MicroRNAs (miRNAs)是内源性的非编码单链小RNA，在识别同源序列并干扰转录、翻译或表观遗传过程中调节基因表达。miRNAs参与各种疾病过程，通过调节靶细胞活性、迁移、侵袭、凋亡、自噬和其他过程，调节疾病的生理与病理状态。其中，let-7i在各系统中高度表达，参与肿瘤、心血管脑血管疾病、纤维化疾病、炎症性疾病、神经退行性疾病等的过程，并通过不同信号通路和关键分子对这些疾病起到正负调节作用。此外，它还可以作为多种疾病的早期诊断和预后标志物，并成为潜在的治疗靶点。作为一种生物标志物，let-7i常常与其他miRNAs联合检测，用于多种疾病的诊断及评估临床治疗或预后。

MicroRNAs (miRNAs) are endogenous non-coding single-stranded small RNAs that regulate gene expression by recognizing homologous sequences and interfering with transcriptional, translational or epigenetic processes. MiRNAs are involved in a variety of disease processes, and regulate the physiological and pathological status of diseases by modulating target cell activity, migration, invasion, apoptosis, autophagy and other processes. Among them, let-7i is highly expressed in various systems, which participates in the process of tumors, cardiovascular and cerebrovascular diseases, fibrotic diseases, inflammatory diseases, neurodegenerative diseases and other diseases, and plays a positive or negative regulatory role in these diseases through different signal pathways and key molecules. Moreover, it can be used as an early diagnosis and prognostic marker for a variety of diseases and become a potential therapeutic target. As a biomarker, let-7i is frequently tested in combination with other miRNAs to diagnose multiple diseases and evaluate the clinical treatment or prognosis.