Effect of a Biological Response Modifier on Expression of Growth Factors and Cellular Proliferation at Drying Off

B. E. DALLARD, V. RUFFINO, S. HEFFEL, AND L.F. CALVINHO

JOURNAL OF DAIRY SCIENCE

AMER DAIRY SCIENCE ASSOC-ADSA

Año: 2007 vol. 90 p. 2229 - 2240

0022-0302

Agents that increase natural protective mechanisms have been proposed for prevention and treatment of intramammary infections. Staphylococcus aureus is a major pathogen causing primarily subclinical chronic mastitis, which responds poorly to antibiotic therapy. The objectives of this study were to describe the effects of a single intramammary infusion of a lipopolysaccharide-based biological response modifier (BRM) on mammary epithelial cellular proliferation and expression of insulin-like growth factor-I (IGF-I) and vascular endothelial growth factor (VEGF) in uninfected and S. aureus-infected bovine mammary glands during involution. Three groups of 12 cows, 6 S. aureus infected and 6 uninfected were infused in two mammary quarters with BRM or placebo and sacrificed at 7, 14 and 21 d of involution. Proportion of infected quarters, mammary cell proliferation and IGF-I and VEGF expression was evaluated. BRM-treatment decreased proportion of S. aureus-infected mammary quarters at 6d of involution but similar number of isolations was observed at 13 and 20 days of involution in either treated or control quarters. Mammary epithelial cell proliferation percentage was higher in infected than uninfected quarters at every observation period, irrespective of administered treatment, while uninfected BRM-treated quarters showed increased cell proliferation at 7d of involution. IGF-I expression in uninfected quarters was not affected by treatment and showed a significant decrease at 21d of involution. IGF-I expression was greater in infected than uninfected quarters at every observation period, irrespective of treatment received. Expression of VEGF was greater in BRM-treated uninfected quarters at 7d of involution compared with controls. In infected quarters VEGF expression was lowest in BRM-treated quarters at 7d of involution increasing through the observation period. Conversely, untreated infected quarters showed highest VEGF expression at 7d decreasing at 21d of involution. Mammary cell proliferation and expression of IGF-I and VEGF was increased in S. aureus-infected quarters. Increased mammary cell proliferation and VEGF expression was observed in BRM-treated quarters during the first wk of involution.