Endovascular Treatment of Acute Ischemic Stroke

Cyclic Aspiration in Mechanical Thrombectomy: Influencing Factors and Experimental Validation

BACKGROUND AND PURPOSE

Mechanical thrombectomy is a fundamental intervention for acute ischemic stroke treatment. While conventional techniques are effective, cyclic aspiration (CyA) shows potential for better recanalization rates. We aim to investigate factors affecting CyA and compare them with static aspiration (StA).

MATERIALS AND METHODS

StA setup consisted of an aspiration pump connected to pressure transducer. CyA was tested with 5 subsequent iterations: single solenoid valve with air plus saline (i1) or saline alone (i2) as aspiration medium; 2 solenoid valves with air plus saline (i3) as aspiration medium; complete air removal and saline feeding (i4); and pressurized saline feeding (i5). To assess the efficacy of clot ingestion, the pressure transducer was replaced with a distal aspiration catheter. Moderately stiff clot analogs (15 mm) were used to investigate the ingestion quantified as clot relative weight loss. Additionally, the aspiration flow rate was assessed for each setup.

RESULTS

With CyA i1, the amplitude of the achieved negative pressure waves declined with increasing frequencies but progressively increased with each subsequent iteration, achieving a maximum amplitude of 81 kPa for i5 at 1 Hz. Relative clot weight loss was significantly higher with i5 at 5 Hz than with StA (100% versus 37.8%; P = .05). Aspiration flow rate was lower with CyA than with StA (i5 at 5 Hz: 199.8 mL/min versus StA: 311 mL/min; P < .01).

CONCLUSIONS

CyA with the appropriate setup may represent an encouraging innovation in mechanical thrombectomy, offering a promising pathway for improving efficacy in clot ingestion and recanalization. The observed benefits warrant confirmation in a clinical setting.

Mechanical thrombectomy using the Nimbus stent-retriever - initial experiences in a single-center observational study

BACKGROUND

The Nimbus stent-retriever (NSR) was developed for mechanical thrombectomy of wall-adherent thrombi in cerebral arteries. It features a novel geometry with a proximal spiral section and a distal barrel section. The new device is designed to retrieve tough clots with a micro-clamping technique. In the first case series reporting on the NSR, we share our initial experience about the first 12 treated cases.

METHODS

In total, 12 patients (5 men, 7 women; mean age 78 years) with occlusion of the internal carotid artery or the middle cerebral artery (M1 or M2 segment) were treated with the NSR, 11 after unsuccessful recanalization attempts with conventional stent-retrievers or aspiration thrombectomy.

RESULTS

Retrieving maneuvers with the NSR recovered a thrombus in 7 patients (58%), of which 6 resulted in vessel recanalization mTICI ≥ 2b. Successful recanalization improved the mTICI score by a median of 3 points. In 5 of 7 cases, this required only one thrombectomy maneuver. In 5 cases, no improvement of recanalization could be achieved with the NSR (1-3 attempts). No NSR-related complications occurred in this case series.

CONCLUSIONS

In our initial experience, the NSR appeared to be a safe and effective second-line stent-retriever after unsuccessful MT with conventional stent-retrievers or aspiration thrombectomy allowing for mTICI ≥ 2b rescue thrombectomy in ab 50% of cases. No NSR associated complications occurred in our case series.

Impact of Local Tailoring on Acute Stroke Care in 21 Disparate Emergency Departments: A Prospective Stepped Wedge Type III Hybrid Effectiveness-Implementation Study

BACKGROUND

Faster delivery of tPA (tissue-type plasminogen activator) results in better health outcomes for eligible patients with stroke. Standardization of stroke protocols in emergency departments (EDs) has been difficult, especially in nonstroke centers. We measured the effectiveness of a centrally led implementation strategy with local site tailoring to sustain adherence to an acute stroke protocol to improve door-to-needle (DTN) times across disparate EDs in a multihospital health system.

METHODS

Prospective, type III hybrid effectiveness-implementation cohort study measuring performance at 21 EDs in Utah and Idaho (stroke centers [4]/nonstroke centers [17]) from January 2018 to February 2020 using a nonrandomized stepped-wedge design, monthly repeated site measures and multilevel hierarchical modeling. Each site received the implementation strategies in 1 of 6 steps providing control and intervention data. Co-primary outcomes were percentage of DTN times ≤60 minutes and median DTN time. Secondary outcomes included percentage of door-to-activation of neurological consult times ≤10 minutes and clinical effectiveness outcomes. Results were stratified between stroke and nonstroke centers.

RESULTS

A total of 855 474 ED patient encounters occurred with 5325 code stroke activations (median age, 69 [IQR, 56-79] years; 51.8% female patients]. Percentage of door-to-activation times ≤10 minutes increased from 47.5% to 59.9% (adjusted odds ratio, 1.93 [95% CI, 1.40-2.67]). A total of 615 patients received tPA of ≤3 hours from symptom onset (median age, 71 [IQR, 58-80] years; 49.6% female patients). The percentage of DTN times ≤60 minutes increased from 72.5% to 86.1% (adjusted odds ratio, 3.38, [95% CI, 1.47-7.78]; stroke centers (77.4%-90.0%); nonstroke centers [59.3%-72.1%]). Median DTN time declined from 46 to 38 minutes (adjusted median difference, -9.68 [95% CI, -17.17 to -2.20]; stroke centers [41-35 minutes]; nonstroke centers [55-52 minutes]). No differences were observed in clinical effectiveness outcomes.

CONCLUSIONS

A centrally led implementation strategy with local site tailoring led to faster delivery of tPA across disparate EDs in a multihospital system with no change in clinical effectiveness outcomes including rates of complication. Disparities in performance persisted between stroke and nonstroke centers.

Observation of efficacy of rt-PA thrombolysis combined with Solitaire AB stent mechanical thrombectomy in patients with acute ischemic stroke: a retrospective analysis

OBJECTIVE

To observe and analyze the efficacy of recombinant tissue-plasminogen activator (rt-PA) thrombolysis combined with Solitaire AB stent mechanical thrombectomy in patients with acute ischemic stroke.

METHODS

Clinical efficacy, neurological function, oxidative stress response, adverse reactions, and quality of life were compared between the two groups.

