ERK1/2 drives IL-1β-induced expression of TGF-β1 and BMP-2 in torn tendons

Ge-gen decoction alleviates primary dysmenorrhoea symptoms in a rat model

BACKGROUND

Existing treatments for primary dysmenorrhoea (PD), such as NSAIDs, impart side effects. Ge-Gen decoction (GGD), a traditional Chinese medicine, has shown promise in treating PD, but its exact mechanisms remain unclear. Here, we aimed to investigate the efficiency of GGD in alleviating PD using a rat model to understand its precise mechanism of action.

METHODS

We established a rat model of dysmenorrhoea induced by oestradiol and oxytocin. The PD rats were administered GGD or Ibuprofen (positive control) intragastrically once daily for seven consecutive days. Serum levels of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2α), β-endorphin (β-EP), thromboxane B2 (TXB2), 6-keto-prostaglandin F1α (6-keto-PGF1α) were determined using an enzyme-linked immunosorbent assay (ELISA). The expression levels of oestrogen receptor alpha (ERα) and cyclooxygenase-2 (COX-2) in uterine tissue were measured using immunohistochemical assays, and those of phosphorylated and total extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) were assessed using western blot analysis.

RESULTS

Treatment with GGD significantly reduced writhing behaviour, histopathological scores, and levels of COX-2, PGE2, and PGF2α in the serum of PD rats. Additionally, GGD increased β-EP content and inhibited ERK1/2 activation and ERα expression in uterine tissues.

CONCLUSIONS

The results of this study suggest that GGD alleviates PD in rats by suppressing the COX-2-mediated release of PGE2 and PGF2α, modulating the ERα/ERK1/2/COX-2 pathway, and increasing β-EP content. These results provide insights into the potential mechanisms of GGD in treating PD and support its further investigation as an alternative therapy for this condition.

Understanding Fibrous Tissue in the Effective Healing of Rotator Cuff Injury

The rotator cuff is a crucial group of muscles and tendons in the shoulder complex that plays a significant role in the stabilization of the glenohumeral joint and enabling a wide range of motion. Rotator cuff tendon tears can occur due to sudden injuries or degenerative processes that develop gradually over time, whether they are partial or full thickness. These injuries are common causes of shoulder pain and functional impairment, and their complex nature highlights the essential role of the rotator cuff in shoulder function. Scar formation is a crucial aspect of the healing process initiated following a rotator cuff tendon tear, but excessive fibrous tissue development can potentially lead to stiffness, discomfort, and movement limitations. Age is a critical risk factor, with the prevalence of these tears increasing among older individuals. This comprehensive review aims to delve deeper into the anatomy and injury mechanisms of the rotator cuff. Furthermore, it will inspect the signaling pathways involved in fibrous tissue development, evaluate the various factors affecting the healing environment, and discuss proactive measures aimed at reducing excessive fibrous tissue formation. Lastly, this review identifed gaps within existing knowledge to advance methods for better management of rotator cuff tendon injuries.

Exogenous interleukin-1 beta stimulation regulates equine tenocyte function and gene expression in three-dimensional culture which can be rescued by pharmacological inhibition of interleukin 1 receptor, but not nuclear factor kappa B, signaling

We investigated how Interleukin 1 beta (IL-1β) impacts equine tenocyte function and global gene expression in vitro and determined if these effects could be rescued by pharmacologically inhibiting nuclear factor-κB (NF-KB) or interleukin 1 signalling. Equine superficial digital flexor tenocytes were cultured in three-dimensional (3D) collagen gels and stimulated with IL-1β for two-weeks, with gel contraction and interleukin 6 (IL6) measured throughout and transcriptomic analysis performed at day 14. The impact of three NF-KB inhibitors on gel contraction and IL6 secretion were measured in 3D culture, with NF-KB-P65 nuclear translocation by immunofluorescence and gene expression by qPCR measured in two-dimensional (2D) monolayer culture. In addition, daily 3D gel contraction and transcriptomic analysis was performed on interleukin 1 receptor antagonist-treated 3D gels at day 14. IL-1β increased NF-KB-P65 nuclear translocation in 2D culture and IL6 secretion in 3D culture, but reduced daily tenocyte 3D gel contraction and impacted > 2500 genes at day 14, with enrichment for NF-KB signaling. Administering direct pharmacological inhibitors of NF-KB did reduce NF-KB-P65 nuclear translocation, but had no effect on 3D gel contraction or IL6 secretion in the presence of IL-1β. However, IL1Ra restored 3D gel contraction and partially rescued global gene expression. Tenocyte 3D gel contraction and gene expression is adversely impacted by IL-1β which can only be rescued by blockade of interleukin 1 receptor, but not NF-KB, signalling.

