Enhanced ß-glucosidase in Western flower thrips affects its interaction with the redox-based strategies of kidney beans under elevated CO2.

ß-Glucosidase is validated as an elicitor for early immune responses in plants and it was detected in the salivary glands of Frankliniella occidentalis in previous research. Seven differentially expressed genes encoding ß-glucosidase were obtained by comparing the transcriptomes of F. occidentalis adults grown under two different CO2 concentrations (800 vs. 400 ppm), which might be associated with the differences in the interaction between F. occidentalis adults and its host plant, Phaseolus vulgaris under different CO2 levels. To verify this speculation, changes in defense responses based on the production and elimination of reactive oxygen species (ROS) in P. vulgaris leaves treated with three levels of ß-glucosidase activity under ambient CO2 (aCO2 ) and elevated CO2 (eCO2 ) were measured in this study. According to the results, significantly higher levels of ROS were noticed under eCO2 compared to aCO2 , which was caused by the increased ß-glucosidase activity in thrips due to increased cellulose content in P. vulgaris leaves under eCO2 . Together with the lower activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in injured leaves under eCO2 , P. vulgaris leaves would be negatively affected on redox-based defense by eCO2 , thus facilitating thrips damage under climate change.

Tuning electronic, magnetic and catalytic behaviors of biphenylene network by atomic doping.

Recently, a new two-dimensional allotrope of carbon named biphenylene has been experimentally synthesized. First-principles calculations are preformed to investigate the electronic properties of biphenylene and the doping effect is also considered to tune its electronic, magnetic, and catalytic properties. The metallic nature with an n-type Dirac cone is observed in the biphenylene. The magnetism can be induced by Fe, Cl, Cr, and Mn doping. More importantly, the doping position dependence of hydrogen evolution reaction (HER) performance of biphenylene is addressed, which can be significantly improved by atomic doping. In particular, the barrier for HER of Fe doping case is only -0.03 eV, denoting its great potential in HER catalysis.

The regulation mechanisms and the Lamarckian inheritance property of DNA methylation in animals.

DNA methylation is a stable and heritable epigenetic mechanism, of which the main functions are stabilizing the transcription of genes and promoting genetic conservation. In animals, the direct molecular inducers of DNA methylation mainly include histone covalent modification and non-coding RNA, whereas the fundamental regulators of DNA methylation are genetic and environmental factors. As is well known, competition is present everywhere in life systems, and will finally strike a balance that is optimal for the animal's survival and reproduction. The same goes for the regulation of DNA methylation. Genetic and environmental factors, respectively, are responsible for the programmed and plasticity changes of DNA methylation, and keen competition exists between genetically influenced procedural remodeling and environmentally influenced plastic alteration. In this process, genetic and environmental factors collaboratively decide the methylation patterns of corresponding loci. DNA methylation alterations induced by environmental factors can be transgenerationally inherited, and exhibit the characteristic of Lamarckian inheritance. Further research on regulatory mechanisms and the environmental plasticity of DNA methylation will provide strong support for understanding the biological function and evolutionary effects of DNA methylation.

Mechanical, electronic and optical properties of a novel B2P6 monolayer: ultrahigh carrier mobility and strong optical absorption.

Two-dimensional (2D) materials with a moderate bandgap and high carrier mobility are useful for applications in optoelectronics. In this work, we present a systematic investigation of the mechanical, electronic and optical properties of a B2P6 monolayer using first-principles calculations. Monolayer B2P6 was estimated to be an anisotropic material from direction-dependent in-plane Young's moduli and Poisson's ratios. Also, B2P6 exhibits an ultrahigh electron mobility of ∼5888 cm2 V-1 s-1, showing advantages for application in high-speed optoelectronic devices. More importantly, for the B2P6 monolayer, a desirable transformation from an indirect to direct band gap was observed at a biaxial tensile strain of ∼4%. Increasing the biaxial strain reduces the gap and preserves the suitable band edge positions for photocatalytic water splitting in the observed strain range of 1-8%. The decreased gap also enhances the visible light absorption of the B2P6 monolayer. These findings indicate that the B2P6 monolayer has promising applications in photocatalytic and photovoltaic devices.

