https://grupoavigase.com/includes/392/6435-florida-park-discoteca.php It is becoming ever more clear that this conceptual come up to therapy, named regenerative medicine, will have its place in clinical practice in the future.
It has been shown that stem cells will play an important role in future medical treatments because they can be readily grown and induced to differentiate into any cell type in culture. Stem cells are cells that have the ability to renew themselves through mitosis and can differentiate into several specialized cells.
The embryonic stem cells ESC are pluripotent and have the ability to become almost any kind of cell of the body 4. The local microenvironment represents an important compartment in maintaining the stem cells status. The microenvironment regulates the balance between self-renewal and differentiation.
This intercellular communication has been characterized between embryonal carcinoma cells and stromal cells, and indicates changes in the expression on both cellular compartments 5. Scientists can induce these cells to replicate themselves in an undifferentiated state. However, the use of ESC is controversial and associated with ethical and legal issues, thus conditioning their application for the development of new therapies 4. Another source of stem cells is the umbilical cord.
Blood from the umbilical cord contains stem cells that are genetically identical to those of the newborn baby. These cells are multipotent, and are able to differentiate into certain cell types. Umbilical cord stem cells can be stored cryogenically after birth for use in a future medical therapy 2.
Mesenchymal stem cells MSC are multipotent progenitor cells, originally isolated from adult bone marrow and subsequently from other tissues in both adult and fetal life. Adult stem cells normally generate cell types of the tissue in which they reside.
However, studies have shown that stem cells from one tissue could generate cell types of a completely different tissue 3. Unlike ESC, adult stem cells have the potential to be used for treatment of regenerative disease, cardiac ischemia, and bone or tooth loss. The use of adult stem cells in research and medical applications is less controversial because they can be harvested without destroying an embryo. Postnatal stem cells have been found in almost all body tissues, including dental tissues.
Dental stem cells have been identified as candidates for tissue engineering 6. Because of their multipotent differentiation ability, they provide an alternative for use in regenerative medicine since they can be used for not only to dental tissue regeneration, but also to facilitate repair of non-dental tissues such as bone and nerves 6,7. A new source of stem cell has been generated from human somatic cells into a pluripotent stage, the induced pluripotent stem cells iPS cells 8,9.
Unlike ESC, iPS cell technology can derive patient-specific stem cells allowing derivation of tissue-matched differentiation donor cells for basic research, disease modeling, and regenerative medicine 9. This technology might be the new era of personalized medicine. This review discusses the perspectives in the field of stem cell-based regenerative medicine, addressing sources of stem cells identified in dental tissues; and new findings in the field of dental stem cell research and their potential use in the dental tissue engineering.
Several cell populations with stem cells properties have been isolated from different parts of the tooth. Since the discovery of the existence of adult stem cells from the dental pulp in 10 , several other types of dental stem cells have been successively isolated from mature and immature teeth, including stem cells derived from exfoliated deciduous teeth 11 , stem cells derived from the apical papilla 12 , MSC from tooth germs 13 and from human periodontal ligament PDL It is considered that these stem cells are undifferentiated mesenchymal cells present in dental tissues and characterized by their unlimited self-renewal, colony forming capacity, and multipotent differentiation 1.
During the characterization of these newly identified dental stem cells, certain aspects of their proprieties have been compared with those of bone-marrow-derived stromal stem cells BMMSC. Therefore, these cells have been used for tissue-engineering studies to assess their potential in preclinical applications 6. It is, however, important to consider that, although different types of dental-tissue derived MSC share several common characteristics and present significant heterogeneity, expressed by multiple phenotypic differences, which most probably reflect distinct functional properties 1.
There is already evidence that there are significant variations, for example, in the odontogenic potential of single colony-derived populations isolated from the dental pulp, reflecting differences in their genotypic and protein expression patterns In addition, this heterogeneity may be significantly enhanced as a function of their tissue microenvironment This issue becomes more complicated as researchers have used quite different methods to isolate and culture dental MSC and evaluate their differentiation potential.
The first stem cells isolated from adult human dental pulp were termed dental pulp stem cells DPSC. They were isolated from permanent third molars and exhibited high proliferation and high frequency of colony formation that produced calcified nodules DPSC cultures from impacted third molars at the stage of root development were able to differentiate into odontoblast-like cells with a very active migratory and mineralization potential, leading to organized three-dimensional dentin-like structures in vitro There are different cell densities of the colonies in DPSC, suggesting that each cell clone may have different grown rate Different cell morphologies and sizes can be observed in the same colony.
The differentiation of DPSC to a specific cell lineage is mainly determined by the components of local microenvironment, such as, growth factors, receptor molecules, signaling molecules, transcription factors and extracellular matrix protein. DPSC can be reprogrammed into multiple cell lineages such as, odontoblast, osteoblast, chondrocyte, myocyte, neurocyte, adipocyte, corneal epithelial cell, melanoma cell, and even induced pluripotent stem cells iPS cells 18, Almushayt et al.
