microRNA biomarkers in cystic diseases

Therapeutic potential of urinary extracellular vesicles in delivering functional proteins and modulating gene expression for genetic kidney disease

Chronic kidney disease (CKD) is a widespread health concern, impacting approximately 600 million individuals worldwide and marked by a progressive decline in kidney function. A common form of CKD is autosomal dominant polycystic kidney disease (ADPKD), which is the most inherited genetic kidney disease and affects greater than 12.5 million individuals globally. Given that there are over 400 pathogenic PKD1/PKD2 mutations in patients with ADPKD, relying solely on small molecule drugs targeting a single signaling pathway has not been effective in treating ADPKD. Urinary extracellular vesicles (uEVs) are naturally released by cells from the kidneys and the urinary tract, and uEVs isolated from non-disease sources have been reported to carry functional polycystin-1 (PC1) and polycystin-2 (PC2), the respective products of PKD1 and PKD2 genes that are mutated in ADPKD. uEVs from non-disease sources, as a result, have the potential to provide a direct solution to the root of the disease by delivering functional proteins that are mutated in ADPKD. To test our hypothesis, we first isolated uEVs from healthy mice urine and conducted a comprehensive characterization of uEVs. Then, PC1 levels and EV markers CD63 and TSG101 of uEVs were confirmed via ELISA and Western blot. Following characterization of uEVs, the in vitro cellular uptake, inhibition of cyst growth, and gene rescue ability of uEVs were demonstrated in kidney cells. Next, upon administration of uEVs in vivo, uEVs showed bioavailability and accumulation in the kidneys. Lastly, uEV treatment in ADPKD mice (Pkd1fl/fl;Pax8-rtTA;Tet-O-Cre) showed smaller kidney size, lower cyst index, and enhanced PC1 levels without affecting safety despite repeated treatment. In summary, we demonstrate the potential of uEVs as natural nanoparticles to deliver protein and gene therapies for the treatment of chronic and genetic kidney diseases such as ADPKD.

A Brief Review on the Regulatory Roles of MicroRNAs in Cystic Diseases and Their Use as Potential Biomarkers

miRNAs are small endogenous conserved non-coding RNA molecules that regulate post-transcriptional gene expression through mRNA degradation or translational inhibition, modulating nearly 60% of human genes. Cystic diseases are characterized by the presence of abnormal fluid-filled sacs in the body, and though most cysts are benign, they can grow inside tumors and turn malignant. Recent evidence has revealed that the aberrant expression of a number of miRNAs present in extracellular fluids, including plasma or serum, urine, saliva, follicular fluid, and semen, contribute to different cystic pathologies. This review aims to describe the role of different miRNAs in three worldwide relevant cystic diseases: polycystic ovarian syndrome (PCOS), polycystic kidney disease (PKD), and pancreatic cyst tumors (PCTs), as well as their potential use as novel biomarkers.

A Brief Review on the Regulatory Roles of MicroRNAs in Cystic Diseases and Their Use as Potential Biomarkers

miRNAs are small endogenous conserved non-coding RNA molecules that regulate post-transcriptional gene expression through mRNA degradation or translational inhibition, modulating nearly 60% of human genes. Cystic diseases are characterized by the presence of abnormal fluid-filled sacs in the body, and though most cysts are benign, they can grow inside tumors and turn malignant. Recent evidence has revealed that the aberrant expression of a number of miRNAs present in extracellular fluids, including plasma or serum, urine, saliva, follicular fluid, and semen, contribute to different cystic pathologies. This review aims to describe the role of different miRNAs in three worldwide relevant cystic diseases: polycystic ovarian syndrome (PCOS), polycystic kidney disease (PKD), and pancreatic cyst tumors (PCTs), as well as their potential use as novel biomarkers.

A Brief Review on the Regulatory Roles of MicroRNAs in Cystic Diseases and Their Use as Potential Biomarkers

miRNAs are small endogenous conserved non-coding RNA molecules that regulate post-transcriptional gene expression through mRNA degradation or translational inhibition, modulating nearly 60% of human genes. Cystic diseases are characterized by the presence of abnormal fluid-filled sacs in the body, and though most cysts are benign, they can grow inside tumors and turn malignant. Recent evidence has revealed that the aberrant expression of a number of miRNAs present in extracellular fluids, including plasma or serum, urine, saliva, follicular fluid, and semen, contribute to different cystic pathologies. This review aims to describe the role of different miRNAs in three worldwide relevant cystic diseases: polycystic ovarian syndrome (PCOS), polycystic kidney disease (PKD), and pancreatic cyst tumors (PCTs), as well as their potential use as novel biomarkers.

