The Ras antagonist, farnesylthiosalicylic acid (FTS), decreases fibrosis and improves muscle strength in dy/dy mouse model of muscular dystrophy

Immunosuppressants Tacrolimus and Sirolimus revert the cardiac antifibrotic properties of p38-MAPK inhibition in 3D-multicellular human iPSC-heart organoids

Cardiac reactive fibrosis is a fibroblast-derived maladaptive process to tissue injury that exacerbates an uncontrolled deposition of large amounts of extracellular matrix (ECM) around cardiomyocytes and vascular cells, being recognized as a pathological entity of morbidity and mortality. Cardiac fibrosis is partially controlled through the sustained activation of TGF-β1 through IL-11 in fibroblasts. Yet, preclinical studies on fibrosis treatment require human physiological approaches due to the multicellular crosstalk between cells and tissues in the heart. Here, we leveraged an iPSC-derived multi-lineage human heart organoid (hHO) platform composed of different cardiac cell types to set the basis of a preclinical model for evaluating drug cardiotoxicity and assessing cardiac fibrosis phenotypes. We found that the inhibition of the p38-MAPK pathway significantly reduces COL1A1 depositions. Yet, concomitant treatment with organ-rejection immunosuppressant drugs Tacrolimus or Sirolimus reverts this effect, opening new questions on the clinical considerations of combined therapies in reducing fibrosis after organ transplantation.

The role of endothelin and RAS/ERK signaling in immunopathogenesis-related fibrosis in patients with systemic sclerosis: an updated review with therapeutic implications

Systemic sclerosis (SSc) is a disease of connective tissue with high rate of morbidity and mortality highlighted by extreme fibrosis affecting various organs such as the dermis, lungs, and heart. Until now, there is no specific cure for the fibrosis occurred in SSc disease. The SSc pathogenesis is yet unknown, but transforming growth factor beta (TGF-β), endothelin-1 (ET-1), and Ras-ERK1/2 cascade are the main factors contributing to the tissue fibrosis through extracellular matrix (ECM) accumulation. Several studies have hallmarked the association of ET-1 with or without TGF-β and Ras-ERK1/2 signaling in the development of SSc disease, vasculopathy, and fibrosis of the dermis, lungs, and several organs. Accordingly, different clinical and experimental studies have indicated the potential therapeutic role of ET-1 and Ras antagonists in these situations in SSc. In addition, ET-1 and connective tissue growth factor (CTGF) as a cofactor of the TGF-β cascade play a substantial initiative role in inducing fibrosis. Once initiated, TGF-β alone or in combination with ET-1 and CTGF can activate several kinase proteins such as the Ras-ERK1/2 pathway that serve as the fundamental factor for developing fibrosis. Furthermore, Salirasib is a synthetic small molecule that is able to inhibit all Ras forms. Therefore, it can be used as a potent therapeutic factor for fibrotic disorders. So, this review discusses the role of TGF-β/ET-1/Ras signaling and their involvement in SSc pathogenesis, particularly in its fibrotic situation.

Twist1 sustains the apoptosis resistance in eosinophils in nasal mucosa of allergic rhinitis

Eosinophils (Eos) are the canonical effector cells in allergic rhinitis (AR) and many inflammatory diseases. The mechanism of eosinophilia occurring in the lesion sites is not fully understood yet. Twist1 protein (Twist, in short) is an apoptosis inhibitor that also has immune regulatory functions. This study aims to investigate the role of Twist in the pathogenesis of eosinophilia in AR. In this study, surgically removed human nasal mucosal samples were obtained from patients with chronic sinusitis and nasal polyps with AR (the AR group) or without AR (the nAR group). Eos were isolated from the samples by flow cytometry. We found that abundant Eos were obtained from the surgically removed nasal mucosa tissues of both nAR and AR groups. Significantly higher Ras activation was detected in AR Eos than that in nAR Eos. Ras activation was associated with the apoptosis resistance in AR Eos. The Twist (an apoptosis inhibitor) expression was higher in AR Eos, which was positively correlated with the Ras activation status. The sensitization to IgG induced Twist expression in Eos, in which Ras activated the MAPK-HIF-1α pathway, the latter promoted the Twist gene transcription. Twist bound Rac GTPase activating protein-1 to sustain the Ras activation in Eos. Ras activation sustained the apoptosis resistance in Eos. In conclusion, high Ras activation was detected in the AR nasal mucosal tissue-isolated Eos. IgG-sensitization induced Ras activation and Twist expression in Eos, that conferred Eos the apoptosis resistance.