RESULTS

Lower NIHSS scores were observed among patients who received treatment within 2 h after stroke onset when compared with those in a timeframe of 2-6 h, suggesting better neurological function recovery of the patients with early intervention and thus emphasizing the importance of early treatment for patients with stroke onset. Clinical efficacy in the combination group was significantly higher than in the control group (p < 0.05). After treatment, Paraoxonase-1 (PON-1) levels were higher, while lipoprotein-associated phospholipase A2 (Lp-PLA2) and Serum Amyloid A (SAA) levels were lower in the combination group compared to the control group (p < 0.05). The incidence of adverse reactions was significantly lower in the combination group (p < 0.05). At discharge, we observed significantly more patients with good recovery in the combination group when compared to the control group (p < 0.05), suggesting better quality of life of the patients, while this statistical significance was no longer observable at 90 days after discharge (p > 0.05).

CONCLUSION

For acute ischemic stroke patients, rt-PA thrombolysis combined with Solitaire AB stent mechanical thrombectomy treatment is effective. It promotes neurological function recovery, improves vascular stenosis, reduces inflammation and adverse reactions, and enhances quality of life, showing promising clinical applications.

Efficacy of antiplatelet drugs combined with Argatroban in treating acute ischemic stroke and its impact on patients' coagulation function and neurological function: a preliminary trial

This retrospective study analyzed the efficacy of combined antiplatelet therapy with Argatroban in treating acute ischemic stroke (AIS) and its impact on patients' coagulation and neurological functions. Clinical data of 113 AIS patients admitted between January 2021 and January 2023 were retrospectively analyzed. Patients were divided into control (n = 56) and observation (n = 57) groups based on treatment interventions. The control group patients were treated with antiplatelet drugs, while the observation group patients received combination therapy with apatinib on the basis of the control group treatment. Compared to the control group, the observation group demonstrated higher clinical efficacy, improved coagulation parameters, reduced stroke severity (measured by NIHSS), enhanced daily living abilities (BI scores), and lowered inflammatory and neural injury markers post-treatment. Adverse reaction incidence was similar between groups. Combining Argatroban with antiplatelet drugs in AIS management showed superior efficacy without increasing adverse effects, suggesting its potential for clinical application.

The effects of visual skills training on cognitive and executive functions in stroke patients: a systematic review with meta-analysis

The visual system and associated skills are of particular importance in stroke rehabilitation. The process of neuroplasticity involved in restoring cognitive function during this period is mainly based on anatomical and physiological mechanisms. However, there is little evidence-based knowledge about the effects of visual skills training that could be used to improve therapeutic outcomes in cognitive rehabilitation. A computerized systematic literature search was conducted in the PubMed, Medline, and Web of Science databases from 1 January 1960 to 11 Febuary 2024. 1,787 articles were identified, of which 24 articles were used for the calculation of weighted standardized mean differences (SMD) after screening and eligibility verification. The findings revealed moderate effects for global cognitive function (SMD = 0.62) and activities of daily living (SMD = 0.55) as well as small effects for executive function (SMD = 0.20) - all in favor of the intervention group. The analyses indicate that the results may not be entirely robust, and should therefore be treated with caution when applied in practice. Visual skills training shows positive effects in improving cognitive and executive functions, especially in combination with high cognitive load and in an early phase of rehabilitation. An improvement in activities of daily living can also be observed with this type of intervention. The high heterogeneity of the studies and different treatment conditions require the identification of a relationship between certain visual skills and executive functions in future research.

MRPS9-Mediated Regulation of the PI3K/Akt/mTOR Pathway Inhibits Neuron Apoptosis and Protects Ischemic Stroke

Neuronal apoptosis is crucial in the pathophysiology of ischemic stroke (IS), albeit its underly24ing mechanism remaining elusive. Investigating the mechanism of neuronal apoptosis in the context of IS holds substantial clinical value for enhancing the prognosis of IS patients. Notably, the MRPS9 gene plays a pivotal role in regulating mitochondrial function and maintaining structural integrity. Utilizing bioinformatic tactics and the extant gene expression data related to IS, we conducted differential analysis and weighted correlation network analysis (WGCNA) to select important modules. Subsequent gene interaction analysis via the STRING website facilitated the identification of the key gene-mitochondrial ribosomal protein S9 (MRPS9)-that affects the progression of IS. Moreover, possible downstream signaling pathways, namely PI3K/Akt/mTOR, were elucidated via Kyoto Encyclopedia of Gene and Genomes (KEGG) and Gene Ontology (GO) pathway analysis. Experimental models were established utilizing oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro and middle cerebral artery occlusion/reperfusion (MCAO/R) in mice. Changes in gene and protein expression, as well as cell proliferation and apoptosis, were monitored through qPCR, WB, CCK8, and flow cytometry. An OGD/R cell model was further employed to investigate the role of MRPS9 in IS post transfusion of MRPS9 overexpression plasmids into cells. Further studies were conducted by transfecting overexpressed cells with PI3K/Akt/mTOR signaling pathway inhibitor LY294002 to unveil the mechanism of MRPS9 in IS. Bioinformatic analysis revealed a significant underexpression of MRPS9 in ischemic stroke patients. Correspondingly, in vitro experiments with HN cells subjected to OGD/R treatment demonstrated a marked reduction in MRPS9 expression, accompanied by a decline in cell viability, and an increase cell apoptosis. Notably, the overexpression of MRPS9 mitigated the OGD/R-induced decrease in cell viability and augmentation of apoptosis. In animal models, MRPS9 expression was significantly lower in the MCAO/R group compared to the sham surgery group. Further, the KEGG pathway analysis associated MRPS9 expression with the PI3K/Akt/mTOR signaling pathway. In cells treated with the specific PI3K/Akt/mTOR inhibitor LY294002, phosphorylation levels of Akt and mTOR were decreased, cell viability decreased, and apoptosis increased compared to the MRPS9 overexpression group. These findings collectively indicate that MRPS9 overexpression inhibits PI3K/Akt/mTOR pathway activation, thereby protecting neurons from apoptosis and impeding IS progression. However, the PI3K/Akt/mTOR inhibitor LY294002 is capable of counteracting the protective effect of MRPS9 overexpression on neuronal apoptosis and IS. Our observations underscore the potential protective role of MRPS9 in modulating neuronal apoptosis and in attenuating the pathophysiological developments associated with IS. This is achieved through the regulation of the PI3K/Akt/mTOR pathway. These insights forge new perspectives and propose novel targets for the strategic diagnosis and treatment of IS.

