MMP9 and chronic kidney disease: Emerging candidate biomarkers for CKD progression include surrogates of tubulointersitital injury (NGAL, IL-18, KIM-1, EGF), tubulointerstitial fibrosis (MMP-9, PIIINP, TGF-β1, BMP-7), and inflammation (MCP-1, TNFR 1/2, suPAR) [38].