ObjectiveTo study the pharmacological substances and mechanisms through which sesquiterpene ZH-13 from Aquilariae Lignum Resinatum improves neuroinflammation. MethodsBV-2 microglial cells were stimulated with lipopolysaccharide （LPS） to induce neuroinflammation. The cells were divided into the normal group， the model group， and the ZH-13 low- and high-dose treatment groups （10， 20 μmol·L^-1）. The model group was treated with 1 μmol·L^-1 LPS. Cell viability was assessed using the cell proliferation and activity assay （CCK-8 kit）. Nitric oxide （NO） release in the cell supernatant was measured using a nitric oxide kit （Griess method）. The mRNA expression levels of interleukin-1β （IL-1β）， tumor necrosis factor-α （TNF-α）， inducible nitric oxide synthase （iNOS）， and interleukin-6 （IL-6） were detected by real-time fluorescence quantitative polymerase chain reaction （Real-time PCR）. The phosphorylation of mitogen-activated protein kinase （MAPK） pathway proteins was assessed by Western blot. ResultsCompared with the model group， ZH-13 dose-dependently reduced NO release from BV-2 cells under LPS stimulation （P<0.05， P<0.01）. In the 20 μmol·L^-1 ZH-13 treatment group， the mRNA expression levels of IL-1β， TNF-α， iNOS， and IL-6 were significantly reduced compared to the model group （P<0.05， P<0.01）. In both the low- and high-dose ZH-13 groups， the expression of the inflammatory factor TNF-α and the phosphorylation of c-Jun N-terminal kinase （JNK） in the upstream MAPK pathway were significantly reduced （P<0.05）. After stimulation with the JNK agonist anisomycin （Ani）， both low- and high-dose ZH-13 treatment groups showed reduced phosphorylation of JNK proteins compared to the Ani-treated group （P<0.01）. ConclusionThe sesquiterpene compound ZH-13 from Aquilariae Lignum Resinatum significantly ameliorates LPS-induced neuroinflammatory responses in BV-2 cells by inhibiting excessive JNK phosphorylation and reducing TNF-α expression. These findings elucidate the pharmacological substances and mechanisms underlying the sedative and calming effects of Aquilariae Lignum Resinatum.

ObjectiveBy comparing the composition and content of volatile components in raw products， wine-washed products and wine-fried products of Ligusticum sinense cv. Chaxiong rhizome（LSCR）， to investigate the influence of wine processing on the volatile components of LSCR， in order to provide a basis for the development of quality standards for LSCR and its processed products. MethodsElectronic nose was used to identify the odors of LSCR， wine-washed and wine-fried LSCR， and their volatile components were detected by headspace gas chromatography-mass spectrometry（HS-GC-MS）， and the relative mass fractions of these components were determined by peak area normalization method. Principal component analysis（PCA） and orthogonal partial least squares-discriminant analysis（OPLS-DA） were performed on the obtained sample data by SIMCA 14.1 software， and the differential components of LSCR， wine-washed and wine-fried LSCR were screened according to the variable importance in the projection（VIP） value>1. Pearson correlation analysis was used to explore the relationship between volatile differential flavor components and electronic nose sensors. ResultsElectronic nose detection results showed that there were significant differences in the odors of LSCR， wine-washed and wine-fried LSCR， mainly reflected in the sensors S2， S4， S5， S6， S11， S12， S13. And a total of 62 compounds were identified from LSCR and its wine-processed products， among which 46， 50 and 51 compounds were identified from LSCR， wine-fried and wine-washed LSCR， respectively. There were 21 differential components between the raw products and wine-fried products， of which 10 components were increased and 11 were decreased after processing. There were 20 differential components between the raw products and wine-washed products， of which 11 constituents increased and 9 decreased after processing. There were 17 differential components between the wine-wash products and wine-fried products. Compared with the wine-washed products， the contents of 13 components in the wine-fried products increased， and the contents of 4 components decreased. The increasing trend of the content of phthalides in the wine-washed products was more obvious than that in the wine-fried products， but the content of total volatile components was higher in the wine-fried products than the wine-washed products. Correlation analysis showed that there were different degrees of correlation between the 7 differential sensors of electronic nose and 24 differential volatile components， mainly phthalides and olefins. ConclusionThe odor and the content of volatile components in LSCR changed obviously after wine processing， and n-butylphthalide， Z-butylidenephthalide and E-ligustilide can be used as the candidate differential markers of volatile components in LSCR before and after wine processing.

