Gene profiling in human periodontal ligament fibroblasts by subtractive hybridization

Non-bacterial protein expression in periodontal pockets by proteome analysis

OBJECTIVES

To compare the proteomic profile of inter-proximal pocket tissues with inter-proximal healthy tissues in the same subject to reveal proteins associated with periodontal disease in sites where periodontopathogenic bacteria were not detectable.

METHODS

Twenty-five healthy patients, with moderate-to-advanced chronic periodontitis and presenting with at least one intra-bony defect next to a healthy inter-proximal site were enrolled. The periodontal defects were treated with osseous resective surgery, and the flap design included both the periodontal pockets and the neighbouring inter-proximal healthy sites. Pocket-associated and healthy tissues were harvested for proteomic analyses.

RESULTS

Fifteen proteins were differently expressed between pathological and healthy tissues. In particular, annexin A2, actin cytoplasmic 1, carbonic anhydrase 1 & 2; Ig kappa chain C region (two spots) and flavinreductase were overexpressed, whereas 14-3-3 protein sigma and zeta/delta, heat-shock protein beta -1 (two spots), triosephosphateisomerase, peroxiredoxin-1, fatty acid-binding protein-epidermal, and galectin-7 were underexpressed in pathological tissue.

CONCLUSIONS

The unbalanced functional network of proteins involved could hinder adequate tissue response to pathogenic noxa. The study of periodontal pocket tissue proteomic profile would be crucial to better understand the pathogenesis of and the therapeutic strategies for periodontitis.

Identification of marker genes distinguishing human periodontal ligament cells from human mesenchymal stem cells and human gingival fibroblasts

BACKGROUND AND OBJECTIVE

Molecular gene markers, which can distinguish human bone marrow mesenchymal stem cells from human fibroblasts, have recently been reported. Messenger RNA levels of tissue factor pathway inhibitor-2, major histocompatibility complex-DR-alpha, major histocompatibility complex-DR-beta, and neuroserpin are higher in human bone marrow mesenchymal stem cells than in human fibroblasts. However, human bone marrow mesenchymal stem cells express less apolipoprotein D mRNA than human fibroblasts. Periodontal ligament cells are a heterogeneous cell population including fibroblasts, mesenchymal stem cells, and progenitor cells of osteoblasts or cementoblasts. The use of molecular markers that distinguish human bone marrow mesenchymal stem cells from human fibroblasts may provide insight into the characteristics of human periodontal ligament cells. In this study, we compared the molecular markers of human periodontal ligament cells with those of human bone marrow mesenchymal stem cells and human gingival fibroblasts.

MATERIAL AND METHODS

The mRNA expression of the molecular gene markers was analyzed using real-time polymerase chain reaction. Statistical differences were determined with the two-sided Mann-Whitney U-test.

RESULTS

Messenger RNA levels of major histocompatibility complex-DR-alpha and major histocompatibility complex-DR-beta were lower and higher, respectively, in human periodontal ligament cells than in human bone marrow mesenchymal stem cells or human gingival fibroblasts. Human periodontal ligament cells showed the lowest apolipoprotein D mRNA levels among the three types of cells.

CONCLUSION

Human periodontal ligament cells may be distinguished from human bone marrow mesenchymal stem cells and human gingival fibroblasts by the genes for apolipoprotein D, major histocompatibility complex-DR-alpha, and major histocompatibility complex-DR-beta.