Catalytically Selective Chemotherapy from Tumor-Metabolic Generated Lactic Acid.

Lactic acid (LA) is a powerful molecule as the metabolic driver in tumor microenvironments (TMEs). Inspired by its high intratumoral level (5-20 µmol g-1 ), a novel treatment paradigm via the cascade release of H2 O2 and ·OH from the LA generated by tumor metabolism is developed for catalytic and pH-dependent selective tumor chemotherapy. By utilizing the acidity and overexpression of LA within the TME, the constructed lactate oxidase (LOD)-immobilized Ce-benzenetricarboxylic acid (Ce-BTC) metal organic framework enables the intratumoral generation of ·OH via a cascade reaction: 1) the in situ catalytic release of H2 O2 from LA by LOD, and 2) the catalytic production of ·OH from H2 O2 by Ce-BTC with peroxidase-like activity. Highly toxic ·OH effectively induces tumor apoptosis/death. A new strategy for selective tumor chemotherapy is provided herein.

Effect of cold atmospheric plasma treatment on the metabolites of human leukemia cells.

BACKGROUND: Acute myeloid leukemia (AML) is a typically fatal malignancy and new drug and treatment need to be developed for a better survival outcome. Cold atmospheric plasma (CAP) is a novel technology, which has been widely applied in biomedicine, especially in various of cancer treatment. However, the changes in cell metabolism after CAP treatment of leukemia cells have been rarely studied. METHODS: In this study, we investigated the metabolite profiling of plasma treatment on leukemia cells based on Gas Chromatography Tandem Time-of-Flight Mass Spectrometry (GC-TOFMS). Simultaneously, we conducted a series of bioinformatics analysis of metabolites and metabolic pathways with significant differences after basic data analysis. RESULTS: 800 signals were detected by GC-TOF mass-spectrometry and then evaluated using PCA and OPLS-DA. All the differential metabolites were listed and the related metabolic pathways were analyzed by KEGG pathway. The results showed that alanine, aspartate and glutamate metabolism had a significant change after plasma treatment. Meanwhile, d-glutamine and d-glutamate metabolism were significantly changed by CAP. Glutaminase activity was decreased after plasma treatment, which might lead to glutamine accumulation and leukemia cells death. CONCLUSIONS: We found the above two metabolic pathways vulnerable to plasma treatment, which might result in leukemia cells death and might be the cornerstone of further exploration of plasma treatment targets.

Using van der Waals heterostructures based on two-dimensional blue phosphorus and XC (X = Ge, Si) for water-splitting photocatalysis: a first-principles study.

Solar-powered production of hydrogen from water has been pursued as one of the solutions to the global energy crisis. Meanwhile, two-dimensional (2D) materials have attracted significant attention as photocatalysts. In this paper, the geometric structures, electronic band structures, band alignment, and optical properties of two novel van der Waals (vdW) heterostructures based on 2D blue phosphorus (BlueP) and 2D XC (X = Ge, Si) were systematically explored using first-principles calculations. We found that both BlueP/GeC and BlueP/SiC vdW heterostructures possess type-II band structures, which can continuously separate the photogenerated electron-hole pairs. The calculated band-edge positions suggest that the BlueP/SiC and BlueP/GeC vdW heterostructures act as potential photocatalysts for water-splitting at pH 0 and pH 7, respectively. Furthermore, XC acts as an electron-donating layer in the BlueP/XC vdW heterostructure, and the potential drop across the interface can generate a large built-in electric field across the interface; this electric field plays a crucial role in preventing the recombination of photogenerated charges. Finally, the optical properties of the BlueP/XC vdW heterostructures demonstrate that they have excellent ability to capture visible light, making them promising high-performance photocatalysts for water splitting.

Alteration of metabolite profiling by cold atmospheric plasma treatment in human myeloma cells.

