ADRB2 and Myocardial fibrosis: In the pathogenesis of myocardial fibrosis, evidence also supports that transforming growth factor-β (TGF-β) acts as a profibrotic cytokine to drive CTGF expression.26 However, we didn’t detect a significant change of TGF-β expression in the young β2AR-CKO heart, indicating that CTGF acts upstream of TGF-β in this model, and supporting a feedback loop between CTGF and TGF-β to promote cardiac fibrosis.