Transforming growth factors alpha and beta-1 are differentially expressed in the bovine mammary gland during mammogenesis, lactogenesis, galactopoiesis and involution

Anatomical change and the scale of metabolic and biosynthetic reprogramming of the mammary gland during the life cycle imply an enormous tissue remodeling in the adult mammal. Growth factors are involved in the local control of the gland. Our aim was to analyze expression of transforming growth factors alpha and beta-1 (TGFa, TGFb-1) during different stages of growth and function. Tissue was obtained after slaughter from non-pregnant control heifers, from pregnant heifers (mammogenesis) and from cows during lactogenesis, galactopoiesis and involution (day 21, non-pregnant). Additional samples were obtained after mammary biopsies during involution (days 3, 7, 21, non-pregnant) and during redevelopment of a pregnant, dry cow. Other samples were obtained from heifers after induced mammogenesis and lactogenesis, with and without additional prolactin inhibition. Total RNA was isolated from mammary tissue and analyzed by reverse transcription-polymerase chain reaction and ribonuclease protection assay. TGFb-1 mRNA levels were highest during involution, especially during early involution (days 3 and 7). Lowest levels were detected during lactogenesis and galactopoiesis, with intermediate levels in the gland of control heifers and pregnant heifers. Highest TGFa expression was detected in glands of control heifers and dry cows. TGFa expression decreased during pregnancy and reached very low levels during lactation. TGFa mRNA increased in biopsy samples during involution of non-pregnant animals and increased further in the redeveloping, dry gland of a cow 2 weeks before parturition. TGFa mRNA levels were higher after induced mammogenesis than after induced lactogenesis. TGFa mRNA expression increased further during prolactin inhibition. These data suggest that TGFa may be important for development and TGFb-1 mainly important for involution of the bovine mammary gland. (This work was supported by the German Research Fundation; Scha 257/13-1). Published by Elsevier Science B.V.