ObjectiveTo explore the mechanism by which Xiaoyaosan regulates HPT axis dysfunction in the rat model with the syndrome of liver depression and spleen deficiency by observing its effect on the glycoprotein hormone α-subunit （CGA）/glutathione peroxidase 2 （GPX2）/thyroid-stimulating hormone β-subunit （TSHβ） pathway for thyroid hormone synthesis. MethodsSeventy-two male SD rats were randomized into six groups： normal， model， high-dose （16.7 g·kg^-1）， medium-dose （8.35 g·kg^-1）， and low-dose （4.175 g·kg^-1） Xiaoyaosan， and fluoxetine （0.001 8 g·kg^-1） groups， with 12 rats in each group. The rat model of liver depression and spleen deficiency was induced by chronic restraint stress for 21 days. The intervention groups were treated with Xiaoyaosan decoctions or fluoxetine suspension， respectively. After modeling， hematoxylin-eosin staining was employed to observe morphological changes in the thyroid and pituitary tissue of the rats. Serum levels of triiodothyronine （T3）， tetraiodothyronine （T4）， and thyroid-stimulating hormone （TSH） were measured by enzyme-linked immunosorbent assay （ELISA）. Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） and Western blot were employed to determine the mRNA and protein levels， respectively， of TSH receptor （TSHR） in the thyroid tissue， thyrotropin-releasing hormone receptor （TRHR） and TSHβ in the pituitary tissue， and thyrotropin-releasing hormone （TRH）， CGA， GPX2， and TSHβ in the hypothalamic tissue. ResultsCompared with the normal group， the model group showed significant atrophy and irregularity of thyroid follicles， a marked reduction in colloid secretion， extensive vacuolar degeneration of adenocytes in the anterior pituitary， lowered serum levels of T3， T4， and TSH （P<0.01）， and down-regulated mRNA and protein levels of TSHR in the thyroid tissue， TRHR and TSHβ in the pituitary tissue， and TRH， CGA， GPX2， and TSHβ in the hypothalamic tissue （P<0.01）. Compared with the model group， high- and medium-dose Xiaoyaosan and fluoxetine alleviated the pathological changes in the thyroid and pituitary tissue， outperforming the low-dose Xiaoyaosan group. Moreover， they elevated the serum levels of T3， T4， and TSH （P<0.05， P<0.01）. The serum TSH level was also elevated in the low-dose Xiaoyaosan group （P<0.05）. The mRNA and protein levels of TSHR in the thyroid， TRHR and TSHβ in the pituitary， and TRH， CGA， GPX2， and TSHβ in the hypothalamus were up-regulated in the high- and medium-dose Xiaoyaosan groups （P<0.05， P<0.01）. Additionally， the mRNA and protein levels of TSHβ in the hypothalamus were up-regulated in the low-dose Xiaoyaosan group （P<0.01）. In the fluoxetine group， the mRNA and protein levels of TSHR in the thyroid， TRHR in the pituitary， and TRH， CGA， and GPX2 in the hypothalamus were up-regulated （P<0.05， P<0.01）. ConclusionThe downregulation of CGA/GPX2/TSHβ pathway may be one of the biological mechanisms underlying HPT axis dysfunction in the rat model with the syndrome of liver depression and spleen deficiency. Xiaoyaosan may regulate the HPT axis dysfunction by up-regulating the CGA/GPX2/TSHβ pathway.

