Study On Gene Expression Profile Of Astrocytes And Their Reactions To Injury

Astrocytes are one of the major cell types found in the central nervous system (CNS). They are important for maintaining the environment around neurons and abnormal changes in astrocyte behaviour cause problems for neuronal function. The latest studies suggest that, astrocytes not only nourish and protect neurons, but take part in senior activites of CNS.According to the theory of astrocyte lineages including T1A lineage and O-2A lineage, astrocytes contain two populations: type-1 astrocytes ( T1A ) and type-2 astrocytes ( T2A ). The former population is derived from T1A progenitor cells that express Ran-2 epitope, whereas the later population and oligodendrocytes ( OL ) derived from bipotential O-2A progenitor cells that express A2B5 epitope. Many research have revealed that there are differences in generation time, morphology and function between T1A and T2A. Our experiments have also found that the antigenic expressions of the cytoskeletal protein vimentin and calcium-binding protein S-1000 are differentially expressed during the differentiation process of T1A and T2A.Objectives (1).To establish the method of obtaining more pure O-2A lineage cells; (2).To compare the gene expression profile of T1A and T2A; (3) To observe the differential reactions of Tl A and T2A to mechanical injury.Methods (1) Based on the differential properties of cellular adhesions and developmental time-course, O-2A lineage cells were isolated at the onset of the layer of T1A with a standard shaking method and then purified with the differential adhesion method combining with using the serum-riched medium, resulted in obtaining purified T2A; (2) With the technique of gene chip, gene expression profile of purified Tl A and T2A was compared; (3) We establish mechanical injury model to mixed glial culture in serum-free medium to observe the differential reactions of Tl A and T2A.Results (1) The fully-differentiated T2A presented bigger soma, with lower reflection rate of light and a nucleolus can be seen. The soma extended many thinprocesses, from which even thinner processes extended. Identified by immunostaining with A2B5 and GFAP, both are positive. (2) The resuli of gene chip showed that 267 genes are differentially expressed in T1A and T2A, 113 of which are higher expressed in T1A, whereas 154 in T2A. (3) After mechanical injury, T1 A send hypertrophic processes into the wounded area and do not migrate individually, whereas O-2A progenitor cells at the onset migrate into the damaged area rapidly and change their differentiation way to T2A.Conclusions (1) A simple method of obtaining enough O-2A lineage cells have been established, and we have acquired enough T2A for further experiment. (2) Genes are differentially expressed in T1A and T2A, suggesting that some functions of these two types of astrocytes are different. (3) Tl A and T2A respond differentially to mechanical injury, suggesting that they play different roles in glial repair process after injury.