We isolated and expanded stem cells from dental pulp from extracted third molars using an innovative culture method consisting of low serum-containing medium supplemented with epidermal growth factor and platelet-derived growth factor BB. We evaluated the differentiation potential of these cells when they were growing either adherently or as micromass/spheroid cultures in various media. Undifferentiated and differentiated cells were analyzed by flow cytometry, immunocytochemistry and immunoblotting. The flow cytometry results showed that the dental pulp stem cells (DPSCs) were positive for mesenchymal stromal cell markers, but negative for hematopoietic markers. Immunocytochemical and/or immunoblotting analyses revealed the expression of numerous stem cell markers, including nanog, Sox2, nestin, Musashi-1 and nucleostemin, whereas they were negative for markers associated with differentiated neural, vascular and hepatic cells. Surprisingly, the cells were only slightly positive for α-smooth muscle actin, and a heterogeneous expression of CD146 was observed. When cultured in osteogenic media, they expressed osteonectin, osteopontin and procollagen I, and in micromass cultures, they produced collagen I. DPSCs cultured in TGF-β1/3-supplemented media produced extracellular matrix typical of cartilaginous tissue. The addition of vascular endothelial growth factor to serum-free media resulted in the expression of endothelial markers. Interestingly, when cultured in neurogenic media, DPSCs exhibited de novo or upregulated markers of undifferentiated and differentiated neural cells. Collectively, our data show that DPSCs are self-renewing and able to express markers of bone, cartilage, vascular and neural tissues, suggesting their multipotential capacity. Their easy accessibility makes these cells a suitable source of somatic stem cells for tissue engineering.

Purpose: Mesenchymal stem cells isolated from bone marrow (BM-MSC) and periodontal ligament (PLSC) are cells with high proliferative potential and ability to self-renewal. Characterization of these cells under genotoxic stress conditions contributes to the assessment of their prospective usage. The aim of our study was to evaluate changes in BM-MSC and PLSC caused by ionizing radiation. Methods: Human BM-MSC and PLSC were irradiated with the doses up to 20 Gy by Co⁶⁰ and observed 13 days; viability, proliferation, apoptosis and senescence induction, and changes in expression and phosphorylation status of related proteins were studied. Results: Irradiation with the doses up to 20 Gy significantly reduces proliferation, but has no significant effect on cell viability. The activation of tumor suppressor protein 53 (p53) and its phosphorylations on serines 15 and 392 were detected from the first day after irradiation by 20 Gy and remained elevated to day 13. Expression of cyclin-dependent kinases inhibitor 1A (p21^Cip1/Waf1) increased. The cell cycle was arrested in G2 phase. Instead of apoptosis we have detected hallmarks of stress-induced premature senescence: increase in cyclin-dependent kinases inhibitor 2A (p16^INK4a) and increased activity of senescence-associated β-galactosidase. Conclusion: Mesenchymal stem cells isolated from bone marrow and periodontal ligament respond to ionizing radiation by induction of stress-induced premature senescence without apparent differences in their radiation response.

Aims : Our aims were to isolate stem cells from human exfoliated deciduous teeth (SHED), to cultivate them in vitro and to investigate their basic biological properties, phenotype and to compare our findings with dental pulp stem cells (DPSC) isolated from permanent teeth. Methods : Dental pulp was gently evacuated from exfoliated teeth. After enzymatic dissociation of dental pulp, SHED were cultivated in modified cultivation media for mesenchymal adult progenitor cells containing 2 % FCS and supplemented with growth factors and insulin, transferrin, sodium (ITS) supplement. Cell viability and other biological properties were examined using a Vi-Cell analyzer and a Z2-Counter. DNA analyses and phenotyping were performed with flow cytometry. Results : We were able to cultivate SHED over 45 population doublings. Our results showed that SHED cultivated under same conditions as DPSC had longer average population doubling time (41.3 hrs for SHED vs. 24.5 hrs for DPSC). Phenotypic comparison of cultivated SHED to that of cultivated DPSC showed differential expression CD29, CD44, CD71, CD117, CD166. During long-term cultivation, SHED did not showed any signs of degeneration or spontaneous differentiation. Conclusions : We isolated stem cells from exfoliated teeth. In comparison to DPSC, SHED proliferation rate was about 50% slower, and SHED showed slightly different phenotype. These cells may be extremely useful for stem cell tissue banking, further stem cell research and future therapeutic applications.

AIMS: Our aims were to isolate dental pulp stem cells, to cultivate them in various media and to investigate their basic biological properties and phenotype. METHODS: 16 lines of dental pulp stem cells (DPSCs) were isolated from an impacted th...