ObjectiveTo explore the effect of serum containing Zhenwutang on myocardial mast cell apoptosis induced by angiotensin Ⅱ （AngⅡ） and the mechanism of the correlation between apoptosis and mitochondrial autophagy. MethodsIn this experiment， AngⅡ and serum containing Zhenwutang with different concentrations were used to interfere with H9C2 cardiomyocytes for 24 h， and the survival rate of H9C2 cardiomyocytes was detected by cell counting kit-8 （CCK-8） to screen the optimal concentration for the experiment. Enzyme-linked immunosorbent assay （ELISA） was used to detect the content of B-type natriuretic peptide （BNP） in cell culture supernatant， and immunofluorescence was used to detect the cell surface area to verify the construction of the myocardial mast cell model. Subsequently， the experiment was divided into a blank group （20% blank serum）， a model group （20% blank serum + 5×10^-5 mol·L^-1 AngⅡ）， low-， medium-， and high-dose （5%， 10% and 20%） serum containing Zhenwutang groups， an autophagy inhibitor group （1×10^-4 mol·L^-1 3-MA）， and autophagy inducer group （1×10^-7 mol·L^-1 rapamycin）. The apoptosis level of H9C2 cells and the changes of mitochondrial membrane potential were detected by flow cytometry. The lysosomal probe （Lyso Tracker） and mitochondrial probe （Mito Tracker） co-localization was employed to detect autophagy. Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） was used to detect Caspase-3， Caspase-9， B-cell lymphoma 2 （Bcl-2）， Bcl-2-related X protein （Bax）， and cytochrome C （Cyt C） in apoptosis-related pathways and the relative mRNA expression of ubiquitin ligase （Parkin）， phosphatase and tensin homolog （PTEN）-induced kinase 1 （PINK1）， and p62 protein in mitochondrial autophagy-related pathways. Western blot was used to detect cleaved Caspase-3， cleaved Caspase-9， Bax， Bcl-2， and Cyt C in apoptosis-related pathways， phosphorylated ubiquitin ligase （p-Parkin）， phosphorylated PTEN-induced kinase 1 （p-PINK1）， p62， and Bcl-2 homology domain protein Beclin1 in mitochondrial autophagy-related pathways， and the change of microtubule-associated protein 1 light chain 3 （LC3） Ⅱ/Ⅰ ratio. ResultsCCK-8 showed that when the concentration of AngⅡ was 5×10^-5 mol·L^-1， the cell activity was the lowest， and there was no cytotoxicity. At this concentration， the surface area of cardiomyocytes was significantly increased （P<0.01）， and the content of BNP in the supernatant of culture medium was significantly increased （P<0.05）. Therefore， AngⅡ with a concentration of 5×10^-5 mol·L^-1 was selected for the subsequent modeling of myocardial mast cells. Compared with the blank group， the model group and the autophagy inhibitor 3-MA group had a significantly increased apoptosis rate （P<0.01） and significantly decreased mitochondrial membrane potential （P<0.01）. The results of immunofluorescence co-localization showed that compared with the blank group， the model group had a significantly decreased number of red and green fluorescence spots. The results of Real-time PCR showed that compared with that in the blank group， the relative mRNA expression of Bax， Caspase-3， Caspase-9， Cyt C， and p62 in the model group was significantly up-regulated （P<0.01）， while the relative mRNA expression of Bcl-2， Parkin， and PINK1 was significantly down-regulated （P<0.01）. In addition， the relative protein expression of Bax， cleaved Caspase-3， cleaved Caspase-9， Cyt C， and p62 was significantly up-regulated （P<0.01）. The LC3Ⅱ/Ⅰ was significantly decreased， and the relative protein expression of Bcl-2， p-Parkin， p-PINK1， and Beclin1 was significantly down-regulated （P<0.01）. Compared with the model group， the serum containing Zhenwutang groups and the autophagy inducer group had significantly decreased apoptosis rate （P<0.01）， and the decrease ratio of mitochondrial membrane potential is significantly lowered （P<0.01） in a dose-dependent manner. Additionally， both red and green fluorescence spots became more in these groups. In the 3-MA group， the number of red and green fluorescence spots decreased significantly. The relative mRNA expression of Bax， Caspase-3， Caspase-9， Cyt C， and p62 was significantly down-regulated （P<0.05， P<0.01）， while that of Bcl-2， Parkin， and PINK1 was significantly up-regulated （P<0.01）. In the serum containing Zhenwutang groups， the relative protein expression levels of Bax， cleaved Caspase-3， cleaved Caspase-9， Cyt C， and p62 were significantly down-regulated （P<0.05，P<0.01）. The LC3Ⅱ/Ⅰ was significantly increased， and the relative protein expression levels of Bcl-2， p-Parkin， p-PINK1， and Beclin1 were significantly up-regulated （P<0.01）. ConclusionThe serum containing Zhenwutang can reduce the apoptosis of myocardial mast cells and increase mitochondrial autophagy. This is related to the inhibition of intracellular Bax/Bcl-2/Caspase-3 apoptosis pathway and regulation of Parkin/PINK1 mitochondrial autophagy pathway.

