[Dynamic change and prediction of vegetation cover in Shenzhen, China from 2000 to 2018]. / 2000­2018年深圳市植被覆盖动态变化与预测.

With landsat-series multi-temporal image data, percentage of vegetation cover (PVC) was estimated by pixel dichotomy. The linear regression analysis and center of gravity migration methods were used to explore the characteristics of the spatiotemporal changes of vegetation cover in Shenzhen from 2000 to 2018. The CA-Markov model was combined to predict future land cover in Shenzhen. The results showed that the PVC in Shenzhen demonstrated obvious regional differentiation characteristics from 2000 to 2018. The eastern region occupied larger proportion than the wes-tern part, while the southern region was larger than the north part. This feature exhibited good consistency with regional topographic effect. The spatial migration characteristic of the center of gravity of PVC was from northwest to southeast, and then from southeast to northwest, with a migration rate of 551.2 m·a-1. This process was closely related to urbanization in Shenzhen. The PVC in Shen-zhen tended to be generally improved from 2000-2018, with a improvement rate of 0.005·a-1. The percentage of significantly improved and degraded PVC area was 30.8% and 12.8%, respectively. The CA-Markov method was used to predict the land cover/use pattern of Shenzhen in 2024 under two scenarios, theoretical scenario and natural scenario. There was no significant difference in proportion of the area of the land cover/use patterns obtained by the two kinds of prediction method, with the difference threshold being 0-1.2%. Compared with the data before 2018, the proportion of arbor forests and arable land converted into construction land in Shenzhen would be significantly reduced in 2024, whereas the contradiction between supply and demand would be still tense.

Odontogenic potential of mesenchymal cells from hair follicle dermal papilla.

Dental pulp stem cells from teeth can be used for tooth regeneration. Although nondental stem cells derived from bone marrow can differentiate into odontoblast-like cells when recombined with embryonic oral epithelium, these cells can lose their ability to differentiate after an extended number of cell culture passages. There has been limited research to identify stem cells from other tissue sources to regenerate teeth. As another candidate source for mesenchymal stem cells, hair follicle has obtained much more attention recently because of its easy accessibility. In this study, cultured vibrissae follicle dermal papilla mesenchymal cells (FDPMCs) from adult C57BL/6 GFP mice can differentiate into adipocytes and osteoblasts in vitro. Moreover, in the inductive microenvironment generated by apical bud and dental mesenchyme from 7-day-old C57 mice, FDPMCs in vitro demonstrated odontogenic potential, as indicated by the morphological transformation, cell-cycle change and expression of tooth-specific markers. Under the same microenvironment, FDPMCs were incubated in vivo for 3 weeks. Coexpression of GFP and DSP proteins in the odontoblast layer was detected in the recovered implants, suggesting that GFP(+) FDPMCs can function as odontoblasts in vivo. Together, our data indicate for the first time that whisker FDPMCs from adult mice can differentiate to odontoblast-like cells.

[Experiment on inducing human dental pulp stem cells into neural-like cells].

OBJECTIVE: To explore the multi-differentiated capability of human dental pulp stem cells (hDPSCs) obtained by cell-clone culture approach and to determine the appropriate induced medium. METHODS: The cloned isolation and expansion of hDPSCs were preinduced for 24 h, and were subsequently replaced with neural-inductive medium containing certain concentration of dimethylsulfoxide (DMSO), butylated hydroxyanisode (BHA), forskolin, P-mercaptoethanol (p-ME) and hydrocortisone for 4 days. Then induced cells were analyzed by morphological observation, immnocytochemical staining for non-specific esterase (NSE) and glial fibrillary acidic protein (GFAP) expression, RT-PCR for GFAP mRNA. Meanwhile, the uninduced hDPSCs were used as negative control. RESULTS: The morphology of induced cells changed at the initial 12 h, and displayed a typical neuron-like cells at 24 h. There was a gradual increase in the number of these neuronal differentiated cells with continuous induction. Furthermore, immnocytochemical staining showed that the induced cell expressed NSE and GFAP, two marked enzymes of neuron cell. The GFAP mRNA was also detected in induced cells by RT-PCR assay. In contrast, the uninduced cells maintained its original appearance and had no expression on them. CONCLUSION: hDPSCs may possess potential of multiple-differentiation and may differentiate into neuron-like cells on certain inductive condition.

