Transforming growth factor signalling: a common pathway in pulmonary arterial hypertension and systemic sclerosis

Perivascular Cells in Diffuse Cutaneous Systemic Sclerosis Overexpress Activated ADAM12 and Are Involved in Myofibroblast Transdifferentiation and Development of Fibrosis

Objective.

Microvascular damage is pivotal in the pathogenesis of systemic sclerosis (SSc), preceding fibrosis, and whose trigger is not still fully understood. Perivascular progenitor cells, with profibrotic activity and function, are identified by the expression of the isoform 12 of ADAM (ADAM12) and this molecule may be upregulated by transforming growth factor-β (TGF-β). The goal of this work was to evaluate whether pericytes in the skin of patients with diffuse cutaneous SSc (dcSSc) expressed ADAM12, suggesting their potential contribution to the fibrotic process, and whether TGF-β might modulate this molecule.

Methods.

After ethical approval, mesenchymal stem cells (MSC) and fibroblasts (FB) were isolated from bone marrow and skin samples collected from 20 patients with dcSSc. ADAM12 expression was investigated in the skin and in isolated MSC and FB treated with TGF-β by immunofluorescence, quantitative real-time PCR, and western blot. Further, we silenced ADAM12 expression in both dcSSc-MSC and -FB to confirm the TGF-β modulation.

Results.

Pericytes and FB of dcSSc skin showed an increased expression of ADAM12 when compared with healthy control skin. TGF-β in vitro treatment induced a significant increase of ADAM12 in both SSc-MSC and -FB, with the higher levels observed in dcSSc cells. After ADAM12 silencing, the TGF-β ability to upregulate α-smooth muscle actin in both SSc-MSC and SSc-FB was inhibited.

Conclusion.

Our results suggest that in SSc, pericytes that transdifferentiate toward activated FB are present in the vascular tree, and TGF-β, while increasing ADAM12 expression, may modulate this transdifferentiation.

Systemic sclerosis induces pronounced peripheral vascular dysfunction characterized by blunted peripheral vasoreactivity and endothelial dysfunction

Systemic sclerosis (SSc) vasculopathy can result in a digital ulcer (DU) and/or pulmonary arterial hypertension (PAH). We hypothesized that bedside brachial artery flow-mediated dilation (FMD) testing with duplex ultrasound could be used in SSc patients to identify features of patients at risk for DU or PAH. Thirty-eight SSc patients were compared to 52 age-matched healthy controls from the VAMC Utah Vascular Research Laboratory. Peripheral hemodynamics, arterial structure, and endothelial function were assessed by duplex ultrasound. A blood pressure cuff was applied to the forearm and 5-min ischemia was induced. Post-occlusion, brachial artery vascular reactivity (peak hyperemia/area under the curve [AUC]), shear rate, and endothelial function (FMD) were measured. SSc patients had smaller brachial artery diameters (p < 0.001) and less reactive hyperemia (p < 0.001), peak shear rate (p = 0.03), and brachial artery FMD (p < 0.001) compared with healthy controls. Brachial artery FMD was lower (p < 0.05) in SSc patients with DU. Tertile analysis suggested the 2 lower FMD tertiles (<5.40 %) had a 40-50 % chance of presenting with DU while the SSc patients with highest FMD tertile (>5.40 %) had less than 15 % chance of DU. All brachial artery FMD measurements were similar between SSc patients with and without PAH (all p > 0.05). Compared to healthy controls, SSc patients had significantly smaller brachial artery diameter and blunted peripheral vascular reactivity and endothelial function. SSc patients with DU have even greater impairments in endothelial function compared to those without DU. FMD testing has clinical utility to identify SSc patients at risk for DU.

Biventricular remodeling in murine models of right ventricular pressure overload

Right ventricular (RV) failure is a major cause of mortality in acute or chronic lung disease and left heart failure. The objective of this study was to demonstrate a percutaneous approach to study biventricular hemodynamics in murine models of primary and secondary RV pressure overload (RVPO) and further explore biventricular expression of two key proteins that regulate cardiac remodeling: calcineurin and transforming growth factor beta 1 (TGFβ1).

