本试验旨在研究铁、维生素A（VA）及其互作对哺乳仔猪肠道发育和细胞分化的影响。试验选用32头体重相近的0 d新生仔猪，随机分为4组，每组8个重复，每个重复1头猪；所有的小猪都是母乳喂养的；在此基础上，分别于第2、7、12、17 d给予仔猪生理盐水（CON组）、硫酸亚铁（OAFe组）、VA（VA组）或硫酸亚铁+ VA（OAFe + VA组）；于第21天屠宰，采集仔猪肠道样本。
结果表明，1）铁显著提高了小肠长度、重量、相对重量和长重比（P < 0.001）；另一方面，VA对小肠重长比（P = 0.015）和相对重量（P < 0.001）有显著影响。2）肠道形态方面，补铁（P <0.05）对肠绒毛高度（VH）、隐窝深度（CD）、绒毛宽度（VW）和表面积有显著影响；此外，VA、VA与铁的互作均可增加VH（P < 0.05）和表面积（P = 0.001）；铁提高了隐窝杯状细胞、ki67阳性细胞和内分泌细胞的数量（P < 0.01）；VA、VA与铁的互作均增加了绒毛内内分泌细胞数量（P = 0.05）。3）在干细胞分化标记基因mRNA表达水平方面，铁降低了滋养蛋白2（Trop2）、富亮氨酸重复序列含G蛋白偶联受体5阳性（Lgr5+）、异致死效应基因1（Msl1）、BMI 1原癌基因、多梳环指基因（Bmi1）和Ascl2基因的表达（P < 0.05）。另一方面，VA增加了Ascl2的表达（P = 0.001），尽管VA与铁的互作对分泌磷蛋白1（Spp1）和Bmi1的表达有影响（P < 0.05）。尽管铁、VA和铁的互作对这些基因的表达无影响，但VA降低了铁反应元件/铁调节蛋白（IRE/IRP）信号通路中乌头酸酶1（Aco1，P < 0.001）、转铁蛋白受体（TFRC，P = 0.001）和溶质载体家族11成员2（DMT1，P = 0.003）的mRNA表达。
Effects of iron, vitamin A, and the interaction between the two nutrients on intestinal development and cell differentiation in piglets
This study aimed to investigate the effects of iron, vitamin A (VA) and their interaction on intestinal development and differentiation of cells in suckling piglets. Therefore, 32 Duroc × Landrace × Yorkshire 0-d-old newborn boars with similar body weights were randomly divided into four groups, with eight replicates in each group and one pig in each replicate. All the piglets were breastfed. In addition, the piglets were given normal saline (CON group) or ferrous sulfate (OAFe group) or VA (VA group) or ferrous sulfate and VA (OAFe + VA group) on the 2nd, 7th, 12th, and 17th day, respectively. The piglets were then slaughtered on the 21st day, and intestinal samples were collected. The results showed that: 1) iron (P < 0.001) significantly increased the length, weight, relative weight, and the length to weight ratio of the small intestine. On the other hand, VA had a significant effect on the weight to length ratio (P = 0.015) and relative weight (P < 0.001) of the small intestine; 2) with regard to intestinal morphology, supplementation with iron (P <0.05) had obvious effects on the villus height (VH), crypt depth (CD), villus width (VW), and surface area. Additionally, both VA and interaction of VA and iron increased the VH (P < 0.05) and surface area (P = 0.001). The results also showed that iron (P < 0.01) increased the number of crypt goblet cells, Ki67-positive cells, and endocrine cells. Moreover, both VA and the interaction between VA and iron increased the number of endocrine cells in the villi (P = 0.05); 3) With regard to the mRNA expression levels of stem cell differentiation marker genes, iron (P < 0.05) decreased the expression of trophinin 2 (Trop2), leucine-rich repeat containing G protein-coupled receptor 5 positive (Lgr5+), male-specific lethal 1(Msl1), BMI 1 proto-oncogene, polycomb ring finger (Bmi1), and achaete-scute family bHLH transcription factor 2 (Ascl2). On the other hand, VA increased the expression of Ascl2 (P = 0.001) although the interaction of VA and iron (P < 0.05) had an effect on the expression of secreted phosphoprotein 1 (Spp1) and Bmi1. In addition, VA decreased the gene or mRNA expression of aconitase 1 (Aco1; P < 0.001), transferrin receptor (TFRC; P = 0.001), and solute carrier family 11 member 2 (DMT1; P = 0.003) in the Iron Reactive Element/Iron Regulatory Protein (IRE/IRP) signaling pathway although iron and the interaction of VA and iron had no effect on the genes’ expression. The results therefore showed that VA, iron, and their interaction can promote intestinal development and epithelial cell differentiation in piglets.