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Metabolic, paracellular permeability, and immune gene expression in ruminal epithelium during the transition period in dairy cattle
The study was aimed to investigate the mRNA expression linked to systems involved in the metabolic, epithelial integrity, and immune function in ruminal epithelial tissue during the transition period in dairy cattle. Seven multiparous Holstein cows with a ruminal fistula were dried off at d -50 days relative to the expected calving and fed a controlled-energy diet (NEL = 1.24 Mcal/kg of DM) until calving and then a common lactation diet. Ruminal epithelial tissue was biopsied at -14, 10 and 28 DIM. Extracted mRNA was used for profiling of 23 genes via quantitative RT-PCR. The expression of genes was normalized using geometric mean of 3 internal control genes (CMTM6, ERC1 and MRPL39). Data were analyzed as a repeated measures study using the MIXED procedure of SAS. The epithelial integrity genes OCLN and TJP1 had a decrease (P<0.05) of expression from -14 to 10 DIM. For genes involved in the immune function, TNF did not change significantly. In contrast, the expression of CD45 decreased (P<0.05) from -14 to 10 DIM and the expression of TL2 and TLR4 decreased (P<0.01) until 28 DIM compared with -14 DIM. The transporters SLC14A1, SLC16A1 and SLC16A3 increased expression during the transition period with highest (P<0.05) values at 28 DIM. The ketogenic gene HMGCS2 had higher (P<0.05) expression at 28 DIM vs. -14 and 14 DIM. Expression of PPARA, PPARD and PPARG did not change during the transition period; while, the nuclear receptor RXRA decreased (P<0.01)from -14 DIM to 28 DIM. Expression of the insulin receptor (INSR) was lower (P<0.05) at 10 DIM vs. -14 and 28 DIM. Expression of TGFB1, involved in cell growth and proliferation, had the highest (P<0.05)expression at 10 DIM; while, its receptor (TGFBR1) had higher (P<0.05) expression at -14 DIM and subsequently decreased. Results suggest that along with other tissues the ruminal epithelium also experiences changes at the transcriptome level. These are likely important for a successful transition into lactation. The observed changes could be driven by both changes in feed composition and nutrient intake typical of this period, and to the metabolic and hormonal changes that take place in preparation to the time of calving and the onset of lactation.
Keywords:
rumen, transition cow, transcriptomics