Division of Nephrology and Dialysis, Department of Medicine III, Medical University Vienna, Vienna, Austria.
Center for Brain Research, Medical University Vienna, Vienna, Austria.
PeerJ. 2022 Oct 20;10:e14110. doi: 10.7717/peerj.14110. eCollection 2022.
Acute kidney injury (AKI) is a serious condition associated with chronic kidney disease, dialysis requirement and a high risk of death. However, there are specialized repair mechanisms for the nephron, and migrated committed progenitor cells are the key players. Previous work has described a positive association between renal recovery and the excretion of tubular progenitor cells in the urine of kidney transplant recipients. The aim of this work was to describe such structures in non-transplanted AKI patients and to focus on their differentiation.
Morning urine was obtained from four patients with AKI stage 3 and need for RRT on a consecutive basis. Urine sediment gene expression was performed to assess which part of the tubular or glomerular segment was affected by injury, along with measurement of neprilysin. Urine output and sediment morphology were monitored, viable hyperplastic tubular epithelial clusters were isolated and characterized by antibody or cultured . These cells were monitored by phase contrast microscopy, gene, and protein expression over 9 days by qPCR and confocal immunofluorescence. Furthermore, UMOD secretion into the supernatant was quantitatively measured.
Urinary neprilysin decreased rapidly with increasing urinary volume in ischemic, toxic, nephritic, and infection-associated AKI, whereas the decrease in sCr required at least 2 weeks. While urine output increased, dead cells were present in the sediment along with debris followed by hyperplastic agglomerates. Monitoring of urine sediment for tubular cell-specific gene transcript levels NPHS2 (podocyte), AQP1 and AQP6 (proximal tubule), and SLC12A1 (distal tubule) by qPCR revealed different components depending on the cause of AKI. Confocal immunofluorescence staining confirmed the presence of intact nephron-specific epithelial cells, some of which appeared in clusters expressing AQP1 and PAX8 and were 53% positive for the stem cell marker PROM1. Isolated tubule epithelial progenitor cells were grown , expanded, and reached confluence within 5-7 days, while the expression of AQP1 and UMOD increased, whereas PROM1 and Ki67 decreased. This was accompanied by a change in cell morphology from a disproportionately high nuclear/cytoplasmic ratio at day 2-7 with mitotic figures. In contrast, an apoptotic morphology of approximately 30% was found at day 9 with the appearance of multinucleated cells that were associable with different regions of the nephron tubule by marker proteins. At the same time, UMOD was detected in the culture supernatant.
During renal recovery, a high replicatory potential of tubular epithelial progenitor cells is found in urine. expansion and gene expression show differentiation into tubular cells with marker proteins specific for different nephron regions.
急性肾损伤（AKI）是一种与慢性肾脏病、透析需求和高死亡率相关的严重疾病。然而，肾脏有专门的修复机制，而迁移的定向祖细胞是关键因素。先前的研究描述了肾移植受者尿液中肾小管祖细胞的排泄与肾脏恢复之间存在正相关。本研究旨在描述非移植 AKI 患者中存在的这种结构，并关注其分化。
连续采集 4 名 AKI 患者的晨尿，这些患者处于 3 期且需要 RRT。通过尿沉渣基因表达评估损伤影响的肾小管或肾小球段，同时测量 Neprilysin。监测尿排量和尿沉渣形态，分离并鉴定有活力的增生性管状上皮簇，通过抗体或培养进行鉴定。通过相差显微镜、qPCR 和共聚焦免疫荧光在 9 天内监测这些细胞的基因和蛋白表达。此外，定量测量上清液中 UMOD 的分泌。
在缺血性、中毒性、肾炎性和感染相关性 AKI 中，尿 Neprilysin 随尿量增加而迅速下降，而 sCr 下降至少需要 2 周。随着尿排量的增加，沉淀物中出现了死亡细胞和碎片，随后出现了增生性聚集物。通过 qPCR 监测尿沉渣中肾小管细胞特异性基因转录水平 NPHS2（足细胞）、AQP1 和 AQP6（近端小管）和 SLC12A1（远端小管），发现不同的成分取决于 AKI 的原因。共聚焦免疫荧光染色证实了完整的肾单位特异性上皮细胞的存在，其中一些细胞以表达 AQP1 和 PAX8 的簇的形式出现，并且 53%的细胞对干细胞标记物 PROM1 呈阳性。分离的肾小管上皮祖细胞在 5-7 天内生长、扩增并达到汇合，同时 AQP1 和 UMOD 的表达增加，而 PROM1 和 Ki67 的表达减少。这伴随着细胞形态的变化，从第 2-7 天不成比例的高核/细胞质比和有丝分裂图开始。相比之下，在第 9 天发现了约 30%的凋亡形态，出现了多核细胞，这些细胞通过标记蛋白与肾小管的不同区域相关联。同时，在培养上清液中检测到 UMOD。
在肾脏恢复过程中，尿液中存在高增殖潜能的肾小管上皮祖细胞。扩增和基因表达显示出向具有不同肾单位区域特异性标记蛋白的肾小管细胞的分化。