Collagen VI Deficiency Impairs Tendon Fibroblasts Mechanoresponse in Ullrich Congenital Muscular Dystrophy

The pericellular matrix (PCM) is a specialized extracellular matrix that surrounds cells. Interactions with the PCM enable the cells to sense and respond to mechanical signals, triggering a proper adaptive response. Collagen VI is a component of muscle and tendon PCM. Mutations in collagen VI genes cause a distinctive group of inherited skeletal muscle diseases, and Ullrich congenital muscular dystrophy (UCMD) is the most severe form. In addition to muscle weakness, UCMD patients show structural and functional changes of the tendon PCM. In this study, we investigated whether PCM alterations due to collagen VI mutations affect the response of tendon fibroblasts to mechanical stimulation. By taking advantage of human tendon cultures obtained from unaffected donors and from UCMD patients, we analyzed the morphological and functional properties of cellular mechanosensors. We found that the length of the primary cilia of UCMD cells was longer than that of controls. Unlike controls, in UCMD cells, both cilia prevalence and length were not recovered after mechanical stimulation. Accordingly, under the same experimental conditions, the activation of the Hedgehog signaling pathway, which is related to cilia activity, was impaired in UCMD cells. Finally, UCMD tendon cells exposed to mechanical stimuli showed altered focal adhesions, as well as impaired activation of Akt, ERK1/2, p38MAPK, and mechanoresponsive genes downstream of YAP. By exploring the response to mechanical stimulation, for the first time, our findings uncover novel unreported mechanistic aspects of the physiopathology of UCMD-derived tendon fibroblasts and point at a role for collagen VI in the modulation of mechanotransduction in tendons.

The superior healing capacity of MRL tendons is minimally influenced by the systemic environment of the MRL mouse

Murphy Roths Large mice (MRL) exhibit improved tendon healing and are often described as a "super-healer" strain. The underlying mechanisms that drive the superior healing response of MRL remain a controversial subject. We utilized a tendon transplantation model between MRL and "normal-healer" B6-mice to differentiate between the contribution of MRL's innate tendon and systemic environment to its improved healing capacity. Patellar tendons with a midsubstance punch injury were transplanted back into the same animal (autograft) or into an animal of the other strain (allograft). Findings at 4 weeks showed that the innate MRL tendon environment drives its improved healing capacity as demonstrated by improved stiffness and maximum load in MRL-grafts-in-B6-host-allografts compared to B6-autografts, and higher modulus in MRL-autografts compared to B6-graft-in-MRL-host-allografts. Groups with an MRL component showed an increase in pro-inflammatory cytokines in the 3 days after injury, suggesting an early enhanced inflammatory profile in MRL that ultimately resolves. A preserved range of motion of the knee joint in all MRL animals suggests a systemic "shielding effect" of MRL in regard to joint adhesiveness. Our findings 4-weeks post injury are consistent with previous studies showing tissue-driven improved healing and suggest that the systemic environment contributes to the overall healing process.

