REN and chronic kidney disease: TGF-β signaling interacts with other cell signaling pathways such as the renin-angiotensin-aldosterone system (RAAS), a critical pathway leading to CKD, in which renin promotes production of angiotensin I (Ang I), which is converted to Ang II by angiotensin-converting enzyme (ACE) (AlQudah et al., 2020).