DENTAL STEM CELLS: MIRACLE CELLS OF DENTISTRY

By: Dr. Abhishek kr. Pandey, Medical Correspondent-ICN

Stem cells are the unique cells that have the potential to develop into different type of cells in the body. These are undifferentiated cells that can differentiate into specialized cells and can divide (through Mitosis) to produce more stem cells. They are found in multicellular organisms .

Stem cells have been isolated from many tissues and organs, including dental tissue. The tooth is a nature’s safe place for these precious stem cells and there are loads of these cells in wisdom teeth, permanent teeth and deciduous teeth. The stem cells contained within teeth are capable of reproducing themselves and can be voluntarily recovered at the time of an intended dental procedure. When stem cells divide, each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function, such as muscle cell, a red blood cell or a brain cell.

INTRODUCTION

Stem cells are biological cells that possess two properties: self-renewal, i.e. the ability to go through unlimited cycles of cell division for the purpose of replenishing the cell pool, and potency, i.e. the capacity to differentiate into other cell types .Stem cells are defined as clonogenic cells capable of both self-renewal and multilineage differentiation .. In mammals, there are 2 broad types of cells-Embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and adult stem cells which are found in various adult tissues including skin, adipose tissues, peripheral blood, bone marrow, pancreas, intestine, brain, hair follicles, as well as in the dental pulp cells. Dental stem cells can differentiate into odontoblasts, adipocytes, neuronal like cells, glial cells, osteoblasts, chondrocytes, melanocytes, myotubes and endothelial cells.

CHARECTERSTICS OF STEM CELLAccording to the ability and potency to differentiate into different cellular types, 4 types of Stem cells have been established-

TOTIPOTENCYProduce all types of cells as well as germ cells.

PLURIPOTENCY-Produce all types of cells apart from cells apart from cells of the embryonic membrane.

MULTIPOTENCY-Distinguish into more than one adult cell.

UNIPOTENCY-Produce one particular cell type.

Stem cells are distinguished from other cell types by two important characteristics. First, they are unspecialized cells capable of renewing themselves through cell division, sometimes after long periods of inactivity. Second, under certain physiologic or experimental conditions, they can be induced to become tissue-or organ-specific cells with special functions.

At present, teeth can only be replaced with prosthesis i.e. removable, fixed or implants with prior bone augmentation if necessary. Stem cell biology and tissue engineering may present new options for replacing damaged or lost tooth.

DENTAL STEM CELLS The finding of stem cells in natal teeth, supernumerary teeth and odontoma reinforces the concept that stem cells play a key role in the formation of every tooth. Two main cell types are involved in dental tissue formation: the ameloblasts, of epithelial origin, that form enamel and the odontoblasts of mesenchymal origin, that are responsible for dentin production. Uses of stem cells in dentistry are to regenerate the dental hard and soft tissues i.e. enamel, dentin, pulp and periodontal tissues.

Advantages of dental stem cellThe advantages of dental stem cells are that:

1.) These cells have high plasticity.

2).Dental stem cells are ideal for stem cell banking as they can be preserved for a longer period.

3).These cells have shown a favorable response with scaffold and growth factors.

SOURCES OF DENTAL STEM CELLS- According to the position of mesenchymal stem cells in the tooth, they can be grouped as:

1).DPSC- Dental pulp stem cells.

2).SHED-Stem cells from exfoliated deciduous teeth.

3).SCAP-Stem cells from apical papilla.

4).PDLSC-Periodontal ligament stem cells.

5).DFPC-Dental follicle progenitor cells.

ABMSCs: alveolar bone-derived mesenchymal stem cells; DFPCs: dental follicle progenitor cells; DPSCs: dental pulp stem cells; GMSCs: gingival mesenchymal stem cells; PDLSCs: periodontal ligament stem cells; SCAP: stem cells from the apical part of the human dental papilla;

SHED: stem cells from human exfoliated deciduous teeth; TGPCs:tooth germ progenitor cells.

Dental Pulp Stem Cells (DPSC)- The presence of stem cells in dental pulp was proposed by Fitzgerald et al. Dental pulp tissue is extracted from the teeth recovered during routine dental procedure throughout the life and these teeth are the most convenient and valuable source of DPSC. These cells are the most attractive cells for periodontal tissue engineering based on their good growth and differentiation capacity. Dental pulp stem cells can be found both in adults and children. As DPSCs have comparable therapeutic potential similar to BMMSCs, DPSCs is another alternative noninvasive source to be used for future regenerative therapies.

