Role of interstitial inflammation in the pathogenesis of polycystic kidney disease

Interstitial infiltrates, consisting of macrophages and other inflammatory cells, have been consistently reported in human and animal models of polycystic kidney diseases (PKD). However, the mechanisms underlying this inflammation are not well defined. Evidence suggests that interstitial inflammation in PKD is driven by pro-inflammatory chemoattractants such as monocyte chemoattractant protein-1 (MCP-1), and cytokines such as tumour necrosis factor (TNF)-α. Putative upregulated inflammatory pathways include JAK-STAT and nuclear factor (NF)-κB signalling. In addition, the genetic mutations of PKD may further complicate the relationship between inflammation and cystic disease, by increasing the susceptibility to inflammatory injury, and facilitating interactions between the genetically determined cystoproteins and biological mediators of inflammation. Moreover, the roles of interstitial inflammation in promoting cyst growth and progression to kidney failure in PKD are not clearly understood. Although anti-inflammatory therapies have attenuated cystogenesis in animal models, inflammatory cells may also have reparative actions. Thus, in developing therapies for PKD, it is prudent to consider the potential negative outcomes of ablating inflammation, and whether it is more viable to target certain inflammatory pathways over others.