Identification of key biomarkers in ischemic stroke: single-cell sequencing and weighted co-expression network analysis

PURPOSE

At present, there is a lack of accurate early diagnostic markers for ischemic stroke.

METHODS

By using dimensionality reduction cluster analysis, differential expression analysis, weighted co-expression network analysis, protein-protein interaction network analysis, cell heterogeneity and key pathogenic genes were identified in ischemic stroke. Immunomicroenvironment analysis was used to explore the immune landscape and immune associations of key genes in ischemic stroke. The analysis platform we use is R software (version 4.0.5). PCR experiments were used to verify the expression of key genes.

RESULTS

Single cell sequencing data in ischemic stroke can be annotated as fibroblast cells, pre-B cell CD34, neutrophils cells, bone marrow (BM), keratinocytes, macrophage, neurons and mesenchymal stem cells (MSC). By the intersection of differential expression analysis and WGCNA analysis, 385 genes were obtained. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that these genes were highly correlated with multiple functions and pathways. Protein-protein interaction network analysis revealed that MRPS11 and MRPS12 were key genes, both of which were down-regulated in ischemic stroke. The Pseudo-time series analysis found that the expression of MRPS12 decreased gradually with the differentiation of pre-B cell CD34 cells in ischemic stroke, suggesting that the downregulation of MRPS12 expression may play an important role in ischemic stroke. At last, PCR showed that MRPS11 and MRPS12 were significantly down-regulated in peripheral blood of patients with ischemic stroke.

CONCLUSIONS

Our study provides a reference for the study of pathogenesis and key targets of ischemic stroke.

In vivo imaging of cerebral glucose metabolism informs on subacute to chronic post-stroke tissue status - A pilot study combining PET and deuterium metabolic imaging

Recanalization therapy after acute ischemic stroke enables restoration of cerebral perfusion. However, a significant subset of patients has poor outcome, which may be caused by disruption of cerebral energy metabolism. To assess changes in glucose metabolism subacutely and chronically after recanalization, we applied two complementary imaging techniques, fluorodeoxyglucose (FDG) positron emission tomography (PET) and deuterium (2H) metabolic imaging (DMI), after 60-minute transient middle cerebral artery occlusion (tMCAO) in C57BL/6 mice. Glucose uptake, measured with FDG PET, was reduced at 48 hours after tMCAO and returned to baseline value after 11 days. DMI revealed effective glucose supply as well as elevated lactate production and reduced glutamate/glutamine synthesis in the lesion area at 48 hours post-tMCAO, of which the extent was dependent on stroke severity. A further decrease in oxidative metabolism was evident after 11 days. Immunohistochemistry revealed significant glial activation in and around the lesion, which may play a role in the observed metabolic profiles. Our findings indicate that imaging (altered) active glucose metabolism in and around reperfused stroke lesions can provide substantial information on (secondary) pathophysiological changes in post-ischemic brain tissue.

Insight into the mechanism of DNA methylation and miRNA-mRNA regulatory network in ischemic stroke

BACKGROUND

Epigenetic changes, such as DNA methylation and miRNA-target gene mechanisms, have recently emerged as key provokers in Ischemic stroke (IS) onset. However, cellular and molecular events harboring these epigenetic alterations are poorly understood. Therefore, the present study aimed to explore the potential biomarkers and therapeutic targets for IS.

METHODS

miRNAs, mRNAs and DNA methylation datasets of IS were derived from the GEO database and normalized by PCA sample analysis. Differentially expressed genes (DEGs) were identified, and GO and KEGG enrichment analyses were performed. The overlapped genes were utilized to construct a protein-protein interaction network (PPI). Meanwhile, differentially expressed mRNAs and miRNAs interaction pairs were obtained from the miRDB, TargetScan, miRanda, miRMap and miTarBase databases. We constructed differential miRNA-target gene regulatory networks based on mRNA-miRNA interactions.

RESULTS

A total of 27 up-regulated and 15 down-regulated differential miRNAs were identified. Dataset analysis identified 1053 and 132 up-regulated and 1294 and 9068 down-regulated differentially expressed genes in the GSE16561 and GSE140275 datasets, respectively. Moreover, 9301 hypermethylated and 3356 hypomethylated differentially methylated sites were also identified. Moreover, DEGs were enriched in terms related to translation, peptide biosynthesis, gene expression, autophagy, Th1 and Th2 cell differentiation, primary immunodeficiency, oxidative phosphorylation and T cell receptor signaling pathway. MRPS9, MRPL22, MRPL32 and RPS15 were identified as hub genes. Finally, a differential miRNA-target gene regulatory network was constructed.

CONCLUSIONS

RPS15, along with hsa-miR-363-3p and hsa-miR-320e have been identified in the differential DNA methylation protein interaction network and miRNA-target gene regulatory network, respectively. These findings strongly posit the differentially expressed miRNAs as potential biomarkers to improve ischemic stroke diagnosis and prognosis.

Thiolutin attenuates ischemic stroke injury via inhibition of NLRP3 inflammasome: an in vitro and in vivo study

A recent study confirmed that thiolutin is effective in the treatment of nucleotide-binding domain-like receptor protein 3 (NLRP3)-related inflammatory diseases. Nevertheless, whether thiolutin (THL) is involved in the regulation of NLRP3 inflammasome in ischemic stroke is not known. The murine neuronal cell oxygen-glucose deprivation (OGD) model was first established, and then different concentrations (25 nM and 50 nM) of THL were administered for 48 h incubation, respectively. Subsequently, cell viability and toxicity, and the levels of intracellular inflammatory factors interleukin-1β (IL-1β), interleukin-18 (IL-18), oxidative stress factors superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and malondialdehyde (MDA), and NLRP3 inflammasome activation-related proteins pro-caspase, caspase-1, apoptosis-associated speck like-protein (ASC) and NLRP3 were examined, respectively. We further established the mouse middle cerebral artery occlusion (MCAO) model to evaluate the therapeutic effects of THL on cerebral infarction like behaviors in mice and the preventive effects on NLRP3 inflammasome activation in vivo. Cell cytotoxic, and the levels of inflammatory factors and oxidative stress were conspicuously increased, and NLRP3 inflammasome was materially activated in the OGD-induced cell model and MCAO-established mouse model, which were partially countered by THL treatment. Besides, intraperitoneal injection of THL could prominently reduce the cerebral infarct volume and neuromotor deficit scores in MCAO mice. The present study confirmed that THL attenuated neuronal and cerebral inflammatory injury caused by OGD and MCAO models in mice through restraining NLRP3 inflammasome activation in vitro and in vivo.

