The epithelial-mesenchymal transition (EMT) is an important event in a series of steps that result in tissue fibrosis. The transdifferentiation is the process by which renal and extrarenal cells, affected by cytokines released during the inflammatory process such as TGF-² (transforming growth factor-²), angiotensin II and endothelin, modify their phenotype and start to produce extracellular matrix components (EMC), various types of collagens and fibronectin. The excessive accumulation of EMC can lead to progressive loss of renal function. After kidney injury, renal and extrarenal cells can transform into activated myofibroblasts that are responsible for the accumulation of EMC in the kidney. The exact origin of these myofibroblasts is unclear. It has been shown that during renal fibrosis in mice, approximately 12% of the fibroblasts are derived from bone marrow and 30% are derived from endothelial mesenchymal transdifferentiation of cells associated with renal microvasculature. Tubular epithelial cells can be transformed into myofibroblasts after injury, expressing ±-smooth muscle actin (± -SMA), a marker for myofibroblasts. In this process the cells of renal tubules lose their epithelial cell marker (cytokeratin) and begin to express mesenchymal cell markers (± -SMA). Endothelial cells have an important role in the inflammatory process that is associated with acute tubular necrosis induced by the chemotherapeutic drug cisplatin. Clinical and experimental evidence show beneficial effects of exercise training on endothelial function and structure. Our hypothesis is that the physical preconditioning could have beneficial effects on the evolution of renal damage caused by cisplatin, attenuating the inflammatory process and cytokine release, reducing the process of transdifferentiation and residual fibrosis that occurs in renal cortex of these animals. Male Wistar rats will be placed in small treadmill for a week before the training to adapt to standardized exercise. After standardization of the protocol of aerobic exercise, the animals will be trained five days a week for 8 weeks. Twenty-four hours after the last training day, animals will be divided into four groups: A. Untrained control (U, n=10 ), animals will receive an injection of saline (0.9 %, ip); B. Untrained+cisplatin (U+CP, n=10), animals will receive an injection of cisplatin (5 mg/kg, ip); C. Trained control (TC, n=20), animals subjected to physical training prior to an injection of saline; D. Trained+Cisplatin (T+CP, n=20), animals subjected to physical training prior to an injection of cisplatin (5 mg/kg, ip). Five and 20 days after administration of saline or cisplatin blood and urine will be collected to assess renal function. The animals will be euthanized, and kidneys removed for histological, morphometric and immunohistochemical studies, in which markers of inflammation (neutrophils, macrophages and lymphocytes antibodies) and fibrosis (anti-fibronectin antibody) will be used. It will be also conducted studies with double labeling to evaluate epithelial-mesenchymal transdifferentiation, using anti ±-SMA (myofibroblast marker) and anti-cytokeratin (epithelial cell marker) antibodies. Samples of blood and urine of animals from the different groups collected on the fifth and 20th days after administration of saline or cisplatin will be used for the determination of plasma creatinine, Na+, K+, and urine osmolality.
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