Abstract
BackgroundEpidermal growth factor (EGF) is an important growth factor in regulation of cell proliferation, differentiation, survival and apoptosis. Studies showed that food-grade Lactococcus lactis (L. lactis) and NICE expression system have superior performance in exogenous protein expression. This study aimed to construct and express porcine EGF (pEGF), and use L. lactis as vehicle for producing and delivering pEGF. Furthermore, investigating biological activity of pEGF and exploring applications feasibility of combination effects of L. lactis and pEGF on early weaned piglets’ production.ResultsA recombinant Lactococcus lactis which produced and secreted pEGF at 1000 ng/ml in culture supernatant was generated. Secreted pEGF was a fully biologically active protein, as demonstrated by its capacity to stimulate L929 mouse fibroblast cell line proliferation in vitro. For in vivo study, forty piglets were randomly allocated to control, antibiotic control, empty vector-expressing L. lactis (LL-EV) and pEGF-secreting L. lactis (LL-pEGF). After 14 d of rearing, final body weight and average daily gain in LL-pEGF were greater (P < 0.05, 8.95 vs. 8.37 kg, 206.1 vs. 157.7 g/day, respectively) than those in control, but no significant differences between LL-pEGF, LL-EV and antibiotic control. Overall period average daily feed intake was higher in LL-pEGF, LL-EV and antibiotic control than in control (P < 0.05, 252.9, 255.6, 250.0, 207.3 g/day, respectively). No significant difference was observed on ADFI/ADG. LL-pEGF increased villous height in the duodenum, jejunum and ileum than in control and LL-EV (P < 0.05). Sucrase in the 3 intestinal segments, aminopeptidase A in the duodenum and Jejunum, aminopeptidase N and dipeptidase IV in the duodenum in LL-pEGF were higher than those in control (P < 0.05). Furthermore, Escherichia coli and Enterococcus counts decreased in the ileum and Lactobacillus increased in the ileum and cecum digesta in LL-pEGF compare with the control (P < 0.05). Lactobacillus increased in the cecum in LL-EV compared with control and antibiotic control (P < 0.05).ConclusionWe have generated a recombinant Lactococcus lactis which produced and secreted fully biologically active porcine EGF. Oral administration of pEGF-secreting L. lactis had beneficial effects on intestinal health and performance of early-weaned piglets.
Highlights
Epidermal growth factor (EGF) is an important growth factor in regulation of cell proliferation, differentiation, survival and apoptosis
Characterization of pEGF production by L. lactis The secreted porcine EGF bands of 6.0 kDa were detected in nisin-induced cultures of the L. lactis NZ9000/pNZ8148–SPUsp45-MPpEGF (LL-pEGF) strain, and no signal was detected in non-induced LL-pEGF cultures by western blotting (Figure 3A)
No significant differences were observed in final body weight (BW) and average daily gain (ADG) among LL-pEGF, antibiotic control and Empty vector-expressing Lactococcus lactis (LL-EV) groups
Summary
Epidermal growth factor (EGF) is an important growth factor in regulation of cell proliferation, differentiation, survival and apoptosis. Based on information from several experiments and surveys, it has been concluded that early weaning at 3-4 weeks can be an effective management strategy to improve wean-tofinish growth performance and provide a higher number of piglets per sow per year in commercial multi-site production systems which would well control the disease transfer from the sow to the piglet [6]. When weaning at this time, a piglet’s digestive apparatus is undeveloped and an abrupt transition from maternal milk to solid feed entails several problems. How to help piglets overcoming post-weaning stress without any side effects are attracting people's attention at the present stage
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