STEM CELLS FROM EXFOLIATED DECIDUOUS TEETH (SHED)-

Dental pulp from deciduous (baby) teeth, which are discarded after exfoliation, represents an advantageous source of young stem cells. SHED were isolated from dental pulp derived from exfoliated deciduous teeth. Compared to DPSC,SHED show a higher proliferation rate, increased cell-population doublings, sphere-like cell-cluster formation, osteoinductive capacity in vivo, and failure to reconstitute a complete dentin pulp–like complex. These cells have the ability to differentiate into odontoblast-like cells and the regenerated dentin shows immunoreactivity to dentin-specific dentin sialophosphoprotein (DSPP) antibody. Also, SHED is capable of inducing recipient murine cells to differentiate into bone-forming cells. Due to their origin; DTSCs could be expected to be a good candidate for dental tissue regeneration.

STEM CELLS FROM APICAL PAPILLA (SCAP)-

Stem cells from apical papilla (SCAP) are the cells which are found at the tooth root apex. In developing teeth, root formation starts as the epithelial cells from the cervical loop proliferate apically, and influence the differentiation of odontoblasts from undifferentiated mesenchymal cells and cementoblasts from follicle mesenchyme. It has been known that the dental papilla contributes to tooth formation and eventually converts to pulp tissue. As the root continues to develop after the bell stage, the location of the dental papilla becomes apical to the pulp tissue. They have higher proliferation rates as well as have a differentiation property in vitro similar to DPSCs. SCAP, similar to DPSC, are more committed to osteo/dentinogenicity. They are capable of differentiating into odontoblast cells and produce dentin in vivo. Due to their higher proliferative potential, SCAPs are also suitable for cell-based therapy for formation of apex roots.

PERIODONTAL LIGAMENT STEM CELLS (PDLSC)-

The periodontal ligament (PDL) is a specialized connective tissue derived from the dental follicle and originates from neural crest cells. The PDL connects the cementum to the alveolar bone, and functions primarily to support the tooth in the alveolar socket. Human periodontal ligament stem cells (PDLSCs) can differentiate into cementoblast-like cells. They also have a capacity to form connective tissue which is riched in collagen I fiber. Human PDLSCs when seeded on 3D scaffolds such as fibrin sponge generate bone in vivo and retain stem cell properties and tissue regeneration capacity.

A recent report identified stem cells in human PDL and found that PDLSC implanted into nude mice generated cementum/PDL-like structures that resemble the native PDL as a thin layer of cementum that interfaced with dense collagen fibers, similar to Sharpey’s fibers. These cells can also differentiate into adipocytes, odontoblasts, myotubes, NFM-positive neuron-like cells, GFAP-positive astrocyte-like cells, and CNPase-positive oligodendrocyte-like cells. Periodontal ligament stem cells are responsible for the osseointegration of titanium implants. It has been demonstrated that stem cells proliferate more efficiently on rough surfaces

DENTAL FOLLICLE PROGENITOR CELLS (DFPC)-

Dental follicle precursor cells (DFPCs) are derived from dental follicle tissue which is a loose connective tissue that surrounds the developing tooth. These cells have an ability to produce bone and cementum. Therefore, these stem cells have great potentiality to use in periodontal and bone regeneration therapies.

DFPC are localized in the dental follicle, a mesenchymal tissue that surrounds the tooth germ and can be easily isolated after wisdom tooth extraction. However, these cells are available only from patients during wisdom tooth eruption, usually between 15 and 28 years of age. Human DFPC have the ability to differentiate toward alveolar osteoblasts, PDL fibroblasts, cementoblasts, adipocytes, and neuron-like cells.

CONCLUSION-

Stem cell therapy has a promising future in tissue regeneration and the management of disease. It allows the repair of defective tissues or functions through the transplantation of autologous cells. Several kinds of stem cells have been isolated from human adult teeth and have been used for tooth and periodontal regeneration. Stem cell therapy has got a cardinal role as a forthcoming treatment modality in dentistry. The ultimate goal of tooth regeneration is to replace the lost teeth by a natural tooth. Stem cell-based tooth engineering is conceived as an upcoming approach in the making of a biological tooth (biotooth). Stem cell-based therapies represent the most promising alternative for successful regeneration of damaged or pathological dental tissues or even the entire tooth following tooth loss. The identification of a good stem cell source is a major key for a success in tissue regeneration. It is therefore fundamental to understand the exact mechanisms underlying the potential of the various dental stem cell populations as well as their behavior after transplantation in ectopic sites.

 

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