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.

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.

Both Chitosan and PHBHHx are natural, biodegradable biomedical materials. In this article, their ability to be made as nerve regeneration conduits are evaluated by studying their wettability, changes of the second structure of protein absorbed on their surface, growing status of fetal rat cerebral cortex nerve cells cultured on them, mechanical properties and ability to be processed later. The results indicate that both Chitosan and PHBHHx are promising nerve conduit materials.
Animals ; Biocompatible Materials ; Carboxylic Acids ; Cell Adhesion ; Cells, Cultured ; Cerebral Cortex ; cytology ; Chitin ; analogs & derivatives ; Chitosan ; Female ; Hydroxybutyrates ; Nerve Regeneration ; physiology ; Polymers ; Pregnancy ; Rats ; Rats, Wistar ; Surface Properties