Contribution of mammary epithelial cells to the immune response during early stages of a bacterial infection to Staphylococcus aureus.

To differentiate between the contribution of mammary epithelial cells (MEC) and infiltrating immune cells to gene expression profiles of mammary tissue during early stage mastitis, we investigated in goats the in vivo transcriptional response of MEC to an experimental intra mammary infection (IMI) with Staphylococcus aureus, using a non-invasive RNA sampling method from milk fat globules (MFG). Microarrays were used to record gene expression patterns during the first 24 hours post-infection (hpi). This approach was combined with laser capture microdissection of MEC from frozen slides of mammary tissue to analyze some relevant genes at 30 hpi. During the early stages post-inoculation, MEC play an important role in the recruitment and activation of inflammatory cells through the IL-8 signalling pathway and initiate a sharp induction of innate immune genes predominantly associated with the pro-inflammatory response. At 30 hpi, MEC express genes encoding different acute phase proteins, including SAA3, SERPINA1 and PTX3 and factors, such as S100A12, that contribute directly to fighting the infection. No significant change in the expression of genes encoding caseins was observed until 24 hpi, thus validating our experimental model to study early stages of infection before the occurrence of tissue damage, since the milk synthesis function is still operative. This is to our knowledge the first report showing in vivo, in goats, how MEC orchestrate the innate immune response to an IMI challenge with S. aureus. Moreover, the non-invasive sampling method of mammary representative RNA from MFG provides a valuable tool to easily follow the dynamics of gene expression in MEC to search for sensitive biomarkers in milk for early detection of mastitis and therefore, to successfully improve the treatment and thus animal welfare.

Identification of microRNAs controlling human ovarian cell proliferation and apoptosis.

Previous studies have shown that microRNAs (miRNAs) can control steroidogenesis in cultured granulosa cells. In this study we wanted to determine if miRNAs can also affect proliferation and apoptosis in human ovarian cells. The effect of transfection of cultured primary ovarian granulosa cells with 80 different constructs encoding human pre-miRNAs on the expression of the proliferation marker, PCNA, and the apoptosis marker, Bax was evaluated by immunocytochemistry. Eleven out of 80 tested miRNA constructs resulted in stimulation, and 53 miRNAs inhibited expression of PCNA. Furthermore, 11 of the 80 miRNAs tested promoted accumulation of Bax, while 46 miRNAs caused a reduction in Bax in human ovarian cells. In addition, two selected antisense constructs that block the corresponding miRNAs mir-15a and mir-188 were evaluated for their effects on expression of PCNA. An antisense construct inhibiting mir-15a (which precursor suppressed PCNA) increased PCNA, whereas an antisense construct for mir-188 (which precursor did not change PCNA) did not affect PCNA expression. Verification of effects of selected pre-mir-10a, mir-105, and mir-182 by using other markers of proliferation (cyclin B1) and apoptosis (TdT and caspase 3) confirmed specificity of miRNAs effects on these processes. This is the first direct demonstration of the involvement of miRNAs in controlling both proliferation and apoptosis by ovarian granulose cells, as well as the identification of miRNAs promoting and suppressing these processes utilizing a genome-wide miRNA screen.

Involvement of microRNA Mir15a in control of human ovarian granulosa cell proliferation, apoptosis, steroidogenesis, and response to FSH.

Our study aimed to examine the role of micro RNA Mir15a in control of basic ovarian cell functions: proliferation, apoptosis, and secretory activity. In the first series of experiments, primary human ovarian granulosa cells were transfected with antisense construct blocking Mir15a (anti-Mir15a) and cultured without hormonal treatments. Accumulation of markers of proliferation (MAPK/ERK1,2 and PCNA) and apoptosis (caspase 3 and bax), and release of steroid hormones (progesterone, testosterone, and estradiol) were evaluated by immunocytochemical analysis and by enzyme immunoassay. In the second series of experiments, granulosa cells were transfected with gene construct encoding Mir15a precursor (pre-Mir15a) and cultured with and without follicle-stimulating hormone (FSH; 0, 1, 10, and 100 ng/ml). Expression of markers of proliferation (MAPK/ERK1,2) apoptosis (caspase 3), and steroidogenesis (release of progesterone, testosterone, and estradiol) were evaluated. Transfection of cells with anti-Mir15a resulted in a significant increase in accumulation of both proliferation and apoptosis markers, a reduction in progesterone and testosterone release, and an increase in estradiol release. Transfection of cells with pre-Mir15a had an opposite effect: it reduced accumulation of proliferation- and apoptosis-related proteins MAPK/ERK1,2 and caspase 3, and promoted release of progesterone and testosterone, but not estradiol. Moreover, pre-Mir15a reversed the effect of FSH on caspase 3, progesterone, and testosterone, but not on MAPK/ERK1,2 and estradiol. Our observations demonstrate involvement of Mir15a in control of multiple ovarian functions: proliferation, apoptosis, release of progesterone, androgen, and estrogen, and response to gonadotropin. Moreover, this is the first demonstration that miRNAs can affect response of cells to hormonal regulators. We propose that Mir15 could potentially be used for control of different reproductive processes.

Comparison of five different RNA sources to examine the lactating bovine mammary gland transcriptome using RNA-Sequencing.

The objective of this study was to examine five different sources of RNA, namely mammary gland tissue (MGT), milk somatic cells (SC), laser microdissected mammary epithelial cells (LCMEC), milk fat globules (MFG) and antibody-captured milk mammary epithelial cells (mMEC) to analyze the bovine mammary gland transcriptome using RNA-Sequencing. Our results provide a comparison between different sampling methods (invasive and non-invasive) to define the transcriptome of mammary gland tissue and milk cells. This information will be of value to investigators in choosing the most appropriate sampling method for different research applications to study specific physiological states during lactation. One of the simplest procedures to study the transcriptome associated with milk appears to be the isolation of total RNA directly from SC or MFG released into milk during lactation. Our results indicate that the SC and MFG transcriptome are representative of MGT and LCMEC and can be used as effective and alternative samples to study mammary gland expression without the need to perform a tissue biopsy.