Investigation on the mechanisms for biocompatibility of chitosan using agarose/chitosan blended hydrogels as a model / 国际生物医学工程杂志

ObjectiveTo investigate the possible mechanisms for biocompatibility of chitosan material using agarose/chitosan blended hydrogels as a model.Methods A series of agarose/chitosan blended hydrogels with different chitosan content were prepared by the blending method.The chemical groups of the blended hydrogels were analyzed by the Fourier transform infrared (FTIR) spectroscopy.The blending compatibility between the agarose and chitosan was evaluated with the fluorescein-4-isothiocyanate (FITC) staining method.The charge of the blended hydrogels was determined by the zeta potential measurement.The adsorption of total fetal bovine serum (FBS) proteins and bovine serum albumin (BSA) on the blended hydrogels was measured by the bicinchoninic acid (BCA) method.The adsorption of fibronectin (FN) on the blended hydrogels was measured with ELISA.Cell culture experiment adopted human microvascular endothelial cell line (HMEC-1) as the model.The cytocompatibility was studied by evaluating adhesion,proliferation,and morphology of the cells on the blended hydrogels.Results Characteristic chemical groups of chitosan could be detected in the agarose/chitosan blended hydrogels.The chitosan had a good blending compatibility with the agarose.The amino groups of chitosan were uniformly distributed in the blended hydrogels.The blended hydrogels were strongly positively charged at acidic pH (pH 3.0),however,the zeta potentials of all the hydrogels were reduced to nearly 0 mV at neutral pH (pH 7.4).There were no significant differences in the adsorption of total FBS proteins and BSA between the blended hydrogel groups.However,the adsorption of FN on the hydrogels significantly increased with the increase of chitosan content.Cell culture experiment indicated that the cytocompatibihty of the blended hydrogels was significantly improved with the increase of chitosan content.The HMECs exhibited higher levels of adhesion,spreading,and proliferation on the hydrogels with higher chitosan content.ConclusionResults in this study indicated that the chitosan component preferentially adsorbed FN compared to the other serum proteins,leading to adhesion and spreading of the cells on the blended hydrogels.In contrast to prevailing views,it was found in the present study that the biocompatibility of chitosan did not relate to its positive charge.

Suppression of GSK3β by ERK mediates lipopolysaccharide induced cell migration in macrophage through β-catenin signaling

We investigate the role of β-catenin signaling in the response of macrophage to lipopolysaccharide (LPS) using RAW264.7 cells. LPS rapidly stimulated cytosolic β-catenin accumulation. β-catenin-mediated transcription was showed to be required for LPS induced gene expression and cell migration. Mechanically, ERK activation-primed GSK3β inactivation by Akt was demonstrated to mediate the LPS induced β-catenin accumulation. Overall, our findings suggest that suppression of GSK3β by ERK stimulates β-catenin signaling therefore contributes to LPS induced cell migration in macrophage activation.

Adipose derived mesenchymal stem cell transplantation for Alzheimer's disease / 中国组织工程研究

Alzheimer's disease is an irreversible neurodegenerative disease characterized by progressive neuronal loss. To date, there has been no effective medicine or therapy for neurodegenerative disease. With development of stem cell technique and theory, neural stem cell transplantation has been found to be prospective in Alzheimer's disease treatment. However, it was challenged by the deficiency of autologous neural stem cell, which can bypass immunological barrier. Compared with neural stem cells, mesenchymal stem cells exhibit extensive resources, such as liver, bone marrow and adipose, and multiple differentiations into bone, muscle or adipose. Considering the easy access, the minor trauma to the patients, and the neuron differentiation potential of adipose derived mesenchymal stem cells (A-MSC), we hypothesize that A-MSC graft is a potential and innovative strategy for the treatment of Alzheimer's disease.

Preparation and evaluation of porous poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) hydroxyapatite composite scaffolds.