Equine induced pluripotent stem cells are responsive to inflammatory cytokines before and after differentiation into musculoskeletal cell types

Persistent inflammation is associated with the poor regeneration of musculoskeletal tissues. Embryonic stem cells (ESCs) have an attenuated response to inflammatory cytokines, but there are mixed reports on the response of induced pluripotent stem cells (iPSCs) to inflammation. Horses provide a relevant large animal model for studying musculoskeletal tissue diseases and the testing of novel therapies. The aim of this study was to determine if equine iPSCs are responsive to the inflammatory cytokines IL-1β, TNFα and IFN-γ in their undifferentiated state, or following differentiation into tendon and cartilage-like cells. We demonstrated that in undifferentiated iPSCs, the cytokines induce NF-κB P65 and STAT1 nuclear translocation which leads to cell death, decreased OCT4 expression and increased expression of inflammatory genes. Following differentiation towards cartilage-like cells exposure to the cytokines resulted in STAT1 nuclear translocation, changes in cartilage gene expression and increased expression of matrix metalloproteinases (MMPs) and inflammatory genes. Exposure of iPSC-derived tendon-like cells to the cytokines resulted nuclear translocation of NF-κB P65 and STAT1, altered tendon gene expression, increased MMP expression and increased expression of inflammatory genes. Equine iPSCs are therefore capable of responding to inflammatory stimulation and this may have relevance for their future clinical application.

TLR7 Agonists Modulate the Activation of Human Conjunctival Epithelial Cells Induced by IL-1β via the ERK1/2 Signaling Pathway

Conjunctival epithelia cells play an important role in the development of allergic reactions. TLR7 agonists have been shown in studies to increase the body's immunological tolerance by controlling the proportion of Th1/Th2 cells, although it is still unknown what impact this has on conjunctival epithelial cells. In this study, we examined the effect of TLR7 agonists on the inflammatory-activation of conjunctival epithelial cells induced by IL-1β. Quantitative PCR and ELISA analysis confirmed that TLR7 agonists could impair the proinflammatory cytokines released by the epithelia cells, whereas pro-inflammatory cytokines led to subsequent reactive oxygen species and neutrophil chemotaxis. Phosphorylation analysis and nucleocytoplasmic separation further confirmed that TLR7 agonists inhibit IL-1β-induced epithelia cells activation and ATP depletion via modulating the cytoplasmic residence of ERK1/2. Our finding indicated that TLR7 of conjunctival epithelia cells could be as a potent anti-inflammatory target for the ocular surface. And TLR7 agonists may become potential new drug for the treatment of allergic conjunctivitis.

Physalin A alleviates intervertebral disc degeneration via anti-inflammatory and anti-fibrotic effects

Background

The incidence of intervertebral disc degeneration (IVDD) is a common degenerative disease with inflammation, decreased autophagy, and progression of fibrosis as its possible pathogenesis. Physalin A (PA) is a widely studied anti-inflammatory drug. However, its therapeutic effects on IVDD remain unexplored. Therefore, we aimed to explore the therapeutic potential of PA in IVDD progression.

Materials and methods

In vivo, we investigated PA bioactivity using a puncture-induced IVDD rat model. IVDD signals and height changes were detected using X-ray, micro-CT, and MRI, and structural and molecular lesions using histological staining and immunohistochemistry of intervertebral disc sections. In vivo, interleukin-1 beta (IL-1β) and TGF-β1 were employed to establish inflammation fibrotic nucleus pulposus (NP) cells. The PA effect duration, concentration, influence pathways, and pathological changes in IVDD treatment were elucidated using western blotting, real-time PCR, and immunofluorescence.

Results

PA exerted significant effects on IVDD remission due to anti-inflammation, fibrosis reduction, and autophagy enhancement. In vitro, PA improved inflammation by blocking the NF-κB and MAPK pathways, whereas it promoted autophagy via the PI3K/AKT/mTOR pathway and affected fibrotic progression by regulating the SMAD2/3 pathway. Moreover, PA improved the disc degeneration process in IVDD model.

Conclusions

PA exhibited significant anti-inflammatory and anti-fibrotic effects and improved autophagy in vivo and in vitro IVDD models, thus effectively relieving IVDD progression, indicating it is a promising agent for IVDD treatment.

