Calcification capacity of dental papilla mesenchymal cells transplanted in the isogenic mouse spleen

Establishment of Stable Cell Lines from Primary Human Dental Pulp Stem Cells

This protocol is for the isolation of primary human dental pulp stem cells (DPSCs) from adult extracted molars and for the generation of high-titer lentivirus for in vitro infection of the DPSCs. Stable cell lines of dental pulp stem cells are generated, maintained in culture, and used for subsequent experiments.

Isolation, culture and evaluation of multilineage-differentiating stress-enduring (Muse) cells

Multilineage-differentiating stress-enduring (Muse) cells are distinct stem cells in mesenchymal cell populations with the capacity to self-renew, to differentiate into cells representative of all three germ layers from a single cell, and to repair damaged tissues by spontaneous differentiation into tissue-specific cells without forming teratomas. We describe step-by-step procedures for isolating and evaluating these cells. Muse cells are also a practical cell source for human induced pluripotent stem (iPS) cells with markedly high generation efficiency. They can be collected as cells that are double positive for stage-specific embryonic antigen-3 (SSEA-3) and CD105 from commercially available mesenchymal cells, such as adult human bone marrow stromal cells and dermal fibroblasts, or from fresh adult human bone marrow samples. Under both spontaneous and induced differentiation conditions, they show triploblastic differentiation. It takes 4-6 h to collect and 2 weeks to confirm the differentiation and self-renewal capacity of Muse cells.

Dental pulp stem cells

Postnatal stem cells have been isolated from a variety of tissues. These stem cells are thought to possess great therapeutic potential for repairing damaged and/or defective tissues. Clinically, hematopoietic stem cells have been successfully used for decades in the treatment of various diseases and disorders. However, the therapeutic potential of other postnatal stem cell populations has yet to be realized, because of the lack of detailed understanding of their stem cell characteristics at the cellular and molecular levels. Furthermore, there is limited knowledge of their therapeutic value at the preclinical level. Therefore, it is necessary to develop optimal strategies and approaches to overcome the substantial challenges currently faced by researchers examining the clinical efficacy of different postnatal stem cell populations. In this review, we introduce methodologies for isolating postnatal stem cells from human dental pulp and discuss their potential role in tissue regeneration.

Immunolocalization of bone extracellular matrix proteins (type I collagen, osteonectin and bone sialoprotein) in human dental pulp and cultured pulp cells

AIM

To simultaneously analyse the expression of type I collagen, osteonectin and bone sialoprotein (BSP) in human dental pulp of different ages.

METHODOLOGY

Cultured dental pulp fibroblasts (FP1 cell line), pulps from dental germs with incomplete root formation (n = 4) and pulps of erupted teeth with total root formation (n = 4) were used. Bone proteins were searched by immunohistochemistry and immunofluorescence using polyclonal antibodies and compared among the three groups assessed.

RESULTS

Immunohistochemistry detected the three proteins in dental pulp tissue, as it labelled extracellular matrix, predentine and odontoblasts. The BSP label was weaker, when compared to both type I collagen and osteonectin. The presence of type I collagen was more evident in pulps from erupted teeth, when compared to germ dental pulps. On the other hand, a strong expression of osteonectin in germ dental pulps was observed.

CONCLUSIONS

Regardless of the degree of maturation, dental pulps present type I collagen, osteonectin and BSP in the extracellular matrix (ECM) and in the odontoblastic layer. Thus, the results suggest that these proteins are related to the production and mineralization of dentine.

Postnatal human dental pulp stem cells (DPSCs) in vitro and in vivo

Dentinal repair in the postnatal organism occurs through the activity of specialized cells, odontoblasts, that are thought to be maintained by an as yet undefined precursor population associated with pulp tissue. In this study, we isolated a clonogenic, rapidly proliferative population of cells from adult human dental pulp. These DPSCs were then compared with human bone marrow stromal cells (BMSCs), known precursors of osteoblasts. Although they share a similar immunophenotype in vitro, functional studies showed that DPSCs produced only sporadic, but densely calcified nodules, and did not form adipocytes, whereas BMSCs routinely calcified throughout the adherent cell layer with clusters of lipid-laden adipocytes. When DPSCs were transplanted into immunocompromised mice, they generated a dentin-like structure lined with human odontoblast-like cells that surrounded a pulp-like interstitial tissue. In contrast, BMSCs formed lamellar bone containing osteocytes and surface-lining osteoblasts, surrounding a fibrous vascular tissue with active hematopoiesis and adipocytes. This study isolates postnatal human DPSCs that have the ability to form a dentin/pulp-like complex.