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and PHBHHx-hydroxyapatite (HAP) composite scaffolds have been prepared by phase separation and subsequent sublimation of the solvent for bone tissue engineering. Scanning electron microscopy (SEM), porosity measurement, mechanical tests, and thermogravimertric analysis (TGA) are used to analyze the physical properties of the scaffolds. The biocompatibility and osteoconductivity are assessed by examining the morphology, proliferation, and differentiation of MC3T3-E1 osteoprogenitor cells seeded on the scaffolds. The PHBHHx-HAP composite scaffolds show better mechanical properties, biocompatibility, and osteoconductivity than the PHBHHx scaffolds. The results suggest that PHBHHx-HAP composite scaffolds can be employed as a promising candidate for bone reconstruction.

Mechanisms for biocompatibility of chitosan: A new viewpoint / 中国组织工程研究

OBJECTIVE:In recent years, chitosan has been widely used as tissue engineering scaffolds. In this paper we reviewed the research progress in chitosan biocompatibility and gave a hypothesison possible mechanism of interactions between cells and chitosan. A model system to test this hypothesis was also discussed. DATA SOURCES: Literatures about chitosan biocompatibility were retrieved with computer in Medline, Pubmed and Elsevier from January 1998 to December 2006 with the key words of."chitosan, biocompatibility, surface charge, cell adhesion" in English.STUDY SELECTION: Literatures about chitosan biocompatibility and interactions between chitosan and cells, especially the influence of chitosan charges on cell attachment, were included, whereas repeated experiments were excluded.DATA EXTRACTION: Totally 374 literatures were collected. Among which, 30 were admitted and reviewed.DATA SYNTHESIS: Many mammalian cells can adhere, spread and proliferate on chitosan materials. It is widely accepted that the biocompatibility of chitosan is due to the electrostatic attractive force between positively charged amino groups on chitosan chains and negatively charged cell membranes. However, the pKa value of chitosan amino groups is 6.2-6.8 and the positive charge of chitosan chains is largely decreased under physiological condition as a result of amino groups unprotonation. Thus whether the chitosan's biocompatibility is due to its positive charge remains doubtful and needs further study.CONCLUSION: Based on prior studies, we hypothesize that the positive charge of amino groups on chitosan chains might not be the major factor in biocompatibility of chitosan material. Agarose/chitosan blending hydrogels is supposed to be an appropriate model system to test this hypothesis.

Effects of the degree of deacetylation on the physicochemical properties and Schwann cell affinity of chitosan films.

Chitosan is a potential material for the preparation of nerve repair conduits. In order to find a better chitosan for the application in peripheral nerve regeneration, the effects of the degree of deacetylation (DD) on the physicochemical properties and Schwann cell affinity of chitosan films have been evaluated. Six kinds of chitosan samples with similar molecular weight, but various DD in a range from 70.1 to 95.6% were prepared from one stock chitosan material and fabricated into films. X-ray diffraction analysis showed that there were more crystalline regions in the higher DD chitosan films. Swelling and mechanical property measurements revealed that the swelling index of chitosan films decreased and their elastic modulus and tensile strength increased with the increase in DD. The adsorption amount of fibronectin and laminin on chitosan films was measured by means of enzyme-linked immunosorbent assay (ELISA). Culture of adult rat Schwann cells on the films showed that the chitosan films with higher DD provided better substrata for Schwann cell spreading and proliferation. In conclusion, DD of chitosan plays an important role in their physicochemical properties and affinity with Schwann cells. The results suggest that chitosan with a DD higher than 90% is considered as a promising material for application in peripheral nerve regeneration.

Surface modification and characterization of chitosan film blended with poly-L-lysine.

Biodegradable nerve guidance conduits (NGCs) represent a promising alternative to current clinical nerve repair procedures. Chitosan, a natural polysaccharide that has excellent biocompatibility and biodegradability, can be used as a nerve conduit material. The purpose of this work was to study the nerve cell affinity of chitosan modified by blending with different content of poly-L-lysine. PC12 cells culture was used to evaluate the nerve cell affinity of the chitosan-poly-L-lysine composite materials. The results showed that composite materials had significantly improved nerve cell affinity compared to chitosan as indicated by increased attachment, differentiation, and growth of nerve cells. The improved nerve cell affinity might be due to both the increased surface charge and hydrophilicity of composite materials. Composite material with 3 wt% poly-L-lysine content (PL-3) is an even better material in nerve cell affinity than collagen, suggesting that poly-L-lysine-blended chitosan is a promising candidate material for nerve regeneration.