Enhancement of the dry-off process by intramammary infusion of metalloproteinase 9 nanoparticles

Abstract Text:

The dry-off of dairy cows is associated to welfare and high risk of intramammary infections that could be improved by fostering involution and immune system during early dry period. Metalloproteinase 9 (MMP-9) is a tissue-remodeling enzyme physiologically released in the mammary gland during the dry period. The objective of this study was to explore the role of the infusion of MMP-9 at dry-off. MMP-9 was produced in Lactococcus lactis as a soluble protein and nanoparticulated (NP) format. Twelve cows with Somatic Cell Count (SCC) <200.000 and >15 kg of milk/d at dry-off were enrolled in the study. Treatments were randomly assigned to the front or rear quarters, thus 24 quarters were distributed in 2 treatments: 1 mg of soluble MMP-9 and 100 mg of NP MMP-9, providing both the equivalent metalloproteinase activity measured by zymography. Saline solution was infused in the contralateral quarters as a negative control for each treatment. Samples of mammary secretion were collected at 0, 1, 2, 3, and 7 d relative to dry-off and processed for SCC determination or kept frozen for subsequent determination of MMP-9 activity, and bovine serum albumin (BSA), lactoferrin, sodium, and potassium concentrations. SCC was analyzed with a Scepter cell counter, MMP-9 activity by zymography, lactoferrin by ELISA, BSA using a colorimetric assay, and sodium and potassium by ICP-OES. All data were analyzed by ANOVA. As expected, both the soluble and NP forms increased (P < 0.0001) the metalloproteinase activity in mammary gland compared with controls. However, only the NP form was able to modulate some involution and immune markers. The NP form increased immunity markers including SCC up to 400 fold (P < 0.001) at days 1-7, and lactoferrin concentration up to 1.8 folds (P < 0.05) at days 1 and 2 after dry-off, compared with saline controls. Also, there was an increase (P < 0,001) in involution markers. Concentration of BSA in mammary secretion raised up to 8 fold at 1, 2 and 3 d and the sodium/potassium ratio (P < 0.001) by 4.5 fold at day 1 after dry-off, compared with controls. In conclusion, infusions of either soluble or NP forms of MMP-9 at dry-off, increased the metalloproteinase activity in mammary gland, but only the NP form enhanced the of the involution process and immune system.

Keywords: dry period, nanoparticles, metalloproteinase 9