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The role of pericytes in systemic sclerosis (SSc) is unclear because of the difficulty in phenotyping them. They are mainly distributed in the pre-capillary, capillary and post-capillary abluminal side of non-muscular micro-vessels, express platelet-derived growth factor receptors (PDGFRs), and preside over vascular integrity and regeneration. By establishing close contact with many endothelial cells, a single pericyte can regulate ion influx, mechanical stress, leukocyte diapedesis, and platelet activation. Moreover, under pathological conditions such as SSc, pericytes may acquire a contractile phenotype and respond to various stimuli, including endothelin, angiotensin II and reactive oxygen species. The pericytes of SSc patients share some molecular patterns with myofibroblasts or fibroblasts, including A disintegrin and metalloproteinase domain 12 (ADAM-12), α-smooth muscle actin (α-SMA), the extra domain A (ED-A) variant of fibronectin, and Thy-1. Following stimulation with PDGF-β or transforming growth factor-β (TGF-β), pericytes may acquire a myofibroblast phenotype, and produce extracellular matrix or indirectly promote fibroblast activation. They may also contribute to fibrosis by means of epigenetic regulation. The pericyte plasmalemma is particularly rich in caveolae containing caveolin-1, a deficit of which has been associated with defective vessel tone control and lung fibrosis in mice. Consequently, dysfunctional pericytes may underlie the microangiopathy and fibrosis observed in SSc patients. However, given its variability in biological behaviour and the lack of a pan-pericyte marker, the exact role of these cells in SSc warrants further investigation.

The effectiveness of dothiepin (a tricyclic anti-depressant) at a dose of 75 mg given orally at night was compared with placebo for 4 weeks in alleviating pain in 60 patients with classical or definite active rheumatoid arthritis. Patients were classified as either ‘depressed’ or ‘not depressed’. The week before, during and 2 weeks after the study, 600 mg ibuprofen was given orally three times daily to all patients. Compared with placebo, dothiepin produced a significant reduction in daytime pain by the end of the treatment period. The Hamilton rating scale in ‘depressed’ patients was significantly improved in patients given dothiepin. The Cassano–Castrogiovanni self-evaluation rating scale in both ‘depressed’ and ‘not depressed’ patients showed a tendency (not significant) to be improved following dothiepin treatment compared with placebo. These results suggest that patients with rheumatoid arthritis may experience an increase in pain symptoms due to an alteration of mood. Therapy with tricyclic anti-depressants, such as dothiepin, therefore, may determine an improvement of pain indexes besides having an anti-depressant effect.