Generation of bone grafts using cryopreserved mesenchymal stromal cells and macroporous collagen-nanohydroxyapatite cryogels.

Bone tissue engineering strategy involves the 3D scaffolds and appropriate cell types promoting the replacement of the damaged area. In this work, we aimed to develop a fast and reliable clinically relevant protocol for engineering viable bone grafts, using cryopreserved adipose tissue-derived mesenchymal stromal cells (MSCs) and composite 3D collagen-nano-hydroxyapatite (nanoHA) scaffolds. Xeno- and DMSO-free cryopreserved MSCs were perfusion-seeded into the biomimetic collagen/nanoHA scaffolds manufactured by cryotropic gelation and their osteoregenerative potential was assessed in vitro and in vivo. Cryopreserved MSCs retained the ability to homogenously repopulate the whole volume of the scaffolds during 7 days of post-thaw culture. Moreover, the scaffold provided a suitable microenvironment for induced osteogenic differentiation of cells, confirmed by alkaline phosphatase activity and mineralization. Implantation of collagen-nanoHA cryogels with cryopreserved MSCs accelerated woven bone tissue formation, maturation of bone trabeculae, and vascularization of femur defects in immunosuppressed rats compared to cell-free collagen-nanoHA scaffolds. The established combination of xeno-free cell culture and cryopreservation techniques together with an appropriate scaffold design and cell repopulation approach accelerated the generation of viable bone grafts.

Physical Processes in Polymeric Filters Used for Dialysis.

The key physical processes in polymeric filters used for the blood purification include transport across the capillary wall and the interaction of blood cells with the polymer membrane surface. Theoretical modeling of membrane transport is an important tool which provides researchers with a quantification of the complex phenomena involved in dialysis. In the paper, we present a dense review of the most successful theoretical approaches to the description of transport across the polymeric membrane wall as well as the cell⁻polymer surface interaction, and refer to the corresponding experimental methods while studying these phenomena in dialyzing filters.

Investigation of mechanisms involved in postprandial glycemia and insulinemia attenuation with dietary fibre consumption.

This work examines the mechanisms involved in the attenuation of postprandial glycemic and insulinemic responses associated with soluble dietary fibre (SDF) consumption. The effect of SDF, including yellow mustard mucilage, soluble flaxseed gum and fenugreek gum on in vitro amylolysis and maltose transport was studied. Furthermore, a human clinical trial was conducted to investigate the effect of SDF consumption on postprandial glycemic and insulinemic responses and gastric emptying, as estimated based on the absorption of paracetamol. Participants (n = 15) at risk for type II diabetes consumed maltose syrup- and starch-based pudding treatments supplemented with each SDF, each at a concentration to match three times the apparent viscosity (18.54 mPa s at 60 s-1) equivalent to the European Food Safety Authority (2011) glycemia control health claim for cereal ß-glucan, measured under simulated small intestinal conditions. The presence of each SDF delayed in vitro amylolysis to a similar extent, but had no effect on maltose transport. Generally, all SDF-containing treatments attenuated blood glucose and plasma insulin peak concentrations and plasma paracetamol 1 h incremental area under the curve values to a similar extent, relative to the controls, despite differences in the amounts at which each SDF was used (from 5.9 to 15.5 g). The postprandial attenuations were related to the ability of each SDF to modify digesta viscosity, perhaps through the delay of gastric emptying, as a delay of amylolysis and sugar transport under simulated upper intestinal conditions did not seem to have a substantial effect.

Shape of red blood cells in contact with artificial surfaces.

The phenomenon of physical contact between red blood cells and artificial surfaces is considered. A fully three-dimensional mathematical model of a bilayer membrane in contact with an artificial surface is presented. Numerical results for the different geometries and adhesion intensities are found to be in agreement with experimentally observed geometries obtained by means of digital holographic microscopy.

Application of cryoirradiation-modified xenopericardium for building bladder wall defect.