BACKGROUND: Despite new progress of chemotherapy in multiple myeloma (MM) clinical treatment, MM is still a refractory disease and new technology is needed to improve the outcomes and prolong the survival. Cold atmospheric plasma is a rapidly developed technology in recent years, which has been widely applied in biomedicine. Although plasma could efficiently inactivate various tumor cells, the effects of plasma on tumor cell metabolism have not been studied yet. METHODS: In this study, we investigated the metabolite profiling of He plasma treatment on myeloma tumor cells by gas-chromatography time-of-flight (GC-TOF) mass-spectrometry. Meanwhile, by bioinformatic analysis such as GO and KEGG analysis we try to figure out the metabolism pathway that was significantly affected by gas plasma treatment. RESULTS: By GC-TOF mass-spectrometry, 573 signals were detected and evaluated using PCA and OPLS-DA. By KEGG analysis we listed all the differential metabolites and further classified into different metabolic pathways. The results showed that beta-alanine metabolism pathway was the most significant change after He gas plasma treatment in myeloma cells. Besides, propanoate metabolism and linoleic acid metabolism should also be concerned during gas plasma treatment of cancer cells. CONCLUSIONS: Cold atmospheric plasma treatment could significantly alter the metabolite profiling of myeloma tumor cells, among which, the beta-alanine metabolism pathway is the most susceptible to He gas plasma treatment.

Enhanced molecular recognition for imprinted monolithic column containing polyhedral oligomeric silsesquioxanes by dendritic effect of mesoporous molecular sieve scaffolds.

The dendritic effect of nano mesoporous molecular sieve was first used to enhance molecular recognition of molecularly imprinted polymers (MIPs)-based polyhedral oligomeric silsesquioxanes (POSS). In this study, the MIPs were made using S-naproxen (S-NAP) as template molecule, 4-vinylpyridine (4-VP) as functional monomer, ethylene glycol dimethacrylate as cross-linker, 1-butyl-3-methylimidazoliumtetrafluoroborate ([BMIM]BF4)/DMSO as binary porogens, 1-propylmethacrylate-heptaisobutyl substituted as POSS monomer, and mesoporous molecular sieve (Mobil composition of matter No. 41, MCM-41) as dendritic scaffold. The influence of synthesis parameters on the imprinting effect, including the content of POSS monomer and derivatized MCM-41-MPS, the ratio of template to monomer, and the ratio of binary porogens were also investigated, respectively. The morphology of the polymers was characterized by scanning electron microscopy, nitrogen adsorption, and X-ray powder diffraction. The results showed that POSS&MCM-41-MPS MIP had a stronger imprinting effect with an imprinting factor 6.86, which is approximately 2.4, 2.3, and 3 times than that of POSS MIP, MCM-41-MPS MIP, and conventional MIP, respectively. The increase of affinity might be attributed to impediment of the chain motion of polymer due to improved POSS aggregation and the dipole interaction between the POSS units by introduce of MCM-41-MPS as scaffolds. The resulting POSS&MCM-41-MPS MIP was used as adsorbent for the enrichment of S-NAP in solid-phase extraction with a high recovery of 97.65% and the value of RSD was 0.94%.

Affinity capillary electrophoresis and fluorescence spectroscopy for studying enantioselective interactions between omeprazole enantiomer and human serum albumin.

Baseline separation of omeprazole (OME) enantiomers was achieved by affinity capillary electrophoresis (ACE), using human serum albumin (HSA) as the chiral selector. The influence of several experimental variables such as HSA concentration, the type and content of organic modifiers, applied voltage and running buffer concentration on the separation was evaluated. The binding of esomeprazole (S-omeprazole, S-OME) and its R-enantiomer (R-omeprazole, R-OME) to HSA under simulated physiological conditions was studied by ACE and fluorescence spectroscopy which was considered as a reference method. ACE studies demonstrated that the binding constants of the two enantiomers and HSA were 3.18 × 103 M-1 and 5.36 × 103 M-1 , respectively. The binding properties including the fluorescence quenching mechanisms, binding constants, binding sites and the number of binding sites were obtained by fluorescence spectroscopy. Though the ACE method could not get enough data when compared with the fluorescence spectrum method, the separation and binding studies of chiral drugs could be achieved simultaneously via this method. This study is of great significance for the investigation and clinical application of chiral drugs.

