For example, inactive fibroblasts express ET-1 and intracellular adhesion molecules 1 (ICAM-1), whereas fibroblasts exposed to mechanical stress in the microenvironment, a situation that occurs in systemic sclerosis, express α-SMA, TGF-β, and genes associated with the production of extracellular matrix proteins. The gene discussed is TGFB1; the disease is systemic sclerosis.