Project description:Mastitis remains one of the most prevalent and costly diseases impacting the dairy industry worldwide. Escherichia coli is an environmental bacterium that frequently causes intramammary infections, the outcome of which depends on the capacity of the host to recognize and clear the bacterial pathogen. E. coli intramammary infection elicits localized and systemic responses, some of which have been characterized in mammary secretory tissue. However, nothing is known about early transcriptome-wide responses to infection that occur within regions of the teat and mammary parenchyma. Therefore, the objective of the current study was to use microarray analysis to characterize gene expression patterns and process networks that become activated in different regions of the mammary gland during the acute phase of experimentally induced intramammary infection with E. coli. Tissues evaluated were from Furstenberg’s rosette, teat cistern, gland cistern, and lobulo-alveolar regions of control and infected mammary glands, 12 and 24 h after bacterial (or control) infusions. For selected genes, quantitative RT-PCR was performed to confirm the microarray findings (Toll-like receptors; TLR1, TLR2, TLR4, TLR6) and evaluate the correspondence between mRNA level in tissues and protein level in milk (interleukin 8, tumor necrosis factor-alpha, haptoglobin, lipopolysaccharide-binding protein). The main networks activated by E. coli infection pertained to immune and inflammatory response, with marked induction of genes encoding proteins that function in chemotaxis, leukocyte activation and signaling. Genomic response was greatest in tissues of the teat and gland cisterns at 12 h post-infection, while tissue of the lobulo-alveolar region responded only, and most strongly of the regions, 24 h following the infection. Up regulation of TLR2, TLR4, IL8, TNF-alpha and bactericidal/permeability-increasing protein peaked at 12 h post infection in tissues of the teat and in the gland cistern, while the highest level of lipopolysaccharide-binding protein was reached at 24 h in the lobular alveoli region of infected quarters. Very few genes were down–regulated within the timeframe of this study. Similar genetic networks were impacted in all regions during early phases of E. coli intramammary infection, although regional differences throughout the gland were noted. Importantly, the tissues of the teat, which are first to encounter invading bacteria during a natural infection, responded rapidly and intensely, suggesting an important sentinel function for this region. Both resident mammary cells and infiltrating immune cells likely play an important role in recognition of pathogens and production of inflammatory mediators during mastitis. Three healthy lactating Holstein cows were used in this study. All mammary glands were bacteria-free. Immediately following the morning milking, 4 mL of E. coli suspension (100 colony forming units/mL) were infused into one mammary gland of the udder and the contralateral gland was infused with PBS (control gland). After the PM milking 12 h later, the remaining ipsilateral quarter was infused with E. coli. Cows were euthanized 24 h after initial infusions and tissues were collected from 4 regions of each mammary gland: Furstenburg’s rosette, teat cistern, gland cistern and lobuloalveolar regions. Tissues were snap frozen in liquid nitrogen, stored at -80C until processing.

Project description:Establishment of an in vitro system to explore molecular mechanisms of mastitis susceptibility in cattle by comparative expression profiling of Escherichia coli and Staphylococcus aureus inoculated primary cells sampled from cows with different genetic predisposition for somatic cell score Primary bovine mammary gland epithelial cells (pbMEC) were sampled from the udder parenchyma of cows that were selected for high and low mastitis susceptibility by applying a marker assisted selection strategy considering QTL and molecular marker information of a repetitively confirmed QTL for SCS in the telomeric region on BTA18 The cells were cultivated and subsequently inoculated with heat inactivated mastitis pathogens Escherichia coli and Staphylococcus aureus, respectively. After 1, 6 and 24 hours the cells were harvested and comparatively analyzed using microarray expression chip technology to identify differences in mRNA expression profiles attributed to cultivation, inoculation or to genetic predisposition. Six heifers inheriting the favorable paternal QTL allele and five heifers inheriting the unfavorable QTL allele were selected by applying a marker assisted selection strategy. All heifers were kept under the same environmental conditions, had no clinical mastitis and did not show any indication of bacterial infection at slaughter. Primary bovine mammary gland epithelial cell cultures were established from cells sampled from the udder parenchyma of each cow. The cells were challenged with heat inactivated Escherichia coli and Staphylococcus aureus or with PBS for control. After 1, 6 and 24 hours the cells were harvested and mRNA expression was comparatively analyzed between time points for each treatment and each paternally inherited SCS-BTA18-QTL allele, respectively. In addition, the differences in gene expression at time points 1, 6 and 24h between inoculated and respective uninoculated control cells were investigated using the short time series expression miner STEM for co-expression profiling and GO cattegory enrichment analyses.

Project description:Mastitis remains one of the most prevalent and costly diseases impacting the dairy industry worldwide. Escherichia coli is an environmental bacterium that frequently causes intramammary infections, the outcome of which depends on the capacity of the host to recognize and clear the bacterial pathogen. E. coli intramammary infection elicits localized and systemic responses, some of which have been characterized in mammary secretory tissue. However, nothing is known about early transcriptome-wide responses to infection that occur within regions of the teat and mammary parenchyma. Therefore, the objective of the current study was to use microarray analysis to characterize gene expression patterns and process networks that become activated in different regions of the mammary gland during the acute phase of experimentally induced intramammary infection with E. coli. Tissues evaluated were from Furstenberg’s rosette, teat cistern, gland cistern, and lobulo-alveolar regions of control and infected mammary glands, 12 and 24 h after bacterial (or control) infusions. For selected genes, quantitative RT-PCR was performed to confirm the microarray findings (Toll-like receptors; TLR1, TLR2, TLR4, TLR6) and evaluate the correspondence between mRNA level in tissues and protein level in milk (interleukin 8, tumor necrosis factor-alpha, haptoglobin, lipopolysaccharide-binding protein). The main networks activated by E. coli infection pertained to immune and inflammatory response, with marked induction of genes encoding proteins that function in chemotaxis, leukocyte activation and signaling. Genomic response was greatest in tissues of the teat and gland cisterns at 12 h post-infection, while tissue of the lobulo-alveolar region responded only, and most strongly of the regions, 24 h following the infection. Up regulation of TLR2, TLR4, IL8, TNF-alpha and bactericidal/permeability-increasing protein peaked at 12 h post infection in tissues of the teat and in the gland cistern, while the highest level of lipopolysaccharide-binding protein was reached at 24 h in the lobular alveoli region of infected quarters. Very few genes were down–regulated within the timeframe of this study. Similar genetic networks were impacted in all regions during early phases of E. coli intramammary infection, although regional differences throughout the gland were noted. Importantly, the tissues of the teat, which are first to encounter invading bacteria during a natural infection, responded rapidly and intensely, suggesting an important sentinel function for this region. Both resident mammary cells and infiltrating immune cells likely play an important role in recognition of pathogens and production of inflammatory mediators during mastitis.

Dataset Information

Expression data from mouse model of Ecoli mastitis

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