Effetti del chitosano su composti polifenolici in colture cellulari di vite: aspetti molecolari e metabolici

Polyphenols, including flavonoids and stilbenes, are an essential part of human diet and constitute one of the most abundant and ubiquitous group of plant secondary metabolites. The level of these compounds is inducible by stress or fungal attack, so attempts are being made to identify likely biotic and abiotic elicitors and to better understand the underlying mechanism. Resveratrol (3,5,4’-trihydroxystilbene), which belongs to the stilbene family, is a naturally occurring polyphenol, found in several fruits, vegetables and beverages including red wine. It is one of the most important plant polyphenols with proved benefic activity on animal health. In the last two decades, the potential protective effects of resveratrol against cardiovascular and neurodegenerative diseases, as well as the chemopreventive properties against cancer, have been largely investigated. The most important source of polyphenols and in particular resveratrol for human diet is grape (Vitis vinifera). Since stilbenes and flavonoids play a very important role in plant defence responses and enviromental interactions, and their effects on human health seem promising, the aim of the research of this Thesis was to study at different levels the activation and the regulation of their biosynthetic pathways after chitosan treatment. Moreover, the polyphenol production in grape cells and the optimisation of cultural conditions bioreactor scale-up, were also investigated. Cell suspensions were obtained from cv. Barbera (Vitis vinifera L.) petioles and were treated with a biotic elicitor, chitosan (50 μg/mL, dissolved in acetic acid) to promote phenylpropanoid metabolism. Chitosan is a D-glucosamine polymer from fungi cell wall and therefore mimes fungal pathogen attack. Liquid cultures have been monitored for 15 days, measuring cell number, cell viability, pH and grams of fresh weight. The endogenous and released amounts of 7 stilbenes (trans and cis isomers of resveratrol, piceid and resveratroloside, and piceatannol), gallic acid, 6 hydroxycinnamic acids (trans-cinnamic, p-coumaric, caffeic, ferulic, sinapic and chlorogenic acids), 5 catechines (catechin, epicatechin, epigallocatechin-gallate (EGCG), epigallocatechin and epicatechin-gallate) and other 5 flavonoids (chalcon, naringenin, kaempferol, quercetin and rutin) in cells and cultural medium, were measured by HPLC-DAD analysis and total anthocyanins were quantified by spectrophotometric analysis. Chitosan was effective in stimulating trans-resveratrol endogenous accumulation with a sharp peak at day 4 (exceeding acetic acid and water controls by 36% and 63%, respectively), while it did not influence the production of the cis-isomer. Compared to both water and acetic acid controls, chitosan decreased the release of both trans- and cis-resveratrol respect to controls. No effect was shown on the accumulation of single resveratrol mono-glucoside isomers, but considering their total amount, normalized for the relative water control, it was possible to evidence an increase in both accumulation and release of those compounds, in chitosan-treated cells, throughout the culture period and particularly during the second week. Many of the analysed flavonoids and hydroxycinnamic acids were not present or detectable in trace amounts. Catechin, epicatechin and epigallocatechin-gallate (EGCG) were detectable both inside the cells and in the culture media, but chitosan did not affect their amounts. On the contrary, total anthocyanins have been stimulated by chitosan and their level, from day 4 to 14, was about 2-fold higher than in both controls, confirming macroscopic observations that treated suspensions showed an intense brown-red color, from day 3 onwards. These elicitation results suggest that chitosan selectively up-regulates specific biosynthetic pathways, without modifying the general accumulation pattern of other flavonoids. Proteins have been extracted from cells at day 4 of culture (corresponding to the production peak of trans-resveratrol) and separated by bidimensional electrophoresis. The 73 proteins that showed a consistently changed amount between untreated, chitosan and acetic acid (chitosan solvent) treated cells, have been identified by mass spectrometry. Chitosan induced an increase in stilbene synthase (STS, the resveratrol biosynthetic enzyme), chalcone-flavanone isomerase (CHI, that switches the pathway from chalcones to flavones and anthocyanins), pathogenesis-related proteins 10 (PRs10, a large family of defence proteins), and a decrease in many proteins belonging to primary metabolisms. A train of six distinct spots of STS encoded by the same gene and increased by chitosan, was detected on the 2-D gels, and related to the different phosphorylation degree of STS spots. Northern blot analyses have been performed on RNA extracted from cells treated with chitosan and relative