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BACKGROUND: Mesenchymal stem cells are derived from a variety of tissues, such as bone marrow, pulp, placenta, umbilical cord and adipose tissue. Mesenchymal stem cells from deciduous pulp have strong stemness and biological activity, no rejection, and strong immunoregulation, which are one of excellent cell sources for biotherapy. It is easy and suitable for large-scale production of mesenchymal stem cells from deciduous pulp, thereby laying a good foundation for the industrialization of dental pulp stem cells. OBJECTIVE: To investigate the effect of primary tooth root resorption on the isolation and expansion of dental pulp stem cells, in order to further determine the proper period for tooth extraction for pulp stem cell isolation. METHODS: Totally 173 primary teeth from 173 pupils aged 7-9 years were extracted for the isolation and expansion of dental pulp stem cells. Before tooth extraction, we took X-ray periapical film or orthopantomography of the primary teeth, in accordance with the World Health Organization (WHO) professional inspection standard. Root resorption in primary teeth could be divided into five kinds: root resorption 1/3, root resorption 1/2, root resorption 2/3, complete root resorption, and natural loss of primary teeth. Collected teeth after tooth extraction were placed into a medium within 7 seconds, and stored at in a refrigerator of 2-4 ℃. Then, the teeth were sent to the Oral Stem Cell Bank in Beijing within 24 hours by a professional cold-chain logistics for the isolation, expansion and preservation of dental pulp stem cells. Statistical analysis of the test results was performed. RESULTS AND CONCLUSION: For 32 primary teeth with root resorption 1/3, dental pulp stem cells were successfully extracted from 30 teeth, with a success rate of 94%, and ectopic eruption of permanent teeth was found in 12 cases, with an average eruption time of (2.19±0.18) months. For 35 primary teeth with root resorption 1/2, dental pulp stem cells were successfully extracted from 32 teeth, with a success rate of 92%, and ectopic eruption of permanent teeth was found in 11 cases, with an average eruption time of (1.89±0.13) months. For 59 primary teeth with root resorption 2/3, dental pulp stem cells were successfully extracted from 54 teeth, with a success rate of 92%, and ectopic eruption of permanent teeth was found in 8 cases, with an average eruption time of (1.42±0.12) months. For 37 primary teeth with complete root resorption (the bottom of the pulp was intact), dental pulp stem cells were successfully extracted from 34 teeth, with a success rate of 92%, and ectopic eruption of permanent teeth was found in 2 cases, with an average eruption time of (1.03±0.15) months. For 10 naturally exfoliated primary teeth, dental pulp stem cells were not extracted, and ectopic eruption of permanent teeth was found in 4 cases, with an average eruption time of (0.65±0.23) months. To conclude, the primary teeth naturally exfoliated have no dental pulp with no stem cells; the success rate of extraction is relatively high in primary teeth that have mobility I-II, root resorption 2/3 or complete root resorption but with the complete bottom of the pulp. Moreover, it has no effect on permanent tooth eruption, and it is the best time for collection of primary teeth.
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<p><b>OBJECTIVE</b>To determine whether the sonic hedgehog (Shh) signaling could regulate the expression of histone demethylases in the head and neck squamous cell carcinoma(SCC).</p><p><b>METHODS</b>Human recombinant SHH-N protein or over-expression of the mutant 2 smoothened (M2-SMO) was applied to activate the Shh signaling in tongue squamous cell carcinoma cell line-SCC-6 in this study. Cyclopamine was used to block the Shh signaling in SCC-6. The real-time reverse transcription (RT)-PCR was used to detect the expression of histone demethylases at the mRNA level.</p><p><b>RESULTS</b>The data showed that activation of the Shh signaling up-regulated the expression of histone demethylase, lysine-specific demethylase 8 (KDM-8) at the mRNA level by human recombinant SHH-N protein (1.841 ∼ 3.591 fold compare with untreated group; P < 0.01), over-expression of the M2-SMO also increased the expression of KDM-8 (1.358 ∼ 3.013 fold compared with empty vector group; P < 0.05), and after the Shh signaling was blocked by Cyclopamine, the expression of KDM-8 was down regulated (decreased 25.6% ∼ 66.6% compared with control cells, P < 0.05).</p><p><b>CONCLUSIONS</b>Histone demethylase KDM-8 was downstream target gene of Shh signaling in head and neck squamous cell carcinoma cell line SCC-6, and its expression was positively regulated by the Shh signaling.</p>