Kumar Parveen, Patel Mikita, Thomas Vinoy, Knight John, Holmes Ross P, Mitchell Tanecia
Department of Urology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Department of Materials Science and Engineering, University of Alabama at Birmingham, Birmingham, Alabama, USA.
Kidney Int Rep. 2020 May 7;5(7):1040-1051. doi: 10.1016/j.ekir.2020.04.029. eCollection 2020 Jul.
Crystalluria is thought to be associated with kidney stone formation and can occur when urine becomes supersaturated with calcium, oxalate, and phosphate. The principal method used to identify urinary crystals is microscopy, with or without a polarized light source. This method can detect crystals above 1 μm in diameter (microcrystals). However, analyses of calcium oxalate kidney stones have indicated that crystallite components in these calculi are 50-100 nm in diameter. Recent studies have suggested that nanocrystals (<200 nm) elicit more injury to renal cells compared to microcrystals. The purpose of this study was to determine whether (i) urinary nanocrystals can be detected and quantified by nanoparticle tracking analysis (NTA, a high-resolution imaging technology), (ii) early-void urine samples from healthy subjects contain calcium nanocrystals, and (iii) a dietary oxalate load increases urinary nanocrystal formation.
Healthy subjects consumed a controlled low-oxalate diet for 3 days before a dietary oxalate load. Urinary crystals were isolated by centrifugation and assessed using NTA before and 5 hours after the oxalate load. The morphology and chemical composition of crystals was assessed using electron microscopy, Fourier-transform infrared spectroscopy (FTIR), and ion chromatography-mass spectrometry (IC-MS).
Urinary calcium oxalate nanocrystals were detected in pre-load samples and increased substantially following the oxalate load.
These findings indicate that NTA can quantify urinary nanocrystals and that meals rich in oxalate can promote nanocrystalluria. NTA should provide valuable insight about the role of nanocrystals in kidney stone formation.
结晶尿被认为与肾结石形成有关，当尿液中的钙、草酸盐和磷酸盐过饱和时就会出现。识别尿结晶的主要方法是显微镜检查，可使用或不使用偏振光源。这种方法可以检测直径大于1μm的晶体（微晶）。然而，草酸钙肾结石的分析表明，这些结石中的微晶成分直径为50-100nm。最近的研究表明，与微晶相比，纳米晶体（<200nm）对肾细胞造成的损伤更大。本研究的目的是确定：（i）是否可以通过纳米颗粒跟踪分析（NTA，一种高分辨率成像技术）检测和量化尿纳米晶体；（ii）健康受试者的晨尿样本中是否含有钙纳米晶体；（iii）饮食中的草酸盐负荷是否会增加尿纳米晶体的形成。
健康受试者在接受草酸盐负荷饮食前3天食用控制低草酸盐饮食。通过离心分离尿结晶，并在草酸盐负荷前和负荷后5小时使用NTA进行评估。使用电子显微镜、傅里叶变换红外光谱（FTIR）和离子色谱-质谱（IC-MS）评估晶体的形态和化学成分。
在负荷前样本中检测到草酸钙尿纳米晶体，草酸盐负荷后显著增加。
这些发现表明，NTA可以量化尿纳米晶体，富含草酸盐的膳食可促进纳米结晶尿。NTA应为纳米晶体在肾结石形成中的作用提供有价值的见解。