ObjectiveTo explore the therapeutic mechanism of Buchong Tiaojing prescription for rats with diminished ovarian reserve （DOR） from the perspectives of nucleotide-binding oligomerization domain （NOD）-like receptor protein 3 （NLRP3） inflammasome and ferroptosis. MethodsA total of 48 female SD rats were randomly divided into a normal group， a model group， low， medium， and high dose groups of Buchong Tiaojing prescription， and an MCC950 group， with eight rats in each group. Except the normal group， all the other groups were injected subcutaneously on the back of the neck with D-galactose to prepare the DOR rat model. From the 15th day of modeling， the rats in the low， medium， and high dose groups of Buchong Tiaojing prescription were subjected to gavage daily at doses of 14.4， 28.8， 57.6 g·kg^-1， respectively. Rats in the MCC950 group were injected intraperitoneally with MCC950 at a dose of 10 mg·kg^-1， once every other day. The interventions of all the groups lasted for 4 weeks. The estrous cycle of the rats was observed with vaginal exfoliated cell smear. Hematoxylin-eosin （HE） staining was performed to observe the development of follicles and corpus luteum in the ovary. Enzyme-linked immunosorbent assay （ELISA） was performed to detect the levels of serum sex hormones and interleukin-1β （IL-1β）. Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） and Western blot assay were performed to detect the mRNA and protein expression of NLRP3 inflammasome， acyl-CoA synthetase long-chain family member 4 （ACSL4）， transferrin receptor 1 （TFR1）， and glutathione peroxidase 4 （GPX4）， and oxidative stress kits were used to detect ovarian superoxide dismutase （SOD） and malondialdehyde （MDA） levels. ResultsDuring the experiment， one rat died in the high dose group of Buchong Tiaojing prescription， and a total of 47 rats were finally included in the index tests and statistics. Compared with those in the normal group， rats in the model group had significantly disturbed estrous cycles， increased number of atretic follicles， and significant disorder of serum sex hormones. The mRNA and protein expression of NLRP3 inflammasome， ACSL4， and TFR1 in ovarian tissue was up-regulated （P<0.01）， while that of GPX4 was significantly down-regulated （P<0.01）. The SOD content in the ovary was decreased significantly， while the MDA level was increased （P<0.01）. After drug intervention， the estrous cycle of rats was basically resumed， and the follicles at all levels were more structurally intact and significantly increased in number. Additionally， the levels of serum sex hormones and IL-1β were significantly improved. The mRNA and protein expression of NLRP3 inflammasome， ACSL4， and TFR1 were down-regulated， while that of GPX4 was significantly up-regulated， and the ovarian oxidative stress was alleviated （P<0.05， P<0.01）， especially in the high dose group of Buchong Tiaojing prescription and the MCC950 group. ConclusionInflammatory injury and ferroptosis occur in the ovaries of DOR rats， and the Buchong Tiaojing prescription is able to inhibit ovarian NLRP3 inflammasome， alleviate the degree of ovarian ferroptosis， and improve ovarian reserve.

As biological sample biobanks progressively demonstrate their significant value in the field of biomedical research， they also pose challenges to existing social norms and ethical rules， making the normative issue of informed consent of participants highly concerned. The current research has insufficient exploration of informed consent in the collection， preservation， utilization， and other links of the sample. In response to the complexity and diversity of each link， it is advocated to refine informed consent strategies to ensure comprehensive protection of participants’ rights and interests. Given the continuity and dynamism of informed consent， it is recommended to establish a flexible review mechanism to address changes in research content， increased risks， and changes in participant capabilities， ensuring the ethical legitimacy of the research and the autonomy in making decisions of participants. Meanwhile， it is emphasized to fully confirm informed consent before sample entry into the bank， adopt suitable consent forms for outbound utilization and waste disposal， and pay special attention to ethical and legal issues related to human genetic resources.

