Effects of sustained hyperprolactinemia in late gestation on the mammary parenchymal transcriptome of gilts

The study objective was to determine the effects of hyperprolactinemia on the mammary parenchymal
transcriptome in late-pregnant gilts. Gilts were divided into 3 groups on day 90 of gestation to receive IM injections of 1) canola oil (CTL, n = 18) until day 109 of gestation, 2) domperidone (dopamine antagonist)
until day 96 (T7, n = 17) or, 3) domperidone until day 109 (T20, n = 17). Mammary glands were collected
on day 110 and parenchymal tissue was sampled for transcriptomic analyses. Total RNA was isolated from
6 CTL and 6 T20 gilts for microarray analysis. The GeneChip® Porcine Gene 1.0 ST Array (19,202 genes)
was used for hybridization. Array quality control, data normalization and expression level analyses were
performed with the Affymetrix Expression Console and Transcriptome Analysis Console (TAC) software. Using a threshold cut-off of 1.5 fold (P < 0.05), a total of 313 upregulated and 480 downregulated gene transcripts were identified in T20 vs CTL gilts. A qPCR validation analysis of selected upregulated (n = 13) and downregulated (n = 13) genes was conducted on all animals (CTL, T7, T20). The MIXED procedure of SAS was used for statistical analyses. All selected genes were validated for the CTL vs T20 comparison (P < 0.01). Only 4 selected genes (CAMK1G, COL9A1, P2RX7, TDRD1) were downregulated in the T7 treatment (vs CTL, P < 0.05). Functional analyses of differentially expressed genes were performed using the PANTHER classification system. The top upregulated Biological Process enriched GO terms were Inflammatory Response (GO:0006954) and Response to Lipid (GO:0033993). The Positive Regulation of Cell Population Proliferation (GO:0008284) and Regulation of Cellular Catabolic Process (GO:0031329) GO terms were identified for downregulated genes. Results suggest that a sustained hyperprolactinemia during latepregnancy (T20 treatment) may increase mammary inflammatory response and reduce cell proliferation.