Our first objective was to determine if mammary remodeling during the dry period of dairy cows is characterized by a transient increase in stromal fibronectin, myofibroblasts, stromelysin (MMP-3), transforming growth factor-beta1 (TGF-beta1) and its receptor, TGF-betaR2. The second objective was to determine if TGF-beta1 increases mammary stromal remodeling during the dry period. Mammary biopsies were obtained from nine cows at: late lactation, 1 week after dry-off, 3 weeks before expected calving, and 1 week before expected calving. For objective 2, tissue was incubated for 2 h with 0 or 5 ng TGF-beta1/ml. Intralobular stromal area was greater at 1 week dry and 3 weeks before calving than at 1 week before calving (P=0.02). The number of fibroblasts was greater at one week dry than 1 week before calving (P=0.02). Stromal TGF-beta1 was 15% lower during the dry period than in late lactation (P=0.02). The number of myofibroblasts and the expression of fibronectin, MMP-3, or TGF-betaR2 did not differ. Incubation with TGF-beta1 had no effect on the percent intralobular stroma area expression of fibronectin or MMP-3. The number of myofibroblasts increased by 19% in the intralobular stroma (P=0.03) and the percent of myofibroblasts tended to increase by 4% (P=0.06) in tissue incubated with TGF-beta1. Based on these findings, TGF-beta1 may be important in the activation of stromal cells during involution and mammogenesis of the bovine mammary gland.Photomicrograph Analysis Stained slides were examined with a Nikon Eclipse 50i light microscope (Nikon Instruments Inc., ... using the free-hand area-of- interest tool to measure area or the manual tag tool for counting cells in Image Pro Plus.
|Title||:||Stromal Changes and Transforming Growth Factor-beta1 in the Mammary Gland During the Dry Period of Dairy Cows|
|Author||:||Lindsey De Vries|
|Publisher||:||ProQuest - 2009|