Analyse der Genexpression von humanen Stro-1-positiven Zahnkeim- und Beckenkammzellen in DME-Medium und osteogenem Differenzierungsmedium
Analysis of gene expression of human Stro-1 positive cells from dental pulp and iliac crest bone in DME medium and osteogenic differentiation medium
by Charlotte Caroline Merten
Date of Examination:2020-08-25
Date of issue:2020-08-18
Advisor:Prof. Dr. Dr. Karl Günter Wiese
Referee:Prof. Dr. Dr. Karl Günter Wiese
Referee:Prof. Dr. Tim Beißbarth
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Abstract
English
Because of the ethically controversial use of embryonic stem cells in tissue engineering there has been an increased interest in mesenchymal stem cells, which can be found in various adult tissues. The present study concentrates on a specific Stro-1 positive population of mesenchymal stem cells found in human dental pulp (Stro-1+ZK) and bone marrow (Stro-1+BK). The aim was to determine the impact of the cell culture medium used on the gene expression profile of both stem cell types. Therefore, the isolated Stro-1+ZK and Stro-1+BK were cultivated on the one hand in Dulbecco’s Modified Eagle’s medium (DMEM) and on the other hand in an osteogenic differentiation medium (ODM). The subsequent microarray analysis included 22.454 registered genes. Highly significant differential gene expression was detected using a threshold with an FDR ≤ 1%. With the change from DMEM in ODM there was a significant differential expression of 624 genes for Stro-1+BK and 437 genes for Stro-1+ZK, with more genes upregulated in ODM for Stro-1+BK. This suggests a stronger stimulus of ODM on the gene expression profile of Stro-1+BK. By using the software “DAVID” these differential expressed genes were linked to their biological pathways. Both stem cell types showed an overrepresentation of processes associated with wound healing and inflammation in ODM versus DMEM. There were four identical genes among the ten most significant upregulated genes in ODM for Stro-1+ZK and Stro-1+BK, namely SAA1, BMP6, FKBP5 and MAOA. The direct comparison of both stem cell types in ODM (FDR ≤ 1%) detected 375 genes with significant differential expression. The 109 genes upregulated for Stro-1+ZK were mainly related to functions such as extracellular matrix organization and epithelium development, whereas Stro-1+BK revealed an enhanced expression of genes associated with skeletal system development and angiogenesis. Furthermore, the Stro-1+ZK showed specific expression patterns with regard to genes that are important for tooth development. In addition to an increased expression of the Hox genes MSX1, DLX1, SIX1 and PAX9, the genes FOX1, FOX2, GREM1, PTN and FST were upregulated. These genes play some important key roles in odontogenesis, as known mutations result in defects of dental hard tissue or aplasia of teeth. In conclusion, the present study was able to detect significant differences in the gene expression profile of Stro-1+ZK and Stro-1+BK when cultivated either in DMEM or ODM. Further studies may be needed to identify the importance of the cell culture medium used on gene expression to establish favorable culture conditions for tissue engineering.
Keywords: mesenchymal stem cells; dental pulp stem cells; Stro-1; gene expression