COL4A3 and chronic kidney disease: While one week of DMP1 injections was sufficient to completely prevent the early increase in Fgf23 mRNA expression in 6-week-old 129 Sv Col4a3−/−, the same treatment only partially corrected Fgf23 mRNA expression in 9-week-old 129 Sv mice with advanced CKD (Fig. 4o).