Dietary calcium restriction affects mesenchymal stem cell activity and bone development in neonatal pigs.

The effects of dietary calcium (Ca) deficiency on skeletal integrity are well characterized in growing and mature mammals; however, less is known about Ca nutrition during the neonatal period. In this study, we examined the effects of neonatal Ca nutrition on bone integrity, endocrine hormones, and mesenchymal stem cell (MSC) activity. Neonatal pigs (24 ± 6 h of age) received either a Ca-adequate (1.2 g/100 g) or an ~40% Ca-deficient diet for 18 d. Ca deficiency reduced (P < 0.05) bone flexural strength and bone mineral density without major differences in plasma indicators of Ca status. There were no meaningful differences in plasma Ca, phosphate (PO(4)), parathyroid hormone, or 1,25-dihydroxycholecalciferol due to Ca nutrition throughout the study. Calcium deficiency also reduced (P < 0.05) the in vivo proliferation of MSC by ~50%. In vitro studies utilizing homologous sera demonstrated that MSC activity was affected (P < 0.05) by both the Ca status of the pig and the sera as well as by their interaction. The results indicate that neonatal Ca nutrition is crucial for bone integrity and suggest that early-life Ca restriction may have long-term effects on bone integrity via programming of MSC.

Sublethal staphylococcal enterotoxin B challenge model in pigs to evaluate protection following immunization with a soybean-derived vaccine.

In an effort to develop a sustainable platform for manufacturing protein-based vaccine candidates, we expressed a triple mutant of staphylococcal enterotoxin B carrying the L45R, Y89A, and Y94A modifications in transgenic soybean seeds (soy-mSEB). Soy-mSEB possessed no detectable superantigen activity in vitro. We found that this soybean-derived, nontoxic mutant of SEB could be stably expressed, stored in seeds for extended periods at room temperature without degradation, and easily purified from contaminating soy proteins. Vaccination of pigs with purified soy-mSEB, or the identical triple mutant expressed in Escherichia coli (E. coli-mSEB), resulted in high antibody titers against the native toxin in immunized animals. In fact, titers were indistinguishable regardless of the immunogen used, demonstrating the equivalence of soy-mSEB and E. coli-mSEB vaccinations. Antisera from either immunized group were able to block native SEB superantigen activity in an in vitro neutralization assay. Similar results were obtained when immunized animals were challenged with a sublethal dose of native toxin. Significant reductions in toxin-induced serum cytokine levels were observed in soy-mSEB- and E. coli-mSEB-immunized pigs compared to control animals. The reductions in SEB-induced cytokine responses were similar regardless of the immunogen used for vaccination. Surprisingly, however, some clinical symptoms, such as prostration, lethargy, emesis, and/or diarrhea, were still observed in all immunized animals. These studies demonstrate the potential for soybean-derived proteins as a platform technology for sustainable vaccine manufacturing and the usefulness of a sublethal challenge model in pigs for evaluating the efficacy of potential SEB vaccine candidates.

Neonatal phosphate nutrition alters in vivo and in vitro satellite cell activity in pigs.

Satellite cell activity is necessary for postnatal skeletal muscle growth. Severe phosphate (PO(4)) deficiency can alter satellite cell activity, however the role of neonatal PO(4) nutrition on satellite cell biology remains obscure. Twenty-one piglets (1 day of age, 1.8 ± 0.2 kg BW) were pair-fed liquid diets that were either PO(4) adequate (0.9% total P), supra-adequate (1.2% total P) in PO(4) requirement or deficient (0.7% total P) in PO(4) content for 12 days. Body weight was recorded daily and blood samples collected every 6 days. At day 12, pigs were orally dosed with BrdU and 12 h later, satellite cells were isolated. Satellite cells were also cultured in vitro for 7 days to determine if PO(4) nutrition alters their ability to proceed through their myogenic lineage. Dietary PO(4) deficiency resulted in reduced (P < 0.05) sera PO(4) and parathyroid hormone (PTH) concentrations, while supra-adequate dietary PO(4) improved (P < 0.05) feed conversion efficiency as compared to the PO(4) adequate group. In vivo satellite cell proliferation was reduced (P < 0.05) among the PO(4) deficient pigs, and these cells had altered in vitro expression of markers of myogenic progression. Further work to better understand early nutritional programming of satellite cells and the potential benefits of emphasizing early PO(4) nutrition for future lean growth potential is warranted.