Supplementary Material for: Differences in urine protein profiles between preterm and full-term infants based on urine proteomic analysis

Background Urine samples could partially reflect the renal condition and could provide possible mechanism of high-risk factor for the long-term development of chronic kidney disease caused by prematurity. Methods Urine samples were collected from preterm infants (gestational age <28 weeks) when their corrected gestational weeks reached ≥37 weeks. In addition, urine samples were collected from full term infants beyond three days after birth as the control group. The urine proteome was investigated by using LC‒MS/MS analysis, and subsequent bioinformatics analysis was performed. Differentially expressed proteins were validated using ELISA. Results A total of 2634 proteins were identified, 366 proteins were highly expressed in the preterm group, while 102 proteins were enriched in the full-term group. Based on functional analysis, proteins enriched in preterm group were implicated in structure organization, cell adhesion, and extracellular part, while proteins enriched in urine of the full-term group were implicated in the immune response. Kidney inherent cells accelerated into urine have been examined in preterm infants group. Each of the top 20 differentially expressed proteins enriched in the urine of preterm infants was used as a keyword for literature retrieval, ultimately leading to the selection and validation of CDH6 and CDH11 through ELISA. Both proteins were found to be more abundant in the urine of preterm infants than in that of full-term infants. Conclusions The present study provides differences in urine protein profiles between preterm and full-term infants and a new potential explanation for the high risk of CKD development caused by preterm birth.背景：尿液样本可在一定程度上反映肾脏功能状态，可为早产引发的慢性肾脏病（Chronic Kidney Disease, CKD）远期发病的高危因素潜在机制提供研究线索。 方法：本研究收集胎龄<28周的早产儿在矫正胎龄≥37周时的尿液样本；同时收集足月新生儿出生后3天以上的尿液样本作为对照组。采用液相色谱-串联质谱（LC‒MS/MS）分析尿液蛋白质组，并开展后续生物信息学分析；通过酶联免疫吸附试验（ELISA）验证差异表达蛋白。 结果：本研究共鉴定出2634种蛋白质，其中早产组高表达蛋白质366种，足月组富集蛋白质102种。功能富集分析显示，早产组富集的蛋白质参与结构组织、细胞黏附及细胞外组分相关生物学过程；足月组富集的蛋白质则与免疫应答相关。早产组尿液中可检测到肾脏固有细胞。选取早产组尿液中富集的前20种差异表达蛋白作为关键词进行文献检索，最终通过ELISA验证筛选出CDH6与CDH11，二者在早产组尿液中的丰度均显著高于足月组。 结论：本研究明确了早产儿与足月儿尿液蛋白质组的表达差异，为早产导致的慢性肾脏病高发风险提供了全新的潜在解释机制。