Immortalization of bovine dental papilla cells with simian virus 40 large t antigen

Primary cultures of dental papilla-derived cells have a limited lifespan in vitro and can be maintained only up to passage 7-9 before showing senescence, but in vitro investigations often require a large number of cells showing phenotypic characteristics of the original tissue. To overcome this shortcoming, second-passage cells established from calf molar tooth germs by enzymatic pretreatment of the dental papilla were transfected by electroporation with pSV3neo, coding for the oncogene simian virus 40 large t antigen and a neomycin-resistance gene. Under selection by G418 (neomycin), four cell clones were isolated by single cell dilution at passage 15. Integration of simian virus 40 large t antigen and expression of the gene products were determined in cell clones by polymerase chain reaction (PCR) and immunohistochemistry. Four transfected cell lines (clones B, C, D and no. 12) were maintained in culture for over 1.5 years. For cell characterization, gene expression of procollagen alpha1 (I) and osteocalcin was evaluated by reverse transcriptase (RT)-PCR with cDNA obtained from the established cell lines at passage 20. Expression of collagen type I, osteocalcin and dentine phosphoprotein was evaluated immunohistochemically at passage 20 and after 1.5 years of continuous cell culture. Gene expression and the expression of mineralized tissue-specific proteins was demonstrated with RT-PCR and immunohistochemistry within all four immortalized cell lines. Expression of dentine phosphoprotein was observed in three simian virus 40 large t antigen-transfected cell lines, suggesting the immortalization of odontoblast-like cells in vitro. Thus, transfection of bovine dental papilla-derived cells resulted in immortal cell lines exhibiting phenotypic characteristics of the original tissue.

Mouse Meckel's cartilage chondrocytes evoke bone-like matrix and further transform into osteocyte-like cells in culture

BACKGROUND

We reported that when Meckel's cartilage was transplanted ectopically, chondrocytes transformed into osteocyte-like cells accompanying the extracellular calcified matrix. However, we could not determine whether the osteocyte-like cells were derived from host tissues or from Meckel's cartilage itself. Therefore, we examined whether the Meckel's cartilage chondrocytes, which have a retrogressive ultimate fate, are capable of inducing the observed calcification and further transform into osteocyte-like cells in culture.

METHODS

Meckelian chondrocytes isolated enzymatically were plated at a low density and grown in alpha-MEM containing 10% FBS at 37 degrees C under 5% CO2 in air for up to 4 weeks.

RESULTS

Chondrocytes were fibroblast-like cells early in culture, but gradually transformed from polygonal cells into typical chondrocytes showing metachromasia with toluidine blue staining. After an additional week of culture, the chondrocytes transformed from large to small round cells accompanying nodule formations. Small round cells multiple-layered actively, and showed more intense alkaline phosphatase (ALPase) activity. Immunostaining identified type II collagen in the extracellular matrix at 2 weeks of culture, and type I collagen and osteocalcin were later synthesized by round cells. von Kossa's reaction showed extensive precipitation of calcification throughout the flocculent materials. Ultrastructural analysis showed that the cells surrounded by calcified matrix strongly resembled osteocytes.

CONCLUSIONS

The present study suggested that the Meckel's cartilage chondrocytes can express the osteocyte-like phenotype in vitro during synthesis of bone-type marker proteins such as osteocalcin or type I collagen.

Pulpo-dentinal complex revisited

OBJECTIVES AND METHODS

The value of the concept of a pulpo-dentinal complex was assessed on human teeth treated according to the ISO test on biological evaluation. The teeth were extracted after 1 or 3 months and examined histologically. Biochemical and biological data available from the dental literature were also re-examined.

RESULTS

During the early development of the tooth, pulp and dentine establish close links and form an undivided organ. However, examination of the tissues at later stages of development casts doubt on the validity of such a concept. Major differences are reviewed in this report between the cells (odontoblasts and heterogeneous pulpal cells) and extracellular matrix (collagens, non-collagenic proteins and phospholipids) located either in the odontoblast-dentine area or in the pulp. It seems also that clear-cut differences are detected during inflammatory and repair processes.

CONCLUSION

It is concluded that, although the existence of a dentino-pulpal reaction cannot be denied, the concept of a pulpo-dentinal complex is an oversimplification and should be revisited. This may have implications in the evaluation of restorative treatments and in the design of a tissue repair strategy.

Mechanisms controlling secondary initiation of dentinogenesis: a review

Dentinogenesis can be initiated secondarily as an intrinsic ability of the dental pulp to repair, or after interaction of pulp cells with specific exogenous inductive factors. In the present article the basic developmental aspects, highlighting the mechanism by which dentinogenesis is initiated during tooth development, are discussed. Furthermore, clinical and experimental observations concerning the events taking place during secondary initiation of dentine formation, as part of exposed or non-exposed pulp tissue repair, or as a result of dentine matrix or other chemical-pulp cell interactions, are reviewed. Discussion includes hypotheses relating to the crucial biological steps leading to expression of odontoblastic-like cell phenotype and secondary initiation of dentine histogenesis.