The translational potential of this article

This study successfully reveals that PA, a natural bioactive withanolide, effectively relieved IVDD progression via inflammation inhibition, fibrosis reduction, and autophagy enhancement, indicating it is a promising agent for IVDD treatment.

Transforming growth factor-β signalling pathway in tendon healing

Transforming growth factor-β(TGF-β) plays an important but diverse role in tendon injuries, such as collagen synthesis, cell proliferation, cell differentiation, and cell adhesion, leading to tendon healing and tendon fibrosis. In the well-known canonical TGF-β signalling pathway, TGF-β activates Smad signalling through its two cell surface receptors, which leads to Smad-mediated transcriptional regulation and is also regulated by inhibitory Smads, forming a negative feedback regulatory pathway. In the context of the canonical TGF-β signalling mechanism mediated by Smad, the activated receptors also send signals through other signal transducers, which in the backdrop of TGF-β signaling are collectively known as non-Smad signalling pathways. Activated TGF-β binds to the receptor and acts through these signalling pathways. Understanding the mechanism of the TGF-β signalling pathway and its role in tendon repair is of great significance for targeting the TGF-β signalling pathway to accelerate tendon healing and reduce tendon fibrosis.

MiR-192-5p Alleviated Fibrosis and Inflammatory Responses of Tendon Cells by Targeting NFAT5

Objective

To explore the effect of microRNA (miR)-192-5p on the inflammatory and fibrotic responses of tendon cells.

Methods

Tendon cells were treated with transforming growth factor-β1 (TGF-β1). The expression of miR-192-5p and nuclear factor of activated T cells 5 (NFAT5) in tendon cells were detected by RT-qPCR. The expressions of inflammatory and fibrosis-related factors were detected by RT-qPCR and Western blot. MiR-192-5p binds to NFAT5 targeting by TargetScan and dual-luciferase reporter gene assay. The expression of the NFAT5 gene was detected by RT-qPCR and Western blot. Detection of apoptosis in tendon cells by flow cytometry.

Results

MiR-192-5p was downregulated in tendon cells, and the expression level gradually decreased with the prolong of TGF-β1 treatment. The expression of NFAT5 increased with the treatment time of TGF-β1. The expression of miR-192-5p decreased collagen III (COLIII), α smooth muscle actin (α-SMA), matrix metalloproteinase- (MMP-) 1, and MMP-8 expression, thereby inhibiting TGF-β1-induced fibrosis in tendon cells. The expression of miR-192-5p decreased the expression of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β, thereby alleviating TGF-β1-induced inflammatory response and reduce apoptosis in tendon cells. NFAT5 is a direct target of miR-192-5p in tendon cells. The upregulation of NFAT5 reversed the effect of miR-192-5p on the fibrotic activity and inflammatory response of TGF-β1-stimulated tendon cells.

Conclusions

MiR-192-5p alleviates fibrosis and inflammatory responses of tendon cells by targeting NFAT5.

Malfunction of airway basal stem cells plays a crucial role in pathophysiology of tracheobronchopathia osteoplastica

Understanding disease-associated stem cell abnormality has major clinical implications for prevention and treatment of human disorders, as well as for regenerative medicine. Here we report a multifaceted study on airway epithelial stem cells in Tracheobronchopathia Osteochondroplastica (TO), an under-detected tracheobronchial disorder of unknown etiology and lack of specific treatment. Epithelial squamous metaplasia and heterotopic bone formation with abnormal cartilage proliferation and calcium deposits are key pathological hallmarks of this disorder, but it is unknown whether they are coincident or share certain pathogenic mechanisms in common. By functional evaluation and genome-wide profiling at both transcriptional and epigenetic levels, we reveal a role of airway basal cells in TO progression by acting as a repository of inflammatory and TGFβ-BMP signals, which contributes to both epithelial metaplasia and mesenchymal osteo-chondrogenesis via extracellular signaling and matrix remodeling. Restoration of microenvironment by cell correction or local pathway intervention may provide therapeutic benefits.

