Biomarkers and Research, Nordic Bioscience, Herlev, Denmark.
Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark.
Nephrol Dial Transplant. 2019 Aug 1;34(8):1301-1309. doi: 10.1093/ndt/gfy345.
Maintenance of kidney function in kidney allografts remains a challenge, as the allograft often progressively develops fibrosis after kidney transplantation. Fibrosis is caused by the accumulation of extracellular matrix proteins like type I and III collagen (COL I and III) that replace the functional tissue. We assessed the concentrations of a neo-epitope fragment of COL III generated by matrix metalloproteinase-9 cleavage (C3M) in two rat models resembling the ischaemic injury taking place following kidney transplantation.
We measured C3M in urine (U-C3M) and plasma (P-C3M) samples of rats subjected to unilateral nephrectomy followed by sham operation (NTx) or ischaemia reperfusion injury (NTxIRI) as well as in rats subjected to bilateral ischaemia reperfusion injury (BiIRI). Levels of U-C3M were normalized to urinary creatinine and were correlated to plasma creatinine, blood urea nitrogen, messenger ribonucleic acid (mRNA) of markers of kidney injury, and mRNA and protein levels of markers of tissue repair and fibrosis.
Levels of U-C3M were significantly elevated 7 days after ischaemia reperfusion in the NTxIRI. BiIRI animals showed higher levels of U-C3M after 7 and 14 days of reperfusion but not at 21 days. P-C3M did not change in any of the models. There was a significant correlation between U-C3M and mRNA levels of fibronectin, COL I alpha 1 chain (COL Ia1) and neutrophil gelatinase-associated lipocalin (NGAL), and protein levels of alpha smooth muscle actin (αSMA), fibronectin and COL III in NTxIRI but not in NTx animals. Levels of U-C3M increased significantly in the BiIRI animals subsequent to reperfusion, and mirrored the histological alterations. Furthermore, U-C3M was associated with the extent of fibrosis, and remained elevated even after plasma creatinine levels decreased.
These results demonstrate that degradation of COL III increases after ischaemia reperfusion injury, and that U-C3M may be a non-invasive marker of tissue repair and fibrosis in the ischaemic kidney.
在肾移植后，维持移植肾的功能仍然是一个挑战，因为移植肾通常会逐渐发生纤维化。纤维化是由细胞外基质蛋白（如 I 型和 III 型胶原蛋白 COL I 和 COL III）的积累引起的，这些蛋白取代了功能性组织。我们评估了两种类似于肾移植后发生缺血损伤的大鼠模型中，基质金属蛋白酶 9 切割产生的 COL III 新表位片段（C3M）的浓度。
我们测量了单侧肾切除术后假手术（NTx）或缺血再灌注损伤（NTxIRI）大鼠以及双侧缺血再灌注损伤（BiIRI）大鼠的尿液（U-C3M）和血浆（P-C3M）样本中的 C3M。U-C3M 水平与尿肌酐进行了标准化，并与血浆肌酐、血尿素氮、肾损伤标志物的信使核糖核酸（mRNA）以及组织修复和纤维化标志物的 mRNA 和蛋白水平进行了相关性分析。
在 NTxIRI 大鼠中，缺血再灌注后 7 天 U-C3M 水平显著升高。BiIRI 大鼠在再灌注后 7 天和 14 天 U-C3M 水平升高，但在 21 天没有升高。在任何模型中，P-C3M 均未发生变化。在 NTxIRI 大鼠中，U-C3M 与纤维连接蛋白、COL I alpha 1 链（COL Ia1）和中性粒细胞明胶酶相关脂质运载蛋白（NGAL）的 mRNA 水平以及 α 平滑肌肌动蛋白（αSMA）、纤维连接蛋白和 COL III 的蛋白水平之间存在显著相关性，但在 NTx 大鼠中则没有。BiIRI 大鼠再灌注后 U-C3M 水平显著升高，且与组织学改变相吻合。此外，U-C3M 与纤维化程度相关，甚至在血浆肌酐水平降低后仍保持升高。
这些结果表明，缺血再灌注损伤后 COL III 的降解增加，U-C3M 可能是缺血肾组织修复和纤维化的非侵入性标志物。