ObjectiveTo study the effect of Wulingsan on cerebral edema after intracerebral hemorrhage （ICH） in mice and explore the treatment mechanism. MethodsThe mouse model of ICH was established by injection of collagenase into the caudate nucleus. Mice were randomly assigned into the following groups： sham， ICH， intervention before modeling with low-dose and high-dose （3.69， 11.07 g·kg^-1， respectively） Wulingsan， and intervention after modeling with high-dose Wulingsan. The modified neurological severity score （mNSS） was recorded， and the small animal MRI T2 sequential scanning was performed to measure the volume of cerebral hemorrhage after the modeling of ICH in each group. The Y-maze test， open field test， and Morris water maze test were conducted to evaluate the neurological behaviors of mice in each group. Hematoxylin-eosin staining was employed to observe the pathological changes in the brain tissue. Immunohistochemistry was employed to observe the expression of aquaporin 4 （AQP4）， neuronal nuclei （NeuN）， and glial fibrillary acidic protein （GFAP） in the brain tissue. Western blot was employed to determine the protein levels of AQP4， Claudin-5， and zonula occludens-1 （ZO-1） in the hematoma area. ResultsCompared with the sham group， the ICH group showed increases in the mNSS， the cerebral hemorrhage volume， and the escape latency in the Morris water maze test （P<0.01）， decreases in the times of touching the platform and times of entering the quadrant where the platform was located in the Morris water maze test， and reductions in the spontaneous alternation rate in the Y-maze test and the ratio of distance of center travel to total travel distance in the open field test （P<0.01）. Moreover， pathological changes such as cell disarrangement， cell space enlargement， and cell swelling were observed in the ICH group. Immunohistochemistry results showed that the ICH group had higher proportions of AQP4- and GFAP-positive cells and lower proportion of NeuN-positive cells than the sham group （P<0.01）. Compared with the sham group， the ICH group showed an up-regulated protein level of AQP4 and down-regulated protein levels of Claudin-5 and ZO-1 （P<0.01）. Compared with the ICH group， the intervention with Wulingsan decreased the mNSS， the volume of cerebral hemorrhage， and the escape latency in the Morris water maze test （P<0.05， P<0.01）， while increasing the times of touching the platform and times of entering the quadrant where the platform was located in the Morris water maze test， the spontaneous alternation rate in the Y-maze test， and the ratio of distance of center travel to total travel distance in the open field test （P<0.05， P<0.01）. Furthermore， the intervention with Wulingsan alleviated the pathological changes in the brain tissue after ICH， decreased the proportion of AQP4- and GFAP-positive cells （P<0.01）， increased the proportion of NeuN-positive cells （P<0.01）， down-regulated the protein level of AQP4 （P<0.01）， and up-regulated the protein levels of Claudin-5 and ZO-1 （P<0.01）. ConclusionThe intervention with Wulingsan could reduce the neural function score and the cerebral hemorrhage volume， up-regulate the expression of Claudin-5 and ZO-1， and down-regulate the expression of AQP4 to ameliorate the neurological function defect and cerebral edema after ICH， thereby protecting the brain.

AIM:To investigate myopia status and analyze the influence factors in children and adolescent in Wulong district of Chongqing.METHODS:Cross-sectional study. A stratified cluster sampling method was used to select 2 504 primary and secondary school students in Wulong district, and all students underwent myopia screen and questionnaire survey, statistics and analyses the data.RESULTS:Totally 2 431 students were participated in this study, and 1 217 students with myopia were screened out, the prevalence rate of myopia was 50.06%, awareness rate of myopia was 64.59%, glasses wearing rate of myopia was 51.85%. The prevalence of myopia increased with age and grade(P<0.05), the prevalence of myopia in male(46.97%)was lower than in female(53.18%), and the prevalence of myopia in township(47.06%)was lower than in urban area(52.11%; all P<0.05). Regression analysis showed that outdoor activities were protective factor for myopia, while female, myopic parents, near vision work, short sleep duration and sweet tooth were risk factors for myopia.CONCLUSION:The prevalence rate of myopia was higher in children and adolescent in Wulong district of Chongqing, awareness rate of myopia and glasses wearing rate of myopia were lower, and the genesis of myopia is highly relevant to outdoor activities, gender, myopic parents, near vision work, short sleep duration and sweet tooth.

