Systemic vasculopathy with altered vasoreactivity in a transgenic mouse model of scleroderma

The pan-PPAR agonist lanifibranor reduces development of lung fibrosis and attenuates cardiorespiratory manifestations in a transgenic mouse model of systemic sclerosis

Background

The TβRII∆k-fib transgenic (TG) mouse model of scleroderma replicates key fibrotic and vasculopathic complications of systemic sclerosis through fibroblast-directed upregulation of TGFβ signalling. We have examined peroxisome proliferator-activated receptor (PPAR) pathway perturbation in this model and explored the impact of the pan-PPAR agonist lanifibranor on the cardiorespiratory phenotype.

Methods

PPAR pathway gene and protein expression differences from TG and WT sex-matched littermate mice were determined at baseline and following administration of one of two doses of lanifibranor (30 mg/kg or 100 mg/kg) or vehicle administered by daily oral gavage up to 4 weeks. The prevention of bleomycin-induced lung fibrosis and SU5416-induced pulmonary hypertension by lanifibranor was explored.

Results

Gene expression data were consistent with the downregulation of the PPAR pathway in the TβRII∆k-fib mouse model. TG mice treated with high-dose lanifibranor demonstrated significant protection from lung fibrosis after bleomycin and from right ventricular hypertrophy following induction of pulmonary hypertension by SU5416, despite no significant change in right ventricular systolic pressure.

Conclusions

In the TβRII∆k-fib mouse strain, treatment with 100 mg/kg lanifibranor reduces the development of lung fibrosis and right ventricular hypertrophy induced by bleomycin or SU5416, respectively. Reduced PPAR activity may contribute to the exaggerated fibroproliferative response to tissue injury in this transgenic model of scleroderma and its pulmonary complications.

Inhibition of transforming growth factor-β signaling in myeloid cells ameliorates aortic aneurysmal formation in Marfan syndrome

Increased transforming growth factor-β (TGF-β) signaling contributes to the pathophysiology of aortic aneurysm in Marfan syndrome (MFS). Recent reports indicate that a small but significant number of inflammatory cells are infiltrated into the aortic media and adventitia in MFS. However, little is known about the contribution of myeloid cells to aortic aneurysmal formation. In this study, we ablated the TGF-β type II receptor gene Tgfbr2 in myeloid cells of Fbn1^C1039G/+ MFS mice (Fbn1^C1039G/+;LysM-Cre/+;Tgfbr2^fl/fl mice, hereinafter called Fbn1^C1039G/+;Tgfbr2^MyeKO) and evaluated macrophage infiltration and TGF-β signaling in the aorta. Aneurysmal formation with fragmentation and disarray of medial elastic fibers observed in MFS mice was significantly ameliorated in Fbn1^C1039G/+;Tgfbr2^MyeKO mice. In the aorta of Fbn1^C1039G/+;Tgfbr2^MyeKO mice, both canonical and noncanonical TGF-β signals were attenuated and the number of infiltrated F4/80-positive macrophages was significantly reduced. In vitro, TGF-β enhanced the migration capacity of RAW264.7 macrophages. These findings suggest that TGF-β signaling in myeloid cells promotes aortic aneurysmal formation and its inhibition might be a novel therapeutic target in MFS.

Aortic root dilation in associated with the reduction in capillary density observed at nailfold capillaroscopy in SSc patients

Systemic sclerosis (SSc) is an autoimmune disease characterized by endothelial dysfunction and fibroblasts activation. Microvascular disease may be easily observed by means of nailfold capillaroscopy. Recent evidences emphasized also the involvement of large-medium arteries in SSc, mainly in terms of increased stiffness of the vessel wall. The study aims to measure aortic root diameter in a cohort of SSc patients and to correlate echocardiographic findings with the capillaroscopic pictures. We analyzed the clinical records of 125 consecutive SSc patients (M/F 14/111, mean age 55 ± 12.7 years, median disease duration 11 years) referring in 3 second-level rheumatology centers. All subjects underwent to heart ultrasound evaluation and videocapillaroscopic evaluation. At capillaroscopy, the patients with early SSc pattern belonged to the subgroup 1, while those with the active/late patterns (characterized by the reduction of capillary density) belonged to the subgroup 2. We found aortic root dilation in 8 (6.4%) SSc patients, with a mean value of 37.8 ± 1.2 mm (range 37-40 mm). Aortic root dilation was observed in only one patient in the subgroup 1 (1/62, 1.6%) and in 7 cases of the subgroup 2 (7/63, 11.1%; p = 0.03). Our study found a significant association between aortic root dilation and impairment of capillary density at nailfold videocapillaroscopy in SSc patients. We hypothesize that SSc-related microangiopathy revealed by nailfold videocapillaroscopy could mimic that of aortic vasa vasorum, contributing to deteriorate the aortic wall structure and favoring aortic root dilation and stiffening.