Oligonucleotide array analysis of cyclic tension-responsive genes in human periodontal ligament fibroblasts

Mechanical stress results in differential gene expression that is critical to convert the stimulus into biochemical signals. Under physiological stress such as occlusal force, human periodontal ligament fibroblasts (HPLF) are associated with homeostasis of periodontal tissues however the changes in response to mechanotransduction remain uncharacterized. We hypothesized that cyclic tension-responsive (CT) genes may be used to identify a set of fundamental pathways of mechanotransduction. Our goal was to catalogue CT genes in cultured HPLF. HPLF were subjected to cyclic tension up to 16h, and total RNA was isolated from both tension-loaded and static HPLF. The oligonucleotide arrays analysis revealed significant changes of mRNA accumulation for 122 CT genes, and their kinetics were assigned by the K-means clustering methods. Ingenuity Pathway Analysis was completed for HPLF mechanotransduction using 50 CT genes. This analysis revealed that cyclic tension immediately down-regulated all nuclear transcription factors except v-fos FBJ murine osteosarcoma viral oncogene homolog (FOS) reacting as an early responsive gene. In turn, transcription factors such as tumor protein p53 binding protein 2 (TP53BP2), and extra-nuclear molecules such as adrenergic receptor beta2 (ADRB2) were up-regulated after 1-2h, which may result in fundamental HPLF functions to adapt to cyclic tension. Subsequent inhibition assays using Y27632, a pharmacologic inhibitor of Rho-associated kinase (ROCK), suggested that HPLF has both ROCK-dependent and ROCK-independent CT genes. Mechanical stress was found to effect the expression of numerous genes, in particular, expression of an early responsive gene; FOS initiates alteration of HPLF behaviors to control homeostasis of the periodontal ligament.

Dental follicle progenitor cell heterogeneity in the developing mouse periodontium

As a developmental precursor for diverse periodontal tissues, the dental follicle (DF) harbors great promise for periodontal tissue regeneration. However, development of optimal therapy awaits the answer to a key question that impinges on many issues in development-Do adult progenitor tissues form a homogeneous cell population that differentiates into target tissues when they arrive at the site, or they contain heterogeneous cell populations that are committed to specific fates? To address the homogeneity/heterogeneity question, we analyzed differentiation pathways and markers in several cloned DF cell lines. Our studies revealed that each of our cloned DF lines featured remarkably unique characteristics, indicative of a separate and distinct lineage. One line, DF1, was high in proliferative activity but did not display any mineralization behavior, suggesting that it might be related to a periodontal ligament-type lineage. DF2 was similar to DF1, but featured remarkably high alkaline phosphatase activity indicative of a highly undifferentiated state. DF3 matched the mineralization characteristics of a same stage alveolar bone line AB1 in terms of gene expression and von Kossa staining, indicating that DF3 might be of cementoblastic or alveolar bone osteoblastic lineage. To verify the multilineage potential of the DF for purposes of tissue engineering, a series of differentiation induction experiments was conducted. For identification purposes, characteristics of these heterogeneous follicular progenitor cells were compared with follicle components in tissue sections of the postnatal developing periodontium. The presence of heterogeneous cell populations in the DF mirrors individual developmental pathways in the formation of the dental integument. The profound cellular heterogeneity of the DF as an adult progenitor for tissue regeneration also suggests that heterogeneous cellular constituents might play as much of a role in tissue regeneration as the inducible characteristics of individual lineages might do.

Identification of genes preferentially expressed in periodontal ligament: Specific expression of a novel secreted protein, FDC-SP

Gene expression in human periodontal ligament (PDL) was examined by suppression subtractive hybridization to identify genes that are preferentially expressed in tissue compared to cultured PDL fibroblasts. The most enriched genes in a subtracted cDNA library are primarily genes for extracellular matrix components, types I and III collagen, lumican, periostin, and asporin, among others, whose expression conveys unique mechanical properties to the PDL. Also within this group is the gene for follicular dendritic cell secreted protein (FDC-SP), a small protein like statherin in saliva, not previously found in PDL. FDC-SP's presence in PDL was confirmed by in situ hybridization in mouse which also showed that it was definitely present in the parotid gland, but, surprisingly, not in the other salivary glands: submandibular and sublingual. Since only normal tissue was examined, these findings suggest that FDC-SP plays an important but previously unsuspected role within oral connective tissue.