The effects of cold atmospheric plasma on cell adhesion, differentiation, migration, apoptosis and drug sensitivity of multiple myeloma.

Cold atmospheric plasma was shown to induce cell apoptosis in numerous tumor cells. Recently, some other biological effects, such as induction of membrane permeation and suppression of migration, were discovered by plasma treatment in some types of tumor cells. In this study, we investigated the biological effects of plasma treatment on multiple myeloma cells. We detected the detachment of adherent myeloma cells by plasma, and the detachment area was correlated with higher density of hydroxyl radical in the gas phase of the plasma. Meanwhile, plasma could promote myeloma differentiation by up-regulating Blimp-1 and XBP-1 expression. The migration ability was suppressed by plasma treatment through decreasing of MMP-2 and MMP-9 secretion. In addition, plasma could increase bortezomib sensitivity and induce myeloma cell apoptosis. Taking together, combination with plasma treatment may enhance current chemotherapy and probably improve the outcomes.

Should thorough Debridement be used in Fibular Allograft with impaction bone grafting to treat Femoral Head Necrosis: a biomechanical evaluation.

BACKGROUND: Fibular allograft with impaction bone grafting (FAIBG) is an effective hip-preservation method for avoiding total hip arthroplasty in the early stage of femoral head necrosis. However, whether thorough debridement should be used with FAIBG is controversial. This study compared the mechanical performance between FAIBG with and without thorough debridement, which provides a biomechanical basis for selecting the proper treatment in clinical settings. METHODS: Eighteen computational models were constructed and used to simulate two subtypes of femoral head collapse with seven debridement radii. The initial model was validated using the bony density distribution from X-ray images and a photograph of the cadaver bone cross-section. The stress of the anterolateral column and the debridement efficiency were computed and analyzed. RESULTS: (1) The peak stress of the anterolateral column in all conditions could return to the physiological level, and in two cases, the decrement/increment of stress was almost less than 0.1 % when the debridement radius increased. (2) The load share ratio (LSR) of the cortical and cancellous bone was markedly decreased in the untreated condition and increases with an increase in the debridement radius. (3) A debridement radius greater than 1/2r yields a LSR value larger than that obtained in the normal condition. CONCLUSIONS: The simulation results provide specific biomechanical evidence to support the finding that FAIBG with a debridement region of 3/8 -1/2 appears to be a better choice for resisting femoral head collapse (FHC). Furthermore, FAIBG without thorough debridement, which requires relatively simple surgical devices and reduces artificial damage, appears to be a better method for resisting FHC than FAIBG with thorough debridement.

Heterotopic cesarean scar pregnancy: diagnosis, treatment, and prognosis.

