The stromal cell-derived factor-1 α (SDF-1α)/cysteine-X-cysteine chemokine receptor 4 (CXCR4) axis: a possible prognostic indicator of acute ischemic stroke

Prognostic significance of plasma SDF-1 in acute ischemic stroke patients with diabetes mellitus: the CATIS trial

BACKGROUND AND OBJECTIVES

Evidence on the associations between baseline stromal cell-derived factor (SDF)-1 and clinical outcomes in acute ischemic stroke patients is lacking. The present study aimed to examine the relationship between plasma SDF-1 levels and clinical outcomes based on a large multicenter study of the China Antihypertensive Trial in Acute Ischemic Stroke (CATIS).

METHODS

Secondary analysis was conducted among 3,255 participants from the CATIS trial with a baseline measurement of plasma SDF-1 levels. We evaluated the associations between plasma SDF-1 levels and one-year recurrent stroke, cardiovascular events, and all-cause mortality using Cox regression models. We further investigated the prognostic effect of SDF-1 on clinical outcomes in patients with different characteristics.

RESULTS

Higher plasma SDF-1 levels were not associated with recurrent stroke, cardiovascular events, and all-cause mortality at one-year after ischemic stroke (all P trend ≥ 0.05). There were significant interactions between plasma SDF-1 levels and history of diabetes mellitus on recurrent stroke (P = 0.005), cardiovascular events (P = 0.007) and all-cause mortality (P = 0.04) at one year. In patients with diabetes mellitus, plasma SDF-1 was significantly associated with an increased risk of recurrent stroke and cardiovascular events after adjustment for confounders. For example, 1-SD higher log-SDF-1 was associated with a hazard ratio (95% confidence interval) of 1.65 (1.18-2.32) for recurrent stroke and 1.47 (1.08-1.99) for the cardiovascular events, but not all-cause mortality 1.36 (0.96-1.93) at one year. However, there were no associations between plasma SDF-1 and clinical outcomes in patients without diabetes mellitus (all P > 0.05). The addition of plasma SDF-1 to the conventional risk factors model significantly improved the risk prediction of all outcomes. Similarly, findings between elevated SDF-1 levels and two-year outcomes were found only in patients with diabetes mellitus.

CONCLUSIONS

Elevated plasma SDF-1 was significantly associated with an increased risk of recurrent stroke and cardiovascular events only in ischemic patients with diabetes mellitus.

Chemokine receptor 7 mediates miRNA-182 to regulate cerebral ischemia/reperfusion injury in rats

AIMS

Chemokine receptor 7 (CXCR7) exerts protective effects on the brain. MicroRNAs (miRNAs) are involved in cerebral ischemia/reperfusion (I/R) injury, but their involvement in CXCR7-mediated brain protection is unknown. In this study, we investigated the role of miRNAs in CXCR7-mediated brain protection.

METHODS

CXCR7 levels in peripheral blood samples from patients with acute ischemic stroke (AIS) and ischemic penumbra area brain tissues from middle cerebral artery occlusion (MCAO) rats after recanalization were measured. An miRNA microarray analysis was performed to examine the expression of miRNAs caused by CXCR7 knockdown in ischemic penumbra area brain tissue in middle cerebral artery occlusion-reperfusion rats and to predict corresponding downstream target genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed the most enriched pathways. A dual-luciferase reporter assay confirmed the direct regulation of miR-182 on the target gene TCF7L2. The correlation between TCF7L2 and CXCR7/miR-182 was verified using rescue assays.

RESULTS

CXCR7 expression was upregulated in MCAO rats and mechanical thrombectomy patients with AIS compared to that in controls. The motor and sensory functions of MCAO rats with CXCR7 knockdown further decreased, and the infarct volume and cerebral edema increased. miRNA microarray data showed that seven miRNAs were differentially expressed after shRNA-CXCR7 treatment. The dual-luciferase reporter assay confirmed that miR-182 directly targeted the TCF7L2 gene. Rescue assays confirmed that TCF7L2 is downstream of CXCR7/miR-182. KEGG pathway analysis showed that the Hippo pathway may be a key pathway in CXCR7 upregulation and plays a role in protecting the brain after interventional surgery. Animal experiments have shown that CXCR7-mediated cerebral I/R injury promotes the phosphorylation of key molecules YAP and TAZ in the Hippo pathway.

