SOX9 and acute kidney injury: There were also increased numbers of Sox9+, but not Ki67+ PTECs (Figure 5, A–D, and Figure 6A), and increased expression of Kim1, Sox9, and FoxM1 mRNAs — the latter of which is also upregulated in dedifferentiated, proliferating PTECs after IRI-AKI (31) — in uninjured PTEC DN RAR mouse kidneys compared with Cre– controls (Figure 6B).