Institute of Nephrology, Zhongda Hospital, Southeast University School of Medicine, 87 Ding Jia Qiao Road, Nanjing, 210009, Jiangsu, China.
J Transl Med. 2021 Aug 17;19(1):355. doi: 10.1186/s12967-021-03030-x.
Diabetic nephropathy (DN) is a leading cause of renal failure, whereas the effective and early diagnostic biomarkers are still lacking.
Fourteen cytokines and chemokines mRNA were detected in urinary extracellular vesicles (EVs) from the screening cohort including 4 healthy controls (HC), 4 diabetes mellitus (DM) and 4 biopsy-proven DN patients, and was validated in another 16 HC and 15 DM and 28 DN patients. Correlation analysis was performed between the candidate biomarkers and clinic parameters as well as kidney histological changes. The findings were also confirmed in DN rat model with single injection of STZ.
The number of small EVs secreted in urine was increased in DN patients compared to DM patients and healthy controls, with expression of AQP1 (a marker of proximal tubules) and AQP2 (a marker of distal/collecting tubules). Small EVs derived CCL21 mRNA increased significantly in DN patients and correlated with level of proteinuria and eGFR. Interestingly, elevated CCL21 mRNA from urine small EVs was observed in DN patients with normal renal function and could discriminate early DN patients from DM more efficiently compared to eGFR and proteinuria. CCL21 also showed an accurate diagnostic ability in distinguishing incipient from overt DN. Histologically, CCL21 mRNA expression increased progressively with the deterioration of tubulointerstitial inflammation and showed the highest level in nodular sclerosis group (class III) in DN patients. Remarkable infiltration of CD3 positive T cells including both CD4 and CD8 positive T cell population were observed in DN patients with high-CCL21 expression. Besides, accumulation of CD3 positive T cells correlated with level of urinary small EVs derived CCL21 and co-localized with CCL21 in the tubulointerstitium in DN patients. Finally, the correlation of CCL21 expression in renal cortex and urinary small EVs was confirmed in STZ-induced DN rat model.
Urinary small EVs derived CCL21 mRNA may serve as early biomarker for identifying DN linked with pathogenesis. CCL21 mRNA mediated T cell infiltration may constitute the key mechanism of chronic inflammation in DN.
糖尿病肾病 (DN) 是肾衰竭的主要原因，而有效的早期诊断生物标志物仍缺乏。
在包括 4 名健康对照 (HC)、4 名糖尿病 (DM) 和 4 名经活检证实的 DN 患者的筛选队列中，检测了尿细胞外囊泡 (EV) 中的 14 种细胞因子和趋化因子 mRNA，并在另 16 名 HC、15 名 DM 和 28 名 DN 患者中进行了验证。对候选生物标志物与临床参数以及肾脏组织学变化之间的相关性进行了分析。在单次 STZ 注射的 DN 大鼠模型中也证实了这一发现。
与 DM 患者和健康对照组相比，DN 患者尿液中小 EV 的分泌数量增加，AQP1（近端肾小管标志物）和 AQP2（远端/收集管标志物）的表达也增加。DN 患者尿液中小 EV 衍生的 CCL21 mRNA 显著增加，与蛋白尿和 eGFR 水平相关。有趣的是，在肾功能正常的 DN 患者中也观察到尿液中小 EV 衍生的 CCL21 mRNA 升高，与 eGFR 和蛋白尿相比，其能更有效地将早期 DN 患者与 DM 患者区分开来。CCL21 也能准确地区分初发和显性 DN。组织学上，随着肾小管间质炎症的恶化，CCL21 mRNA 的表达逐渐增加，在 DN 患者的结节性硬化组（III 类）中表达水平最高。在 CCL21 高表达的 DN 患者中，观察到显著浸润的 CD3 阳性 T 细胞，包括 CD4 和 CD8 阳性 T 细胞。此外，CD3 阳性 T 细胞的积聚与尿液中小 EV 衍生的 CCL21 水平相关，在 DN 患者中与 CCL21 在肾小管间质中共同定位。最后，在 STZ 诱导的 DN 大鼠模型中证实了肾皮质中 CCL21 表达与尿液中小 EV 之间的相关性。
尿中小 EV 衍生的 CCL21 mRNA 可能作为识别与发病机制相关的 DN 的早期生物标志物。CCL21 mRNA 介导的 T 细胞浸润可能构成 DN 慢性炎症的关键机制。