Impaired Regeneration in Dystrophic Muscle-New Target for Therapy

Muscle stem cells (MuSCs), known as satellite cells (SCs) have an incredible ability to regenerate, which enables the maintenance and growth of muscle tissue. In response to damaging stimuli, SCs are activated, proliferate, differentiate, and fuse to repair or generate a new muscle fiber. However, dystrophic muscles are characterized by poor muscle regeneration along with chronic inflammation and fibrosis. Indications for SC involvement in muscular dystrophy pathologies are accumulating, but their contribution to muscle pathophysiology is not precisely understood. In congenital muscular dystrophy type 1A (LAMA2-CMD), mutations in Lama2 gene cause either complete or partial absence in laminin-211 protein. Laminin-211 functions as a link between muscle extracellular matrix (ECM) and two adhesion systems in the sarcolemma; one is the well-known dystrophin-glycoprotein complex (DGC), and the second is the integrin complex. Because of its protein interactions and location, laminin-211 has a crucial role in muscle function and survival by maintaining sarcolemma integrity. In addition, laminin-211 is expressed in SCs and suggested to have a role in SC proliferation and differentiation. Downstream to the primary defect in laminin-211, several secondary genes and pathways accelerate disease mechanism, while at the same time there are unsuccessful attempts to regenerate as compensation for the dystrophic process. Lately, next-generation sequencing platforms have advanced our knowledge about the secondary events occurring in various diseases, elucidate the pathophysiology, and characterize new essential targets for development of new treatment strategies. This review will mainly focus on SC contribution to impaired regeneration in muscular dystrophies and specifically new findings suggesting SC involvement in LAMA2-CMD pathology.

Pax7, Pax3 and Mamstr genes are involved in skeletal muscle impaired regeneration of dy2J/dy2J mouse model of Lama2-CMD

Congenital muscular dystrophy type-1A (Lama2-CMD) and Duchenne muscular dystrophy (DMD) result from deficiencies of laminin-α2 and dystrophin proteins, respectively. Although both proteins strengthen the sarcolemma, they are implicated in clinically distinct phenotypes. We used RNA-deep sequencing (RNA-Seq) of dy2J/dy2J, Lama2-CMD mouse model, skeletal muscle at 8 weeks of age to elucidate disease pathophysiology. This study is the first report of dy2J/dy2J model whole transcriptome profile. RNA-Seq of the mdx mouse model of DMD and wild-type (WT) mouse was carried as well in order to enable a novel comparison of dy2J/dy2J to mdx. A large group of shared differentially expressed genes (DEGs) was found in dy2J/dy2J and mdx models (1834 common DEGs, false discovery rate [FDR] < 0.05). Enrichment pathway analysis using ingenuity pathway analysis showed enrichment of inflammation, fibrosis, cellular movement, migration and proliferation of cells, apoptosis and necrosis in both mouse models (P-values 3E-10-9E-37). Via canonical pathway analysis, actin cytoskeleton, integrin, integrin-linked kinase, NF-kB, renin-angiotensin, epithelial-mesenchymal transition, and calcium signaling were also enriched and upregulated in both models (FDR < 0.05). Interestingly, significant downregulation of Pax7 was detected in dy2J/dy2J compared to upregulation of this key regeneration gene in mdx mice. Pax3 and Mamstr genes were also downregulated in dy2J/dy2J compared to WT mice. These results may explain the distinct disease course and severity in these models. While the mdx model at that stage shows massive regeneration, the dy2J/dy2J shows progressive dystrophic process. Our data deepen our understanding of the molecular pathophysiology and suggest new targets for additional therapies to upregulate regeneration in Lama2-CMD.

Current understanding and treatment of cardiac and skeletal muscle pathology in laminin-α2 chain-deficient congenital muscular dystrophy

Congenital muscular dystrophy (CMD) is a class of severe early-onset muscular dystrophies affecting skeletal/cardiac muscles as well as the central nervous system (CNS). Laminin-α2 chain-deficient congenital muscular dystrophy (LAMA2 MD), also known as merosin-deficient congenital muscular dystrophy type 1A (MDC1A), is an autosomal recessive CMD characterized by severe muscle weakness and degeneration apparent at birth or in the first 6 months of life. LAMA2 MD is the most common congenital muscular dystrophy, affecting approximately 4 in 500,000 children. The most common cause of death in early-onset LAMA2 MD is respiratory tract infection, with 30% of them dying within the first decade of life. LAMA2 MD is caused by loss-of-function mutations in the LAMA2 gene encoding for the laminin-α2 chain, one of the subunits of laminin-211. Laminin-211 is an extracellular matrix protein that functions to stabilize the basement membrane and muscle fibers during contraction. Since laminin-α2 is expressed in many tissue types including skeletal muscle, cardiac muscle, Schwann cells, and trophoblasts, patients with LAMA2 MD experience a multi-systemic clinical presentation depending on the extent of laminin-α2 chain deficiency. Cardiac manifestations are typically associated with a complete absence of laminin-α2; however, recent case reports highlight cardiac involvement in partial laminin-α2 chain deficiency. Laminin-211 is also expressed in the brain, and many patients have abnormalities on brain imaging; however, mental retardation and/or seizures are rarely seen. Currently, there is no cure for LAMA2 MD, but various therapies are being investigated in an effort to lessen the severity of LAMA2 MD. For example, antisense oligonucleotide-mediated exon skipping and CRISPR-Cas9 genome editing have efficiently restored the laminin-α2 chain in mouse models in vivo. This review consolidates information on the clinical presentation, genetic basis, pathology, and current treatment approaches for LAMA2 MD.