Transforming Growth Factor β Activation Primes Canonical Wnt Signaling Through Down-Regulation of Axin-2

OBJECTIVE

Aberrant activation of Wnt signaling has been observed in tissues from patients with systemic sclerosis (SSc). This study aimed to determine the role of transforming growth factor β (TGFβ) in driving the increased Wnt signaling, through modulation of axis inhibition protein 2 (Axin-2), a critical regulator of the Wnt canonical pathway.

METHODS

Canonical Wnt signaling activation was analyzed by TOPflash T cell factor/lymphoid enhancer factor promoter assays. Axin-2 was evaluated in vitro by analysis of Axin-2 primary/mature transcript expression and decay, TGFβ receptor type I (TGFβRI) blockade, small interfering RNA-mediated depletion of tristetraprolin 1, and XAV-939-mediated Axin-2 stabilization. In vivo, Axin-2 messenger RNA (mRNA) and protein expression was determined in skin and lung biopsy samples from mice that express a kinase-deficient TGFβRII specifically on fibroblasts (TβRIIΔk-fib-transgenic mice) and from littermate controls.

RESULTS

SSc fibroblasts displayed an increased response to canonical Wnt ligands despite basal levels of Wnt signaling that were comparable to those in healthy control fibroblasts in vitro. Notably, we showed that SSc fibroblasts had reduced basal expression of Axin-2, which was caused by an endogenous TGFβ-dependent increase in Axin-2 mRNA decay. Accordingly, we observed that TGFβ decreased Axin-2 expression both in vitro in healthy control fibroblasts and in vivo in TβRIIΔk-fib-transgenic mice. Additionally, using Axin-2 gain- and loss-of-function experiments, we demonstrated that the TGFβ-induced increased response to Wnt activation characteristic of SSc fibroblasts depended on reduced bioavailability of Axin-2.

CONCLUSION

This study highlights the importance of reduced bioavailability of Axin-2 in mediating the increased canonical Wnt response observed in SSc fibroblasts. This novel mechanism extends our understanding of the processes involved in Wnt/β-catenin-driven pathology and supports the rationale for targeting the TGFβ pathway to regulate the aberrant Wnt signaling observed during fibrosis.

Updates on animal models of systemic sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology that is characterized by fibrosis of the skin and several internal organs, vasculopathy, inflammation and autoimmunity. Animal models have improved our understanding of the pathogenesis of SSc. Many inducible and genetic animal models of SSc have been developed and characterized in the last years. All of these models have different strengths and limitations and mimic different aspects of the pathogenesis of SSc. The purpose of this review is to summarize the characteristics of the various animal models of SSc and to provide an outline of how to use these models to study certain aspects in the pathogenesis of SSc and to test the effects of potential therapeutic approaches.

Simvastatin prevents vascular complications in the chronic reactive oxygen species murine model of systemic sclerosis

Aims Systemic sclerosis (SSc) is characterized by vasculopathy and organ fibrosis. Although microvascular alterations are very well characterized, structural and functional abnormalities of large vessels are not well defined. Therefore, we evaluated the effect of simvastatin administration on aortic and small renal arteries thickening, and on myofibroblasts differentiation in a murine model of SSc. Methods and results SSc was induced in BALB/c mice by daily subcutaneous injections of hypochlorous acid (HOCl, 100 μl) for 6 weeks. Mice (n = 23) were randomized to receive: HOCl (n = 10); HOCl plus simvastatin (40 mg/kg; n = 8); or vehicle (n = 5). Simvastatin administration started 30 min after HOCl injection, and up to week 6. Aortic and small renal arteries intima-media thickness was evaluated by histological analysis. Immunostaining for α-smooth muscle actin (SMA), vascular endothelial growth factor receptor 2 (VEGFR2), and CD31 in aortic tissues was performed to evaluate myofibroblast differentiation and endothelial markers.In HOCl-treated mice, intima-media thickening with reduced lumen diameter was observed in the aorta and in small renal arteries and simvastatin administration prevented this increase. Aortic and renal myofibroblasts count, as expressed by α-SMA + density, was lower in the group of mice treated with simvastatin compared to HOCl-treated mice. Simvastatin prevented the reduction in VEGFR2 and CD31 expression induced by HOCl. Conclusions The administration of simvastatin regulates collagen deposition in the aortic tissues and in the small renal arteries by modulating myofibroblasts differentiation and vascular markers. Further studies are needed to better address the effect of statins in the macrovascular component of SSc.