Tracheobronchopathia osteoplastica (TO), is an underreported affliction characterized by squamous metaplasia and heterotopic bone formation in trachea and bronchi. Here the authors apply functional, as well as genome-wide transcriptional and epigenetic profiling to identify airway basal cells dysfunction underlying TO.

Pegylated insulin-like growth factor-1 biotherapeutic delivery promotes rotator cuff regeneration in a rat model

Tears in the rotator cuff are challenging to repair because of the complex, hypocellular, hypovascular, and movement-active nature of the tendon and its enthesis. Insulin-like Growth Factor-1 (IGF-1) is a promising therapeutic for this repair. However, its unstable nature, short half-life, and ability to disrupt homeostasis has limited its clinical translation. Pegylation has been shown to improve the stability and sustain IGF-1 levels in the systemic circulation without disrupting homeostasis. To provide localized delivery of IGF-1 in the repaired tendons, we encapsulated pegylated IGF-1 mimic and its controls (unpegylated IGF-1 mimic and recombinant human IGF-1) in polycaprolactone-based matrices and evaluated them in a pre-clinical rodent model of rotator cuff repair. Pegylated-IGF-1 mimic delivery reestablished the characteristic tendon-to-bone enthesis structure and improved tendon tensile properties within 8 weeks of repair compared to controls, signifying the importance of pegylation in this complex tissue regeneration. These results demonstrate a simple and scalable biologic delivery technology alternative to tissue-derived grafts for soft tissue repair.

VEGF-D-mediated signaling in tendon cells is involved in degenerative processes

Vascular endothelial growth factor (VEGF) signaling is crucial for a large variety of cellular processes, not only related to angiogenesis but also in nonvascular cell types. We have previously shown that controlling angiogenesis by reducing VEGF-A signaling positively affects tendon healing. We now hypothesize that VEGF signaling in non-endothelial cells may contribute to tendon pathologies. By immunohistochemistry we show that VEGFR1, VEGFR2, and VEGFR3 are expressed in murine and human tendon cells in vivo. In a rat Achilles tendon defect model we show that VEGFR1, VEGFR3, and VEGF-D expression are increased after injury. On cultured rat tendon cells we show that VEGF-D stimulates cell proliferation in a dose-dependent manner; the specific VEGFR3 inhibitor SAR131675 reduces cell proliferation and cell migration. Furthermore, activation of VEGFR2 and -3 in tendon-derived cells affects the expression of mRNAs encoding extracellular matrix and matrix remodeling proteins. Using explant model systems, we provide evidence, that VEGFR3 inhibition prevents biomechanical deterioration in rat tail tendon fascicles cultured without load and attenuates matrix damage if exposed to dynamic overload in a bioreactor system. Together, these results suggest a strong role of tendon cell VEGF signaling in mediation of degenerative processes. These findings give novel insight into tendon cell biology and may pave the way for novel treatment options for degenerative tendon diseases.

Interleukin-17 Cytokines and Receptors: Potential Amplifiers of Tendon Inflammation

Interleukin (IL)-17A, a pro-inflammatory cytokine that is linked to the pathology of several inflammatory diseases, has been shown to be upregulated in early human tendinopathy and to mediate inflammatory and tissue remodelling events. However, it remains unclear which cells in tendons can respond to IL-17A, and how IL-17A, and its family members IL-17F and IL-17AF, can affect intracellular signalling activation and mRNA expression in healthy and diseased tendon-derived fibroblasts. Using well-phenotyped human tendon samples, we show that IL-17A and its receptors IL-17RA and IL-17RC are present in healthy hamstring, and tendinopathic and torn supraspinatus tendon tissue. Next, we investigated the effects of IL-17A, IL-17F, or IL-17AF on cultured patient-derived healthy and diseased tendon-derived fibroblasts. In these experiments, IL-17A treatment significantly upregulated IL6, MMP3, and PDPN mRNA expression in diseased tendon-derived fibroblasts. IL-17AF treatment induced moderate increases in these target genes, while little change was observed with IL-17F. These trends were reflected in the activation of intracellular signalling proteins p38 and NF- κ B p65, which were significantly increased by IL-17A, modestly increased by IL-17AF, and not increased by IL-17F. In combination with TNF-α, all three IL-17 cytokines induced IL6 and MMP3 mRNA expression to similar levels. Therefore, this study confirms that healthy and diseased tendon-derived fibroblasts are responsive to IL-17 cytokines and that IL-17A induces the most profound intracellular signalling activation and mRNA expression of inflammatory genes, followed by IL-17AF, and finally IL-17F. The ability of IL-17 cytokines to induce a direct response and activate diverse pro-inflammatory signalling pathways through synergy with other inflammatory mediators suggests a role for IL-17 family members as amplifiers of tendon inflammation and as potential therapeutic targets in tendinopathy.

