Role of mitochondria in endogenous renal repair

Renal tubules have potential to regenerate and repair after mild-to-moderate injury. Proliferation of tubular epithelial cells represents the initial step of this reparative process. Although for many years, it was believed that proliferating cells originated from a pre-existing intra-tubular stem cell population, there is now consensus that surviving tubular epithelial cells acquire progenitor properties to regenerate the damaged kidney. Scattered tubular-like cells (STCs) are dedifferentiated adult renal tubular epithelial cells that arise upon injury and contribute to renal self-healing and recovery by replacing lost neighboring tubular epithelial cells. These cells are characterized by the co-expression of the stem cell surface markers CD133 and CD24, as well as mesenchymal and kidney injury markers. Previous studies have shown that exogenous delivery of STCs ameliorates renal injury and dysfunction in murine models of acute kidney injury, underscoring the regenerative potential of this endogenous repair system. Although STCs contain fewer mitochondria than their surrounding terminally differentiated tubular epithelial cells, these organelles modulate several important cellular functions, and their integrity and function are critical to preserve the reparative capacity of STCs. Recent data suggest that the microenviroment induced by cardiovascular risk factors, such as obesity, hypertension, and renal ischemia may compromise STC mitochondrial integrity and function, limiting the capacity of these cells to repair injured renal tubules. This review summarizes current knowledge of the contribution of STCs to kidney repair and discusses recent insight into the key role of mitochondria in modulating STC function and their vulnerability in the setting of cardiovascular disease.