PGE2 receptor (EP1 or EP2) deficiency markedly suppressed the extracellular matrix accumulation and COX-2 expression in mouse mesangial cells induced by TGF-β1 which is a pivotal mediator of renal fibrosis and glomerulosclerosis in diabetic nephropathy [38, 39]. The gene discussed is PTGER1; the disease is renal fibrosis.