Comparison of Cellular Responses to TGF-β1 and BMP-2 Between Healthy and Torn Tendons

BACKGROUND

Tendons heal by fibrotic repair, increasing the likelihood of reinjury. Animal tendon injury and overuse models have identified transforming growth factor beta (TGF-β) and bone morphogenetic proteins (BMPs) as growth factors actively involved in the development of fibrosis, by mediating extracellular matrix synthesis and cell differentiation.

PURPOSE

To understand how TGF-β and BMPs contribute to fibrotic processes using tendon-derived cells isolated from healthy and diseased human tendons.

STUDY DESIGN

Controlled laboratory study.

METHODS

Tendon-derived cells were isolated from patients with a chronic rotator cuff tendon tear (large to massive, diseased) and healthy hamstring tendons of patients undergoing anterior cruciate ligament repair. Isolated cells were incubated with TGF-β1 (10 ng/mL) or BMP-2 (100 ng/mL) for 3 days. Gene expression was measured by real-time quantitative polymerase chain reaction. Cell signaling pathway activation was determined by Western blotting.

RESULTS

TGF-β1 treatment induced ACAN mRNA expression in both cell types but less in the diseased compared with healthy cells (P < .05). BMP-2 treatment induced BGN mRNA expression in healthy but not diseased cells (P < .01). In the diseased cells, TGF-β1 treatment induced increased ACTA2 mRNA expression (P < .01) and increased small mothers against decapentaplegic (SMAD) signaling (P < .05) compared with those of healthy cells. Moreover, BMP-2 treatment induced ACTA2 mRNA expression in the diseased cells only (P < .05).

CONCLUSION

Diseased tendon-derived cells show reduced expression of the proteoglycans aggrecan and biglycan in response to TGF-β1 and BMP-2 treatments. These same treatments induced enhanced fibrotic differentiation and canonical SMAD cell signaling in diseased compared with healthy cells.

CLINICAL RELEVANCE

Findings from this study suggest that diseased tendon-derived cells respond differently than healthy cells in the presence of TGF-β1 and BMP-2. The altered responses of diseased cells may influence fibrotic repair processes during tendon healing.

Interleukin-17A Causes Osteoarthritis-Like Transcriptional Changes in Human Osteoarthritis-Derived Chondrocytes and Synovial Fibroblasts In Vitro

Increased interleukin (IL)-17A has been identified in joints affected by osteoarthritis (OA), but it is unclear how IL-17A, and its family members IL-17AF and IL-17F, can contribute to human OA pathophysiology. Therefore, we aimed to evaluate the gene expression and signalling pathway activation effects of the different IL-17 family members in chondrocytes and synovial fibroblasts derived from cartilage and synovium of patients with end-stage knee OA. Immunohistochemistry staining confirmed that IL-17 receptor A (IL-17RA) and IL-17RC are expressed in end-stage OA-derived cartilage and synovium. Chondrocytes and synovial fibroblasts derived from end-stage OA patients were treated with IL-17A, IL-17AF, or IL-17F, and gene expression was assessed with bulk RNA-Seq. Hallmark pathway analysis showed that IL-17 cytokines regulated several OA pathophysiology-related pathways including immune-, angiogenesis-, and complement-pathways in both chondrocytes and synovial fibroblasts derived from end-stage OA patients. While overall IL-17A induced the strongest transcriptional response, followed by IL-17AF and IL-17F, not all genes followed this pattern. Disease-Gene Network analysis revealed that IL-17A-related changes in gene expression in these cells are associated with experimental arthritis, knee arthritis, and musculoskeletal disease gene-sets. Western blot analysis confirmed that IL-17A significantly activates p38 and p65 NF-κB. Incubation of chondrocytes and synovial fibroblasts with anti-IL-17A monoclonal antibody secukinumab significantly inhibited IL-17A-induced gene expression. In conclusion, the association of IL-17-induced transcriptional changes with arthritic gene-sets supports a role for IL-17A in OA pathophysiology. Future studies should further investigate the role of IL-17A in the OA joint to establish whether anti-IL-17 treatment could be a potential therapeutic option in OA patients with an inflammatory phenotype.