Cell pellets from dental papillae can reexhibit dental morphogenesis and dentinogenesis.

We isolated dental papilla mesenchymal cells (DPMCs) from different rat incisor germs at the late bell stage and incubated them as cell pellets in polypropylene tubes. In vitro pellet culture of DPMCs presented several crucial characteristics of odontoblasts, as indicated by accelerated mineralization, positive immunostaining for dentin sialophosphoprotein and dentin matrix protein 1, and expression of dentin sialophosphoprotein mRNA. The allotransplantation of these pellets into renal capsules was also performed. Despite the absence of dental epithelial components, dissociated DPMCs with a complete loss of positional information rapidly underwent dentinogenesis and morphogenesis, and formed a cusp-like dentin-pulp complex containing distinctive odontoblasts, predentin, dentin, and dentinal tubules. These results imply that DPMCs at the late bell stage can reexhibit the dental morphogenesis and dentinogenesis by themselves, and epithelial-mesenchymal interactions at this stage may not be indispensable. Furthermore, different DPMC populations from the similar stage may keep the same developmental pattern.

[Sequencing and bioinformatical analysis of virulent strain-specific DNA fragments from Streptococcus mutans].

OBJECTIVE: To search the DNA sequences specific to virulent strain of Streptococcus mutans in the public database and explore new genes or new functions of already known genes from Streptococcus mutans of serotype c and suppose their functions. METHODS: Thirty-one DNA fragments unique to virulent strain of Streptococcus mutans were sequenced. The sequences of these presumptive virulence DNA fragments were subjected to search through software BLASTn and BLASTx in public database, and their putative biological functions were analyzed. RESULTS Two clones were picked repeatedly. The size of the remaining DNA fragments ranged from 113 bp to 776 bp. The average G+C content was 38.59%, similar to that of the gene-coding sequences in Streptococcus mutans strain UA159 whose genome sequences were just complete. Of the twenty-nine DNA fragments, five potentially represented new DNA fragments in Streptococcus mutans, thus registered and obtained their gene's accession number in GenBank. The remaining DNA fragments showed high homology to known genes of Streptococcus mutans strain UA159. Their predicted functions of these fragments were associated to bacterial signal transduction, transcriptional regulation, stress-damage repair, biochemical metabolism, outer membrane protein synthesis, adhesion on tooth surface and hypothetical proteins. CONCLUSION: The gene analysis, identification and functional forecasting were carried out through bioinformatics associated software and database to find out new genes and new functions of known genes, and to supply the groundwork for researches in gene functions.

[Tissue engineering of dentin-pulp complex-like structures by human dental mesenchymal cells].

OBJECTIVE: To establish three-dimensional culture model of human dental mesenchymal cells and bioengineer in vivo with ceramic bovine bone (CBB) and Collagraft as scaffolds. METHODS: Human dental mesenchymal cells induced upon stimulation of bFGF and IGF-1 or TGF-beta(1) were implanted onto CBB and Collagraft containing the same kinds of growth factors respectively. Then cell/scaffold constructs were transplanted into nude mice to establish in vivo culture model of dental mesenchymal cells. Control groups were set up at the same time. After 4 weeks or 10 weeks, the implants were taken out for histological and immunohistochemical analysis. RESULTS: Within 10-week implant tissues, typical dentin-pulp complex-like structures were generated in scaffolds containing growth factors. Human dentin sialoprotein (DSP) was expressed in the newly formed dentin. This phenomenon wasn't observed in control groups and 4-week implants. CONCLUSIONS: Dentin-pulp complex-like structures could be bioengineered successfully with human dental mesenchymal cells and CBB or Collagrafts containing growth factors in nude mice.

[IRF6 gene mutation analysis in a van Der Woude syndrome family in Henan province].

PURPOSE: To investigate IRF6 gene mutation in a van Der Woude syndrome (VWS) family in Henan province. METHODS: PCR and DNA sequencing was employed to detect the mutation of IRF6.Secondary construction transformation analysis was performed using PIX-Protein Identification software. RESULTS: A CGC>TGC(r.279c-->t) transversion of IRF6 was identified in condon 6, showing complete segregation with the disease phenotypes and was resulting in changes of the secondary constructure of IRF6. CONCLUSION: VWS is caused by mutations in IRF6 gene, and IRF6 is closely related to the development of lip, palate and tooth.

