BACKGROUND: By comparing fibroblasts collected from animals at 5-months or 
16-months of age we have previously found that the cultures from older animals 
produce much more IL-8 in response to lipopolysaccharide (LPS) stimulation. We 
now expand this finding by examining whole transcriptome differences in the LPS 
response between cultures from the same animals at different ages, and also 
investigate the contribution of DNA methylation to the epigenetic basis for the 
age-dependent increases in responsiveness.
RESULTS: Age-dependent differences in IL-8 production by fibroblasts in response 
to LPS exposure for 24 h were abolished by pretreatment of cultures with a DNA 
demethylation agent, 5-aza-2'deoxycytidine (AZA). RNA-Seq analysis of 
fibroblasts collected from the same individuals at either 5 or 16 months of age 
and exposed in parallel to LPS for 0, 2, and 8 h revealed a robust response to 
LPS that was much greater in the cultures from older animals. Pro-inflammatory 
genes including IL-8, IL-6, TNF-α, and CCL20 (among many other immune associated 
genes), were more highly expressed (FDR < 0.05) in the 16-month old cultures 
following LPS exposure. Methylated CpG island recovery assay sequencing 
(MIRA-Seq) revealed numerous methylation peaks spread across the genome, 
combined with an overall hypomethylation of gene promoter regions, and a 
remarkable similarity, except for 20 regions along the genome, between the 
fibroblasts collected at the two ages from the same animals.
CONCLUSIONS: The fibroblast pro-inflammatory response to LPS increases 
dramatically from 5 to 16 months of age within individual animals. A better 
understanding of the mechanisms underlying this process could illuminate the 
physiological processes by which the innate immune response develops and 
possibly individual variation in innate immune response arises. In addition, 
although relatively unchanged by age, our data presents a general overview of 
the bovine fibroblast methylome as a guide for future studies in cattle 
epigenetics utilizing this cell type.