Various studies have reported that both Smad2 and Smad3, the two major downstream mediators of the TGF‐β/Smad signalling pathway, are highly activated in diabetic nephropathy, obstructive kidney disease and hypertensive nephropathy 34, 35, 36; similarly, our in vivo findings also show that these two proteins are activated in kidney transplant patients with CAD. The gene discussed is SMAD3; the disease is diabetic kidney disease.