcription factor 2 (RUNX2) and type I collagen (COL‑I) expression were analysed by reverse transcription‑quantitative polymerase chain reaction and western blot analysis. Additionally, alkaline phosphatase activity was measured, and the mineralization profile was evaluated by alizarin red S staining. PDLCs exposed to tensile strength in inflammatory microenvironments exhibited reduced proliferation and mineralization potential. Treatment with the inflammatory cytokines IL‑1β and TNF‑α increased RUNX2 expression levels; however, decreased COL‑I expression levels, indicating that bone formation and matrix deposition involve different mechanisms in PDL tissues. Notably, RUNX2 and COL‑I expression levels were decreased in PDLCs exposed to a combination of an inflammatory environment and loading strength. The decreased osteogenic potential in an inflammatory microenvironment under tensile strength suggests that orthodontic force may amplify periodontal destruction in orthodontic patients with periodontitis.

MMP-2 and 9 in Chronic Kidney Disease

Gelatinases are members of the matrix metalloproteinase (MMPs) family; they play an important role in the degradation of the extracellular matrix (ECM). This effect is also crucial in the development and progression of chronic kidney disease (CKD). Its expression, as well as its activity regulation are closely related to the cell signaling pathways, hypoxia and cell membrane structural change. Gelatinases also can affect the development and progression of CKD through the various interactions with tumor necrosis factors (TNFs), monocyte chemoattractant proteins (MCPs), growth factors (GFs), oxidative stress (OS), and so on. Currently, their non-proteolytic function is a hot topic of research, which may also be associated with the progression of CKD. Therefore, with the in-depth understanding about the function of gelatinases, we can have a more specific and accurate understanding of their role in the human body.

MGF E peptide pretreatment improves collagen synthesis and cell proliferation of injured human ACL fibroblasts via MEK-ERK1/2 signaling pathway

Injured anterior cruciate ligament (ACL) is hard to heal due to the poor proliferative potential of ACL fibroblasts. To verify whether mechano-growth factor (MGF) E peptide can restore the cell proliferation of injured ACL fibroblasts, ACL fibroblasts pretreated with MGF E peptide were subjected to injurious stretch and the outcomes were evaluated at 0 and 24 h. After injured, the type III collagen synthesis was increased at 0 h while inhibited at 24 h. The matrix metalloproteinase-2 (MMP-2) activity/expression was up-regulated, but the cell proliferation was inhibited. Fortunately, exogenous MGF E peptide decreased the type I/III collagen synthesis at 0 h but improved the type III collagen synthesis at 24 h. It decreased the MMP-2 activity/expression of injured ACL fibroblasts. Besides, MGF E peptide accelerated the cell proliferation via MEK-ERK1/2 signaling pathway. Our results implied that MGF E peptide pretreatment could provide a new efficient approach for ACL regeneration.

Silencing of hypoxia inducible factor-1α gene attenuated angiotensin Ⅱ-induced abdominal aortic aneurysm in apolipoprotein E-deficient mice

BACKGROUND AND AIMS

We aimed to determine the effect of HIF-1α, the main regulatory subunit of the hypoxia inducible factor 1 (HIF-1), on the development of the abdominal aortic aneurysm (AAA).

METHODS

AAA was induced in ApoE(-/-) mice by angiotensinⅡ (AngⅡ) infusion. In vivo silencing of HIF-1α was achieved by transfection of lentivirus expressing HIF-1α shRNA.

RESULTS

Time course analysis of the AngⅡ infusion model revealed that HIF-1α was persistently upregulated during a 28-day period of AAA development. Silencing of the HIF-1α gene reduced the aneurysm size (2.84 ± 1.96 mm vs. 1.41 ± 0.85 mm respectively at day 28, p = 0.0002). Silencing of HIF-1α also alleviated infiltration of macrophages (38.8 ± 14.7 vs. 11.4 ± 4.4 macrophages/0.1 mm(2), p = 0.0006) and neovascularity (5.56 ± 2.14 vs. 1.27 ± 1.05 microvessels/0.1 mm(2), p = 0.0008) in the AngⅡ infusion model, at day 28. The activity of MMP-2 and MMP-9 was also decreased by knockdown of HIF-1α. The early increased expression of pro-inflammatory factors, angiogenic factors, and MMPs during AAA induction was alleviated by HIF-1α silencing.

