C7 and diabetic kidney disease: Based on the heterogeneity of the diabetic nephropathy (DN) microenvironment, this study identified 15 key pathogenic genes: FN1, EGR1, TPM1, CCND2, COL1A2, TGFB2, COL6A3, ITGA11, ABCC9, THBS2, TNC, COL3A1, C7, C1QC, and ITGB6.