Efficacy of flavonoids in the management of high blood pressure

Plant compounds such as flavonoids have been reported to exert beneficial effects in cardiovascular disease, including hypertension. Information on the effects of isolated individual flavonoids for management of high blood pressure, however, is more limited. This review is focused on the flavonoids, as isolated outside of the food matrix, from the 5 main subgroups consumed in the Western diet (flavones, flavonols, flavanones, flavan-3-ols, and anthocyanins), along with their effects on hypertension, including the potential mechanisms for regulating blood pressure. Flavonoids from all 5 subgroups have been shown to attenuate a rise in or to reduce blood pressure during several pathological conditions (hypertension, metabolic syndrome, and diabetes mellitus). Flavones, flavonols, flavanones, and flavanols were able to modulate blood pressure by restoring endothelial function, either directly, by affecting nitric oxide levels, or indirectly, through other pathways. Quercetin had the most consistent blood pressure-lowering effect in animal and human studies, irrespective of dose, duration, or disease status. However, further research on the safety and efficacy of the flavonoids is required before any of them can be used by humans, presumably in supplement form, at the doses required for therapeutic benefit.

Interleukin-17A promotes functional activation of systemic sclerosis patient-derived dermal vascular smooth muscle cells by extracellular-regulated protein kinases signalling pathway

INTRODUCTION

Dermal vascular smooth muscle cells (DVSMCs) are important for vascular wall fibrosis in microangiopathy of systemic sclerosis (SSc). T helper 17 cell-associated cytokines, particularly interleukin-17A (IL-17A), have been demonstrated to play a role in the pathogenesis of SSc. However, the effect of IL-17A on the DVSMCs in microangiopathy of SSc has not been established. In the present study, we investigated the effect of IL-17A on the SSc patient-derived DVSMCs.

METHODS

DVSMCs from patients with SSc and healthy subjects were incubated using IL-17A or serum derived from patients with SSc. Subsequently, the proliferation, collagen synthesis and secretion, and migration of DVSMCs were analysed using a cell counting kit-8 (CCK-8), dual-luciferase reporter assay, real-time reverse transcription-polymerase chain reaction (RT-PCR), Western blot, enzyme-linked immunosorbent assay (ELISA) and transwell assay. The protein phosphorylation of signalling pathways in the process of IL-17A-mediated DVSMC activation was investigated and validated by specific signalling pathway inhibitor.

RESULTS

IL-17A and serum from patients with SSc could promote the proliferation, collagen synthesis and secretion, and migration of DVSMCs. IL-17A neutralising antibody could inhibit the IL-17A-induced activation of DVSMCs. Additionally, IL-17A induced the activation of extracellular-regulated protein kinases 1/2 (ERK1/2) in DVSMCs, and ERK1/2 inhibitor could block the IL-17A-elicited activation of DVSMCs.

CONCLUSIONS

Our results suggested that IL-17A derived from patients with SSc might induce the proliferation, collagen synthesis and secretion, and migration of DVSMCs via ERK1/2 signalling pathway, raising the likelihood that IL-17A and ERK1/2 might be promising therapeutic targets for the treatment of SSc-related vasculopathy.

Scleroderma pathogenesis: a pivotal role for fibroblasts as effector cells

Scleroderma (systemic sclerosis; SSc) is characterised by fibrosis of the skin and internal organs in the context of autoimmunity and vascular perturbation. Overproduction of extracellular matrix components and loss of specialised epithelial structures are analogous to the process of scar formation after tissue injury. Fibroblasts are the resident cells of connective tissue that become activated at sites of damage and are likely to be important effector cells in SSc. Differentiation into myofibroblasts is a hallmark process, although the mechanisms and cellular origins of this important fibroblastic cell are still unclear. This article reviews fibroblast biology in the context of SSc and highlights the potentially important place of fibroblast effector cells in fibrosis. Moreover, the heterogeneity of fibroblast properties, multiplicity of regulatory pathways and diversity of origin for myofibroblasts may underpin clinical diversity in SSc, and provide novel avenues for targeted therapy.

Endothelial injury in a transforming growth factor β-dependent mouse model of scleroderma induces pulmonary arterial hypertension

OBJECTIVE

To delineate the constitutive pulmonary vascular phenotype of the TβRIIΔk-fib mouse model of scleroderma, and to selectively induce pulmonary endothelial cell injury using vascular endothelial growth factor (VEGF) inhibition to develop a model with features characteristic of pulmonary arterial hypertension (PAH).

METHODS

The TβRIIΔk-fib mouse strain expresses a kinase-deficient transforming growth factor β (TGFβ) receptor type II driven by a fibroblast-specific promoter, leading to ligand-dependent up-regulation of TGFβ signaling, and replicates key fibrotic features of scleroderma. Structural, biochemical, and functional assessments of pulmonary vessels, including in vivo hemodynamic studies, were performed before and following VEGF inhibition, which induced pulmonary endothelial cell apoptosis. These assessments included biochemical analysis of the TGFβ and VEGF signaling axes in tissue sections and explanted smooth muscle cells.