controls, using probes for STS, PAL (phenylalanine ammonia lyase, the first enzyme of the biosynthetic pathway), CHS (chalcone synthase, that shares with STS the same precursors), CHI and PR-10. The up-regulation of PAL, CHS and CHI transcript expression levels correlated with the accumulation of anthocyanins. The strong increase of different molecular weight PR-10 mRNAs, correlated with the 11 PR-10 protein spots identified in proteomic analyses. The sudden decrease in trans-resveratrol endogenous accumulation after day 4 of culture, could be simply explained by the diminished resveratrol biosynthetic activity due to the lower amount of biosynthetic enzymes. This might be indirectly demonstrated by northern blot expression analyses, that showed lower levels of phenylalanine ammonia lyase (PAL) and stilbene synthase (STS) mRNAs starting from day 4. Other possible explanations could be a resveratrol oxidation process and/or the formation of other different mono-, di-glucosides and resveratrol oligomers such as viniferins. Immunolocalisation experiments performed on grape protoplasts and the subsequent analyses by confocal microscope, showed that STS, and therefore the resveratrol synthetic site, is mostly associated to intracellular membranes close to the cytosolic side of plasma membrane and in a smaller amount is localized in the cytosol. STS seemed not to be present inside vacuole and nucleus. There were no differences in the STS intracellular localisation between the different treatments. Since it was shown that stilbenes are largely released in the culture medium and that STS is a soluble protein, a possible interaction of STS with a plasma membrane transporter responsible for the extrusion of stilbenes in the culture medium, might be hypothesized. Proteomic analyses performed on subcellular fractions identified in the microsomial fraction 5 proteins taking part in channel complexes or associated with channels, that significantly changed their amount after chitosan treatment. In soluble and membrane fractions respectively 3 and 4 STS and 6 and 3 PR-10 have been identified. Proteomic results obtained from subcellular fractions substantially confirmed previous result obtained from total cell protein extracts and added more information about protein localisation and co-localisation. The interesting results obtained on Barbera cell cultures with the aim to increase polyphenol (especially stilbenes) production, have encouraged scale up tests in 1 litre bioreactors. The first trial fermentation was performed in parallel with a normal time-course in 20 mL flasks, showing that the scale-up (bigger volume and different conditions) process influenced in a very relevant way stilbenes production. In order to optimise culture parameters such as medium sucrose amount, fermentation length and inoculum cell concentration, few other fermentations were performed. Chitosan treatments were also performed. The modification of each parameter brought relevant variations in stilbenes and catechins levels, so that the production of a certain compound (or class of compounds) could be hypothetically promoted by modulating one or more culture parameters. For example the catechin yield could be improved by increasing sucrose content and the time of fermentation. The best results in stilbene yield were obtained in a 800 mL fermentation inoculated with 10.8 grams of cells and supplemented with chitosan. The culture was fed with MS medium added with 30 g/L sucrose, 25 μg/mL rifampicin and 50 μg/mL of chitosan, and was maintained at 24°C, stirred by marine impeller at 100 rpm and supplied of air at 0.16 L/min rate. Resveratroloside was the stilbene present in the larger amount, 3-5 times more than resveratrol. Because resveratrol glucosides are similarly active and more stable than free resveratrol, their production using a bioreactor could be a great advantage in an hypothetical industrial process. In my bioreactor tests, stilbenes were mainly released in the culture medium (60-80% of the total) and this fact could be another advantage for industrial applications, because it allows recovering the products directly from the culture medium without stopping the fermentation and/or killing the cells. In my best cultural conditions, it was possible to obtain 3.95 mg/L of stilbenes at day 4 (maximum resveratrol accumulation) and 5.13 mg/L at day 14 (maximum resveratroloside production). In conclusion, chitosan effect in inducing Vitis vinifera defense mechanisms can be related to its ability to increase the intracellular content of a large spectrum of antioxidants, and in particular of resveratrol, its derivates and anthocyanins. Its effect can be observed at transcriptional, proteomic (variation of soluble and membrane protein amounts) and metabolic (polyphenols production) level. The chitosan ability to elicit specific plant matabolisms can be useful to produce large quantities of antioxidant compounds from cell culture in bioreactor.