CONCLUSION

CXCR7 protects against cerebral I/R injury, possibly via the miR-182/TCF7L2/Hippo pathway. These results indicate that CXCR7 affects cerebral ischemia-reperfusion injury through miRNA regulation and downstream pathways.

Evaluation of circulating endothelial progenitor cells and the severity of transient ischemic attack

OBJECTIVE

Endothelial progenitor cells (EPCs) are believed to have a positive effect on maintaining endothelial integrity and participate in angiogenesis after cerebral infarction. Numerous studies have demonstrated that EPCs promote ischemic tissue angiogenesis after stroke. However, there are few studies on the relationship between the level of EPCs and the severity of transient ischemic attacks (TIAs). The current study aimed to investigate the evaluation value of EPCs and serum stromal cell-derived factor-1α(SDF-1α) levels on the severity of TIA.

METHODS

A total of 144 patients with TIA who had an onset of symptoms within 24 h were enrolled and divided into a high-risk TIA (HR-TIA) group (79 cases) and a nonhigh-risk TIA (NHR-TIA) group (65 cases). Clinical data of these patients were collected. Flow cytometry (FCM) was used to measure the number of CD34⁺KDR⁺ EPCs, and enzyme-linked immunosorbent assay (ELISA) was used to determine the concentration of serum SDF-1α and vascular endothelial growth factor (VEGF). Fifteen healthy donors were selected as the normal control (NC) group. Circulating EPCs were isolated by density gradient centrifugation from the first 15 patients in the high-risk TIA group, the nonhigh-risk TIA group, and the NC group. A colony assay and MTT assay were used to determine the proliferation ability of each group, and a Boyden chamber was used to determine the migration potential of EPCs.

RESULTS

Compared with the nonhigh-risk group, patients in the high-risk TIA group were older and had a higher incidence of hypertension and diabetes and stroke recurrence. Patients in the high-risk TIA group had higher levels of triglycerides, cholesterol, and low-density lipoprotein. However, there were no significant differences between the two groups in sex, time from onset to blood draw, smoking, body mass index, or homocysteine (P > 0.05). The number of circulating EPCs in the nonhigh-risk TIA group was higher than that in the high-risk TIA group (P < 0.01). SDF-1α and VEGF levels in the nonhigh-risk TIA group were lower than those in the high-risk TIA group (P < 0.01). The results of multivariate regression analysis showed that age, hypertension, diabetes, smoking, and SDF-1α were risk factors for high-risk TIA, and EPCs were protective factors for high-risk TIA. EPCs were separated and cultured for 72 h. Compared with the NC group, EPCs functions were weakened in the high-risk TIA group and nonhigh-risk TIA group (P < 0.05). Compared with the nonhigh-risk TIA group, EPC functions were decreased in the high-risk TIA group (P < 0.01).

CONCLUSION

CD34⁺KDR⁺ EPCs are protective factors for high-risk TIA. The number of circulating CD34⁺KDR⁺ EPCs and the concentration of SDF-1α have important clinical value in predicting the progression of TIA to high-risk TIA.

Brain-targeting, acid-responsive antioxidant nanoparticles for stroke treatment and drug delivery

Stroke is the leading cause of death and disability. Currently, there is no effective pharmacological treatment for this disease, which can be partially attributed to the inability to efficiently deliver therapeutics to the brain. Here we report the development of natural compound-derived nanoparticles (NPs), which function both as a potent therapeutic agent for stroke treatment and as an efficient carrier for drug delivery to the ischemic brain. First, we screened a collection of natural nanomaterials and identified betulinic acid (BA) as one of the most potent antioxidants for stroke treatment. Next, we engineered BA NPs for preferential drug release in acidic ischemic tissue through chemically converting BA to betulinic amine (BAM) and for targeted drug delivery through surface conjugation of AMD3100, a CXCR4 antagonist. The resulting AMD3100-conjugated BAM NPs, or A-BAM NPs, were then assessed as a therapeutic agent for stroke treatment and as a carrier for delivery of NA1, a neuroprotective peptide. We show that intravenous administration of A-BAM NPs effectively improved recovery from stroke and its efficacy was further enhanced when NA1 was encapsulated. Due to their multifunctionality and significant efficacy, we anticipate that A-BAM NPs have the potential to be translated both as a therapeutic agent and as a drug carrier to improve the treatment of stroke.