Natural disease history of the dy2J mouse model of laminin α2 (merosin)-deficient congenital muscular dystrophy

Merosin deficient congenital muscular dystrophy 1A (MDC1A) is a very rare autosomal recessive disorder caused by mutations in the LAMA2 gene leading to severe and progressive muscle weakness and atrophy. Although over 350 causative mutations have been identified for MDC1A, no treatment is yet available. There are many therapeutic approaches in development, but the lack of natural history data of the mouse model and standardized outcome measures makes it difficult to transit these pre-clinical findings to clinical trials. Therefore, in the present study, we collected natural history data and assessed pre-clinical outcome measures for the dy^2J/dy^2J mouse model using standardized operating procedures available from the TREAT-NMD Alliance. Wild type and dy^2J/dy^2J mice were subjected to five different functional tests from the age of four to 32 weeks. Non-tested control groups were taken along to assess whether the functional test regime interfered with muscle pathology. Respiratory function, body weights and creatine kinase levels were recorded. Lastly, skeletal muscles were collected for further histopathological and gene expression analyses. Muscle function of dy^2J/dy^2J mice was severely impaired at four weeks of age and all mice lost the ability to use their hind limbs. Moreover, respiratory function was altered in dy^2J/dy^2J mice. Interestingly, the respiration rate was decreased and declined with age, whereas the respiration amplitude was increased in dy^2J/dy^2J mice when compared to wild type mice. Creatine kinase levels were comparable to wild type mice. Muscle histopathology and gene expression analysis revealed that there was a specific regional distribution pattern of muscle damage in dy^2J/dy^2J mice. Gastrocnemius appeared to be the most severely affected muscle with a high proportion of atrophic fibers, increased fibrosis and inflammation. By contrast, triceps was affected moderately and diaphragm only mildly. Our study presents a complete natural history dataset which can be used in setting up standardized studies in dy^2J/dy^2J mice.

Inhibition of farnesyl pyrophosphate synthase prevents norepinephrine-induced fibrotic responses in vascular smooth muscle cells from spontaneously hypertensive rats

Both norepinephrine (NE) and connective tissue growth factor (CTGF) contribute to vascular fibrosis during hypertension. Recent studies indicate that farnesyl pyrophosphate synthase (FPPS) plays an important role in cardiac remodeling in hypertension. However, the role of FPPS in NE-induced fibrotic responses and related molecular mechanisms is unknown. Vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were stimulated with NE. The fibrotic responses were assessed by measuring CTGF, hydroxyproline (hyp), and α-1 procollagen I levels using Western blot, a hydroxyproline test kit, and real-time quantitative PCR assays, respectively. Ras activity was determined by a pull-down assay using a Ras activation assay kit and detected by Western blot. NE dose-dependently increased fibrosis in SHR-VSMCs, and this increase was significantly reduced by ibandronate, an inhibitor of FPPS. The addition of farnesol, but not geranylgeraniol, partially reversed the inhibitory effects of ibandronate. Furthermore, the anti-fibrotic effects of ibandronate could be mimicked by FTI-276 but not by GGTI-286. A pull-down assay showed that ibandronate reduced the NE-induced Ras activation. Moreover, ibandronate inhibited the NE-induced activation of p38, JNK, and ERK1/2. Only SB203580 (specific inhibitor of p38) diminished the NE-induced CTGF production. These results demonstrated that inhibiting FPPS prevents NE-induced fibrotic responses in SHR-VSMCs and that the Ras kinase and p38 pathways were the underlying mechanisms involved in this process.