Block Copolymer Nanomicelle-Encapsulated Curcumin Attenuates Cerebral Ischemia Injury and Affects Stem Cell Marker Expression by Inhibiting lncRNA GAS5

Stroke has become the most common cause of death among residents in China, among which ischemic stroke accounts for the vast majority reaching 70% to 80%. It is of great importance to actively investigate the protective mechanism of cerebral ischemia injury after IS (ischemic stroke). We constructed cerebral ischemia injury models in vivo MACO rat and in vitro (oxygen-glucose deprivation cell model) and set up different interference groups. RT-PCR (reverse transcription PCR) was conducted to detect the expression of lncRNA in neuronal cells, brain tissue, and plasma of different groups, and ELISA (enzyme-linked immunosorbent assay) and western blot were used to detect the expression of the protein in neuronal cells, brain tissue, and plasma of different groups. Cell activity was detected by the CCK-8 assay, while cell apoptosis was examined by TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay. In the rats' neuronal cells and brain tissue, curcumin can inhibit the expression of lncRNA GAS5 (long noncoding RNA growth arrest-specific 5). In oxygen-glucose-deprived neuronal cells in vitro, curcumin and low-expressed lncRNA GAS5 can enhance cell activity and decline cell apoptosis, but the addition of curcumin and overexpressed lncRNA GAS5 can make this phenomenon disappear. In neuronal cells, plasma, and brain tissue, curcumin and the low-expressed lncRNA GAS5 can inhibit the expression of IL-1β (interleukin 1 beta), TNF-α (tumor necrosis factor alpha), IL-6 (interleukin 6), Sox2 (SRY-box transcription factor 2), Nanog, and Oct4 (octamer-binding transcription factor 4). However, overexpressed lncRNA GAS5 and curcumin made the inhibitory effect disappear. In conclusion, this study demonstrated that curcumin could inhibit the expression of lncRNA GAS5, thereby inhibiting the expression of inflammation-related factors IL-1β, TNF-α, and IL-6, and ultimately achieve the purpose of attenuating cerebral ischemic cell damage. However, curcumin and lncRNA GAS5 may not alleviate cerebral ischemic cell damage by affecting stem cell differentiation.

Elevated NT-proBNP levels are associated with CTP ischemic volume and 90-day functional outcomes in acute ischemic stroke: a retrospective cohort study

Objective

To investigate the impact of N-terminal pro-B-type natriuretic peptide (NT-proBNP) on CTP infarct core volume and poor 90-day functional outcomes in acute ischemic stroke (AIS).

Methods

A total of 403 hospitalized patients with AIS in the Stroke Center of the First Hospital Affiliated to Soochow University were enrolled from March 2018 to January 2021. The association between NT-proBNP and clinical outcomes in acute ischemic patients was assessed by logistic regression and adjusted for confounding factors. Also, subgroup analyses were conducted based on treatment decisions.

Results

NT-proBNP was positively correlated with CTP ischemic volume (p < 0.001), infarct core volume (p < 0.001), and ischemic penumbra volume (p < 0.001). Univariate analysis showed that the influence of NT-proBNP and functional outcomes were statistically significant in model 1 (p = 0.002). This phenomenon was persistent after adjusted for age, sex, and body mass index in model 2 (p = 0.011), adjusted for SBP, current smoking, family history of stroke, hypertension, and diabetes mellitus in model 3 (p < 0.001), and adjusted for TnI, D-dimer, PLT, Cr, TC, TG, HDL-C, treatment decisions, and NIHSS score in model 4 (p = 0.027). A high NT-proBNP was associated with a high 90-days mRS score among the total population, IV rt-PA, and standardized treatment groups, but not in IV rt-PA + EVT, EVT, and EVT/IV rt-PA + EVT groups.

Conclusion

Elevated NT-proBNP levels reveal large CTP infarct core volume and poor 90-day functional outcome in AIS. NT-pro BNP is an independent risk factor for functional outcomes.

Transcriptomic Profiling of Electroacupuncture Regulating the Molecular Network in Hippocampus of Rats with Cerebral Ischemia-Reperfusion Injury

Objective. To explore the mechanism of electroacupuncture stimulation of the hand-taiyin meridian in regulating the molecular network of rats with cerebral ischemia-reperfusion injury based on transcriptomics. Methods. Male SD rats were randomly divided into sham operation group, model group, and electroacupuncture (EA) group. Middle cerebral artery embolization/reperfusion injury (MCAO/R) was used to establish the model group and EA group. The sham operation group only performed sham operation without modeling and any intervention, and the model group was bound daily. The EA group received electroacupuncture to stimulate the acupoints of hand-taiyin meridian for 14 days. Then, neurological scores, pathomorphological observations, and Tunel staining were performed. Finally, the affected hippocampus of the rat was used for transcriptome sequencing and RT-PCR detection. Results. After electroacupuncture intervention in rats, neurological function scores were improved, and neuronal apoptosis was reduced. The results of transcriptomics showed that a total of 1097 differentially expressed genes were obtained, of which 422 were upregulated and 675 were downregulated. The bioinformatics analysis showed that those differentially expressed genes were related to axon development, neuron projection development, neuron projection morphogenesis, plasma membrane cell projection morphogenesis, cell part morphogenesis, notch signaling pathway, long-term potentiation, MAPK signaling pathway, Hedgehog signaling pathway, and so on. The results of RT-PCR showed that Caspase 9 mRNA increased and BDNF, Grin2a, and PlexinD1 mRNA decreased after electroacupuncture intervention $\left(P<0.05\right)$ . Conclusion. Electroacupuncture intervention on hand-taiyin meridian may reduce neurological function scores, inhibit neuron apoptosis, and enhance neuronal repair neuroreparation in MCAO/R rats, which may be related to the regulation of genes such as Caspase 9, BDNF, Grin2a, and PlexinD1.

