Urinary exosomal Wilms' tumor-1 as a potential biomarker for podocyte injury

Abstract

Renal Wilms' tumor-1 (WT-1) staining is used to detect podocyte loss in kidney biopsies. We aimed to determine if urinary exosomal WT-1 could serve as a noninvasive biomarker of podocyte injury. We examined WT-1 by Western blot in a human podocyte-like cell line, a mouse model of podocyte injury, and human subjects with podocyte disorders. WT-1 was detected in exosomal fraction of the conditioned media from podocytes and increased 48 h after hTGF-β1 stimulation. Cellular WT-1 decreased in podocytes following hTGF-β1 incubation. In mice with induced podocyte injury, urinary exosomal WT-1 was detected 1 wk earlier than albuminuria and also tracked the effects of angiotensin receptor blocker (ARB) treatment. In addition, urinary exosomal WT-1 levels at 1 wk post-injury correlated with the severity of glomerular injury at 3 wk later. In human subjects, urinary exosomal WT-1 was significantly increased in focal segmental glomerulosclerosis (FSGS) patients compared with healthy volunteers or steroid-sensitive nephrotic syndrome (SSNS) patients. Urinary exosomal WT-1 was also significantly decreased in patients in remission for either FSGS or SSNS or following steroid treatment in six SSNS subjects. We conclude that urinary exosomal WT-1 is a promising noninvasive biomarker with apparent podocyte specificity that can detect early progression and treatment-induced regression of podocyte injury in FSGS or SSNS. These results warrant longitudinal, prospective studies in a large cohort with a range of podocyte diseases.

Extracellular Vesicles in Renal Diseases

“…Several markers of podocyte damage have been identified in uEVs, including podocalyxin, podoplanin, 83 and WT-1. 80,81 A protective role of EVs derived from MSCs has been described in models of kidney damage. It is suggested that these EVs from MSCs are involved in transfer of mRNA, miRNA, and proteins and reprogramming of their phenotypes.…”

“…In FSGS, 80 a disease with significant podocyte damage, Wilm's tumor-1 (WT-1), a transcription factor required for kidney development, was examined in uEXs as a marker for podocytes damage. Increased expression of WT-1 in uEXs was found 1 week earlier than urinary albumin excretion in a mouse model of collapsing glomerulopathy.…”

“…The same group also examined this in humans and found that exosomal WT-1 levels were significantly higher in children with active nephrotic syndrome caused by FSGS compared with those with steroid-sensitive nephrotic syndrome (SSNS) not yet in remission. 80 However, another group detected exosomal WT-1 only in 60% of 40 children with FSGS and SSNS, 81 suggesting that WT-1 in uEXs may not be a sensitive marker for FSGS and SSNS. Alternatively, the patient groups studied might have been too heterogeneous.…”

Evaluation of MicroRNAs miR-196a, miR-30a-5P, and miR-490 as Biomarkers of Disease Activity among Patients with FSGS

“…The identification of biomarkers specific for the FSGS disease state may also provide insights into the pathomechanism of FSGS. Although increasing efforts have been made to identify such biomarkers, few novel noninvasive biomarkers have yet been identified (2)(3)(4).…”

Islet transplantation promotes podocyte regeneration in a model of diabetic nephropathy

“…The renal tissues were then washed with PBS and fixed with 1% osmium tetroxide. After dehydration in an acetone gradient and embedment with Araldite M (Sigma-Aldrich), the tissues were stained with uranyl acetate and lead citrate (10). The microstructures were detected under a Philips 301 electron microscope.…”