The innate immune system can be boosted in response to subsequent triggers by pre-exposure to microbes or microbial products, known as “trained immunity”. Compared to classical immune memory, innate trained immunity has several different features. Firstly, the molecules involved in trained immunity differ from those involved in classical immune memory. Innate trained immunity mainly involves innate immune cells (e.g., myeloid immune cells, natural killer cells, innate lymphoid cells) and their effector molecules (e.g., pattern recognition receptor (PRR), various cytokines), as well as some kinds of non-immune cells (e.g., microglial cells). Secondly, the increased responsiveness to secondary stimuli during innate trained immunity is not specific to a particular pathogen, but influences epigenetic reprogramming in the cell through signaling pathways, leading to the sustained changes in genes transcriptional process, which ultimately affects cellular physiology without permanent genetic changes (e.g., mutations or recombination). Finally, innate trained immunity relies on an altered functional state of innate immune cells that could persist for weeks to months after initial stimulus removal. An appropriate inducer could induce trained immunity in innate lymphocytes, such as exogenous stimulants (including vaccines) and endogenous stimulants, which was firstly discovered in bone marrow derived immune cells. However, mature bone marrow derived immune cells are short-lived cells, that may not be able to transmit memory phenotypes to their offspring and provide long-term protection. Therefore, trained immunity is more likely to be relied on long-lived cells, such as epithelial stem cells, mesenchymal stromal cells and non-immune cells such as fibroblasts. Epigenetic reprogramming is one of the key molecular mechanisms that induces trained immunity, including DNA modifications, non-coding RNAs, histone modifications and chromatin remodeling. In addition to epigenetic reprogramming, different cellular metabolic pathways are involved in the regulation of innate trained immunity, including aerobic glycolysis, glutamine catabolism, cholesterol metabolism and fatty acid synthesis, through a series of intracellular cascade responses triggered by the recognition of PRR specific ligands. In the view of evolutionary, trained immunity is beneficial in enhancing protection against secondary infections with an induction in the evolutionary protective process against infections. Therefore, innate trained immunity plays an important role in therapy against diseases such as tumors and infections, which has signature therapeutic effects in these diseases. In organ transplantation, trained immunity has been associated with acute rejection, which prolongs the survival of allografts. However, trained immunity is not always protective but pathological in some cases, and dysregulated trained immunity contributes to the development of inflammatory and autoimmune diseases. Trained immunity provides a novel form of immune memory, but when inappropriately activated, may lead to an attack on tissues, causing autoinflammation. In autoimmune diseases such as rheumatoid arthritis and atherosclerosis, trained immunity may lead to enhance inflammation and tissue lesion in diseased regions. In Alzheimer’s disease and Parkinson’s disease, trained immunity may lead to over-activation of microglial cells, triggering neuroinflammation even nerve injury. This paper summarizes the basis and mechanisms of innate trained immunity, including the different cell types involved, the impacts on diseases and the effects as a therapeutic strategy to provide novel ideas for different diseases.

Currently, the drug delivery system (DDS) based on nanomaterials has become a hot interdisciplinary research topic. One of the core issues is drug loading and controlled release, in which the key lever is carriers. Vaterite, as an inorganic porous nano-material, is one metastable structure of calcium carbonate, full of micro or nano porous. Recently, vaterite has attracted more and more attention, due to its significant advantages, such as rich resources, easy preparations, low cost, simple loading procedures, good biocompatibility and many other good points. Vaterite, gained from suitable preparation strategies, can not only possess the good drug carrying performance, like high loading capacity and stable loading efficiency, but also improve the drug release ability, showing the better drug delivery effects, such as targeting release, pH sensitive release, photothermal controlled release, magnetic assistant release, optothermal controlled release. At the same time, the vaterite carriers, with good safety itself, can protect proteins, enzymes, or other drugs from degradation or inactivation, help imaging or visualization with loading fluorescent drugs in vitro and in vivo, and play synergistic effects with other therapy approaches, like photodynamic therapy, sonodynamic therapy, and thermochemotherapy. Latterly, some renewed reports in drug loading and controlled release have led to their widespread applications in diverse fields, from cell level to clinical studies. This review introduces the basic characteristics of vaterite and briefly summarizes its research history, followed by synthesis strategies. We subsequently highlight recent developments in drug loading and controlled release, with an emphasis on the advantages, quantity capacity, and comparations. Furthermore, new opportunities for using vaterite in cell level and animal level are detailed. Finally, the possible problems and development trends are discussed.