INTRODUCTION: The project goal was to study special aspects of biointegration and the functional efficiency of the modified xenopericardium on the experimental model in vivo. Xenopericardium devitalization was performed using low temperatures and ionizing radiation (ß--radiation) in an original manner. METHODS: In rabbits, a urinary bladder (UB) wall defect was repaired through tissue replacement. Observation period: up to 1 year. After implantation, tissue reaction and biomaterial structure changes were studied using light and electron microscopy. Dynamic ultrasound diagnostics were performed. RESULTS: After surgery all animals displayed normal physiological activity. No cases of material rejection or postoperative period complications were detected. At all stages the xenopericardium preserved structural integrity and served as a skeleton for forming an adequate UB wall. Small peripheral areas were exposed to lysis. After 3 months the collagen structure of the graft was rearranged and mucous membrane epithelization appeared. Folding was already formed and invasion of narrow SMC panniculi was registered within deeper layers. After 6 months the inner surface of the UB wall consisted of normal mucosa, lined by fully formed epithelium. By the 7th month an almost solid muscular sheet was formed in the lower layers. CONCLUSIONS: Modified pericardium tissue with the given physical and mechanical properties was sustainable and able to endure the work load in an aggressive environment. It causes minimal inflammatory response, has a potential for cellular repopulation in vivo, stimulates formation of fibrous tissue, and embedded and restored cellular integrity and UB storage function.

Phase behaviour of casein micelles and barley beta-glucan polymer molecules in dietary fibre-enriched dairy systems.

Enrichment of colloidal dairy systems with dietary fibre frequently causes quality defects because of phase separation. We investigate phase separation in skimmed milk enriched with Glucagel (a commercial product made from barley that is predominantly comprised of the polysaccharide ß-glucan). The driving force for phase separation was depletion flocculation of casein micelles in the presence of molecules of the polysaccharide. Depending on the volume fraction of casein micelles and the concentration of Glucagel, the stable system phase separated either as a transient gel or as a sedimented system. The rate at which phase separation progressed also depended on the volume fraction of casein micelles and the concentration of Glucagel. To confirm the role of depletion flocculation in the phase separation process, enzymatic reduction in the molecular weight of ß-glucan was shown to limit the range of attraction between micelles and allow the stable phase to exist at a higher ß-glucan concentration for any given volume fraction of casein micelles. These phase diagrams will be useful to dairy product manufacturers striving to improve the nutrient profile of their products while avoiding product quality impairment.

Thermally induced transformation of mammalian red blood cells during hyperthermia.

The structural and transport characteristics of membranes are mainly determined by the state of the cytoskeleton. The characteristic changes in morphology of human (adult donor and cord) and rat Red Blood Cells (RBC) and of their membrane, induced by hyperthermia (46-51 degrees C) have been analyzed. Two different types of morphological changes have been observed to take place during hyperthermia in all studied RBC groups. We have observed either formation and exfoliation of spiculas from membrane, resulting in the formation of large (4-5 microm) sphere-like cell body and small (0.5-1.5 microm) vesicles or cell fragmentation with formation of large (3-3.5 microm) vesicles. The two distinct phenomena are likely to be determined by the heterogeneity of the RBC population in terms of cell age. There was noted the difference of cord RBC from the donor ones in temperature value of transformation beginning, as well as the character of deformation and vesicle formation, that may testify to their less thermoresistance. The ultrastructure of the membrane, studied with the freeze-fracturing technique, testifies to an irreversible character of membrane changes. The aggregation of intramembrane particles (IMPs) as a continuous network testifies to the strengthening of the interactions between denatured spectrin and bilayer integral components.

Peculiarities of RBCs resistance to acid hemolysis in hibernating mammals.

The binding of acids and alkalis, formed in tissues by metabolism, along with oxygen and CO(2) transport are recognise as the principal functions of red blood cells (RBCs). Decreases in internal environment pH may result in activation of potential endogenous cytotoxic metabolites, OH and oxidant formation and, as a consequence, result in oxidative damage of cell membrane leading to hemolysis. The characteristics of acid hemolysis in hibernating mammals have been determined in this study. Parameters of HCl-hemolysis, such as the average time for RBC hemolysis and the population distribution of the response, have been investigated. Measurements were performed within 40-5 degrees C temperature range. The resistance of hibernator RBCs to increased acidity, determined according to the acid hemolysis parameters, was found to reflect whether the animal was in the summer active period or in hibernation, with differences also apparent at different points with the hibernation season itself. It was demonstrated that hemolysis parameters of naturally cold-tolerant organisms are altered by decreases in temperature. We discuss a role of cytoskeletal-membrane interactions as a fast-acting switch of the structural and functional state of hibernator RBCs as an adaptation mechanism to acidosis arising from hypothermia and hypermetabolism.