RESULTS

In the TβRIIΔk-fib mouse strain, a constitutive pulmonary vasculopathy with medial thickening, a perivascular proliferating chronic inflammatory cell infiltrate, and mildly elevated pulmonary artery pressure resembled the well-described chronic hypoxia model of pulmonary hypertension. Following administration of SU5416, the pulmonary vascular phenotype was more florid, with pulmonary arteriolar luminal obliteration by apoptosis-resistant proliferating endothelial cells. These changes resulted in right ventricular hypertrophy, confirming hemodynamically significant PAH. Altered expression of TGFβ and VEGF ligand and receptor was consistent with a scleroderma phenotype.

CONCLUSION

In this study, we replicated key features of systemic sclerosis-related PAH in a mouse model. Our results suggest that pulmonary endothelial cell injury in a genetically susceptible mouse strain triggers this complication and support the underlying role of functional interplay between TGFβ and VEGF, which provides insight into the pathogenesis of this disease.

Interstitial lung disease: is interstitial lung disease the same as scleroderma lung disease?

PURPOSE OF REVIEW

Pulmonary fibrosis is a devastating disease that affects millions of people worldwide. Among the most common forms of lung fibrosis are idiopathic pulmonary fibrosis (IPF) and scleroderma-related interstitial lung disease (SSc-ILD). Despite a wealth of literature regarding each of these diseases, studies that directly compare IPF and SSc-ILD are rare.

RECENT FINDINGS

This review compares the salient features of IPF and SSc-ILD. Clinical presentation and demographics will be presented, along with the newly released radiographic and pathologic criteria for IPF. Evolving concepts of pathogenesis including the role of structural cell injury, the pathogenic role of macrophages and lymphocytes, and the origin of fibroblasts are described. We conclude with new developments in the search for predictive biomarkers of disease progression, such as markers of epithelial injury, lymphocyte subsets, and circulating fibrocytes, will be presented. We conclude with a discussion of the results of recent clinical trials.

SUMMARY

It is found that despite differences in clinical presentation and response to treatment, similarities are noted in proposed pathogenesis and putative biomarkers. It is hoped that this information will lead to studies aimed at understanding the factors driving these difficult to treat and often deadly diseases.

Regulation of the sphingosine kinase/sphingosine 1-phosphate pathway

Sphingolipids have emerged as pleiotropic signaling molecules with roles in numerous cellular and biological functions. Defining the regulatory mechanisms governing sphingolipid metabolism is crucial in order to develop a complete understanding of the biological functions of sphingolipid metabolites. The sphingosine kinase/ sphingosine 1-phosphate pathway was originally thought to function in the irreversible breakdown of sphingoid bases; however, in the last few decades it has materialized as an extremely important signaling pathway involved in a plethora of cellular events contributing to both normal and pathophysiological events. Recognition of the SK/S1P pathway as a second messaging system has aided in the identification of many mechanisms of its regulation; however, a cohesive, global understanding of the regulatory mechanisms controlling the SK/S1P pathway is lacking. In this chapter, the role of the SK/S1P pathway as a second messenger is discussed, and its role in mediating TNF-α- and EGF-induced biologies is examined. This work provides a comprehensive look into the roles and regulation of the sphingosine kinase/ sphingosine 1-phosphate pathway and highlights the potential of the pathway as a therapeutic target.

A unifying hypothesis for scleroderma: identifying a target cell for scleroderma

We propose that a recent change in the conception of the role of type 1 interferon and the identification of adventitial stem cells suggests a unifying hypothesis for scleroderma. This hypothesis begins with vasospasm. Vasospasm is fully reversible unless, as proposed here, the resulting ischemia leads to apoptosis and activation of type 1 interferon. The interferon, we propose, initiates immune amplification, including characteristic scleroderma-specific antibodies. We propose that the interferon also acts on adventitial stem cells, producing myofibroblasts, rarefaction, and intimal hyperplasia--three morphologic changes that characterize this disease. Regulator of G-protein signaling 5 (RGS5), a regulator of vasoactive G-protein-coupled receptors, is a cell type-specific marker of pericytes and scleroderma myofibroblasts. RGS5 may provide a key link between initial hyperplasia and fibrosis in this disease.

Vascular alterations upon activation of TGFbeta signaling in fibroblasts--implications for systemic sclerosis

Tissue fibrosis and vascular disease are hallmarks of systemic sclerosis (SSc). Transforming growth factor β (TGFβ) is a key-player in fibroblast activation and tissue fibrosis in SSc. In contrast to fibrosis, evidence for a role of TGFβ in vascular disease of SSc is scarce. Using a transgenic mouse model with fibroblast-specific expression of a kinase-deficient TGFβ receptor type II, Derrett-Smith and colleagues demonstrate that aberrant TGFβ signaling in fibroblasts might result in activation of vascular smooth muscle cells and architectural changes of the vessel wall of the aorta.