NGF/TrkA promotes the vitality, migration and adhesion of bone marrow stromal cells in hypoxia by regulating the Nrf2 pathway

BACKGROUND

Bone marrow stromal cells (BMSCs) transplantation is a treatment strategy for ischemic stroke (IS) with great potential. However, the vitality, migration and adhesion of BMSCs are greatly impaired due to the harsh environment of the ischemic area, which affects the therapeutic effects. Herein, we aimed to investigate the roles of nerve growth factor (NGF) in regulating cell behaviors of BMSCs in IS.

METHODS

The mRNA and protein expressions were assessed using qRT-PCR and western blot, respectively. To simulate ischemic-like conditions in vitro, Brain microvascular (bEnd.3) cells were exposed to oxygen and glucose deprivation (OGD). Cell viability and cell proliferation were evaluated by MTT assay and BrdU assay, respectively. Transwell migration and cell adhesion assays were carried out to determine cell migration and adhesion of BMSCs, respectively, coupled with flow cytometry to evaluate cell apoptosis of bEnd.3 cells. Finally, angiogenesis assay was performed to assess the angiogenesis ability of bEnd.3 cells.

RESULTS

NGF overexpression resulted in increased cell vitality, adhesion and migration of BMSCs, while NGF knockdown presented the opposite effects. We subsequently discovered that TrkA was a receptor for NGF, and TrkA knockdown significantly inhibited the cell viability, migration and adhesion of BMSCs. Besides, Nrf2 was confirmed as the downstream target of NGF/TrkA to promote the viability, adhesion and migration of BMSC cells. Finally, NGF-silenced BMSCs could not effectively restore the OGD-induced brain microvascular cell damage.

CONCLUSIONS

NGF/TrkA promoted the viability, migration and adhesion of BMSCs in IS via activating Nrf2 pathway.

Early Diagnosis of Acute Ischemic Stroke by Brain Computed Tomography Perfusion Imaging Combined with Head and Neck Computed Tomography Angiography on Deep Learning Algorithm

The purpose of the research was to discuss the application values of deep learning algorithm-based computed tomography perfusion (CTP) imaging combined with head and neck computed tomography angiography (CTA) in the diagnosis of ultra-early acute ischemic stroke. Firstly, 88 patients with acute ischemic stroke were selected as the research objects and performed with cerebral CTP and CTA examinations. In order to improve the effect of image diagnosis, a new deconvolution network model AD-CNNnet based on deep learning was proposed and used in patient CTP image evaluation. The results showed that the peak signal-to-noise ratio (PSNR) and feature similarity (FSIM) of the AD-CNNnet method were significantly higher than those of traditional methods, while the normalized mean square error (NMSE) was significantly lower than that of traditional algorithms (P < 0.05). 80 cases were positive by CTP-CTA, including 16 cases of hyperacute ischemic stroke and 64 cases of acute ischemic stroke. The diagnostic sensitivity was 93.66%, and the specificity was 96.18%. The cerebral blood flow (CBF), cerebral blood volume (CBV), and the mean transit time (MTT) in the infarcted area were significantly greater than those in the corresponding healthy side area, and the time to peak (TTP) was significantly less than that in the corresponding healthy side area (P < 0.05). The cerebral perfusion parameters CBF, TTP, and MTT in the penumbra were significantly different from those in the infarct central area and the corresponding contralateral area, and TTP was the most sensitive (P < 0.05). To sum up, deep learning algorithm-based CTP combined with CTA could find the location of cerebral infarction lesions as early as possible to provide a reliable diagnostic result for the diagnosis of ultra-early acute ischemic stroke.

Artemisinin Alleviates Cerebral Ischemia/Reperfusion Injury via Regulation of the Forkhead Transcription Factor O1 Signaling Pathway

The effect and mechanism of artemisinin therapy on cerebral ischemia-reperfusion injury (CIRI) was analyzed in this work. 100 healthy male C57BL/6 mice were selected and randomly divided into the sham group (no treatment), CIRI model group (IR), IR + artemisinin posttreatment group (IR + Arte), EX527 + IR group (EX527 + IR), and EX527 + IR + artemisinin posttreatment group (EX527 + IR + Arte), with 20 mice in each group. The cerebral infarct volumes of mice in different groups were measured by the 2,3,5-triphenyltetrazolium chloride (TTC) staining method. The neurological function scores and oxidative stress levels of mice in different groups were measured and compared. In addition, the expressions of silent information regulator 1 (SIRT1), forkhead transcription factor O1 (FOXO1), and p53 protein in brain tissue were detected. The results showed that the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) in the EX527 + IR group and EX527 + IR + Arte group were significantly higher than those in the IR + Arte group (P < 0.05). The expressions of SIRT1 protein in the brain tissue of the IR group and EX527 + IR group were much lower than that of the sham group (P < 0.01); compared with the IR + Arte group, the expression of the X527 + IR group in the brain tissue was greatly reduced (P < 0.05). The expression levels of FOXO1 protein and p53 protein in the brain tissue of mice in the IR group and EX527 + IR group were higher than those in the sham group (P < 0.01). It was concluded that artemisinin treatment can reduce oxidative stress damage and alleviate CIRI through the SIRT1/FOXO1 signaling pathway, thereby achieving neuroprotective effects.

Proteomics-Based Approach to Identify Novel Blood Biomarker Candidates for Differentiating Intracerebral Hemorrhage From Ischemic Stroke-A Pilot Study

Background: A reliable distinction between ischemic stroke (IS) and intracerebral hemorrhage (ICH) is required for diagnosis-specific treatment and effective secondary prevention in patients with stroke. However, in resource-limited settings brain imaging, which is the current diagnostic gold standard for this purpose, is not always available in time. Hence, an easily accessible and broadly applicable blood biomarker-based diagnostic test differing stroke subtypes would be desirable. Using an explorative proteomics approach, this pilot study aimed to identify novel blood biomarker candidates for distinguishing IS from ICH.

Material and Methods: Plasma samples from patients with IS and ICH were drawn during hospitalization and were analyzed by using liquid chromatography/mass spectrometry. Proteins were identified using the human reference proteome database UniProtKB, and label-free quantification (LFQ) data were further analyzed using bioinformatic tools.

