Comparison of phenotype and differentiation marker gene expression profiles in human dental pulp and bone marrow mesenchymal stem cells

Abstract

Objective: Bone marrow (BM) is the most utilized and well-studied source of stem cells. Stem cells from dental tissues have provided an alternate source of mesenchymal stem cells (MSCs). Dental pulp stem cells (DPSCs) have been shown to share a similar pattern of protein expression with BMMSCs in vitro. However, differences have been noted between DPSCs and BMMSCs. This study focuses on variation in expression of stem cell and differentiation markers between DPSCs and BMMSCs.

Materials and methods: The two stem cells were isolated and compared for clonogenic potential, growth characteristics, multipotency, and stem cell marker expression. Specifically, the fatty acid binding protein 4, perilipin, alkaline phosphatase and osteonectic gene expression was analyzed by real-time polymerase chain reaction to confirm the capacity for adipogenic and osteogenic differentiation.

Results: MSCs from these cell sources were similar in their morphology and immune phenotype except for the expression of CD105. Growth curves and colony formation assay revealed proliferation rate of DPSCs was significantly faster than BMMSCs (P < 0.05). DPSCs appeared less able to differentiate into adipogenic lineage, although more able to differentiate into osteogenic lineage.

Conclusion: Data from the present study indicate how DPSCs are different from BMMSCs though they are a population of MSCs. DPSCs are a novel population of MSCs as observed by their unique expression of differentiation and lineage specific genes. Further microarray analysis could be used to determine, which genes are differentially regulated in BMMSCs and DPSCs to establish uniqueness of each population of MSCs.

Keywords: Bone marrow; comparative analysis; dental pulp; differentiation; mesenchymal stem cells.

Figure 1

Flow cytometry results of mesenchymal stem cells (MSC) markers CD29, CD90, CD105, CD34 and CD45. Both MSCs were positive for CD29, CD90 (>90%), and negative for the leukocyte common antigen CD45 and hematopoietic lineage marker CD34 (<5%). There is a significant difference in CD105 and CD 29 expression between bone marrow mesenchymal stem cells and dental pulp stem cells (P < 0.001). The purple area represents isotype control IgG expression and green lines depict the marker expression. The results are representative of four independent experiments. Data results correspond to ±standard deviation

Figure 2

The colony formation capacity and proliferation rates of human dental pulp stem cells (DPSCs) and human bone marrow mesenchymal stem cells (BMMSCs). Representative colonies with the fibroblast-like cells of BMMSCs (a) (×100) and DPSCs (b) (×100), which were visualized by Wright-Giemsa staining (indicated by arrows d and e). (c) Growth curves of BMMSCs and DPSCs at passage 3 are depicted in the graph and it was found that growth curves of DPSCs was higher than BMMSCs. Quantification of colonies after 14 days of culture, shows more number of CFU-F in DPSCs (f)

Figure 3

Results of osteogenic and adipogenic differentiation after 4 weeks in vitro Representative photomicrographs of cultured dental pulp stem cells (DPSCs) (a) and bone marrow mesenchymal stem cells (BMMSCs) (b) stained with alizarin red S. The photomicrographs were processed with the same contrast and brightness. Representative micrographs showing oil red-O stained lipid inclusions in cultured DPSCs (d) and BMMSCs (e). Quantitative analysis of alizarin red S and oil red-O stained areas (c and f) demonstrated that the osteogenic potential of DPSCs was stronger compared with that of BMMSCs, whereas the adipogenic potential was weaker than that of BMMSCs

Figure 4

Expression of adipogenic and osteogenic lineage markers. Bone marrow mesenchymal stem cells and dental pulp stem cells were maintained in induction or control medium for 28 days and then assayed for adipogenic and osteogenic specific mRNA levels. Adipogenic differentiation markers fatty acid binding protein 4 and perilipin, and osteogenic differentiation markers alkaline phosphatase and osteonectin were analyzed by real-time polymerase chain reaction