The intestinal health of chick embryos is vital for their life-long growth, and exogenous nutrition intervention may provide sufficient nutrition for embryonic development. In the present study, we investigated the effect of in ovo injection of L-methionine (L-Met) on the intestinal structure and barrier function of chick embryos. There were 4 groups of treatments: the control (CON) group injected with phosphate-buffered saline (PBS) and the other 3 groups injected with 5, 10, and 20 mg L-Met/egg, respectively. The injection was performed on embryonic day 9 (E9), and intestinal samples were collected on the day of hatching for analysis. The results showed that, compared with the CON group, the groups administered an in ovo injection of L-Met increased relative weights of the duodenum, jejunum, and ileum (P < 0.05). Hematoxylin and eosin (H&E) staining showed that the groups injected with 5, 10, and 20 mg L-Met significantly increased villus height and crypt depth (P < 0.05). Moreover, in ovo injection of 10 mg L-Met also increased the transepithelial electrical resistance (TEER) of the jejunum (P < 0.05). Injection with 10 and 20 mg L-Met increased the expression of the tight junction proteins (ZO-1 and claudin-1) and the fluorescence signal intensity of Ki67 and villin proteins (P < 0.05). Further, the protein expression of phospho-Janus kinase 2 (p-JAK2) and phospho-signal transducer and activator of transcription 3 (p-STAT3) was significantly increased by 10 or 20 mg L-Met injection (P < 0.05). In conclusion, the injection of L-Met, especially at a dose of 10 mg, showed beneficial effects on the intestinal integrity of chick embryos due to the activation of the JAK2/STAT3 signaling pathway. Our results may provide new insights for regulating the intestinal development of embryonic chicks and the rapid growth of chicks after hatching.

鸡胚的肠道健康对其终生生长至关重要，外源性营养干预可为胚胎发育提供充足的营养。在本研究中，我们研究了卵内注射 L-蛋氨酸 (L-Met) 对鸡胚胎肠道结构和屏障功能的影响。有4组治疗：对照组（CON）注射磷酸盐缓冲盐水（PBS），其他3组分别注射5、10和20mg L-Met/egg。在胚胎第 9 天 (E9) 进行注射，并在孵化当天收集肠道样本进行分析。结果显示，与 CON 组相比，卵内注射 L-Met 的组增加了十二指肠、空肠和回肠的相对重量（P < 0.05)。苏木精和伊红 (H&E) 染色显示注射 5、10 和 20 mg L-Met 的组显着增加了绒毛高度和隐窝深度（P  < 0.05）。此外，卵内注射 10 mg L-Met 还增加了空肠的跨上皮电阻 (TEER) ( P  < 0.05)。注射 10 和 20 毫克 L-Met 增加了紧密连接蛋白（ZO-1 和 claudin-1）的表达以及 Ki67 和绒毛蛋白的荧光信号强度（P  < 0.05）。此外，磷酸化 Janus 激酶 2 (p-JAK2) 和磷酸化信号转导和转录激活因子 3 (p-STAT3) 的蛋白表达在注射 10 或 20 毫克 L-Met 后显着增加（P < 0.05)。总之，由于 JAK2/STAT3 信号通路的激活，L-Met 的注射，尤其是 10 mg 的剂量，对鸡胚胎的肠道完整性显示出有益的影响。我们的研究结果可能为调节胚胎雏鸡的肠道发育和孵化后雏鸡的快速生长提供新的见解。