Urinary Podocyte Microparticles Identify Prealbuminuric Diabetic Glomerular Injury

Abstract

Microparticles (MPs) are small (0.1-1.0 mm) vesicles shed from the surface of cells in response to stress. Whether podocytes produce MPs and whether this production reflects glomerular injury are unclear. We examined MP formation in cultured human podocytes (hPODs) and diabetic mice. hPODs were exposed to cyclical stretch, high glucose (HG; 25 mM), angiotensin II, or TGF-b. Urinary podocyte MPs were assessed in three mouse models of diabetic nephropathy: streptozotocin (STZ)-treated, OVE26, and Akita mice. Cyclic stretch and HG increased MP release as assessed by flow cytometry (P,0.01 and P,0.05, respectively, versus controls). Inhibition of Rho-kinase (ROCK) with fasudil blocked HG-induced podocyte MP formation. STZtreated (8 weeks) mice exhibited increased urinary podocyte MPs compared with age-matched nondiabetic mice. Similarly, 16-week-old OVE26 mice had elevated levels of urinary podocyte MPs compared with wild-type littermates (P,0.01). In 1 week post-STZ-treated and 6-and 12-week-old Akita mice, urinary podocyte MPs increased significantly compared with those MPs in nondiabetic mice, despite normal urinary albumin levels. Our results indicate that podocytes produce MPs that are released into urine. Podocyte-derived MPs are generated by exposure to mechanical stretch and high glucose in vitro and could represent early markers of glomerular injury in diabetic nephropathy.

Extracellular Vesicles in Renal Diseases

“…13,27 Here, we show a schematic drawing of the glomerulus and kidney tubule. 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.…”

“…Burger et al 83 detected elevated levels of podocalyxin-and podoplanin-positive urinary MPs in diabetic mice before the onset of albuminuria. Again, analysis of the whole range of vesicles, including exosomes and Annexin-negative populations, might provide additional information.…”

“…Podocalyxin and podoplanin were detected in urinary MPs in diabetic nephropathy (DN), another disease process with podocyte damage. 83 Podocalyxin and podoplanin might, therefore, be more fitting biomarkers for podocyte damage, because they are podocyte surface markers. Other evidence supports that some of these podocyte-derived EVs seem to originate from tip vesiculation of podocytes and are not coming from shed podocytes in the urine, which was shown by histologic examination of patients with nephrotic syndrome.…”

Podocyte‐derived microparticles promote proximal tubule fibrotic signaling via p38 MAPK and CD36

“…These podocyte MPs are released into the urine with levels increased in experimental and human diabetes [24,25]. However, whether podocyte MPs play a role in podocyte-tubular cross-talk has not yet been examined.…”

Microparticles in kidney diseases: focus on kidney transplantation

“…Other methods include western blotting, flow imaging cytometry, and nanoparticle tracking analysis [1,7,9,23] (Table 1). Additionally, MPs of varying origins may be found in urine [24][25][26][27][28][29], bronchoalveolar lavage fluid [30], sputum [31], synovial fluid [32], ascites [33], and saliva [34]. There is presently no reliable approach for obtaining and/or characterizing MPs from tissue samples, and knowledge of MP biology in tissue is lacking.…”