METHODS

Adult, male mice underwent constriction of the pulmonary artery or thoracic aorta as models of primary and secondary RVPO, respectively. Conductance catheterization was performed followed by tissue analysis for changes in myocyte hypertrophy and fibrosis.

RESULTS

Both primary and secondary RVPO decreased biventricular stroke work however RV instantaneous peak pressure (dP/dtmax) and end-systolic elastance (Ees) were preserved in both groups compared to controls. In contrast, left ventricular (LV) dP/dtmax and LV-Ees were unchanged by primary, but reduced in the secondary RVPO group. The ratio of RV:LV ventriculo-arterial coupling was increased in primary and reduced in secondary RVPO. Primary and secondary RVPO increased RV mass, while LV mass decreased in primary and increased in the secondary RVPO groups. RV fibrosis and hypertrophy were increased in both groups, while LV fibrosis and hypertrophy were increased in secondary RVPO only. RV calcineurin expression was increased in both groups, while LV expression increased in secondary RVPO only. Biventricular TGFβ1 expression was increased in both groups.

CONCLUSION

These data identify distinct effects of primary and secondary RVPO on biventricular structure, function, and expression of key remodeling pathways.

MicroRNA-376c impairs transforming growth factor-β and nodal signaling to promote trophoblast cell proliferation and invasion

Preeclampsia is a major disorder of pregnancy and a leading cause of maternal and perinatal morbidity and mortality. MicroRNAs are small noncoding RNAs that regulate gene expression posttranscriptionally. In this study, we examined the expression of miR-376c and found that miR-376c levels were downregulated in both placental and plasma samples collected from preeclamptic patients, when compared with the normal pregnant women at the same gestational stage. Overexpression of miR-376c induced trophoblast cell proliferation, migration, and invasion in HTR8/SVneo cells and promoted placental explant outgrowth. In contrast, inhibition of endogenous miR-376c resulted in a decrease in trophoblast cell invasion and placental explant outgrowth. We identified activin receptor-like kinase 5 (ALK5), a type I receptor for transforming growth factor-β, and ALK7, a type I receptor for Nodal, as targets of miR-376c. Overexpression of miR-376c repressed transforming growth factor-β and Nodal functions, whereas overexpression of ALK5 and ALK7 reversed the effects of miR-376c. These results demonstrate that miR-376c inhibits both ALK5 and ALK7 expression to impair transforming growth factor-β/Nodal signaling, leading to increases in cell proliferation and invasion. An unbalanced Nodal/transforming growth factor-β and miR-376c expression may lead to the development of preeclampsia.

Today's and tomorrow's imaging and circulating biomarkers for pulmonary arterial hypertension

The pathobiology of pulmonary arterial hypertension (PAH) involves a remodeling process in distal pulmonary arteries, as well as vasoconstriction and in situ thrombosis, leading to an increase in pulmonary vascular resistance, right heart failure and death. Its etiology may be idiopathic, but PAH is also frequently associated with underlying conditions such as connective tissue diseases. During the past decade, more than welcome novel therapies have been developed and are in development, including those increasingly targeting the remodeling process. These therapeutic options modestly increase the patients' long-term survival, now approaching 60% at 5 years. However, non-invasive tools for confirming PAH diagnosis, and assessing disease severity and response to therapy, are tragically lacking and would help to select the best treatment. After exclusion of other causes of pulmonary hypertension, a final diagnosis still relies on right heart catheterization, an invasive technique which cannot be repeated as often as an optimal follow-up might require. Similarly, other techniques and biomarkers used for assessing disease severity and response to treatment generally lack specificity and have significant limitations. In this review, imaging as well as current and future circulating biomarkers for diagnosis, prognosis, and follow-up are discussed.