TGFB1 and acute kidney injury: Interestingly, transforming growth factor β 1 (TGFβ1), a key pro-fibrotic factor, was even lower in AKI-KRM and AKI-mono, compared to the renal macrophages at quiescence, suggesting that macrophages may not the major source of the pro-fibrotic factors after AKI (Figure 1C).