Pathophysiology of AKI to CKD progression.

Acute kidney injury (AKI), defined as a rapid decrease in glomerular filtration rate, is a common and devastating pathologic condition. AKI is associated with significant morbidity and subsequent chronic kidney disease (CKD) development. Regardless of the initial insult, CKD progression after AKI involves multiple types of cells, including proximal tubular cells, fibroblasts, and immune cells. Although the mechanisms underlying this AKI to CKD progression have been investigated extensively over the past decade, therapeutic strategies still are lacking. One of the reasons for this stems from the fact that AKI and its progression toward CKD is multifactorial and variable because it is dependent on patient background. In this review, we describe the current understanding of AKI and its maladaptive repair with a focus on proximal tubules and resident fibroblasts. Subsequently, we discuss the unique pathophysiology of AKI in the elderly, highlighting our recent finding of age-dependent tertiary lymphoid tissues.