In vitro dynamic model simulating the digestive tract of 6-month-old infants.

BACKGROUND: In vivo assays cannot always be conducted because of ethical reasons, technical constraints or costs, but a better understanding of the digestive process, especially in infants, could be of great help in preventing food-related pathologies and in developing new formulas with health benefits. In this context, in vitro dynamic systems to simulate human digestion and, in particular, infant digestion could become increasingly valuable. OBJECTIVE: To simulate the digestive process through the use of a dynamic model of the infant gastroenteric apparatus to study the digestibility of starch-based infant foods. DESIGN: Using M.I.D.A (Model of an Infant Digestive Apparatus), the oral, gastric and intestinal digestibility of two starch-based products were measured: 1) rice starch mixed with distilled water and treated using two different sterilization methods (the classical method with a holding temperature of 121°C for 37 min and the HTST method with a holding temperature of 137°C for 70 sec) and 2) a rice cream with (premium product) or without (basic product) an aliquot of rice flour fermented by Lactobacillus paracasei CBA L74. After the digestion the foods were analyzed for the starch concentration, the amount of D-glucose released and the percentage of hydrolyzed starch. RESULTS: An in vitro dynamic system, which was referred to as M.I.D.A., was obtained. Using this system, the starch digestion occurred only during the oral and intestinal phase, as expected. The D-glucose released during the intestinal phase was different between the classical and HTST methods (0.795 grams for the HTST versus 0.512 for the classical product). The same analysis was performed for the basic and premium products. In this case, the premium product had a significant difference in terms of the starch hydrolysis percentage during the entire process. CONCLUSIONS: The M.I.D.A. system was able to digest simple starches and a more complex food in the correct compartments. In this study, better digestibility of the premium product was revealed.

Molecular evidence for a thymus-independent partial T cell development in a FOXN1-/- athymic human fetus.

The thymus is the primary organ able to support T cell ontogeny, abrogated in FOXN1(-/-) human athymia. Although evidence indicates that in animal models T lymphocytes may differentiate at extrathymic sites, whether this process is really thymus-independent has still to be clarified. In an athymic FOXN1(-/-) fetus, in which we previously described a total blockage of CD4(+) and partial blockage of CD8(+) cell development, we investigated whether intestine could play a role as extrathymic site of T-lymphopoiesis in humans. We document the presence of few extrathymically developed T lymphocytes and the presence in the intestine of CD3(+) and CD8(+), but not of CD4(+) cells, a few of them exhibiting a CD45RA(+) naïve phenotype. The expression of CD3εεpTα, RAG1 and RAG2 transcripts in the intestine and TCR gene rearrangement was also documented, thus indicating that in humans the partial T cell ontogeny occurring at extrathymic sites is a thymus- and FOXN1-independent process.

T300A variant of autophagy ATG16L1 gene is associated with decreased antigen sampling and processing by dendritic cells in pediatric Crohn's disease.

BACKGROUND: The single-nucleotide polymorphism T300A of ATG16L1, a Crohn's disease (CD)-associated gene, is responsible for decreased autophagy. This study aimed to investigate the effects of this single-nucleotide polymorphism on the uptake and processing of antigens by dendritic cells (DCs) and the interaction between DC and intestinal epithelium in pediatric patients with CD. METHODS: Pediatric patients who homozygously carry either the protective (wild type, n = 7) or risk allele (risk, n = 13) of ATG16L1, as well as heterozygous patients (het, n = 13) were enrolled. The monocyte-derived DC were analyzed for phenotype, antigen sampling, and processing by flow cytometry, whereas the capability of DC to form transepithelial protrusions was determined by confocal microscopy. RESULTS: DC generated from wild type patients showed higher bacteria sampling and antigen processing compared with risk patients. Additionally, after exposure to either bacteria particles or the antigen DQ-ovalbumin, wild type DC showed a significant increase in the expression of the HLA-DR and CD86 when compared with risk DC. Interestingly, also het patients showed an impairment in bacteria uptake and expression of activation marker when compared with the wild type. In the Caco2/DC coculture, the formation of transepithelial protrusions were less numerous in risk DC compared with wild type and the antigen uptake decreased. CONCLUSIONS: DC of pediatric patients with CD carrying the T300A allele showed a marked impairment of antigen uptake and processing and defective interactions between DC and intestinal epithelium. Collectively, our results suggest that an autophagy defect is associated with an impairment of intestinal innate immunity in pediatric CD.

Humoral immune response to tissue transglutaminase is related to epithelial cell proliferation in celiac disease.

BACKGROUND & AIMS: Tissue transglutaminase (tTG) autoantibodies are markers of celiac disease, and the enzyme is required for several crucial biological processes. The aim of this study was to determine whether these autoantibodies are involved in the pathogenesis of the mucosal lesion typical of celiac disease. METHODS: Using rhodamine-conjugated phalloidin staining, we evaluated whether tTG antibodies, both commercially available and cloned from patients with celiac disease, cause cytoskeletal changes in Caco-2, MCF7, and NIH 3T3 cells. We monitored cell levels of bromodeoxyuridine incorporation to determine whether tTG autoantibodies are able to induce NIH 3T3 fibroblasts and epithelial mucosal cells into S phase. RESULTS: Treatment with tTG antibodies caused a dose-dependent increase of membrane ruffling in Caco-2, MCF7, and NIH 3T3 cells. It also dose-dependently induced G(0)-synchronized NIH 3T3 fibroblasts into S phase but did not affect the rate of apoptosis. Similarly, tTG antibodies induced S-phase entry of epithelial cells in cultured intestinal biopsy specimens from patients with celiac disease. They did not affect biopsy specimens from patients without celiac disease. CONCLUSIONS: Our results suggest that tTG autoantibodies per se, by interacting with the extracellular membrane-bound transglutaminase, may play an important role in epithelial cell proliferation in celiac disease.