Ouellet Véronique, Negrao João, Skibiel Amy L, Lantigua Valerie A, Fabris Thiago F, Marrero Marcela G, Dado-Senn Bethany, Laporta Jimena, Dahl Geoffrey E
Department of Animal Sciences, University of Florida, Gainesville, FL 32611, USA.
Department of Basic Sciences, Faculty of Animal Science and Food Engineering, University of Sao Paulo, Pirassununga, SP 05508-270, Brazil.
Animals (Basel). 2021 Feb 21;11(2):563. doi: 10.3390/ani11020563.
Hormonal alterations occurring under late gestation heat stress may disturb mammary gland remodelling, resulting in a reduced milk yield during the subsequent lactation. We investigated the effects of an altered endocrine environment on mammary gene expression at different stages of the dry period. Mammary gland biopsies from in vivo-cooled (CL) or heat-stressed (HT) cows were collected at d 3 and 35 relative to dry-off and divided into explants. Explants were incubated in vitro for 24 h in one of three media: Basal: no prolactin or estrogen; CL-mimic: Basal + low prolactin + high 17β-estradiol, or HT-mimic: Basal + high prolactin + low 17β-estradiol. Real time qPCR was used to quantify gene expression. We established that late-gestation heat stress changes the expression of prolactin and oestrogen receptors, downregulates genes involved in apoptosis, autophagy and proliferation at d 3 and upregulates genes related to those cellular processes at d 35. Moreover, compared with in vivo treatments, we showed that the expression of fewer genes was impacted by in vitro treatments which aimed to mimic the hormonal response of cows exposed to a different environment. Further research will continue to uncover the mechanisms behind the production impairments caused by late-gestation heat stress.
妊娠后期热应激下发生的激素变化可能会干扰乳腺重塑，导致随后泌乳期的产奶量降低。我们研究了在干奶期不同阶段，内分泌环境改变对乳腺基因表达的影响。在相对于干奶的第3天和第35天，采集体内冷却（CL）或热应激（HT）奶牛的乳腺活检组织，并将其分成外植体。外植体在三种培养基之一中体外培养24小时：基础培养基：无催乳素或雌激素；CL模拟培养基：基础培养基+低催乳素+高17β-雌二醇，或HT模拟培养基：基础培养基+高催乳素+低17β-雌二醇。使用实时定量PCR来量化基因表达。我们发现，妊娠后期热应激会改变催乳素和雌激素受体的表达，在第3天下调参与细胞凋亡、自噬和增殖的基因，并在第35天上调与这些细胞过程相关的基因。此外，与体内处理相比，我们发现旨在模拟暴露于不同环境的奶牛激素反应的体外处理对较少基因的表达有影响。进一步的研究将继续揭示妊娠后期热应激导致生产受损背后的机制。
