Heat stress and recovery induce transcriptomic changes in lactogenic-like bovine mammary epithelial (MAC-T) cells

Heat stress (HS) in cattle significantly challenges the dairy industry by reducing milk production. However, the molecular mechanism behind mammary gland responses to HS and recovery remains poorly understood. This study aimed to determine the transcriptomic changes in lactogenic-like bovine mammary epithelial (MAC-T) cells after HS and post-HS recovery. Six culture conditions were analyzed: MAC-T cells cultured in basal medium, cells in lactogenic medium to induce differentiation, differentiated cells at standard temperature (37°C) or HS (42°C) for 1 h. HS cells were collected after incubation at 37°C for either 2 or 6 h to examine the extent of recovery. A total of 1,668 differentially expressed genes were identified. Differentiated cells expressed genes associated with milk lipid synthesis, indicating lactogenic potential. HS suppressed genes involved in cellular differentiation and activated heat shock protein genes. Several transcription factors were identified as potential regulators of HS response. During recovery, chaperon-mediated protein folding genes remained elevated. Apoptosis regulation genes were induced at 2 h, and cellular homeostasis regulation genes were enriched at 6 h. Overall, these findings provide insight into the transcriptomic response of MAC-T cells to heat stress and recovery under in vitro conditions, offering a foundation for future studies on cellular responses to environmental stressors.NEW & NOTEWORTHY Bovine mammary epithelial (MAC-T) cells were differentiated (D), heat stressed (HS), and recovered (R) under different conditions. Differentiated cells expressed milk lipid synthesis genes, which were repressed by HS. Further, HS upregulated heat shock protein genes and altered several transcription factors involved in HS response. Recovery after HS-induced apoptosis regulation at 2 h and cellular homeostasis regulation at 6 h.