Ras chaperones: new targets for cancer and immunotherapy

The Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS, Salirasib®) interferes with Ras membrane interactions that are crucial for Ras-dependent signaling and cellular transformation. FTS had been successfully evaluated in clinical trials of cancer patients. Interestingly, its effect is mediated by targeting Ras chaperones that serve as key coordinators for Ras proper folding and delivery, thus offering a novel target for cancer therapy. The development of new FTS analogs has revealed that the specific modifications to the FTS carboxyl group by esterification and amidation yielded compounds with improved growth inhibitory activity. When FTS was combined with additional therapeutic agents its activity toward Ras was significantly augmented. FTS should be tested not only in cancer but also for genetic diseases associated with abnormal Ras signaling, as well as for various inflammatory and autoimmune disturbances, where Ras plays a major role. We conclude that FTS has a great potential both as a safe anticancer drug and as a promising immune modulator agent.

Fast skeletal muscle troponin activator in the dy2J muscular dystrophy model

INTRODUCTION

Tirasemtiv is a novel small molecule activator of the fast skeletal muscle troponin complex that produces sensitization of the sarcomere to calcium. Tirasemtiv is currently in Phase II clinical trials for neuromuscular disease.

METHODS

We conducted a blinded, randomized, placebo-controlled preclinical study of the effect of tirasemtiv on forearm grip strength, endurance, respiratory physiology, and muscle pathology in adequate sample sizes of the Lama2(dy-2J) mouse model of congenital muscular dystrophy.

RESULTS

Mice receiving a high dose of tirasemtiv had significantly higher muscle fiber cross-sectional area and respiratory response to CO₂ stimulation at 16 weeks than mice on low dose or placebo. There were no changes in muscle pathology, serum creatine kinase, strength, endurance, or respiration following long-term treatment.

CONCLUSIONS

We conclude that tirasemtiv influences the structure of the skeletal muscle fiber in this model of muscular dystrophy but does not impact muscle function, as evaluated in this study.

Cardiomyopathy in the dystrophin/utrophin-deficient mouse model of severe muscular dystrophy is characterized by dysregulation of matrix metalloproteinases

Cardiomyopathy is a significant component in Duchenne muscular dystrophy. Although mdx mice are deficient in dystrophin, they only develop mild indicators of cardiomyopathy before 1year-of-age, making therapeutic investigations using this model lengthy. In contrast, mdx mice also lacking utrophin (utrn(-/-);mdx) show severely reduced cardiac contractile function and histological indicators of cardiomyopathy by 8-10weeks-of-age. Here we demonstrate that utrn(-/-);mdx mice show a similar pattern of cardiac damage to that in dystrophic patients. Matrix metalloproteinases required for ventricular remodeling during the evolution of heart failure are upregulated in utrn(-/-);mdx mice concurrent with the onset of cardiac pathology by 10weeks-of-age. Matrix metalloproteinase activity is further dysregulated due to reduced levels of endogenous tissue inhibitors and co-localizes with fibroblasts and collagen I-containing scars. utrn(-/-);mdx mice are therefore a very useful model for investigating potential cardiac therapies.

Losartan, a therapeutic candidate in congenital muscular dystrophy: studies in the dy(2J) /dy(2J) mouse

OBJECTIVE

Lamininα2-deficient congenital muscular dystrophy type 1A (MDC1A) is a cureless disease associated with severe disability and shortened lifespan. Previous studies have shown reduced fibrosis and restored skeletal muscle remodeling following treatment with losartan, an angiotensin II type I receptor blocker. We therefore evaluated the effect of losartan treatment in the dy(2J) /dy(2J) mouse model of MDC1A.

METHODS

Homozygous dy(2J) /dy(2J) and control mice were treated with losartan or placebo for 12 weeks from 6 weeks of age. Outcome measures included hindlimb and forelimb muscle strength by Grip Strength Meter and quantitative muscle fibrosis parameters. Losartan's effects on transforming growth factor β (TGF-β) and mitogen-activated protein kinase (MAPK) signaling pathways were evaluated with Western blotting, immunofluorescence, and cytokine measurements.

RESULTS

Losartan treatment was associated with significant impressive improvement in muscle strength and amelioration of fibrosis. Administration of losartan inhibited TGF-β signaling pathway, resulting in decreased serum TGF-β1 level and reduced downstream phosphorylated (P) Smad2/3 proteins. Moreover, losartan activated Smad7 protein, a key negative regulator of TGF-β signaling. In addition, losartan treatment inhibited the MAPK cascade as shown by decreased expression of P-p38 MAPK, P-c-jun-N-terminal kinase, and P-extracellular signal-regulated kinases 1 and 2 in the treated mice.

INTERPRETATION

Losartan, a commonly prescribed US Food and Drug Administration-approved medication for hypertension, demonstrated clinical improvement and amelioration of fibrosis in the dy(2J) /dy(2J) mouse model of MDC1A via TGF-β and MAPK signaling pathways. The results of this study support pursuing a clinical trial of losartan treatment in children with MDC1A.