Extracellular matrix, integrins, and focal adhesion signaling in polycystic kidney disease.

In autosomal dominant polycystic kidney disease (ADPKD), the inexorable growth of numerous fluid-filled cysts leads to massively enlarged kidneys, renal interstitial damage, inflammation, and fibrosis, and progressive decline in kidney function. It has long been recognized that interstitial fibrosis is the most important manifestation associated with end-stage renal disease; however, the role of abnormal extracellular matrix (ECM) production on ADPKD pathogenesis is not fully understood. Early evidence showed that cysts in end-stage human ADPKD kidneys had thickened and extensively laminated cellular basement membranes, and abnormal regulation of gene expression of several basement membrane components, including collagens, laminins, and proteoglycans by cyst epithelial cells. These basement membrane changes were also observed in dilated tubules and small cysts of early ADPKD kidneys, indicating that ECM alterations were early features of cyst development. Renal cystic cells were also found to overexpress several integrins and their ligands, including ECM structural components and soluble matricellular proteins. ECM ligands binding to integrins stimulate focal adhesion formation and can promote cell attachment and migration. Abnormal expression of laminin-332 (laminin-5) and its receptor α6β4 stimulated cyst epithelial cell proliferation; and mice that lacked laminin α5, a component of laminin-511 normally expressed by renal tubules, had an overexpression of laminin-332 that was associated with renal cyst formation. Periostin, a matricellular protein that binds αVβ3- and αVβ5-integrins, was found to be highly overexpressed in the kidneys of ADPKD and autosomal recessive PKD patients, and several rodent models of PKD. αVβ3-integrin is also overexpressed by cystic epithelial cells, and the binding of periostin to αVβ3-integrin activates the integrin-linked kinase and downstream signal transduction pathways involved in tissue repair promoting cyst growth, ECM synthesis, and tissue fibrosis. This chapter reviews the roles of the ECM, integrins, and focal adhesion signaling in cyst growth and fibrosis in PKD.

Zhang Y ，Reif G ，Wallace DP 《-》

Periostin overexpression in collecting ducts accelerates renal cyst growth and fibrosis in polycystic kidney disease.

Raman A ，Parnell SC ，Zhang Y ，Reif GA ，Dai Y ，Khanna A ，Daniel E ，White C ，Vivian JL ，Wallace DP ... -  《-》

Periostin promotes renal cyst growth and interstitial fibrosis in polycystic kidney disease.

Wallace DP ，White C ，Savinkova L ，Nivens E ，Reif GA ，Pinto CS ，Raman A ，Parnell SC ，Conway SJ ，Fields TA ... -  《-》

Integrin-Linked Kinase Signaling Promotes Cyst Growth and Fibrosis in Polycystic Kidney Disease.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by innumerous fluid-filled cysts and progressive deterioration of renal function. Previously, we showed that periostin, a matricellular protein involved in tissue repair, is markedly overexpressed by cyst epithelial cells. Periostin promotes cell proliferation, cyst growth, interstitial fibrosis, and the decline in renal function in PKD mice. Here, we investigated the regulation of these processes by the integrin-linked kinase (ILK), a scaffold protein that links the extracellular matrix to the actin cytoskeleton and is stimulated by periostin. Pharmacologic inhibition or shRNA knockdown of ILK prevented periostin-induced Akt/mammalian target of rapamycin (mTOR) signaling and ADPKD cell proliferation in vitro Homozygous deletion of ILK in renal collecting ducts (CD) of Ilkfl/fl ;Pkhd1-Cre mice caused tubule dilations, apoptosis, fibrosis, and organ failure by 10 weeks of age. By contrast, Ilkfl/+ ;Pkhd1-Cre mice had normal renal morphology and function and survived >1 year. Reduced expression of ILK in Pkd1fl/fl ;Pkhd1-Cre mice, a rapidly progressive model of ADPKD, decreased renal Akt/mTOR activity, cell proliferation, cyst growth, and interstitial fibrosis, and significantly improved renal function and animal survival. Additionally, CD-specific knockdown of ILK strikingly reduced renal cystic disease and fibrosis and extended the life of pcy/pcy mice, a slowly progressive PKD model. We conclude that ILK is critical for maintaining the CD epithelium and renal function and is a key intermediate for periostin activation of signaling pathways involved in cyst growth and fibrosis in PKD.

Raman A ，Reif GA ，Dai Y ，Khanna A ，Li X ，Astleford L ，Parnell SC ，Calvet JP ，Wallace DP ... -  《-》

Polycystic Kidney Disease and Renal Fibrosis.

Xue C ，Mei CL 《-》