Dietary strategies to minimize the detrimental impact of weaning on gut morphology, physiology and microbiota of piglets

Weaning is a crucial period in the management of piglets. In modern piggeries economic interest make weaning age decrease more and more and the detrimental consequences of weaning have as much importance as earlier the weaning occurs. The risk of development of post-weaning diarrhea (PWD) in piglets is high and PWD is the cause of serious economic losses in pig herds. In the past the supplementation of the feed given after weaning with growth promoters antibiotics, in order to keep PWD under control, used to be a common practice, but their usage has been banned in EU since 2006. This measure led to the investigation of alternative suitable feed supplements that would be reasonably efficient in protecting and sustaining animal health and performance. Aim of this thesis was to evaluate the effect of some different alternatives to growth-promoters antibiotics on weaning piglets and to assess if some of them could be considered as valuables options to replace auxinic in animal feeding. The study is composed by four experimental trials. The first one aims to identify mechanisms involved in the auxinic effects of antibiotics in the diets; the following three evaluate the addition butyric acid, tryptophan, and nitrate as alternative to in-feed antimicrobials. Although some results are controversial, it appears from the data presented that the alternatives to in-feed antibiotics considered may exert positive effects on some zootechnical and health parameters on piglet in the post-weaning period. Anyway, the mechanism of action and the interaction with microbiota of such additives should be investigated inside out because many effects remains poorly understood.

Mesenchymal Stromal Cells (MSCs) and induced Plutipotent Stem Cells (iPSCs) in Domestic Animals: Characterization and Differentiation Potential

Derivation of stem cell lines from domesticated animals has been of great interest as it benefits translational medicine, clinical applications to improve human and animal health and biotechnology. The main types of stem cells studied are Embryonic Stem Cells (ESCs), induced Pluripotent Stem Cells (iPSCs) and Mesenchymal Stem/Stromal Cells (MSCs). This thesis had two main aims: (I) The isolation of bovine MSCs from amniotic fluid (AF) at different trimesters of pregnancy and their characterization to study pluripotency markers expression. Stemness markers were studied also in MSCs isolated from equine AF, Wharton’s jelly (WJ) and umbilical cord blood (UCB) as continuation of the characterization of these cells previously performed by our research group; (II) The establishment and characterization of iPSCs lines in two attractive large animal models for biomedical and biotechnology research such as the bovine and the swine, and the differentiation into the myogenic lineage of porcine iPSCs. It was observed that foetal tissues in domestic animals such as the bovine and the horse represent a source of MSCs able to differentiate into the mesodermal lineage but they do not proliferate indefinitely and they lack the expression of many pluripotency markers, making them an interesting source of cells for regenerative medicine, but not the best candidate to elucidate pluripotency networks. The protocol used to induce pluripotency in bovine fibroblasts did not work, as well as the chemical induction of pluripotency in porcine fibroblasts, while the reprogramming protocol used for porcine iPSCs was successful and the line generated was amenable to being differentiated into the myogenic lineage, demonstrating that they could be addressed into a desired lineage by genetic modification and appropriated culture conditions. Only a few cell types have been differentiated from domestic animal iPSCs to date, so the development of a reliable directed-differentiation protocol represents a very important result.