Results: Plasma specimens of three patients with IS and four patients with ICH with a median National Institute of Health Stroke Scale (NIHSS) of 12 [interquartile range (IQR) 10.5–18.5] as well as serum samples from two healthy volunteers were analyzed. Among 495 identified protein groups, a total of 368 protein groups exhibited enough data points to be entered into quantitative analysis. Of the remaining 22 top-listed proteins, a significant difference between IS and ICH was found for Carboxypeptidase N subunit 2 (CPN2), Coagulation factor XII (FXII), Plasminogen, Mannan-binding lectin serine protease 1, Serum amyloid P-component, Paraoxonase 1, Carbonic anhydrase 1, Fibulin-1, and Granulins.

Discussion: In this exploratory proteomics-based pilot study, nine candidate biomarkers for differentiation of IS and ICH were identified. The proteins belong to the immune system, the coagulation cascade, and the apoptosis system, respectively. Further investigations in larger cohorts of patients with stroke using additional biochemical analysis methods, such as ELISA or Western Blotting are now necessary to validate these markers, and to characterize diagnostic accuracy with regard to the development of a point-of-care-system for use in resource-limited areas.

Neutrophils and Platelets: Immune Soldiers Fighting Together in Stroke Pathophysiology

Neutrophils and platelets exhibit a diverse repertoire of functions in thromboinflammatory conditions such as stroke. Most cerebral ischemic events result from longstanding chronic inflammation secondary to underlying pathogenic conditions, e.g., hypertension, diabetes mellitus, obstructive sleep apnea, coronary artery disease, atrial fibrillation, morbid obesity, dyslipidemia, and sickle cell disease. Neutrophils can enable, as well as resolve, cerebrovascular inflammation via many effector functions including neutrophil extracellular traps, serine proteases and reactive oxygen species, and pro-resolving endogenous molecules such as Annexin A1. Like neutrophils, platelets also engage in pro- as well as anti-inflammatory roles in regulating cerebrovascular inflammation. These anucleated cells are at the core of stroke pathogenesis and can trigger an ischemic event via adherence to the hypoxic cerebral endothelial cells culminating in aggregation and clot formation. In this article, we review and highlight the evolving role of neutrophils and platelets in ischemic stroke and discuss ongoing preclinical and clinical strategies that may produce viable therapeutics for prevention and management of stroke.

Protective Properties of the Extract of Chrysanthemum on Patients with Ischemic Stroke

Investigation of the protective effect of chrysanthemum extract in ischemic strokes patients is among the challenging issues with the traditional hospital system in general and smart technology-based hospitals in particular. In this study, we have evaluated the protective effect of chrysanthemum extract on patients with ischemic stroke by detecting the severity of stroke, neuronal indexes, and oxidative stress biomarkers. For this purpose, forty-six patients with ischemic stroke were randomly divided into the control group (n = 30) and chrysanthemum group (n = 30). The control group received standard stroke treatment, and the chrysanthemum group was treated with chrysanthemum extract 400 mg/day (200 mg/day, twice/day) on the basis of standard treatment. The groups were compared the effect of saffron capsules using the National Institute of Health Stoke Scale (NIHSS), serum neuron specific enolase (NSE), S100, brain-derived neurotrophic factor (BDNF), malondialdehyde (MDA), Su-peroxide dismutase (SOD), and total antioxidant capacity (TAC ) levels, at the time of first day and fourth day after treatment. On the first day after treatment, there was no significant difference in the NIHSS score, serum NSE, S100, BDNF, MDA, SOD, and TAC levels between the chrysanthemum group and the control group (P > 0.05). On the fourth day after treatment, the NIHSS, serum NSE, S100, and MDA levels were significantly reduced in the chrysanthemum group compared to the control group, while the BDNF, SOD, and TAC levels were higher (P < 0.05). In addition, compared to the levels on the first day, the NIHSS, serum NSE, S100, and MDA levels were significantly reduced, and the BDNF, SOD, and TAC levels were increased in the chrysanthemum group on the fourth day (P < 0.05). Chrysanthemum extract has the effects of scavenging oxygen free radicals and antioxidation and has a neuroprotective effect on ischemic stroke patients.

Different Scores Predict the Value of Hemorrhagic Transformation after Intravenous Thrombolysis in Patients with Acute Ischemic Stroke

Objective

To evaluate the value of the Alberta stroke project early CT score (ASPECTS), DRAGON score, SEDAN score, and HAT score in predicting hemorrhagic transformation (HT) after intravenous thrombolysis in patients with acute ischemic stroke (AIS).

Methods

The clinical data of 248 AIS patients treated with intravenous thrombolysis in our hospital from December 2017 to December 2019 were analyzed. According to the prognosis, all patients were divided into the non-HT group (n = 200) and the HT group (n = 48). Univariate analysis and multivariate logistic regression models were used to analyze clinical data to determine the influencing factors of HT after intravenous thrombolysis in AIS patients. The receiver operating characteristic curve was used to evaluate the ASPECTS, DRAGON, SEDAN, and HAT scores to the value of predicting HT after intravenous thrombolysis in AIS patients.

Results

The lower the ASPECTS score and the higher the DRAGON, SEDAN, and HAT scores, the higher the incidence of HT after intravenous thrombolysis in AIS patients (P < 0.05). The results of multivariate logistic regression analysis showed that the patient's age, atrial fibrillation, baseline NIHSS score, early signs of infarction on admission with head CT, time from onset to thrombolytic therapy, and thrombolytic drugs were all independent factors affecting intravenous thrombolysis in AIS patients (P < 0.05). The area under the curve (AUC) of the predictive value of ASPECTS for HT is 0.895 (95% CI 0.813–0.977). When the optimal cutoff value is 0.607, the sensitivity is 100% and the specificity is 60.7%. The AUC of the predictive value of DRAGON for HT is 0.877 (95% CI 0.790–0.964). When the optimal cutoff value is 0.665, the sensitivity is 84.4% and the specificity is 82.1%. The AUC of the predictive value of SEDAN for HT is 0.764 (95% CI 0.638–0.890). When the optimal cutoff value is 0.474, the sensitivity is 78.6% and the specificity is 68.8%. The AUC of the predictive value of HAT for HT is 0.777 (95% CI 0.651–0.903). When the optimal cutoff value is 0.509, the sensitivity is 68.8% and the specificity is 82.1%.

