Plasticity of "periodontium derived" stem cells-risk or future?

Objectives: In the periodontium adult periodontal stem cells are often studied using culture systems referred to as mesenchymal stem cell assays. We recently challenged a central tenet of these systems and provided evidence that “periodontium derived“ stem cells are neuronal stem cells (Widera et al. 2007) rendering used culture systems inappropriate for differentiation of PDL stem cells from progenitors. The aim of this study was to characterize putative stem cells in inflamed and healthy human periodontium using immunocytochemical techniques and RT-PCR analysis as described previously (Grimm et al. 2007). Methods: We isolated somatic stem cells (pdSCs) from the human periodontium using minimally invasive periodontal surgery and from pulp tissue (controls). Cultivated, kryopreserved pdSCs from 11 patients with or without periodontal inflammation were unfreezed to allow re-aggregation of the spheres. The cells were differentiated using protocols designed for neuronal, glial and osteogenic differentiation. Results of cell expansion and of proliferation assays were expressed as mean + SEM and determined using two-way ANOVA followed by post hoc t-test with Bonferroni correction. Results: pdSCs from both inflamed and non-inflamed periodontium showed a typical morphology and histological stem cell pattern. Analysis of the karyotypes of “inflamed” pdSCs revealed a high degree of aneuploidity with chromosome counts peaking at 70 chromosomes. “Non-inflamed” pdSCs showed a higher migration capacity in the used Proliferation Assay. Both groups of pdSCs were similar Nestin and Sox2 positive. If differentiated into neuronal lineage both groups of pdSCs showed a similar neuronal morphology and expressed markers like NF-M, NF-H and Map-2. Immunocytochemistry verified the glial lineage in both groups of pdSCs as shown by the high expression of GFAP. Conclusion: We anticipate the proposed serum-free culture system will provide additional clarity in discerning the regenerative power of pdSCs, thereby facilitating further advances in the promising application of pdSCs for therapeutic use.