Heterotopic cesarean scar pregnancy is a rare, life-threatening form of ectopic pregnancy. To provide information regarding the clinical manifestations, diagnosis, management, and prognosis of this condition, we reviewed all cases reported in the English literature. All literature on heterotopic cesarean scar pregnancy was retrieved by searching the PubMed database and tracking references of the relevant literature. Full texts were reviewed, and clinical manifestations, diagnostic methods, and the relationship between the treatment and prognosis were summarized. A total of 14 patients with heterotopic cesarean scar pregnancies were identified, including 6 spontaneous pregnancies and 8 following in vitro fertilization-embryo transfer. Gestational ages at diagnosis ranged from 5 weeks to 8 weeks 4 days. Only 5 cases presented with vaginal bleeding, and the others were asymptomatic. All 14 cases were diagnosed by transvaginal sonography. One patient with no future fertility requirements underwent pregnancy termination by methotrexate. Of the remaining 13 patients who desired to preserve their intrauterine gestations, 10 were treated by sonographically guided selective embryo reduction in situ (by embryo aspiration, drug injection, or both); 2 underwent laparoscopic and hysteroscopic excision of the ectopic pregnancy masses; and 1 was treated by expectant management. All operations were successful and maintained a living intrauterine gestation. Twelve cases resulted in live births by cesarean delivery (3 at term and 9 preterm). One patient underwent pregnancy termination at 12 weeks because of a fetal malformation confirmed by sonography. The possibility of heterotopic cesarean scar pregnancy after cesarean delivery should be considered, especially when pregnancy follows assisted reproductive technology. Transvaginal sonography is an important tool for diagnosis and management. Despite the many options, the best treatment for this condition remains unclear. Selective embryo reduction in situ with sonographic guidance is the main treatment modality and can result in a successful intrauterine gestation, albeit at high risk.

Active substance and mechanisms of Actinidia chinensis Planch for the treatment of breast cancer was explored based on network pharmacology and in silico study.

In this paper, our objective was to investigate the potential mechanisms of Actinidia chinensis Planch (ACP) for breast cancer treatment with the application of network pharmacology, molecular docking, and molecular dynamics. "Mihoutaogen" was used as a key word to query the Traditional Chinese Medicine Systems Pharmacology database for putative ingredients of ACP and its related targets. DrugBank, GeneCards, Online Mendelian Inheritance in Man, and therapeutic target databases were used to search for genes associated with "breast cancer." Using Cytoscape 3.9.0 we then constructed the protein-protein interaction and drug-ingredient-target-disease networks. An enrichment analysis of Kyoto encyclopedia of genes and genomes pathway and gene ontology were performed to exploration of the signaling pathways associated with ACP for breast cancer treatment. Discovery Studio software was applied to molecular docking. Finally, the ligand-receptor complex was subjected to a 50-ns molecular dynamics simulation using the Desmond_2020.4 tools. Six main active ingredients and 176 targets of ACP and 2243 targets of breast cancer were screened. There were 118 intersections of targets for both active ingredients and diseases. Tumor protein P53 (TP53), AKT serine/threonine kinase 1 (AKT1), estrogen receptor 1 (ESR1), Erb-B2 receptor tyrosine kinase 2 (ERBB2), epidermal growth factor receptor (EGFR), Jun Proto-Oncogene (JUN), and Heat Shock Protein 90 Alpha Family Class A Member 1 (HSP90AA1) selected as the most important genes were used for verification by molecular docking and molecular dynamics simulation. The primary active compounds of ACP against breast cancer were predicted preliminarily, and its mechanism was studied, thereby providing a theoretical basis for future clinical studies.

Impact of Brewers' Spent Grain-Containing Biscuit on Postprandial Glycaemic Response in Individuals with Metabolic Syndrome: A Crossover Randomised Controlled Trial.

Brewers' spent grain (BSG) is a fibre and protein-rich by-product of beer-brewing. Fermenting BSG with Rhizopus oligosporus can further increase its content of soluble fibre, protein and certain antioxidants. Since nutrients rich in BSG can improve postprandial glycaemic response, this study assessed the postprandial glucose response (PPGR) and postprandial insulin response (PPIR) controlling effect of consuming 30% wheat flour substituted biscuits with autoclaved BSG (ABSG) or fermented BSG (FBSG) in individuals with metabolic syndrome (MetS). The effect on postprandial lipid panel, breath hydrogen (H2) and methane (CH4) concentration and subjective appetite response was also examined. Fifteen subjects with MetS participated in this crossover randomised controlled trial, and blood was collected at 9 time-points for 4 h after consumption of control biscuits (Control), ABSG and FBSG. A significant interaction effect was observed (Pinteraction = 0.013) for the glucose time-points concentration. At 180 min, the glucose concentration was lowered after the consumption of ABSG (p = 0.010) and FBSG (p = 0.012) compared to the Control. Moreover, the FBSG resulted in a significantly lower glucose incremental area under curve (iAUC) compared to the Control (p = 0.028). Insulin level was also lowered at 180 min after the ABSG (p = 0.010) and FBSG (p = 0.051) consumption compared to the Control. However, no difference was noted for postprandial lipid panel, breath H2 and CH4 concentration and subjective appetite response. In conclusion, the consumption of BSG-incorporated biscuits can attenuate PPGR, and fermented BSG incorporation conferred a further PPGR controlling benefit.