Conclusion

The lower the ASPECTS score and the higher the DRAGON, SEDAN, and HAT scores, the higher the incidence of HT in AIS patients. The patient's age, atrial fibrillation, baseline NIHSS score, early signs of infarction on admission with head CT, time from onset to thrombolytic therapy, and thrombolytic drugs are all independent factors affecting HT in AIS patients. The scores of ASPECTS, DRAGON, SEDAN and HAT have certain value in predicting HT after intravenous thrombolysis in AIS patients, and the predicted value of ASPECTS score is the best.

Predictive Value of Apelin and Vaspin on Hemorrhagic Transformation in Patients with Acute Ischemic Stroke after Intravenous Thrombolysis and Analysis of Related Factors

BACKGROUND

Acute ischemic stroke (CIS) is a high-risk condition among the elderly, and intravenous thrombolytic therapy (ITT) is the most effective means for it. However, ITT is prone to induce hemorrhagic transformation (HT) that further threatens the life and health of patients. As paramount substances in cardiovascular and cerebrovascular diseases, adipocyte factor (Apelin) and serine protease inhibitor (Vaspin) are strongly bound up with CIS.

OBJECTIVE

To analyze the predictive significance of Apelin and Vaspin on HT in CIS patients after ITT and offer effective reference to HT prevention in the future.

METHODS

A total of 109 CIS patients treated with intravenous thrombolysis (IT) in two hospitals between June 2017 and February 2018 were enrolled. Among them, 48 patients who suffered HT after therapy were assigned to the research group (Res group) and the other 61 patients who did not suffer it after therapy were assigned to the control group (Con group). Serum Apelin, Vaspin, inflammatory factors, and oxidative stress levels were quantified, and receiver operating characteristic (ROC) curves were drawn for analyzing the predictive value of Apelin and Vaspin on HT after ITT and their associations with inflammatory factors and oxidative stress. CIS patients who suffered HT were followed up for 3 years for prognostic significance analysis of Apelin and Vaspin.

RESULTS

After ITT, the Res group showed lower Apelin and Vaspin levels than the Con group (all P < 0.05), and patients with a higher HT grade had lower Apelin and Vaspin levels (all P < 0.05). The joint detection of Apelin and Vaspin showed a sensitivity of 77.08% and a specificity of 73.77% for forecasting HT in CIS patients after thrombolytic therapy (all P < 0.001). In addition, after thrombolytic therapy, the Res group presented higher levels of interleukin-1β (IL-1β) and IL-6 as well as malondialdehyde (MDA) than the Con group, and the levels had negative associations with Apelin and Vaspin (all P < 0.05). The Res group showed a lower superoxide dismutase (SOD) level than the Con group, and the level presented a positive association with Apelin and Vaspin (all P < 0.05). According to Logistic analysis, IL-1β, IL-6, and MDA were independent risk factors for HT in CIS patients after IT, while Apelin, Vaspin, and SOD were independent protective factors (all P < 0.05). According to the follow-up results, Apelin and Vaspin demonstrated excellent value in forecasting the death of patients with both CIS and HT (P < 0.05), and their lower levels indicate a higher risk of death (all P < 0.05).

CONCLUSION

Apelin and Vaspin can help effectively forecast the occurrence of HT in CIS patients after ITT as independent protective factors of HT, so they are of a high clinical application value.

Bridging therapy and direct mechanical thrombectomy in the treatment of cardiogenic cerebral infarction with anterior circulation macrovascular occlusion

BACKGROUND

Intravenous thrombolysis is an important treatment for cerebral infarction. However, it is difficult to achieve good results if the patient is complicated with anterior circulation macrovascular occlusion. In addition, the vascular recanalization rate is low, so mechanical thrombectomy, that is, bridging therapy, is needed

AIM

To investigate the efficacy and safety of bridging therapy and direct mechanical thrombectomy in the treatment of cardiogenic cerebral infarction with anterior circulation macrovascular occlusion.

METHODS

Ninety-six patients in our hospital with cardiogenic cerebral infarction with anterior circulation macrovascular occlusion from January 2017 to July 2020 were divided into a direct thrombectomy group (n = 48) and a bridging group (n = 48). Direct mechanical thrombectomy was performed in the direct thrombectomy group, and bridging therapy was used in the bridging treatment group. Comparisons were performed for the treatment data of the two groups (from admission to imaging examination, from admission to arterial puncture, from arterial puncture to vascular recanalization, and from admission to vascular recanalization), vascular recanalization rate, National Institutes of Health Stroke Scale (NIHSS) and Glasgow Coma Scale (GCS) scores before and after treatment, prognosis and incidence of adverse events.

RESULTS

In the direct thrombectomy group, the time from admission to imaging examination was 24.32 ± 8.61 min, from admission to arterial puncture was 95.56 ± 37.55 min, from arterial puncture to vascular recanalization was 54.29 ± 21.38 min, and from admission to revascularization was 156.88 ± 45.51 min, and the corresponding times in the bridging treatment group were 25.38 ± 9.33 min, 100.45 ± 39.30 min, 58.14 ± 25.56 min, and 161.23 ± 51.15 min; there were no significant differences between groups (P=0.564, 0.535, 0.426, and 0.661, respectively). There was no significant difference in the recanalization rate between the direct thrombectomy group (79.17%) and the bridging group (75.00%) (P = 0.627). There were no significant differences between the direct thrombectomy group (16.69 ± 4.91 and 12.12 ± 2.07) and the bridging group (7.13 ± 1.23 and (14.40 ± 0.59) in preoperative NIHSS score and GCS score (P = 0.200 and 0.203, respectively). After the operation, the NIHSS scores in both groups were lower than those before the operation, and the GCS scores were higher than those before the operation. There was no significant difference in NIHSS and GCS scores between the direct thrombectomy group (6.91 ± 1.10 and 14.19 ± 0.65) and the bridging group (7.13 ± 1.23 and 14.40 ± 0.59) (P = 0.358 and 0.101, respectively). There was no significant difference in the proportion of patients who achieved a good prognosis between the direct thrombectomy group (52.08%) and the bridging group (50.008%) (P = 0.838). There was no significant difference in the incidence of adverse events between the direct thrombectomy group (6.25%) and the bridging group (8.33%) (P = 0.913).

CONCLUSION

Bridging therapy and direct mechanical thrombectomy can safely treat cardiogenic cerebral infarction with anterior circulation macrovascular occlusion, achieve good vascular recanalization effects and prognoses, and improve the neurological function of patients.

