Protective Effect of Vitamin D3 Combined with Calcium against Injury in a Caco-2 Cell Model of the Intestinal Barrier

To compare the protective effect of calcium alone and combined with VD3 on intestinal barrier damage, a Caco-2 cell model of intestinal barrier injury was established. Five groups were set up as follows: injury model, low, medium and high VD3 concentrations (1, 10 and 100 nmol/L) combined with calcium (1.8 mmol/L Ca2+), and calcium control. The repairing effect of calcium combined with VD3 on intestinal barrier damage was evaluated. The results demonstrated that the highest survival rate (104.2%) was observed in the low VD3 plus calcium group. After four days of culture, the trans-epithelial electrical resistance (TEER) of the calcium control group and the three combined treatment groups were 5.46, 4.44, 6.03, and 5.21 times higher than the baseline level, respectively, which were significantly increased when compared with those of the model group (P < 0.05). The apparent permeability coefficient (Papp) values of the calcium control group and the combined treatment groups (5.79 × 10-7, 7.20 × 10-7, 4.18 × 10-7 and 7.16 × 10-7 cm/s, respectively) and were all significantly lower when compared with the model group (P < 0.05); there was no significant difference in the morphology of intercellular tight junction proteins or the expression of cellular inflammatory factors between the medium VD3 + calcium group and the calcium control group. In summary, compared with Ca2+ alone, its combination with VD3 did not significantly enhance the repair of damaged intestinal barrier cells or attenuate the intestinal inflammatory response, and the regulatory network on the inflammatory response of intestinal epithelial cells needs to be further investigated. This study provides a theoretical basis for the application of calcium and vitamin D to maintain intestinal barrier function.