Temporal and spatial heterogeneity in milk and immune-related gene expression during mammary gland involution in dairy cows

Abstract

The aim of this study was to investigate heterogeneity in tissue morphology, milk protein and immune-related gene expression, and apoptosis of epithelial cells in the lactating and involuting mammary glands of the dairy cow. Mammary tissue from different regions of the gland (alveolar, cisternal, and peripheral) was collected postmortem from nonpregnant, pasture-fed, Holstein-Friesian primiparous cows in mid-lactation that were killed at different time points postmilking: 0, 6, 12, 18, 24, 36, and 72 h (n = 6 per time point). The CSN1NS1 and LALBA mRNA was decreased in alveolar, cisternal, and peripheral tissue by 12 to 36 h postmilking. In contrast, lactoferrin (LF) and mammary serum amyloid A3 (M-SAA3) mRNA was increased in these regions by 36 to 72 h. During lactation, more variability was present in gene expression in alveolar tissue between cows and between quarters within a cow, than within quarters. Histological analysis indicated the alveolar tissue from lactating cows was mostly uniform in structure; however, in situ hybridization indicated that although most of the alveolar tissue expressed milk proteins, the level of expression varied within and between alveoli. This heterogeneity became more pronounced with involution and with increasing regions of alveoli expressing lactoferrin, indicating that alveoli enter involution asynchronously. The peripheral and cisternal tissue had more variability in gene expression between cows compared with the alveolar tissue. The M-SAA3 signal was more intense in the cisternal tissue and less intense than the peripheral compartment compared with LF particularly in the earlier time points. In addition, between cows within the later time points, differences were observed in tissue morphology, the levels of milk protein and immune-related gene expression, and phosphorylated signal transducer and activator of transcription (STAT) 5-P and STAT3-P proteins, and degree of apoptosis, indicating that involution of the mammary gland occurs at different rates between cows. Understanding the mechanisms initiating the process of involution of the mammary gland provides an opportunity for enhancing milk production of the dairy cow.

Single-step genome-wide association studies (GWAS) and post-GWAS analyses to identify genomic regions and candidate genes for milk yield in Brazilian Girolando cattle

“…During bovine mammary involution, the balance between STAT5 and STAT3 signaling is important in regulation of the transition from lactation to involution. At the onset of mammary gland involution, STAT5 is downregulated while STAT3 is upregulated (Singh et al, 2016(Singh et al, , 2017. The negative relationship between STAT5 and STAT3 activation is important to preventing further STAT5 activation when milk production ceases (Granillo et al, 2007).…”

“…The negative relationship between STAT5 and STAT3 activation is important to preventing further STAT5 activation when milk production ceases (Granillo et al, 2007). According to recent studies, when involution is experimentally induced by abrupt cessation of milking, increased expression of STAT3 can be detected up to 72 h after milking, although it occurs at different rates among cows and quarters within the same mammary gland (Singh et al, 2016(Singh et al, , 2017.…”

The Multifaceted Role of STAT3 in Mammary Gland Involution and Breast Cancer

“…Bovine mammary involution is considered to encompass both a phase of cell death, but also an important period of epithelial cell renewal prior to the next lactation [ 55 , 56 , 57 ]. Interestingly, when involution is experimentally induced by cessation of milking in non-pregnant dairy cows that are close to the point of peak lactation in mid-lactation, increased phosphorylation of STAT3 is observed by 72 h [ 58 , 59 ]. As would be anticipated, the dynamics of the involution process in cows are strikingly different from that of rodents, and, following abrupt cessation of milking at mid lactation, milking can be reinitiated after seven days of non-milking, with a 91% milk yield recovery and milk composition similar to that observed prior to cessation of lactation [ 60 ].…”

Effect of experimental stress and cortisol release induced by ACTH administration on expression of key genes related to milk synthesis and apoptosis during mammary involution of Saanen goats

“…These changes induce the renewal of epithelial cells, resulting in a lobe-alveolar structure that ensures copious milk synthesis during the next lactation (Safayi et al, 2010;Zhao et al, 2019). In this context, the analyses of the expression of casein (CSN2), lactalbumin (LALBA), and lactoferrin (LF) genes related to capacity synthesis and immunomodulation in mammary tissue during dry off are essential to understand the involution (Singh et al, 2005(Singh et al, , 2017. Likewise, the expression of insulin-like growth factor 1 receptor (IGF1R) genes and phosphatidylinositol-3kinase (PIK3CA), protein kinase B (AKT1), mechanistic target of rapamycin (MTOR), all of which are related to apoptosis control in mammary epithelial cell line (Burgos et al, 2010;Li et al, 2017), can contribute to understanding the effects of stress and cortisol release during dry off.…”

“…Some authors have also associated milk accumulation during the dry period to stress, inflammation of the mammary gland and a higher risk of mastitis (Bertulat et al ., 2013; Mehdid et al ., 2019; Zhao et al ., 2019). Other studies have reported increased infiltration of immune cells and an increased rate of apoptosis in mammary tissue within a few hours or days after the start of the dry off (Boutinaud et al ., 2016; Lanctôt et al ., 2017; Singh et al ., 2017). Moreover, milking cessation is marked by decreased casein and lactalbumin synthesis and an increase of lactoferrin synthesis in mammary tissue (Singh et al ., 2017).…”