Early transcriptomic changes in peripheral blood 7 days after embryo transfer in dairy cattle

Area of Science:

• Reproductive immunology
• Dairy cattle reproduction
• Molecular diagnostics

Background:

• Shortening calving intervals is vital for dairy industry profitability and cow fertility.
• Early pregnancy detection is essential for timely re-insemination of non-pregnant cows.
• Current methods lack accuracy for pregnancy prediction within the first three weeks post-insemination.

Purpose of the Study:

• To characterize peripheral blood transcriptomic changes, including interferon-stimulated genes (ISG), as early as 7 days after embryo transfer in Holstein heifers.
• To identify potential biomarkers for early pregnancy detection in cattle.

Main Methods:

• Whole blood was collected from 170 Holstein heifers at 0, 7, and 14 days post-embryo transfer.
• RNA was extracted and sequenced to analyze gene expression differences between pregnant and non-pregnant heifers.
• Reverse-transcription quantitative real-time PCR was used for biological validation of key genes.

Main Results:

• On day 7 post-transfer, EDN1, CXCL3, CCL4, and IL1A were significantly upregulated in pregnant heifers.
• On day 14 post-transfer, ISG15, MX2, OASY1, and IFI6 showed significant upregulation in pregnant heifers.
• Thirteen differentially expressed genes, primarily related to innate immunity, were identified on day 7.

Conclusions:

• Peripheral blood transcriptomic analysis reveals early activation of immune-related genes and ISG within two weeks of embryo transfer.
• These gene expression changes suggest a mechanism for maternal immune system accommodation of the allogenic conceptus.
• Further studies are needed to validate the specificity and sensitivity of these genes as early pregnancy biomarkers.