CONCLUSIONS

Activation of HIF-1 signaling pathway participates in the Ang Ⅱ-induced AAA formation in mice.

Triple negative breast cancer: a multi-omics network discovery strategy for candidate targets and driving pathways

Triple negative breast cancer (TNBC) represents approximately 15% of breast cancers and is characterized by lack of expression of both estrogen receptor (ER) and progesterone receptor (PR), together with absence of human epidermal growth factor 2 (HER2). TNBC has attracted considerable attention due to its aggressiveness such as large tumor size, high proliferation rate, and metastasis. The absence of clinically efficient molecular targets is of great concern in treatment of patients with TNBC. In light of the complexity of TNBC, we applied a systematic and integrative transcriptomics and interactomics approach utilizing transcriptional regulatory and protein-protein interaction networks to discover putative transcriptional control mechanisms of TNBC. To this end, we identified TNBC-driven molecular pathways such as the Janus kinase-signal transducers, and activators of transcription (JAK-STAT) and tumor necrosis factor (TNF) signaling pathways. The multi-omics molecular target and biomarker discovery approach presented here can offer ways forward on novel diagnostics and potentially help to design personalized therapeutics for TNBC in the future.

Enhanced medial collateral ligament healing using mesenchymal stem cells: dosage effects on cellular response and cytokine profile

Mesenchymal stem cells (MSCs) have potential therapeutic applications for musculoskeletal injuries due to their ability to differentiate into several tissue cell types and modulate immune and inflammatory responses. These immune-modulatory properties were examined in vivo during early stage rat medial collateral ligament healing. Two different cell doses (low dose 1 × 10(6) or high dose 4 × 10(6) MSCs) were administered at the time of injury and compared with normal ligament healing at days 5 and 14 post-injury. At both times, the high dose MSC group demonstrated a significant decrease in M2 macrophages compared to controls. At day 14, fewer M1 macrophages were detected in the low dose group compared to the high dose group. These results, along with significant changes in procollagen I, proliferating cells, and endothelialization suggest that MSCs can alter the cellular response during healing in a dose-dependent manner. The higher dose ligaments also had increased expression of several pro-inflammatory cytokines at day 5 (IL-1β, IFNγ, IL-2) and increased expression of IL-12 at day 14. Mechanical testing at day 14 revealed increased failure strength and stiffness in low dose ligaments compared to controls. Based on these improved mechanical properties, MSCs enhanced functional healing when applied at a lower dose. Different doses of MSCs uniquely affected the cellular response and cytokine expression in healing ligaments. Interestingly, the lower dose of cells proved to be most effective in improving functional properties.

The association of genes involved in the angiogenesis-associated signaling pathway with risk of anterior cruciate ligament rupture

Angiogenesis-associated signaling is a fundamental component in the remodeling of the extracellular matrix in response to loading. Genes encoding protein components within this signaling cascade are therefore suitable candidates for investigation into ACL injury susceptibility: namely, vascular endothelial growth factor A isoform (VEGFA), kinase insert-domain receptor (KDR), nerve growth factor (NGF), and hypoxia inducible factor-1α (HIF1A). A case-control genetic association study was conducted on 227 asymptomatic control participants and 227 participants with surgically diagnosed ACL ruptures of which 126 participants reported a non-contact mechanism of rupture. All participants were genotyped for seven polymorphisms within the four genes. The VEGFA rs699947 CC genotype (p=0.010, OR: 1.92, 95% CI: 1.17-3.17) was significantly over-represented within participants with non-contact ACL ruptures. The VEGFA rs1570360 GA genotype was significantly over-represented in the CON group (p=0.007, OR: 1.70, 95% CI: 1.16-2.50). Furthermore, the KDR rs2071559 GA genotype was significantly over-represented in the female controls (p=0.023, OR: 2.16, 95% CI: 1.11-4.22). Inferred haplotype analyses also implicated genomic regions spanning the VEGFA and KDR genes. These novel findings suggest that regions within VEGFA and KDR may be implicated in the pathophysiology of ACL ruptures; highlighting the potential biological significance of angiogenesis-associated signaling in the aetiology of ACL ruptures.

