Systemic sclerosis (SSc) is a complex, autoimmune disease characterized by multiple organ fibrosis and vasculopathy. Experimental and clinical evidence indicates that serotonin is crucially involved in the fibrotic process and mediates vascular manifestations such as Raynaud's phenomenon (RP) or pulmonary arterial hypertension (PAH), all key features of SSc. In this review, we summarize the current knowledge on the potential contribution of serotonin in SSc pathogenesis and provide a rationale for further investigation of this molecule as a therapeutic target.

Medline and Cochrane databases were searched from inception to April 2021 using the search terms (systemic sclerosis OR scleroderma OR Raynaud OR Pulmonary arterial hypertension) AND serotonin.

Serotonin, a key molecule in an array of central and peripheral functions, has a multifaceted role in regulating fibrosis and vasculopathy. Experimental data suggest that serotonin drives fibrosis in the skin and visceral organs, promotes platelet aggregation, induces vasoconstriction and increases pulmonary vascular resistance. Earlier human trials regarding drugs that inhibit serotonin signaling produced mixed results. However, recent advances in the understanding of the underlying molecular mechanisms could help identify novel therapeutics targeting the serotonin pathway and inform future clinical trials.

Serotonin may be a mediator in both fibrosis and vasculopathy. Further exploration of the potential role of serotonin in SSc is justified.