The SDF1-CXCR4 Axis Is Involved in the Hyperbaric Oxygen Therapy-Mediated Neuronal Cells Migration in Transient Brain Ischemic Rats

Neurogenesis is a physiological response after cerebral ischemic injury to possibly repair the damaged neural network. Therefore, promoting neurogenesis is very important for functional recovery after cerebral ischemic injury. Our previous research indicated that hyperbaric oxygen therapy (HBOT) exerted neuroprotective effects, such as reducing cerebral infarction volume. The purposes of this study were to further explore the effects of HBOT on the neurogenesis and the expressions of cell migration factors, including the stromal cell-derived factor 1 (SDF1) and its target receptor, the CXC chemokine receptor 4 (CXCR4). Thirty-two Sprague–Dawley rats were divided into the control or HBO group after receiving transient middle cerebral artery occlusion (MCAO). HBOT began to intervene 24 h after MCAO under the pressure of 3 atmospheres for one hour per day for 21 days. Rats in the control group were placed in the same acrylic box without HBOT during the experiment. After the final intervention, half of the rats in each group were cardio-perfused with ice-cold saline followed by 4% paraformaldehyde under anesthesia. The brains were removed, dehydrated and cut into serial 20μm coronal sections for immunofluorescence staining to detect the markers of newborn cell (BrdU⁺), mature neuron cell (NeuN⁺), SDF1, and CXCR4. The affected motor cortex of the other half rats in each group was separated under anesthesia and used to detect the expressions of brain-derived neurotrophic factor (BDNF), SDF1, and CXCR4. Motor function was tested by a ladder-climbing test before and after the experiment. HBOT significantly enhanced neurogenesis in the penumbra area and promoted the expressions of SDF1 and CXCR4. The numbers of BrdU⁺/SDF1⁺, BrdU⁺/CXCR4⁺, and BrdU⁺/NeuN⁺ cells and BDNF concentrations in the penumbra were all significantly increased in the HBO group when compared with the control group. The motor functions were improved in both groups, but there was a significant difference between groups in the post-test. Our results indicated that HBOT for 21 days enhanced neurogenesis and promoted cell migration toward the penumbra area in transient brain ischemic rats. HBOT also increased BDNF expression, which might further promote the reconstructions of the impaired neural networks and restore motor function.

Role of Stromal Cell-Derived Factor-1 in Endothelial Progenitor Cell-Mediated Vascular Repair and Regeneration

Endothelial progenitor cells (EPCs) are immature endothelial cells that participate in vascular repair and postnatal neovascularization and provide a novel and promising therapy for the treatment of vascular disease. Studies in different animal models have shown that EPC mobilization through pharmacological agents and autologous EPC transplantation contribute to restoring blood supply and tissue regeneration after ischemic injury. However, these effects of the progenitor cells in clinical studies exhibit mixed results. The therapeutic efficacy of EPCs is closely associated with the number of the progenitor cells recruited into ischemic regions and their functional abilities and survival in injury tissues. In this review, we discussed the regulating role of stromal cell-derived factor-1 (also known CXCL12, SDF-1) in EPC mobilization, recruitment, homing, vascular repair and neovascularization, and analyzed the underlying machemisms of these functions. Application of SDF-1 to improve the regenerative function of EPCs following vascular injury was also discussed. SDF-1 plays a crucial role in mobilizing EPC from bone marrow into peripheral circulation, recruiting the progenitor cells to target tissue and protecting against cell death under pathological conditions; thus improve EPC regenerative capacity. SDF-1 are crucial for regulating EPC regenerative function, and provide a potential target for improve therapeutic efficacy of the progenitor cells in treatment of vascular disease.