Influence of TNF-α and biomechanical stress on matrix metalloproteinases and lysyl oxidases expressions in human knee synovial fibroblasts

PURPOSE

It was reported that not only ACL but also the synovium may be the major regulator of matrix metalloproteinases (MMPs) in synovial fluids after ACL injury. In order to further confirm whether synovium is capable of regulating the microenvironment in the process of ACL injury, the complicated microenvironment of joint cavity after ACL injury was mimicked and the combined effects of mechanical injury and inflammatory factor [tumour necrosis factor-α (TNF-α)] on expressions of lysyl oxidases (LOXs) and MMPs in synovial fibroblasts derived from normal human synovium were studied.

METHODS

Human normal knee joint synovial fibroblasts were stimulated for 1-6 h with mechanical stretch and inflammatory factor (TNF-α). Total RNA was harvested, reverse transcribed and assessed by real-time polymerase chain reaction for the expression of LOXs and MMP-1, 2, 3 messenger RNAs. MMP-2 activity was assayed from the collected culture media samples using zymography.

RESULTS

Compared to control group, our results showed that 6% physiological stretch increased MMP-2 and LOXs (except LOXL-3), decreased MMP-1 and MMP-3; injurious stretch (12%) decreased LOXs (except LOXL-2)and increased MMP-1, 2 and 3; the combination of injurious stretch and TNF-α decreased LOXs and increased MMP-1, 2 and 3 in synovial fibroblasts in a synergistical manner.

CONCLUSION

This study demonstrated that combination of mechanical injury and inflammatory factors up-regulated the expressions of MMPs and down-regulated the expressions of LOXs in synovial fibroblasts, eventually alter the balance of tissue healing. Thus, synovium may be involved in regulating the microenvironment of joint cavity. Based on the mechanism, early interventions to inhibit the production of MMPs or promote the production of LOXs in the synovial fibroblasts should be performed to facilitate the healing of tissue.

Osteoarthritis, obesity and weight loss: evidence, hypotheses and horizons - a scoping review

Obesity is widely acknowledged as a risk factor for both the incidence and progression of osteoarthritis, and has a negative influence on outcomes. Loss of at least 10% of body weight, coupled with exercise, is recognized as a cornerstone in the management of obese patients with osteoarthritis, and can lead to significant improvement in symptoms, pain relief, physical function and health-related quality of life. However, questions still remain surrounding optimal management. Given the significant health, social and economic burden of osteoarthritis, especially in obese patients, it is imperative to advance our knowledge of osteoarthritis and obesity, and apply this to improving care and outcomes. This paper overviews what is already known about osteoarthritis and obesity, discusses current key challenges and ongoing hypotheses arising from research in these areas, and finally, postulates what the future may hold in terms of new horizons for obese patients with osteoarthritis.

TNF-α induced down-regulation of lysyl oxidase family in anterior cruciate ligament and medial collateral ligament fibroblasts

BACKGROUND

The lysyl oxidase (LOX) family has the capacity to catalyze the cross-linking of collagen and elastin, implicating its important fundamental role in injury healing. Tumor necrosis factor alpha (TNF-α) is considered to be an important chemical mediator in the acute inflammatory phase of the ligament injury. The role of the lysyl oxidase family induced by TNF-α in the knee ligaments' wound healing process is poorly understood. Our purpose was to determine the different expressions of the LOXs in poorly self-healing anterior cruciate ligament (ACL) and well functionally self-healing medial collateral ligament (MCL) induced by TNF-α.

