Effect of primary tooth root resorption on the isolation of dental pulp stem cells from primary teeth / 中国组织工程研究

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.

Expression and assembly of rotavirus-like particles in insect cells mediated by recombinant Bombyx mori MultiBac / 南方医科大学学报

<p><b>OBJECTIVE</b>To construct recombinant baculoviruses co-expressing three structural genes vp2, vp6 and vp7 of rotavirus, and assemble rotavirus-like particles (VLPs) in BmN cells.</p><p><b>METHODS</b>Human group A rotavirus was cultivated in MA104 cells, and the RNA was extracted and the three genes were obtained by RT-PCR. The PCR products were inserted into the transfer vectors pFBDM and pUCDM, respectively. A enhanced green fluorescent protein gene (egfp) driven by IE1 promoter was introduced into pFBDM to investigate the efficiency of infection. The expression baculoviruse was constructed by Tn7 and Cre-LoxP recombinant and transfected into BmN cells. The gene expression was determined by detecting 6-His tag fused into VP7 C-terminus, and the assembled VLPs were observed by transmission electron micrography.</p><p><b>RESULTS</b>Three genes of rotavirus were cloned and BmMultiBac was constructed. The genes were expressed and the rotavirus-like particles assembled in BmN cells successfully as verified by ELISA and electron microscope.</p><p><b>CONCLUSION</b>We have successfully constructed the recombinant baculovirus co-expressing the 3 structural genes of rotavirus, which provide the basis for producing protein complex containing multiple subunits and investigation of the structure of the macromolecules.</p>

Biological characteristics of a chimeric rabies virus expressing canine parvovirus VP2 protein / 病毒学报

To obtain a bivalence vaccine against canine rabies virus and canine parvovirus, a chimeric rabies virus expressing canine parvovirus VP2 protein was generated by the technique of reverse genetics. It was shown that the chimeric virus designated as HEP-Flury (VP2) grew well on BHK-21 cells and the VP2 gene could still be stably expressed after ten passages on BHK-21 cells. Experiments on the mice immunized with the chimeric virus HEP-Flury (VP2) demonstrated that specific antibodies against rabies virus and canine parvovirus were induced in immunized mice after vaccination with the live chimeric virus.

Rescue of chimeric rabies virus expressing green fluorescent protein / 病毒学报

Green fluorescent protein (GFP) gene was inserted into the pseudogene (psi) region of genome of rabies virus rHep-Flury strain, and a recombinant rabies virus carrying GFP, designated as HEP-GFP, was rescued by reverse genetics system. It was demonstrated that green fluorescent protein could be expressed in the chimeric virus after 5 passages in BHK-21 cell line. The research indicated that the pseudogene (psi) region in the genome of rHEP-Flury strain, as an independent functional unit in the process of virus assembly, could independently carry and express exogenous genes.