De novo expression in the kidney of periostin, a protein involved in odontogenesis and osteogenesis, has been suggested as a biomarker of renal disease. In this study, we investigated the mechanism(s) of induction and the role of periostin in renal disease. Using a combination of bioinformatics, reporter assay, and chromatin immunoprecipitation analyses, we found that NFkB and other proinflammatory transcription factors induce periostin expression in vitro and that binding of these factors on the periostin promoter is enriched in glomeruli during experimental GN. Mice lacking expression of periostin displayed preserved renal function and structure during GN. Furthermore, delayed administration of periostin antisense oligonucleotides in wild-type animals with GN reversed already established proteinuria, diminished tissue inflammation, and improved renal structure. Lack of periostin expression also blunted the de novo renal expression of integrin-b3 and phosphorylation of focal adhesion kinase and AKT, known mediators of integrin-b3 signaling that affect cell motility and survival, observed during GN in wild-type animals. In vitro, recombinant periostin increased the expression of integrin-b3 and the concomitant phosphorylation of focal adhesion kinase and AKT in podocytes. Notably, periostin and integrin-b3 were highly colocalized in biopsy specimens from patients with inflammatory GN. These results demonstrate that interplay between periostin and renal inflammation orchestrates inflammatory and fibrotic responses, driving podocyte damage through downstream activation of integrin-b3 signaling. Targeting periostin may be a novel therapeutic strategy for treating CKD.
GN refers to a variety of renal pathologies that often progress to ESRD, but the molecular mechanisms underlying this progression remain incompletely characterized. Here, we determined whether dysregulated expression of the gap junction protein connexin 43, which has been observed in the progression of renal disease, contributes to GN progression. Immunostaining revealed expression of connexin 43 in damaged glomeruli in patients with glomerular diseases as well as in mice after induction of experimental GN. Notably, 2 weeks after the induction of GN with nephrotoxic serum, mice with a heterozygous deletion of the connexin 43 gene () had proteinuria, BUN, and serum creatinine levels significantly lower than those of wild-type animals. Additionally, the connexin 43+/- mice showed less crescent formation, tubular dilation, monocyte infiltration, and interstitial renal fibrosis. Treatment of cultured podocytes with connexin 43-specific blocking peptides attenuated TGF--induced cytoskeletal and morphologic changes and apoptosis as did treatment with the purinergic blocker suramin. Finally, therapeutic treatment of GN mice with connexin 43-specific antisense oligodeoxynucleotide improved functional and structural renal parameters. These findings suggest that crosstalk between connexin 43 and purinergic signaling contributes to podocyte damage in GN. Given that this protein is highly induced in individuals with glomerular diseases, connexin 43 may be a novel target for therapeutic treatment of GN.
Significance Statement AKI has been associated with increased morbidity and mortality or secondary organ dysfunctions. A better understanding of the mechanisms governing renal injury and repair may lead to a more efficient management of patients suffering from AKI. This paper identifies periostin, produced by damaged epithelial cells after murine ischemic injury, as a novel and important mediator of renal repair after AKI. It demonstrates that periostin protects epithelial cells from persistent cell cycle arrest and death and promotes a proregenerative macrophage phenotype, both of which contribute to a more efficient repair of the injured epithelium. Our findings provide novel insights in the repair mechanisms following AKI, which may contribute to a better care of AKI patients.
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