[Construction of a virulence-related gene library of Streptococcus mutans by suppression subtractive hybridization].

OBJECTIVE: To construct a suppression subtractive library of virulence-related genes from c serotype Streptococcus mutans (S. mutans), and lay foundations for screening the virulent genes. METHODS: After being isolated from virulent and avirulent strain of S. mutans respectively, the intact and high-pure genomic DNA was digested with three appropriate four-base-cutting restriction endonueleases to produce fragments of optimal length. The digested DNA of the virulent strain ligated with adaptor was used as tester DNA, and that of the avirulent strain as driver DNA. Then the suppression subtractive hybridization was carried out, and the efficiency of ligation and subtraction detected respectively. The subtracted fragments were inserted into vector pCR2. 1 using T/A cloning kit, and transformed into E. coli TOP10F' competent cells. Those white colonies were selected to construct the suppression subtractive library. RESULTS: Alu I chosen from three restriction endonucleases was verified to be suitable for preparing restriction fragments from S. mutans genomic DNA. Through electrophoresis of Alu I -digested DNA, a smear ranged from 0.1 to 2.0 kb was observed. The ligation efficiency of tester DNA with adaptor was at least higher than 25 percent. The subtraction efficiency of suppression subtractive hybridization confirmed the success in enrichment of differential genes between virulent and avirulent strain of S. mutans. In the subtracted group, the appearance time of the 23S rRNA gene both in tester and driver DNA was later than that in the unsubtracted group by six cycles. It suggested that suppression subtractive hybridization happened indeed. After the subtracted fragments were cloned, 96 colonies were picked up for constructing the suppression subtractive library of virulence-related genes of S. mutans. CONCLUSION: Suppression subtractive hybridization allows rapid and easy construction of virulence-related gene library of S. mutans.

[The positive effect of transforming growth factor beta on ectomesenchymal stem cells of embryonic facial processes differentiating to smooth muscle cells].

OBJECTIVE: To investigate the effect of transforming growth factor beta (TGF-beta) on ectomesenchymal stem cells differentiating to smooth muscle cells. METHODS: 60 pmol/L TGF-beta was added to the ectomesenchymal stem cells of embryonic facial processes. Immunohistochemistry assay and image analysis were used to value the expression extent of a smooth muscle actin (alpha-SMA) and quantitative RT-PCR was used to value the quantity of alpha-SMA. RESULTS: 2 days later, about 95% cells in TGF-beta group and 65% cells in control group without differentiation inhibitor expressed alpha-SMA. Expression of alpha-SMA in TGF-beta group was stronger than that of control group after one and two days. Quantitative RT-PCR showed the quantity of alpha-SMA mRNA in treated group cells was more than that of in control group. CONCLUSION: Quantity of alpha-SMA in TGF-beta group is more than that of spontaneous differentiation group. TGF-beta has positive effect on ectomesenchymal stem cells differentiating to smooth muscle cells.

[Identification of ectomesenchymal stem cells of human fetal facial processes and spontaneous differentiation to smooth muscle cells].

OBJECTIVE: To investigate the characteristic and phenotype of ectomesenchymal stem cells of human fetal facial processes and the procedure of spontaneous differentiation to smooth muscle cells. METHODS: The primary ectomesenchymal cells of E 50 human fetal facial processes were isolated by 2.5 g/L trypsin and cultured with DMEM/F 12 with 10(-6) U/L leukemia inhibitor factor(LIF). The morphology and growth rate were observed by inverted microscop. After being withdrawn LIF, the characteristic of cells were identified by immunohistochemistry and RT-PCR. Ultrastructure was observed by transmission electron microscope. RESULTS: The cultured cells displayed monolayer growth and were fibroblast-like with 2-4 processes. The cells were stainely positived for anti-human natural killer cell marker-1, Vimentin, S-100, neuron specific enolase, myoglobin and VIII factor, but negatively for glial fibrillary acidic protein, neural fiblament, alpha-SMA and cytokeratin in immunohistochemistry. Two days after being withdrawn the LIF, cells expressed alpha-SMA in protein and mRNA levels. The cells were rich in muscular filament-like structure and dense bodies under transmission electron microscope. CONCLUSION: Cultured cells are undifferentiated ectomesenchymal stem cells. The cells have the potential for differentiating spontaneously to smooth muscle cell.