Key Laboratory of Animal Biotechnology of the Ministry of Agriculture, Northwest A&F University, Yangling, Xianyang 712100, China.
College of Veterinary Medicine, Northwest A&F University, Yangling, Xianyang 712100, China.
Int J Mol Sci. 2023 May 16;24(10):8841. doi: 10.3390/ijms24108841.
Udder traits, influencing udder health and function, are positively correlated with lactation performance. Among them, breast texture influences heritability and impacts on the milk yield of cattle; however, there is a lack of systematic research on its underlying mechanism in dairy goats in particular. Here, we showed the structure of firm udders with developed connective tissue and smaller acini per lobule during lactation and confirmed that there were lower serum levels of estradiol (E) and progesterone (PROG), and higher mammary expression of estrogen nuclear receptor (ER) α and progesterone receptor (PR), in dairy goats with firm udders. The results of transcriptome sequencing of the mammary gland revealed that the downstream pathway of PR, the receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL) signal, participated in the formation of firm mammary glands. During the culture of goat mammary epithelial cells (GMECs), high RANKL level additions promote the Inhibitor kappaB (IκB)/p65/Cyclin D1 expression related to cell proliferation and decrease the phosphorylated signal transduction and transcription activator 5 (Stat5) expression related to milk-protein synthesis of GMECs, which is consistent with electron microscope results showing that there are fewer lactoprotein particles in the acinar cavity of a firm mammary. Furthermore, co-culturing with adipocyte-like cells for 7 d is beneficial for the acinar structure formation of GMECs, while there is a slightly negative effect of high RANKL level on it. In conclusion, the results of this study revealed the structure of firm udders structure and confirmed the serum hormone levels and their receptor expression in the mammary glands of dairy goats with firm udders. The underlying mechanism leading to firm udders and a decrease in milk yield were explored preliminarily, which provided an important foundation for the prevention and amelioration of firm udders and improving udder health and milk yield.
乳房特征与乳房健康和功能呈正相关，影响泌乳性能。其中，乳房质地影响其遗传性，并影响奶牛的产奶量；然而，在奶山羊中，特别是关于其潜在机制的系统研究还很缺乏。在这里，我们展示了在泌乳期具有发达结缔组织和每个小叶中较小腺泡的结实乳房的结构，并证实了具有结实乳房的奶山羊血清雌二醇（E）和孕酮（PROG）水平较低，乳腺雌激素核受体（ER）α和孕激素受体（PR）表达较高。乳腺转录组测序的结果表明，PR 的下游途径，核因子-κB（NF-κB）配体（RANKL）信号的受体激活剂，参与了结实乳腺的形成。在山羊乳腺上皮细胞（GMEC）的培养过程中，高水平的 RANKL 添加促进了与细胞增殖相关的 Inhibitor kappaB（IκB）/p65/Cyclin D1 表达，并降低了与乳蛋白合成相关的磷酸化信号转导和转录激活因子 5（Stat5）表达，这与电子显微镜结果一致，表明在结实的乳腺中，腔中存在较少的乳蛋白颗粒。此外，与脂肪细胞样细胞共培养 7 d 有利于 GMECs 的腺泡结构形成，而高水平的 RANKL 对其有轻微的负面影响。总之，本研究结果揭示了结实乳房的结构，并证实了结实乳房奶山羊的血清激素水平及其乳腺受体表达。初步探讨了导致结实乳房和产奶量下降的潜在机制，为预防和改善结实乳房、改善乳房健康和产奶量提供了重要基础。
