TGFB1 and chronic kidney disease: However, a progressive M2 macrophage polarization signature was evident across CKD stages 1–5 vs. LD, as shown by low transcript levels of CHI3L1, a pro-inflammatory molecule, and reduced levels of NOS2, yet a higher expression of mediators secreted by M2 macrophages, TGF-β1, or CCR-2 (Figure 6A).