Inhibition of ERK 1/2 kinases prevents tendon matrix breakdown

Tendon extracellular matrix (ECM) mechanical unloading results in tissue degradation and breakdown, with niche-dependent cellular stress directing proteolytic degradation of tendon. Here, we show that the extracellular-signal regulated kinase (ERK) pathway is central in tendon degradation of load-deprived tissue explants. We show that ERK 1/2 are highly phosphorylated in mechanically unloaded tendon fascicles in a vascular niche-dependent manner. Pharmacological inhibition of ERK 1/2 abolishes the induction of ECM catabolic gene expression (MMPs) and fully prevents loss of mechanical properties. Moreover, ERK 1/2 inhibition in unloaded tendon fascicles suppresses features of pathological tissue remodeling such as collagen type 3 matrix switch and the induction of the pro-fibrotic cytokine interleukin 11. This work demonstrates ERK signaling as a central checkpoint to trigger tendon matrix degradation and remodeling using load-deprived tissue explants.

Pharmacologic Targeting of BET Proteins Attenuates Hyperuricemic Nephropathy in Rats

Hyperuricemia is an independent risk factor for renal damage and promotes the progression of chronic kidney disease. In this study, we investigated the effect of I-BET151, a small-molecule inhibitor targeting the bromodomain and extraterminal (BET) proteins, on the development of hyperuricemic nephropathy (HN), and the mechanisms involved. Expression levels of bromodomain-containing protein 2 and 4, but not 3 were increased in the kidney of rats with HN; administration of I-BET151 effectively prevented renal dysfunction, decreased urine microalbumin, and attenuated renal fibrosis as indicated by reduced activation of renal interstitial fibroblasts and expression of fibronectin and collagen I in HN rats. Mechanistic studies show that I-BET151 treatment inhibited transition of renal epithelial cells to a mesenchymal cell type as evidenced by preservation of E-cadherin and reduction of vimentin expression. This was coincident with reduced expression of TGF-β1 and dephosphorylation of Smad3 and ERK1/2. I-BET151 was also effective in inhibiting phosphorylation of NF-κB, expression of multiple cytokines and chemokines, and infiltration of macrophages to the injured kidney. Although there were increased serum levels of uric acid and xanthine oxidase, an enzyme that catalyzes production of uric acid, and decreased expression of renal organic anion transporter 1 and 3 that promote urate excretion in the model of HN, and reduced expression levels of urine uric acid, I-BET151 treatment did not affect these responses. Collectively, our results indicate that I-BET151 alleviates HN by inhibiting epithelial to mesenchymal transition and inflammation in association with blockade of TGF-β, ERK1/2 and NF-κB signaling.

Recent advances in tendinopathy

Tendinopathy refers to the clinical diagnosis of activity-related pain resulting in a decline in tendon function. In the last few years, much has been published concerning the basic science and clinical investigation of tendinopathy and debates and discussions to new questions and points of view started many years ago. This advances review will discuss the current thinking on the basic science and clinical management of tendinopathy and in particular new findings in the tendon repair space that are relevant to the pathophysiology of tendinopathy. We will further discuss potential novel therapies on the horizon in human tendon disease.