Heat stress and recovery induce transcriptomic changes in lactogenic 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 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) or HS (42) for 1 hour. HS cells were collected after incubation at 37 for either 2 or 6 hours to examine the extent of recovery. A total of 1,668 differentially expressed genes (DEGs) 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 hours, and cellular homeostasis regulation genes were enriched at 6 hours. Overall, these findings provide a foundation for the molecular mechanisms involved in HS and recovery in cattle.