Breaking-Down Tumoral Physical Barrier by Remotely Unwrapping Metal-Polyphenol-Packaged Hyaluronidase for Optimizing Photothermal/Photodynamic Therapy-Induced Immune Response.

The therapy of solid tumors is often hindered by the compact and rigid tumoral extracellular matrix (TECM). Precise reduction of TECM by hyaluronidase (HAase) in combination with nanotechnology is promising for solid tumor therapeutics, yet remains an enormous challenge. Inspired by the treatment of iron poisoning, here a remotely unwrapping strategy is proposed of metal-polyphenol-packaged HAase (named PPFH) by sequentially injecting PPFH and a clinically used iron-chelator deferoxamine (DFO). The in situ dynamic disassembly of PPFH can be triggered by the intravenously injected DFO, resulting in the release, reactivation, and deep penetration of encapsulated HAase inside tumors. Such a cost-effective HAase delivery strategy memorably improves the subsequent photothermal and photodynamic therapy (PTT/PDT)-induced intratumoral infiltration of cytotoxic T lymphocyte cells and the cross-talk between tumor and tumor-draining lymph nodes (TDLN), thereby decreasing the immunosuppression and optimizing tumoricidal immune response that can efficiently protect mice from tumor growth, metastasis, and recurrence in multiple mouse cancer models. Overall, this work presents a proof-of-concept of the dynamic disassembly of metal-polyphenol nanoparticles for extracellular drug delivery as well as the modulation of TECM and immunosuppressive tumor microenvironment.

Discovery of RORγ Allosteric Fluorescent Probes and Their Application: Fluorescence Polarization, Screening, and Bioimaging.

Retinoic acid receptor-related orphan receptor γ (RORγ) acts as a crucial transcription factor in Th17 cells and is involved in diverse autoimmune disorders. RORγ allosteric inhibitors have gained significant research focus as a novel strategy to inhibit RORγ transcriptional activity. Leveraging the high affinity and selectivity of RORγ allosteric inhibitor MRL-871 (1), this study presents the design, synthesis, and characterization of 11 allosteric fluorescent probes. Utilizing the preferred probe 12h, we established an efficient and cost-effective fluorescence polarization-based affinity assay for screening RORγ allosteric binders. By employing virtual screening in conjunction with this assay, 10 novel RORγ allosteric inhibitors were identified. The initial SAR studies focusing on the hit compound G381-0087 are also presented. The encouraging outcomes indicate that probe 12h possesses the potential to function as a powerful tool in facilitating the exploration of RORγ allosteric inhibitors and furthering understanding of RORγ function.

Characteristics of vascular supply to uterine leiomyoma: an analysis of digital subtraction angiography imaging in 518 cases.

OBJECTIVES: To investigate the characteristics of the vascular supply to uterine leiomyomas based on digital subtraction angiography. METHODS: The feeding artery, vascularity of uterine leiomyoma and visualisation of the ovarian vessel network were studied in 518 patients undergoing uterine artery embolisation (UAE). Mean patient age was 38.97 ± 6.09 years (range, 22-54 years). The types of vascular supply were analysed by the vascular supply to the leimyoma and grades of vascularity by the degree of enhancement of the leimyoma compared with the myometrium. RESULTS: The blood supply of leiomyomas could not be classified in 3.28 % of patients. Blood was supplied solely by the uterine artery in 88.61 % of leiomyomas, 8.11 % of leiomyomas were partially fed by an ovarian artery, and 0.39 % by it exclusively. Leiomyoma blood supply was classified as unilateral predominant, bilateral balanced, single unilateral uterine artery and single ovarian artery in 36.48, 49.23, 10.62 and 0.39 % of cases respectively. Leiomyoma vascularity was classified as extremely hypervascular (8.69 %), hypervascular (46.14 %), isovascular (33.39 %) and hypovascular (11.78 %). CONCLUSIONS: Uterine leiomyomas supplied by both uterine arteries and with rich blood flow were seen in approximately 50 % of patients. However, close attention also should be given to the collateral circulation during UAE.

