Periodontal infectious diseases are characterized by destruction of the periodontium (periodontal ligament, cementum and alveolar bone). Reconstrution of periodontium destroyed by periodontal diseases is a major goal of periodontal therapy. However, clinical results from periodontal regeneration procedures have shown low success rate and unpredictability. Presence of multiple cell types in the periodontal ligament raises speculation that this tissue might contain progenitor cells responsible for tissue homeostasis and regeneration of periodontal tissues. Recent findings suggest that periodontal ligament cells can differentiate into both cementum-forming cells (cementoblasts) and bone-forming cells (osteoblasts). The aim of this study is: 1) to isolate multipotent postnatal stem cells from periodontal ligament of human permanent and deciduous teeth; 2) to characterize the cell populations phenotypically, 3) to compare two groups of multipotent postnatal stem cells (deciduous and permanent) considering: a) proliferation rate, b) celular responses to the growth factors present at the formation and regeneration of periodontal tissues (in vitro) and c) potencial of these cells in regenerating periodontal tissues (in vivo). After primary human periodontal ligament cells are cultured, CD105+ CD34- CD45 cells (phenotype of mesenchymal stem cells) will be isolated by the magnetic activated cell sorting. PCRq will be used to evaluate these cells as to their expression of mesenchymal stem-cell markers, as well as their osteoblastic/cementoblastic and adipogenic phenotype markers, beyond their potential in forming calcified nodules. Stem cells will then be treated with BMP-2 and FGF-8, and the expression of the gene involved at the tooth tissue formation will be evaluated (PCRq). Cells obtained from deciduous and permanent teeth will be transplanted subcutneously into the dorsal surfaces in immunocompromised mice and into periodontal defects in immunodeficient rats to evaluate the formation of ectopic mineralized tissue and the cell potential to regenerate the periodontium tissues, respectively, using histomorphometric analysis.
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