Massively Parallel Sequencing of Human Urinary Exosome/Microvesicle RNA Reveals a Predominance of Non-Coding RNA

Intact RNA from exosomes/microvesicles (collectively referred to as microvesicles) has sparked much interest as potential biomarkers for the non-invasive analysis of disease. Here we use the Illumina Genome Analyzer to determine the comprehensive array of nucleic acid reads present in urinary microvesicles. Extraneous nucleic acids were digested using RNase and DNase treatment and the microvesicle inner nucleic acid cargo was analyzed with and without DNase digestion to examine both DNA and RNA sequences contained in microvesicles. Results revealed that a substantial proportion (∼87%) of reads aligned to ribosomal RNA. Of the non-ribosomal RNA sequences, ∼60% aligned to non-coding RNA and repeat sequences including LINE, SINE, satellite repeats, and RNA repeats (tRNA, snRNA, scRNA and srpRNA). The remaining ∼40% of non-ribosomal RNA reads aligned to protein coding genes and splice sites encompassing approximately 13,500 of the known 21,892 protein coding genes of the human genome. Analysis of protein coding genes specific to the renal and genitourinary tract revealed that complete segments of the renal nephron and collecting duct as well as genes indicative of the bladder and prostate could be identified. This study reveals that the entire genitourinary system may be mapped using microvesicle transcript analysis and that the majority of non-ribosomal RNA sequences contained in microvesicles is potentially functional non-coding RNA, which play an emerging role in cell regulation

Impaired Tubular Uptake Explains Albuminuria in Early Diabetic Nephropathy

Understanding the pathogenesis of albuminuria in diabetic nephropathy is important to improve methods for early diagnosis and treatment. In this study, we addressed whether albuminuria in diabetes results from altered glomerular filtration and/or altered processing of filtered albumin by the proximal tubule. Type 1 diabetic Munich Wistar rats developed albuminuria after 12 wk of diabetes. Intravital two-photon microscopy revealed similar glomerular permeability in the diabetic and control animals, assessed using both albumin-Alexa568 and 69-kD FITC-dextran; however, diabetic animals demonstrated significantly less filtered fluorescent albumin in renal proximal tubule (PT) cells compared with control animals. We also observed increased albumin-derived urinary peptide excretion in diabetic animals, and hyperglycemia modulated this peptideuria. In conclusion, in the early stages of diabetic nephropathy, the PT plays a major role in the development of albuminuria, which may be preceded by peptideuria