miR299a-5p promotes renal fibrosis by suppressing the antifibrotic actions of follistatin

Caveolin-1 in situ expression in glomerular and peritubular capillaries as a marker of ultrastructural progression and severity of renal thrombotic microangiopathy

BACKGROUND

Thrombotic microangiopathy is a severe and potentially life-threatening condition inducing severe endothelial injury in many organs, particularly native and transplanted kidneys. Current pathological studies by our group have identified the use of Caveolin-1 immunohistochemistry as a potential marker of endothelial damage and progression degree of thrombotic microangiopathy. The aim of the present work was to evaluate Caveolin-1 as a marker of severity in thrombotic microangiopathy kidney disease, according to the ultrastructural progression of the disease evaluated by transmission electron microscopy.

MATERIALS AND METHODS

Twenty-nine patients (17 non-transplanted and 12 transplanted) were retrospectively selected, biopsied for suspected or histologically-confirmed thrombotic microangiopathy. Transmission electron microscopy was performed in all cases, and an ultrastructural score of thrombotic microangiopathy-related glomerular disease was assessed (from 0 to 3+). Immunohistochemistry for Caveolin-1 was automatically performed.

RESULTS

The mean percentage of Caveolin-1-positive glomerular capillaries was 53.2 ± 40.6% and 28.0 ± 42.8% in the active thrombotic microangiopathy versus previous thrombotic microangiopathy cases (p = 0.085), considering both native and transplanted kidneys. The presence of progressive disease correlated with diffuse Caveolin-1 immunoreactivity (p = 0.031), and ultrastructural score correlated with glomerular Caveolin-1 positivity, progressively increasing from 22.5% of the Score 0 group to 95.5% of the Score 3 group (p = 0.036).

DISCUSSION

Caveolin-1 proved to be a very useful marker of early endothelial damage in the course of thrombotic microangiopathy for both native and transplanted kidneys, therefore worth considering in routine practice. Diffuse glomerular Caveolin-1 immunoreactivity correlates with the severity of the thrombotic disease and it can appear very early, even before ultrastructurally evident endothelial damage.

The Role of miRNA in Renal Fibrosis Leading to Chronic Kidney Disease

Chronic kidney disease (CKD) is an important health concern that is expected to be the fifth most widespread cause of death worldwide by 2040. The presence of chronic inflammation, oxidative stress, ischemia, etc., stimulates the development and progression of CKD. Tubulointerstitial fibrosis is a common pathomechanism of renal dysfunction, irrespective of the primary origin of renal injury. With time, fibrosis leads to end-stage renal disease (ESRD). Many studies have demonstrated that microRNAs (miRNAs, miRs) are involved in the onset and development of fibrosis and CKD. miRNAs are vital regulators of some pathophysiological processes; therefore, their utility as therapeutic agents in various diseases has been suggested. Several miRNAs were demonstrated to participate in the development and progression of kidney disease. Since renal fibrosis is an important problem in chronic kidney disease, many scientists have focused on the determination of miRNAs associated with kidney fibrosis. In this review, we present the role of several miRNAs in renal fibrosis and the potential pathways involved. However, as well as those mentioned above, other miRs have also been suggested to play a role in this process in CKD. The reports concerning the impact of some miRNAs on fibrosis are conflicting, probably because the expression and regulation of miRNAs occur in a tissue- and even cell-dependent manner. Moreover, different assessment modes and populations have been used. There is a need for large studies and clinical trials to confirm the role of miRs in a clinical setting. miRNAs have great potential; thus, their analysis may improve diagnostic and therapeutic strategies.

Caveolin-1 Regulates Cellular Metabolism: A Potential Therapeutic Target in Kidney Disease

The kidney is an energy-consuming organ, and cellular metabolism plays an indispensable role in kidney-related diseases. Caveolin-1 (Cav-1), a multifunctional membrane protein, is the main component of caveolae on the plasma membrane. Caveolae are represented by tiny invaginations that are abundant on the plasma membrane and that serve as a platform to regulate cellular endocytosis, stress responses, and signal transduction. However, caveolae have received increasing attention as a metabolic platform that mediates the endocytosis of albumin, cholesterol, and glucose, participates in cellular metabolic reprogramming and is involved in the progression of kidney disease. It is worth noting that caveolae mainly depend on Cav-1 to perform the abovementioned cellular functions. Furthermore, the mechanism by which Cav-1 regulates cellular metabolism and participates in the pathophysiology of kidney diseases has not been completely elucidated. In this review, we introduce the structure and function of Cav-1 and its functions in regulating cellular metabolism, autophagy, and oxidative stress, focusing on the relationship between Cav-1 in cellular metabolism and kidney disease; in addition, Cav-1 that serves as a potential therapeutic target for treatment of kidney disease is also described.

Identification of circular RNA expression profiles in renal fibrosis induced by obstructive injury

INTRODUCTION

Advancing renal fibrosis is the common histopathological feature of chronic obstructive nephropathy, representing the final pathway of nearly all chronic and progressive nephropathies. Increasing evidences suggest that circular RNAs (circRNAs) are crucial regulatory molecules present at virtually every level of the cellular pathophysiological process. Nonetheless, there are a few evidences for the role of circRNAs in renal fibrosis induced by obstructive nephropathy.

AIMS

We performed RNA-seq analysis to analyze the expression profiles of circRNAs in the obstructed kidneys to identify the potential circRNAs and their network.

METHODS

With silk ligated the left ureter to establish a mice unilateral ureteral obstruction (UUO) model. Renal tissue circRNAs were obtained and were screened by a circRNA microarray. The circRNA-miRNA-mRNA regulatory network and the target genes were visualized using Cytoscape software.

RESULTS

The microarray results showed that 5454 and 2935 circRNAs were detected in the control and UUO group, respectively. There were 605 circRNAs up-regulated and 745 circRNAs down-regulated in the obstructive kidneys. The top 5 up-regulated and down-regulated circRNAs were chosen for predicting the circRNA/miRNA/target mRNAs triple network. The GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis showed that these circRNAs and the triple network were enriched in the process of apoptosis, p53 signaling pathway, cell growth and cell death, which might participate in the pathogenesis of obstructive nephrology.

CONCLUSION

Our results show that the dis-regulated circRNAs might play crucial roles in the pathogenesis of obstructive nephropathy, which proceeds to identify novel therapeutic targets for chronic kidney disease.