Programmed cell death in bovine mammary tissue during lactation and involution

Area of Science:

• Dairy science
• Cell biology
• Molecular biology

Background:

• Mammary gland involution differs between rodents and cattle.
• Rodent involution involves extensive apoptosis, while bovine tissue shows minimal remodeling.
• Understanding bovine involution is crucial for dairy herd management.

Purpose of the Study:

• To investigate cellular and molecular changes in bovine mammary tissue after cessation of milking.
• To compare bovine involution with rodent models.
• To identify molecular markers associated with lactation termination.

Main Methods:

• Histological analysis of mammary tissue.
• Molecular biology techniques including DNA extraction and messenger RNA (mRNA) analysis.
• Terminal deoxynucleotide transferase-mediated deoxyuridine nick end-labeling (TUNEL) assay for apoptosis detection.

Main Results:

• Apoptosis was detected in lactating bovine mammary tissue.
• Cessation of milking led to a significant decrease in alpha-lactalbumin and alpha S1-casein mRNA.
• Lactoferrin mRNA increased 20-fold post-milking cessation.
• Increased DNA fragmentation and TUNEL-positive cells were observed, particularly in deteriorated alveolar regions.

Conclusions:

• Bovine mammary gland involution involves partial cell loss through apoptosis.
• Lactation termination results in dedifferentiation of remaining mammary cells.
• Gene expression patterns shift significantly, with decreased milk protein synthesis genes and increased lactoferrin.