METHODS

Semi-quantitative PCR, quantitative real-time PCR and western blot were performed for original research.

RESULTS

The results showed that all LOX family members were expressed at higher levels in MCL than those in ACL fibroblasts; the significant differences existed in the down-regulations of the LOXs induced by TNF-α; and the TNF-α-mediated down-regulations of the LOXs were more prominent in ACL than those in MCL fibroblasts. 1-20 ng/ml TNF-α down-regulated mRNA levels in ACL and MCL fibroblasts by up to 76% and 58% in LOX; 90% and 45% in LOXL-1; 97.5% and 90% in LOXL-2; 89% and 68% in LOXL-3; 52% and 25% in LOXL-4, respectively. Protein assay also showed LOXs had lower expressions in ACL than those in MCL.

CLINICAL RELEVANCE

Based on these results, the differential expressions of the LOXs might help to explain the intrinsic differences between the poorly self-healing ACL and well functionally self-healing MCL.

Comparative transcriptional analysis of three human ligaments with distinct biomechanical properties

One major aim of regenerative medicine targeting the musculoskeletal system is to provide complementary and/or alternative therapeutic approaches to current surgical therapies, often involving the removal and prosthetic substitution of damaged tissues such as ligaments. For these approaches to be successful, detailed information regarding the cellular and molecular composition of different musculoskeletal tissues is required. Ligaments have often been considered homogeneous tissues with common biomechanical properties. However, advances in tissue engineering research have highlighted the functional relevance of the organisational and compositional differences between ligament types, especially in those with higher risks of injury. The aim of this study was to provide information concerning the relative expression levels of a subset of key genes (including extracellular matrix components, transcription factors and growth factors) that confer functional identity to ligaments. We compared the transcriptomes of three representative human ligaments subjected to different biomechanical demands: the anterior cruciate ligament (ACL); the ligamentum teres of the hip (LT); and the iliofemoral ligament (IL). We revealed significant differences in the expression of type I collagen, elastin, fibromodulin, biglycan, transforming growth factor β1, transforming growth interacting factor 1, hypoxia-inducible factor 1-alpha and transforming growth factor β-induced gene between the IL and the other two ligaments. Thus, considerable molecular heterogeneity can exist between anatomically distinct ligaments with differing biomechanical demands. However, the LT and ACL were found to show remarkable molecular homology, suggesting common functional properties. This finding provides experimental support for the proposed role of the LT as a hip joint stabiliser in humans.

Differential expressions of lysyl oxidase family in ACL and MCL fibroblasts after mechanical injury

Lysyl oxidase (LOX) family has the capacity to catalyse the cross-linking of collagen and elastin, implicating its important fundamental roles in tissue development and injury healing. However, the variations in expression of the LOX family in the normal and injured anterior cruciate ligament (ACL) are not fully known. To better understand the role of LOX family in the self-healing inability mechanism of injured ACL, this study is to measure the LOX family's differential expressions in ACL and medial collateral ligament (MCL) fibroblasts after mechanical injury induced by using an equi-biaxial stretching chamber. The cells received various degrees of mechanical stretch 0% (resting state), 6% (physiological state) and 12% (injurious state), respectively. The gene profile and protein expressions were analysed by semi-quantitative PCR, quantitative real-time PCR and Western blotting. At physiological state, gene expression showed LOX in ACL was 2.6-5.2 folds higher than that in MCL in all culture time periods, LOXL-4 1.2-3.6 folds, but LOXL-3 in MCL showed 1.1-4.8 folds higher than that in ACL. In injurious state, MCL gene expressions were 2.8-29.6 folds higher than ACL in LOX, LOXL-2, LOXL-3 and LOXL-4 at 2, 6 and 12h periods. These differential expression profiles of the LOX family in the two ligament tissues were further used to explain the intrinsic differences between ACL and MCL, and why injured ACL could not be amenable to repair itself, whereas MCL could.

