Morphological characterization of periodontium derived stem cells

Objectives: It was the aim of this study to characterize adult human somatic stem cells (pdSCs) isolated from the periodontium and to follow up their differentiation after cell culture and transplantation into alveolar bone defects of 12 athymic nude rats. Material and Methods: pdSCs were isolated from human periodontal tissue and cultured in serum-free medium (Widerea et al., 2007). After 10 days the primary spheres were dissociated and the secondary spheres were sub cultured for another 3 days 1 and 2 weeks. Of each time segment spheres were fixed either in formalin or glutaraldehyde for histological, immunohistochemical and electron microscopic investigation. In twelve athymic T-cell deficient rnu/rnu nude rats the superficial bone at the distal root of the first mandibular molar has been removed using a round dental bur (diameter 2mm), denuded of its periodontal ligament, cementum and superficial dentin using a chisel. Small pieces of collagen were incubated in a solution of adult human periodontal ligament stem cells (1×105 to 5×106) and transferred to the defect on the right side (test side). Another piece of collagen was also prepared to fit the bony defect on the left side (control side) but without incubation in the solution of stem cells. After 2 4 and 6 weeks 4 animals were sacrificed and the defects investigated histologically. Results: Histology showed differentiation of spheres deriving from the pdSCs with central production of extracellular matrix. Isolated pdSCs developed pseudopodia which contained tubulin. Two weeks after transplantation of pdSCs on the experimental side in all animals malignant cancerous tumors developed. Conclusions: Human pdSCs differentiate in cell culture into spheres which produce extracellular matrix. In transplantations into bone defects they can develop malignant tumors.