Anticoagulant treatment in patients with pulmonary arterial hypertension associated with systemic sclerosis: More shadows than lights

Is anticoagulative therapy in systemic sclerosis to be reconsidered?

Systemic sclerosis is a rare disease with a high mortality rate. It is a multisystem connective tissue disease due to endothelial autoimmune activation along with tissue and vascular fibrosis, inducing vasculopathy, with an angiogenesis wasting. The endothelial damage provokes platelet activation and immune cell adhesion. The detachment of endothelial cells leads to the interaction of platelets and collagen present in the exposed subendothelial layer. This provokes the activation of several coagulative factors, inducing a pro-thrombotic condition by thrombin generation, which converts fibrinogen into fibrin. Moreover, thrombin has other functions, such as the induction of hyperplasia in smooth muscle cells and fibroblasts, thereby favouring fibrosis. An increased risk of venous thromboembolism has been found in systemic sclerosis, whereas pulmonary hypertension may be due to the obstruction of small pulmonary arteries. Pulmonary veno-occlusive disease may also occur. Warfarin showed inconsistent results, while the outcomes of a randomised, placebo-controlled clinical trial on apixaban versus placebo are still awaited. A new anticoagulation strategy based on anti-factor XI drugs is being developed, with the aim of achieving optimal anticoagulation along with a low risk of bleeding. The molecule types under investigation in this category include monoclonal antibodies, small molecules, natural inhibitors, antisense oligonucleotides, and aptamers. Patients with systemic sclerosis may be ideal candidates for clinical trials planned to analyse the efficacy and safety of these molecules.

A journey to vasculopathy in systemic sclerosis: focus on haemostasis and thrombosis

Systemic sclerosis is a multisystem connective tissue disease, characterized by endothelial autoimmune activation, along with tissue and vascular fibrosis leading to vasculopathy and to a progressive loss of angiogenesis. This condition further deranges the endothelial barrier favouring the opening of the endothelial junctions allowing the vascular leak in the surrounding tissues: this process may induce cell detachment which allows the contact between platelets and collagen present in the exposed subendothelial layer. Platelets first adhere to collagen via glycoprotein VI and then, immediately aggregate because of the release of von Willebrand factor which is a strong activator of platelet aggregation. Activated platelets exert their procoagulant activity, exposing on their membrane phospholipids and phosphatidylserine, enabling the adsorption of clotting factors ready to form thrombin which in turn drives the amplification of the coagulative cascade. An essential role in the activation of blood coagulation is the tissue factor (TF), which triggers blood coagulation. The TF is found abundantly in the subendothelial collagen and is also expressed by fibroblasts providing a haemostatic covering layer ready to activate coagulation when the endothelial injury occurs. The aim of this review is to focus the attention on the underlying mechanisms related to haemostasis and thrombosis pathophysiology which may have a relevant role in SSc as well as on a possible role of anticoagulation in this disease.

The multifaceted problem of pulmonary arterial hypertension in systemic sclerosis

Cardiopulmonary complications are a leading cause of death in systemic sclerosis. Pulmonary hypertension in particular carries a high mortality and morbidity burden. Patients with systemic sclerosis can suffer from all of the clinical groups of pulmonary hypertension, particularly pulmonary arterial hypertension and pulmonary hypertension related to interstitial lung disease. Despite a similar pathogenetic background with idiopathic pulmonary arterial hypertension, different mechanisms determine a worse prognostic outcome for patients with systemic sclerosis. In this Viewpoint, we will consider the link between pathogenetic and potential therapeutic targets for the treatment of pulmonary hypertension in the context of systemic sclerosis, with a focus on the current unmet needs, such as the importance of early screening and detection, the absence of agreed criteria to distinguish pulmonary arterial hypertension with interstitial lung disease from pulmonary hypertension due to lung fibrosis, and the need for a holistic treatment approach to target all the vascular, immunological, and inflammatory components of the disease.