Adenosine A3 receptor stimulation reduces muscle injury following physical trauma and is associated with alterations in the MMP/TIMP response

We have previously demonstrated that in response to traumatic injury in skeletal muscle, there is a dysregulation of the matrix metalloproteases (MMPs) and their inhibitors (TIMPs), a response hypothesized to interfere with proper skeletal muscle regeneration. Moreover, we have shown that pharmacological activation of the adenosine A(3) receptor by Cl-IBMECA in skeletal muscle can protect against ischemia-reperfusion and eccentric exercise injury. However, the mechanism by which Cl-IBMECA protects muscle tissue is poorly defined. This study evaluated the effects of Cl-IBMECA on MMP/TIMP expression in skeletal muscle and tested the hypothesis that adenosine A(3) receptor-stimulated protection of skeletal muscle following traumatic injury is associated with a blunting of MMPs involved in inflammatory processes and collagen degradation, and an increase in MMPs associated with extracellular matrix remodeling. Sixty C57BL/6J male mice were injected with Cl-IBMECA (n = 30) or a vehicle (n = 30), and Evans blue dye. Injury was induced by applying a cold steel probe (-79°C) to the tibialis anterior (TA) muscle for 10 s. TA muscles from uninjured and injured legs were collected 3, 10, and 24 h postinjury for analysis of muscle injury and MMP/TIMP mRNA and protein levels. Twenty-four hours postinjury, 56.8% of the fibers were damaged in vehicle-treated mice vs. 35.4% in Cl-IBMECA-treated mice (P = 0.02). Cl-IBMECA treatment reduced membrane type 1 (MT1)-MMP, MMP-3, MMP-9, and TIMP-1 mRNA expression 2- to 20-fold compared with vehicle-treated mice (P < 0.05). Cl-IBMECA decreased protein levels of latent/shed MT1-MMP 23-2,000%, respectively, 3-10 h postinjury. In Cl-IBMECA-treated mice, latent MMP-2 was decreased 20% 3 h postinjury, active MMP-3 was decreased 64% 3 h postinjury, and latent/active MMP-9 was decreased 417,631% 3 h postinjury and 20% 10 h postinjury. Protein levels of active MMP-2 and latent MMP-3 were increased 25% and 74% 3 h postinjury, respectively. The present study elucidates a new protective role of adenosine A(3) receptor stimulation in posttraumatic skeletal muscle injury.

Differential response to CoCl2-stimulated hypoxia on HIF-1α, VEGF, and MMP-2 expression in ligament cells

The adult human anterior cruciate ligament (ACL) has a poor functional healing response, whereas the medial collateral ligament (MCL) does not. The difference in intrinsic properties of these ligament cells can be due to their different response to their located microenvironment. Hypoxia is a key environmental regulator after ligament injury. In this study, we investigated the differential response of ACL and MCL fibroblasts to hypoxia on hypoxia-inducible factor-1α, vascular endothelial growth factor, and matrix metalloproteinase-2 (MMP-2) expression. Our results show that ACL cells responded to hypoxia by up-regulating the HIF-1α expression significantly as compared to MCL cells. We also observed that in MCL fibroblasts response to hypoxia resulted in increase in expression of VEGF as compared to ACL fibroblasts. After hypoxia treatment, mRNA and protein levels of MMP-2 increased in both ACL and MCL. Furthermore we found in ACL pro-MMP-2 was converted more into active form. However, hypoxia decreased the percentage of wound closure for both ligament cells and had a greater effect on ACL fibroblasts. These results demonstrate that ACL and MCL fibroblasts respond differently under the hypoxic conditions suggesting that these differences in intrinsic properties may contribute to their different healing responses and abilities.