Histologically, dentin lies outside of dental pulp, and they intimately link to each other. Functionally, dental pulp cells can regenerate dentin and provide it with oxygen, nutrition and innervation, whereas the hard dentin can protect soft dental pulp tissue. Together, they maintain the integrity of tooth shape and function. Any physiological or pathological reaction occurring at one part, such as trauma, caries, and cavity preparation, will affect the other.
Both of them act as a dentin-pulp complex and simultaneously participate in various biological activities of the tooth. Several studies have shown that DPSC play a vital role in the dentin-pulp tissue regeneration These polls of heterogeneous DPSC form vascularizad pulp like tissue and are surrounded by a layer of odontoblast-like cells expressing factors that produce dentin containing tubules similar those found in natural dentin 22, Huang et al.
These studies provide a novel advance for future pulp tissue preservation and a new alternative for the biological treatment for endodontic diseases.
In addition, DPSC can express neural markers and differentiate into functionally active neurons, suggesting their potential as cellular therapy for neuronal disorders 7. In recent study, DPSC were transplanted into the cerebrospinal fluid of rats in which cortical lesion was induced. Those cells migrated as single cells into a variety of brain regions and were detected in the injured cortex expressing neuron specific markers.
This showed that DPSC-derived cells integrate into the host brain may serve as useful sources of neuro and gliogenesis in vivo, especially when the brain is injured The spontaneous differentiating potential of these cells strongly suggests their possible applications in regenerative medicine. Stem cells may be also isolated from the pulp of human exfoliated deciduous teeth SHED. These cells have the capacity of inducing bone formation, generate dentin and differentiate into other non-dental mesenchymal cell derivatives in vitro.
SHED exhibit higher proliferation rates, increased population doublings, in addition to osteoinductive capacity in vivo and an ability to form sphere-like clusters. With the osteoinductive potential, SHED can repair critical sized calvarial defects in mice with substantial bone formation Given their ability to produce and secrete neurotrophic factors, dental stem cells may also be beneficial for the treatment of neurodegenerative diseases and the repair of motor neurons following injury.
Indeed, dental stem cells from deciduous teeth have been induced to express neural markers such as nestin The potential of dental stem cells in non-dental regeneration continues to be further explored by researchers. The physical and histological characteristics of the dental papilla located at the apex of developing human permanent teeth has been recently been described and this tissue has been termed apical papilla.
This tissue is loosely attached to the apex of the developing root and can be easily detached. A population of stem cells isolated from human teeth was found at the tooth root apex. These cells are called stem cells from apical papilla SCAP and have been demonstrated to differentiate exhibit higher rates of proliferation in vitro than do DPSC.
There is an apical cell-rich zone lying between the apical papilla and the pulp. The higher proliferative potential of SCAP makes this population of cells suitable for cell-based regeneration and preferentially for forming roots. They are capable of forming odontoblast-like cells and produce dentin in vivo and are likely to be the cell source of primary odontoblasts for the root dentin formation The discovery of SCAP may also explain a clinical phenomenon that was presented in a number of recent clinical case reports showing that apexogenesis can occur in infected immature permanent teeth with apical periodontitis or abscess It is likely that SCAP residing in the apical papilla survived the infection due to their proximity to the periapical tissues.
This tissue may be benefited by its collateral circulation, which enables it to survive during the process of pulp necrosis. Perhaps, after endodontic disinfection, these cells give rise to primary odontoblasts to complete the root formation. Periodontal ligament PDL is a space interlying the cementum and alveolar bone, a replacement of the follicle region surrounding the developing tooth in cap and bud stages of development. The PDL matures during tooth eruption, preparing to support the functional tooth for the occlusal forces. In the mature PDL, major collagen bundles principal fibers occupy the entire PDL, embedding in both cementum and alveolar bone.
Fibers are arranged in specific orientations to maximize absorption of the forces to be placed on the tooth during mastication. The PDL has long been recognized to contain a population of progenitor cells and recently, studies identified a population of stem cells from human PDL capable of differentiating along mesenchymal cell lineages to produce cementoblast-like cells, adipocytes and connective tissue rich in collagen I Human PDLSC expanded ex vivo and seeded in three-dimensional scaffolds fibrin sponge, bovine-derived substitutes were shown to generate bone These cells have also been shown to retain stem cell properties and tissue regeneration capacity.
These findings suggest that this population of cells might be used to create a biological root that could be used in a similar way as a metal implant, by capping with an artificial dental crown. The dental follicle is a loose connective tissue that surrounds the developing tooth. The dental follicle has long been considered a multipotent tissue, based on its ability to generate cementum, bone and PDL from the ectomesenchyme-derived fibrous tissue.
