BACKGROUND: Asthma is characterized by airway hyperresponsiveness (AHR), inflammation and airway remodeling. AHR results from enhanced airway smooth muscle (ASM) contraction potentially under the control of an epithelium-derived relaxing factor (EpDRF). However, relatively rare is known about EpDRF. We aimed to elucidate the role of epithelium-derived stanniocalcin-1 (STC1) on AHR and ASM contraction. METHODS: STC1 levels in the serum of asthmatic patients and healthy volunteers and in bronchoalveolar lavage fluid (BALF) from ovalbumin (OVA)-challenged mice were measured by ELISA. The effects of exogenous STC1 on AHR and on inflammation were examined in mice. IL-13 modulation of STC1 mRNA and protein levels was studied in human bronchial epithelial cell lines (16HBE). The function of STC1 on Ca2+ influx and ASM contraction was examined ex vivo. RESULTS: Serum STC1 was decreased in asthma (n=93) compared with healthy volunteers (1071±30.4 vs 1414±75.1pg/ml, p<0.0001, n=23) and correlated with asthma control (p=0.0270), lung function (FEV1, p=0.0130) and serum IL-13 levels (p=0.0009). Treatment of ten asthmatic subjects with inhaled corticosteroids/long- acting beta2-agonists (ICS/LABA) for one year enhanced STC1 expression which correlated with improved asthma control (p=0.022). STC1 was mainly expressed in bronchial epithelium and intranasal administration of recombinant human STC1 (rhSTC1) reduced AHR and inflammation in mice. IL-13 suppressed STC1 release from 16HBE, whereas rhSTC1 blocked store-operated Ca2+ entry (SOCE) by suppressing stromal interaction molecule 1 (STIM1) and further inhibited ASM cell contractility by suppressing Ca2+ -dependent myosin light chain (MLC) phosphorylation. CONCLUSION: Our data indicate that STC1 deficiency in asthmatic airways promotes STIM1 hyperactivity, enhanced ASM contraction and AHR. STC1 may be a candidate EpDRF.