Fibrotic diseases account for nearly half of all deaths in the developed world. Despite its importance, the pathogenesis of fibrosis remains poorly understood. Recently, the two mechanosensitive transcription cofactors YAP and TAZ have emerged as important profibrotic regulators in multiple murine tissues. Despite this growing recognition, a number of important questions remain unanswered, including which cell types require YAP/TAZ activation for fibrosis to occur and the time course of this activation. Here, we present a detailed analysis of the role that myofibroblast YAP and TAZ play in organ fibrosis and the kinetics of their activation. Using analyses of cells, as well as multiple murine and human tissues, we demonstrated that myofibroblast YAP and TAZ were activated early after organ injury and that this activation was sustained. We further demonstrated the critical importance of myofibroblast YAP/TAZ in driving progressive scarring in the kidney, lung, and liver, using multiple transgenic models in which YAP and TAZ were either deleted or hyperactivated. Taken together, these data establish the importance of early injury-induced myofibroblast YAP and TAZ activation as a key event driving fibrosis in multiple organs. This information should help guide the development of new antifibrotic YAP/TAZ inhibition strategies.

Roughly 10% of the world’s population has chronic kidney disease (CKD). In its advanced stages, CKD greatly increases the risk of hospitalization and death. Although kidney transplantation has revolutionized the care of advanced CKD, clinicians have limited ways of assessing donor kidney quality. Thus, optimal donor kidney–recipient matching cannot be performed, meaning that some patients receive damaged kidneys that function poorly. Fibrosis is a form of chronic damage often present in donor kidneys, and it is an important predictor of future renal function. Currently, no safe, easy-to-perform technique exists that accurately quantifies renal fibrosis. We describe a potentially novel photoacoustic (PA) imaging technique that directly images collagen, the principal component of fibrotic tissue. PA imaging noninvasively quantifies whole kidney fibrotic burden in mice, and cortical fibrosis in pig and human kidneys, with outstanding accuracy and speed. Remarkably, 3-dimensional PA imaging exhibited sufficiently high resolution to capture intrarenal variations in collagen content. We further show that PA imaging can be performed in a setting that mimics human kidney transplantation, suggesting the potential for rapid clinical translation. Taken together, our data suggest that PA collagen imaging is a major advance in fibrosis quantification that could have widespread preclinical and clinical impact.

Background/Aim: Carbonic anhydrase 9 (CAIX) is a transmembrane metalloenzyme that regulates cellular adhesion, proliferation, and intra/extracellular pH. It is expressed primarily through a hypoxia-inducible factor 1 (HIF-1)-dependent mechanism. Its over-expression is closely related to somatic mutations in the Von Hippel-Lindau (VHL) gene. Studies have shown that it is over-expressed in renal cell carcinoma. In this study, we aimed to assess the value of CAIX immunostaining as an ancillary diagnostic tool in renal malignancies and medical renal diseases. Patients and Methods: Slides of kidney tumors and medical kidney diseases were selected to evaluate CAIX expression. Intensity and staining patterns of CAIX were independently assessed by two pathologists. Results: Our results showed strong and diffuse box-like membranous staining pattern in the majority of the clear cell renal cell carcinoma (ccRCC) cases (47/59 cases; 94%). A strong, diffuse cup-shaped staining pattern was observed in clear cell papillary RCC. Variable positivity was observed in other RCC (renal cell carcinoma) subtypes. In non-neoplastic renal conditions, the majority of the cases were negative for CAIX, and only a few cases demonstrated patchy non-specific staining. Of note, a single case of transplanted kidney biopsy taken because of delayed graft function showed a focal area of dilated tubules lined by cells with clear cytoplasm and enlarged nuclei with prominent nucleoli. This area showed diffuse membranous staining for CAIX. Two cases of end-stage renal disease showed a focal circumferential membranous staining pattern for CAIX in dilated tubules. Conclusion: The CAIX immunoreactivity observed in these three cases could be indicative of an early-stage renal cell neoplasm and warrants further investigation.

Background/Aim: Renal cell carcinoma is one of the most common types of cancer worldwide. Understanding tumor pathogenesis is important in developing better treatment. Micro RNAs (miRNAs) are key players in controlling cancer behavior. Transcription factors (TFs) are potentially responsible for controlling miRNA expression and dysregulation in kidney cancer. The objective of this study was to better understand the TF–miRNA axis of interaction. Materials and Methods: We utilized publicly available databases to investigate miRNA–TF interactions, including ChipBase database for TFs that binds to the promoters of miRNAs which are dysregulated in renal cell carcinoma. Renal cancer-specific TFs were extracted from the list using the GENT Database. We assessed the prognostic significance of these TFs using cBioPortal. Results: We identified TFs which bind to miRNA promoters, including hepatocyte nuclear factor-4 alpha (HNF-4α), E2F transcription factor 4 (E2F4), signal transducer and activator of transcription 1 (STAT1), Sp1 transcription factor (SP1), GATA binding protein 6 (GATA6), and nuclear factor kappa B (NFκB). These TFs were positively correlated with their targeted miRNAs, including miR-200c, miR-15a, miR-146b, miR-155, and miR-223. We recognized unique patterns of interactions, including a divergent effect in which multiple miRNAs are simultaneously affected by the same TF. Conclusion: Our results show that miRNA–TF interaction is complex. Expression levels of these TFs were found to correlate with renal carcinoma prognosis and have potential utility as biomarkers for aggressive tumor behavior. Targeting these TFs may result in modulating the expression of their target genes and miRNAs, with subsequent therapeutic implications.

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