中文摘要：

【目的】MicroRNA（miRNA）是一类长度约21-23个核苷酸的非编码小RNA分子,本研究旨在分析高温条件下miRNA-24对乳腺上皮细胞生长、凋亡的作用及其初步机制。【方法】体外培养奶牛乳腺上皮细胞,高温（41℃）处理所培养的细胞;应用miRNA基因沉默技术,抑制高温处理过的乳腺上皮细胞中miRNA-24的表达;采用细胞计数法分析细胞增殖情况;Hoechst33342/PI荧光染色、流式细胞术检测miRNA-24对乳腺上皮细胞凋亡的作用,Western blot检测凋亡相关因子表达变化。【结果】抑制miRNA-24的表达,高温条件下的乳腺上皮细胞增殖能力显著增强（P〈0.05）,凋亡细胞数显著减少（P〈0.05）,促凋亡因子caspases-8和caspases-3表达量下调。【结论】内源性miRNA-24对乳腺组织发育具有重要的调控作用,抑制miRNA-24的表达可以缓解高温诱导下奶牛乳腺上皮细胞凋亡发生率、促进细胞的生长发育。

英文摘要：

【Objective】 MicroRNA （miRNA） is a kind of short non-coding RNA about 22-23 nucleotides in length. The present study was performed to investigate the effects and molecule mechanism of miRNA -24 on mammary epithelial cells growth and apoptosis in response to high temperature. 【Method】 Bovine mammary epithelial cells were cultured in vitro, and gene silencing techniques were used to inhibit the expression of miRNA-24 in mammary epithelial cells which in response to heat stress. Cell proliferation was measured by cell count method. Apoptosis of cells was analyzed by Hoechst33342/PI fluorescent staining and FCM. The expression of apoptosis correlation factors caspases-8 and caspases-3 were detected by western blot. 【Results】 The results showed that miRNA-24 gene silencing in mammary epithelial cells significantly increased （P〈0.05） the proliferation of cells although these cells were treated at high temperature beforehand. In contrast, the apoptosis of these cells were decreased （P〈0.05）, the expression of caspases-8 and caspases-3 were also decreased after miRNA-24 gene silencing. 【Conclusion】 miRNA-24 have important roles in regulation of glandular tissue development, inhibition of miRNA-24 may rescue heat stress-induced apoptosis of bovine mammary epithelial cells and promote the cells growth and development.