Influencing Factors of Early Neurological Deterioration and Short-Term Prognosis after Intravenous Thrombolysis in Patients with Acute Ischemic Stroke

Objective

To explore the factors affecting the early neurological deterioration (END) and short-term prognosis of patients with acute ischemic stroke (AIS) after intravenous thrombolysis.

Methods

The clinical data of 212 patients with AIS who received intravenous thrombolysis in our hospital from July 2017 to November 2020 were selected and divided into the END group (n = 71) and the non-END group (n = 141) according to the National Institute of Health Stroke Scale (NIHSS) score and divided into the poor prognosis group (n = 85) and the good prognosis group (n = 127) according to the modified Rankin scale (mRS) score at discharge. The basic data of patients, vascular risk factors, imaging examinations, and laboratory indicators were collected. A logistic regression model was used to analyze the influencing factors of END and the short-term prognosis of AIS patients after intravenous thrombolysis.

Results

Univariate analysis showed that the patient's age, time from onset to treatment (OTT), NIHSS score, diabetes, hypertension, atrial fibrillation, TOAST classification, infarct size, carotid artery stenosis, white blood cell count (WBC), C-reactive protein (CRP), and D-dimer (DD) were associated with END (P < 0.05). Multiple logistic regression analysis found that NIHSS score, diabetes, atrial fibrillation, infarct size, carotid stenosis, and CRP were independent influencing factors of END after intravenous thrombolysis in AIS patients (P < 0.05). Univariate analysis showed that the patient's age, OTT, NIHSS score, diabetes, hypertension, atrial fibrillation, infarct size, carotid stenosis, and the occurrence of END were all related to the short-term prognosis of AIS patients (P < 0.05). Multiple logistic regression analysis showed that age, NIHSS score, infarct size, carotid artery stenosis, and the occurrence of END were all independent factors affecting the short-term prognosis of AIS patients.

Conclusion

High NIHSS score, combined with diabetes, atrial fibrillation, moderate to severe carotid stenosis, and elevated CRP are all risk factors for END after intravenous thrombolysis in AIS patients. Moreover, advanced age, high NIHSS score, moderate to severe carotid stenosis, and occurrence of END are risk factors for poor short-term prognosis after intravenous thrombolysis in AIS patients.

Identification and Diagnosis of Cerebral Stroke through Deep Convolutional Neural Network-Based Multimodal MRI Images

This study aimed to explore the application value of multimodal magnetic resonance imaging (MRI) images based on the deep convolutional neural network (Conv.Net) in the diagnosis of strokes. Specifically, four automatic segmentation algorithms were proposed to segment multimodal MRI images of stroke patients. The segmentation effects were evaluated factoring into DICE, accuracy, sensitivity, and segmentation distance coefficient. It was found that although two-dimensional (2D) full convolutional neural network-based segmentation algorithm can locate and segment the lesion, its accuracy was low; the three-dimensional one exhibited higher accuracy, with various objective indicators improved, and the segmentation accuracy of the training set and the test set was 0.93 and 0.79, respectively, meeting the needs of automatic diagnosis. The asymmetric 3D residual U-Net network had good convergence and high segmentation accuracy, and the 3D deep residual network proposed on its basis had good segmentation coefficients, which can not only ensure segmentation accuracy but also avoid network degradation problems. In conclusion, the Conv.Net model can accurately segment the foci of patients with ischemic stroke and is suggested in clinic.

Inhibition of miR-448-3p Attenuates Cerebral Ischemic Injury by Upregulating Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2)

BACKGROUND

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key regulator responsible for oxidative stress in brain injury. This study aimed to investigate the potential mechanism of miR-448-3p and Nrf2 in cerebral ischemia/reperfusion (I/R) injury.

METHODS

In vitro and in vivo cerebral I/R injury models were constructed, and Nrf2 expression levels were detected by qRT-PCR and Western blot. The potential miRNAs for Nrf2 were predicted by bioinformatic analysis. The binding interaction between miR-448-3p and Nrf2 was determined by luciferase reporter assay. The effects of miR-448-3p on neurological deficit, infarct volume, and brain water content in mice were tested. The effects of miR-448-3p on oxidative stress indicators (SOD activity, MDA content, and ROS production) were detected by commercial assay kits. The levels of HO-1 and cleaved caspase-3 were evaluated by Western blot. Cell viability was evaluated by MTT assay, and cell apoptosis was evaluated by TUNEL staining and flow cytometry.

RESULTS

Nrf2 was significantly downregulated and miR-448-3p was upregulated in cerebral I/R injury both in vivo and in vitro. MiR-448-3p downregulation efficiently attenuated brain injury and reduced oxidative stress and apoptosis. MiR-448-3p was identified to act as ceRNA of Nrf2 and negatively regulated Nrf2 expression, which was consistent with the animal studies. In addition, Nrf2 silencing obviously attenuated the neuroprotective effects of miR-448-3p inhibitor in vitro.

CONCLUSION

MiR-448-3p participated in the regulation of cerebral I/R injury via inhibiting Nrf2.

[Acute cerebral circulation impairment associated with percutaneous coronary intervention]

The article deals with generalized literature data on the current importance of the problem concerning acute cerebral ischemia occurring during percutaneous coronary interventions. Pathophysiological mechanisms of the development of acute cerebral circulation impairment are described, with their classification. Also considered are various risk factors which may cause this formidable complication, followed by describing modern methods of its surgical treatment. It is noted that the main risk factors for neurological complications appearing after revascularization of coronary arteries include age, accompanying diseases (instability of arterial pressure, diabetes mellitus, atrial fibrillation, atherorosclerotic lesions of the aorta and brachiocephalic arteries, previous stroke), as well as systolic dysfunction, leukocytosis, and a low level of cognitive function prior to operation. The development of acute cerebral circulation impairment during and after percutaneous coronary intervention is an indication for using methods of endovascular treatment. It is most appropriate to use a combination of direct percutaneous thrombectomy and a stent retriever. It is underlined in the article that removal of the thrombus form the cerebral artery is not an independent surgical procedure but rather a methodology envisaging an operation to be performed from the simplest technique to the most complicated one. As the first procedure, it is necessary to perform thrombaspiration and then, if ineffective, a second stage consisting in thrombextraction with the help of a stent retriever. Besides, in order to increase efficacy of thrombaspiration there have been worked out several techniques combining the use of direct thrombextraction and a stent retriever. Described in detail are 4 most commonly used techniques.