| Bone marrow stromal cells (BMSCs) are nonhematopoietic stem cells which can not only support and regulate hematopoietic function of bone marrow, express all kinds of cytokines for growth and development of organism, but also produce various kinds of tissue cells by artificial differentiation-inducing. Previous works found BMSCs could be induced into osteoblasts by adding dexamethasone etc. in culture medium, and some cytokines such as interleukin-1(IL-1), transforming growth factor β (TGF-β) were able to regulate osteotropic differentiation of BMSCs obviously. BMSCs could differentiate into neural cells in vitro, induced by brain derived neurotrophic factor (BDNF) and retinoic acid (RA); also differentiate into cardiomyocytes induced by 5-azacytidine. Along with further studying, applied research of BMSCs as tissue engineering derived cells needs the mechanism of cell differentiation regulation to be explained. So it is necessary from genic level to make the establishment of cell line for clinic use suitable for therapy purpose.Cell differentiation takes place under some correlated genes expressing differentially and mutual regulating strictly. In this process there are many gene expressions to be changed. For the moment, using Northern/Southern blot and DD-PCR, we can only study the expression level of single gene or several genes, and cannot entirely understand the expression level of gene cluster during cell differentiation. BMSC is one of experimental model for studying cell differentiation regulation in recent years. In this report, BMSCs are acquired from rat bone marrow and cultured in vitro. The cells are then incubated in the presence of dexamethasone, β-GP and vitamine C. To observe the growth and morphology changes of the cells in both common and inducing culture, compare one with the others. cDNA is reverse-transcribed from mRNA of the samples and hybridized with 1176 rat genes on the membrane of Atals? Rat 1.2 Array II (Clontech). The experimental data is processed and the gene expression profiles relating differentiation-inducing in ratBMSCs are then initially analyzed in pairs. From the results, try to find out their interaction relations.The experimental results suggest: (1) BMSCs were obtained and showed a strong ability of proliferation by using this method, and in the define medium were induced and differentiated to osteoblasts with dexamethasone, β-GP and vitamine C. Typical calcifying nodules were visible then. (2) cDNA microarray results show that many genes relating differentiation in rat BMSCs are promoted and expressed differentially under the inducement. In the 1176 genes, only 70 genes expressed differentially between P1 and primary (P0) cells, and 260 genes expressed differentially between Dl and P0, but the number of differential genes between Dl and P1 raised to 292. (3) The expression profiles results prove the genes that expressed differentially 3 times more than the normal are necessary genes relating rat BMSCs proliferation and osteotropic differentiation, which should include differentiation-control genes and differentiation-induced genes. Cell differentiation is a continuous developmental process. After the treatment of inducing factors, genes relating differentiation-induced are promoted firstly, then the promoted genes activate the differentiation-control genes, and finally accomplish the cell differentiation. (4) cDNA microarray technique can be used to research the mechanism of cell differentiation, and we can get useful bio-information about gene expression more efficiently and rapidly by using it. Also by multi-time point mensuration, we can more accurately analyze the space-time of every gene expression movement. Base on the function of known genes presently, we will make the interaction relations between some especial genes in the whole space-time of the genome expressions clearer with the help of changes of the expression profiles, and then select some new genes associated with physiology and pathology. Therefore, the application of cDNA microarray technique will help...
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