Dental follicle precursor cells DFPC can be isolated and grown under defined tissue culture conditions, and recent characterization of these stem cells has increased their potential for use in tissue engineering applications, including periodontal and bone regeneration 12, Dental follicle progenitor cells isolated from human third molars are characterized by their rapid attachment in culture, and ability to form compact calcified nodules in vitro DFPC, in common with SCAP, represent cells from a developing tissue and might thus exhibit a greater plasticity than other dental stem cells.
However, in the same way as for SCAP, further research needs to be carried out on the properties and potential uses of these cells Table 1. There are several areas of research for which dental stem cells are presently considered to offer potential for tissue regeneration. These include the obvious uses of cells to repair damaged tooth tissues such as dentin, PDL and dental pulp 6, Even the use of dental stem cells as sources of cells to facilitate repair of additional tissues as bone and nerves 6,7, Efforts to induce tissue regeneration in the pulp space have been a long search.
In , Ostby 31 proposed inducing hemorrhage and blood clot formation in the canal space of mature teeth in the hope of guiding the tissue repair in the canal.
However, the connective tissue that grew into the canal space was limited and the origin of this tissue remains unproved. Regenerative Endodontics represents a new treatment modality that focuses on reestablishment of pulp vitality and continued root development.
This clinical procedure relies on the intracanal delivery of a blood clot scaffold , growth factors possibly from platelets and dentin , and stem cells In a recent study, it was demonstrated that mesenchymal stem cells are delivered into root canal spaces during regenerative endodontic procedures in immature teeth with open apices These findings provide the biological basis for the participation of stem cells in the continued root development and regenerative response that follow this clinically performed procedure. As DPSC have the potent dentinogenic ability, they could be used for the vital pulp therapy.
When DPSC are transplanted alone or in combination with BMP2 in the pulp cavity, these stem cells can significantly promote the repair and reconstruction of dentin-pulp-like complex Prescott et al. After 6 weeks of incubation, well-organized pulp-like tissue could be detected in the perforation site.
Cordeiro et al. One of the most challenging aspects of developing a regenerative endodontic therapy is to understand how the various procedures involved can be optimized and integrated to produce the outcome of a regenerated pulp-dentin complex. The future development of regenerative endodontic procedures will require a comprehensive research program directed at each of these components and their application in the clinical practice. Periodontitis is the most common cause for tooth loss in adults due to irreversible waste of connective tissue attachment and the supporting alveolar bone.
The challenge for cell-based replacement of a functional periodontium is therefore to form new ligament and bone, and to ensure that the appropriate connections are made between these tissues, as well as between the bone and tooth root.
Stem cell therapy involves the transplantation of . the in vivo modulation of MSC biology by TLR. The Mayo Foundation for Medical Education and Research Stem cell therapy is potentially applicable to all subspecialties of medicine, but both cell populations have been used, a single cell type, mesenchymal stem cells (MSCs), has.
This is not a trivial undertaking, as these are very different tissues that are formed in an ordered manner spatially and temporally during tooth development In recent years, guided tissue regeneration has become the gold-standard surgery for periodontal tissue regeneration. The techniques and principles used by hematologists have been successfully applied to stem cells from many other tissues, spawning a large-scale stem cell research effort around the world.
Research on hematopoietic stem cells HSCs has led to significant clinical applications. For instance, HSC transplantation has become the single modality with curative potential for both genetic diseases and hematologic malignancies. The introduction of this clinical procedure has resulted in significant improvements in cure rates for both malignant and non-malignant disorders. The broad application of stem cells can be further optimized to advance the treatment of a variety of diseases.
Maximizing the Promise of Stem Cell and Regenerative Medicine: Priorities for Future Progress New insights and technologies have the potential to optimize the use of stem cells and regenerative medicine, creating "designer" cells that will redefine approaches to the diagnosis and treatment of hematologic diseases. While options for hematopoietic cell transplantation continue to expand, now including increased use of umbilical cord blood UCB and haplo-identical transplantation, our understanding of basic HSC biology remains limited.
Strategies to improve use of gene corrected HSCs to better treat diseases such as sickle cell anemia and congenital immunodeficiencies have also been slow for wide-spread clinical translation. Research in the following areas will help achieve these priorities. Since stem cell numbers in the graft are important for clinical outcome following transplantation, methods to expand hematopoietic stem cells have been examined extensively. This is particularly relevant in UCB transplantation, where low numbers of stem cells are directly related to delayed hematopoietic and immune reconstitution.
Improved HSC expansion strategies may significantly affect transplantation outcome, enabling broader applications for UCB transplantation. These strategies are also needed to realize the full therapeutic potential of genome editing technologies to correct hematopoietic stem cells derived from patients with congenital hematologic disorders.
Efforts to expand HSCs in cytokine-supported liquid cultures have been largely unsuccessful, and there is now general agreement that efficient expansion requires an appropriate context that is provided by the hematopoietic stem cell niche. A series of research programs will help achieve these priorities. Improved characterization and understanding of human pluripotent stem cells, both human embryonic stem cells and iPSCs, provide a unique opportunity to produce specific human blood cell populations suitable for diverse therapies.
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