Comparison of the Expression of Periodontal Markers in Dental and Bone Marrow-derived Mesenchymal Stem Cells

Regulation of gingival fibroblast phenotype by periodontal ligament cells in vitro

Objectives

Stem cell transplantation has shown modest effects on periodontal tissue regeneration, and it is still unclear how regenerative effects utilizing this modality are mediated. A greater understanding of the basic interactions between implanted and host cells is needed to improve future strategies. The aims of this study were to investigate the effects of periodontal ligament (PDL) cells on expression of periodontal markers and alkaline phosphatase (ALP) activity of gingival fibroblasts (GF).

Materials and Methods

Primary human PDL cells were co‐cultured with primary GF cultures either by direct co‐culture with subsequent FACS sorting or indirect co‐culture using transwell cultures and PDL cell conditioned medium. Expression of periodontal markers, asporin, nestin, and periostin, was assessed by qPCR and immunofluorescence staining. Alkaline phosphatase (ALP) expression was assessed by qPCR, histochemical staining, and activity assessed by para‐nitrophenol enzymatic assay. Single cultures of PDL cells and GF were used as controls. The role of Wnt signaling on ALP activity was assessed via Dkk1‐mediated inhibition.

Results

PDL cells significantly upregulated expression of PDL markers in GF with both direct and indirect co‐culture methods when compared to controls (6.05 vs. 0.73 and 59.48 vs. 17.55 fold change of asporin expression). PDL/GF cell co‐cultures significantly increased ALP activity in GF when compared with single GF cultures. Similar results were obtained when using conditioned medium isolated from PDL cell cultures. Dkk1 caused dose‐dependent reduction in ALP activity of GF cultured in PDL cell conditioned medium.

Conclusions

PDL cells stimulate expression of periodontal markers and osteogenic capacity of gingival fibroblasts via paracrine signaling which can be partially inhibited with addition of the Wnt antagonist, Dkk1.Further studies are required to identify specific secreted factors responsible for this activity.

Mineral trioxide aggregate immersed in sodium hypochlorite reduce the osteoblastic differentiation of human periodontal ligament stem cells

White mineral trioxide aggregate (WMTA) is a root canal treatment material, which is known to exhibit a dark brown color when in contact with sodium hypochlorite solution (NaOCl). This study aimed to investigate the effects of NaOCl on the surface properties of WMTA discs and WMTA-induced osteoblastic differentiation of periodontal ligament stem cells (PDLSCs). Mixed WMTA (ProRoot MTA) was filled into the molds to form WMTA discs. These discs were immersed in distilled water (D-WMTA) or 5% NaOCl (Na-WMTA). Their surface structures and Ca²⁺ release level was investigated. Moreover, they were cultured with a clonal human PDLSC line (line 1–17 cells). The main crystal structures of Na-WMTA were identical to the structures of D-WMTA. Globular aggregates with polygonal and needle-like crystals were found on D-WMTA and Na-WMTA, which included Ca, Si, Al, C and O. However, many amorphous structures were also identified on Na-WMTA. These structures consisted of Na and Cl, but did not include Ca. NaOCl immersion also reduced Ca²⁺ release level from whole WMTA discs. Line 1–17 cells cultured with D-WMTA formed many mineralized nodules and exhibited high expression levels of osteoblast-related genes. However, cells incubated with Na-WMTA generated a small number of nodules and showed low expression levels of osteoblast-related genes. These results indicated that NaOCl reduced Ca²⁺ release from WMTA by generating amorphous structures and changing its elemental distribution. NaOCl may also partially abolish the ability of WMTA to stimulate osteoblastic differentiation of PDLSCs.

Bioinformatics Analysis Identified miR-584-5p and Key miRNA-mRNA Networks Involved in the Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

Human periodontal ligament cells (PDLCs) play an important role in periodontal tissue stabilization and function. In the process of osteogenic differentiation of PDLSCs, the regulation of molecular signal pathways are complicated. In this study, the sequencing results of three datasets on GEO were used to comprehensively analyze the miRNA-mRNA network during the osteogenic differentiation of PDLSCs. Using the GSE99958 and GSE159507, a total of 114 common differentially expressed genes (DEGs) were identified, including 62 up-regulated genes and 52 down-regulated genes. GO enrichment analysis was performed. The up-regulated 10 hub genes and down-regulated 10 hub genes were screened out by protein-protein interaction network (PPI) analysis and STRING in Cytoscape. Similarly, differentially expressed miRNAs (DEMs) were selected by limma package from GSE159508. Then, using the miRwalk website, we further selected 11 miRNAs from 16 DEMs that may have a negative regulatory relationship with hub genes. In vitro RT-PCR verification revealed that nine DEMs and 18 hub genes showed the same trend as the RNA-seq results during the osteogenic differentiation of PDLSCs. Finally, using miR-584-5p inhibitor and mimics, it was found that miR-584-5p negatively regulates the osteogenic differentiation of PDLSCs in vitro. In summary, the present results found several potential osteogenic-related genes and identified candidate miRNA-mRNA networks for the further study of osteogenic differentiation of PDLSCs.