Diagnostic Evaluation as a Biomarker in Patients with ADPKD

Recently, newer treatments have been introduced for autosomal dominant polycystic kidney disease (ADPKD) patients. Since cysts grow and renal function declines over a long period of time, the evaluation of treatment effects in ADPKD has been very difficult. Therefore, there has been a great interest to find out the "better" surrogate marker or biomarker which reflects disease progression. Biomarkers in ADPKD should have three clinical implications: (1) They should reflect disease severity, (2) they should distinguish patients with poor versus good prognosis to select those who will benefit better from the treatment, and (3) they should be easy to evaluate short-term outcome after treatment, which will demonstrate hard outcome. Herein, we will discuss currently available surrogate biomarkers including the volume of total kidney and urinary molecular markers.

Improved Structure and Function in Autosomal Recessive Polycystic Rat Kidneys with Renal Tubular Cell Therapy

Autosomal recessive polycystic kidney disease is a truly catastrophic monogenetic disease, causing death and end stage renal disease in neonates and children. Using PCK female rats, an orthologous model of autosomal recessive polycystic kidney disease harboring mutant Pkhd1, we tested the hypothesis that intravenous renal cell transplantation with normal Sprague Dawley male kidney cells would improve the polycystic kidney disease phenotype. Cytotherapy with renal cells expressing wild type Pkhd1 and tubulogenic serum amyloid A1 had powerful and sustained beneficial effects on renal function and structure in the polycystic kidney disease model. Donor cell engraftment and both mutant and wild type Pkhd1 were found in treated but not control PCK kidneys 15 weeks after the final cell infusion. To examine the mechanisms of global protection with a small number of transplanted cells, we tested the hypothesis that exosomes derived from normal Sprague Dawley cells can limit the cystic phenotype of PCK recipient cells. We found that renal exosomes originating from normal Sprague Dawley cells carried and transferred wild type Pkhd1 mRNA to PCK cells in vivo and in vitro and restricted cyst formation by cultured PCK cells. The results indicate that transplantation with renal cells containing wild type Pkhd1 improves renal structure and function in autosomal recessive polycystic kidney disease and may provide an intra-renal supply of normal Pkhd1 mRNA.

MicroRNAs and their applications in kidney diseases

MicroRNAs (miRNAs) are short, non-coding RNAs that employ classic Watson-Crick base-pairing to identify their target genes, ultimately resulting in destabilization of their target mRNAs and/or inhibition of their translation. The role of miRNAs in a wide range of human diseases, including those afflicting the kidney, has been intensely investigated. However, there is still a vast dearth of knowledge regarding their specific mode of action and therapeutic effects in various kidney diseases. This review discusses the latest efforts to further our understanding of the basic biology of miRNAs, their impact on various kidney diseases and their potential as novel biomarkers and therapeutic agents. We initially provide an overview of miRNA biology and the canonical pathway implicated in their biogenesis. We then discuss commonly employed experimental strategies for miRNA research and highlight some of the newly described state-of-the-art technologies to identify miRNAs and their target genes. Finally, we carefully examine the emerging role of miRNAs in the pathogenesis of various kidney diseases.

The ureteric bud epithelium: morphogenesis and roles in metanephric kidney patterning

The mammalian metanephric kidney is composed of two epithelial components, the collecting duct system and the nephron epithelium, that differentiate from two different tissues -the ureteric bud epithelium and the nephron progenitors, respectively-of intermediate mesoderm origin. The collecting duct system is generated through reiterative ureteric bud branching morphogenesis, whereas the nephron epithelium is formed in a process termed nephrogenesis, which is initiated with the mesenchymal-epithelial transition of the nephron progenitors. Ureteric bud branching morphogenesis is regulated by nephron progenitors, and in return, the ureteric bud epithelium regulates nephrogenesis. The metanephric kidney is physiologically divided along the corticomedullary axis into subcompartments that are enriched with specific segments of these two epithelial structures. Here, we provide an overview of the major molecular and cellular processes underlying the morphogenesis and patterning of the ureteric bud epithelium and its roles in the cortico-medullary patterning of the metanephric kidney.