Understanding older adults' smartphone addiction in the digital age: empirical evidence from China.

Background: Despite the fact that an increasing number of older adults are addicted to smartphones, the existing addiction literature still focuses primarily on adolescents. To address this issue, this study draws from the perspectives of subjective cognitive decline and family relationship conflict to examine older adults' smartphone addiction based on their key characteristics. Methods: This study investigates the effects of subjective cognitive decline and family relationship conflict on older adults' smartphone addiction through a survey of 371 subjects in China. Results: The results show that subjective cognitive decline and family relationship conflict affect older adults' smartphone addiction through a sense of alienation. In addition, older adults' perceived power moderates the relationship between alienation and smartphone addiction. Discussion: This study offers new perspectives on the study of smartphone addiction from the perspective of older adults, and sheds light on how to improve the older adults' quality of life in their later years.

Risk prediction of placenta previa based on the distance from the lower edge of the gestational sac to the internal cervical os in early pregnancy.

OBJECTIVES: To explore the relationship between the distance from the lower edge of the gestational sac to the internal cervical os in early pregnancy and placenta previa. MATERIAL AND METHODS: A prospective cohort study of women who underwent pregnancy examination in Weifang People's Hospital or Sunshine Union Hospital from January 2020 to June 2021. The distance from the lower edge of the gestational sac to the internal cervical os was measured at 5-6 weeks' gestation. There were 86 women with distance < 2.5 cm, and 105 women with distance ≥ 2.5 cm were randomly selected. There were 92 cases of scarred uterus and 99 cases of non-scarred uterus among the 191 women. They were divided into six groups according to the distance: (1) < 1.0 cm; (2) 1.0 cm to < 1.5 cm; (3) 1.5 cm to < 2.0cm; (4) 2.0 cm to < 2.5 cm; (5) 2.5 cm to < 3.0 cm; (6) ≥ 3.0 cm. All included women were followed-up during pregnancy and pregnancy outcome, and the likelihood ratio of different distances in early pregnancy was calculated and risk stratification was performed, and ROC curve was constructed. RESULTS: There were 15 women in the included studies who were lost to follow-up, 47 had a scarred uterus with placenta previa and 29 had a non-scarred uterus with placenta previa after delivery at 28 weeks or later. The distance from the lower edge of the gestational sac to the internal cervical os in early pregnancy of the scarred uterus < 1.5 cm, and the likelihood ratio was ∞; and the distance ≥ 3.0 cm, the likelihood ratio was 0. The distance from the lower edge of the non-scarred gestational sac to the internal cervical os < 1.0 cm, and the likelihood ratio was ∞; and the distance ≥ 3.0 cm, the likelihood ratio was 0. The ROC curve showed that when the area AUC under the curve was 87%, the optimal diagnostic cut-off value was 2.4 cm. CONCLUSIONS: When the distance from the lower edge of the gestational sac to the internal cervical os was < 1.5 cm and the distance between the non-scarred uterus was < 1.0 cm, it eventually developed into placenta previa; the distance from the lower edge of the gestational sac to the internal cervical os in the first trimester of pregnancy between the scarred uterus and the non-scarred uterus was ≥ 3.0 cm, and it would hardly develop into placenta previa. When the distance from the lower edge of the gestational sac to the internal cervical os in early pregnancy was ≤ 2.4 cm, it could be used as a predictor of placenta previa.