Placental Mesenchymal Stem Cells Alleviate Podocyte Injury in Diabetic Kidney Disease by Modulating Mitophagy via the SIRT1-PGC-1alpha-TFAM Pathway

The use of mesenchymal stem cells (MSCs) has become a new strategy for treating diabetic kidney disease (DKD). However, the role of placenta derived mesenchymal stem cells (P-MSCs) in DKD remains unclear. This study aims to investigate the therapeutic application and molecular mechanism of P-MSCs on DKD from the perspective of podocyte injury and PINK1/Parkin-mediated mitophagy at the animal, cellular, and molecular levels. Western blotting, reverse transcription polymerase chain reaction, immunofluorescence, and immunohistochemistry were used to detect the expression of podocyte injury-related markers and mitophagy-related markers, SIRT1, PGC-1α, and TFAM. Knockdown, overexpression, and rescue experiments were performed to verify the underlying mechanism of P-MSCs in DKD. Mitochondrial function was detected by flow cytometry. The structure of autophagosomes and mitochondria were observed by electron microscopy. Furthermore, we constructed a streptozotocin-induced DKD rat model and injected P-MSCs into DKD rats. Results showed that as compared with the control group, exposing podocytes to high-glucose conditions aggravated podocyte injury, represented by a decreased expression of Podocin along with increased expression of Desmin, and inhibited PINK1/Parkin-mediated mitophagy, manifested as a decreased expression of Beclin1, the LC3II/LC3I ratio, Parkin, and PINK1 associated with an increased expression of P62. Importantly, these indicators were reversed by P-MSCs. In addition, P-MSCs protected the structure and function of autophagosomes and mitochondria. P-MSCs increased mitochondrial membrane potential and ATP content and decreased the accumulation of reactive oxygen species. Mechanistically, P-MSCs alleviated podocyte injury and mitophagy inhibition by enhancing the expression of the SIRT1-PGC-1α-TFAM pathway. Finally, we injected P-MSCs into streptozotocin-induced DKD rats. The results revealed that the application of P-MSCs largely reversed the markers related to podocyte injury and mitophagy and significantly increased the expression of SIRT1, PGC-1α, and TFAM compared with the DKD group. In conclusion, P-MSCs ameliorated podocyte injury and PINK1/Parkin-mediated mitophagy inhibition in DKD by activating the SIRT1-PGC-1α-TFAM pathway.