Xinying Fan

Cell based therapies for ischemic stroke: from basic science to bedside.

Cell therapy is emerging as a viable therapy to restore neurological function after stroke. Many types of stem/progenitor cells from different sources have been explored for their feasibility and efficacy for the treatment of stroke. Transplanted cells not only have the potential to replace the lost circuitry, but also produce growth and trophic factors, or stimulate the release of such factors from host brain cells, thereby enhancing endogenous brain repair processes. Although stem/progenitor cells have shown a promising role in ischemic stroke in experimental studies as well as initial clinical pilot studies, cellular therapy is still at an early stage in humans. Many critical issues need to be addressed including the therapeutic time window, cell type selection, delivery route, and in vivo monitoring of their migration pattern. This review attempts to provide a comprehensive synopsis of preclinical evidence and clinical experience of various donor cell types, their restorative mechanisms, delivery routes, imaging strategies, future prospects and challenges for translating cell therapies as a neurorestorative regimen in clinical applications.

Intranasal delivery of transforming growth factor-beta1 in mice after stroke reduces infarct volume and increases neurogenesis in the subventricular zone

BackgroundThe effect of neurotrophic factors in enhancing stroke-induced neurogenesis in the adult subventricular zone (SVZ) is limited by their poor blood-brain barrier (BBB) permeability.Intranasal administration is a noninvasive and valid method for delivery of neuropeptides into the brain, to bypass the BBB. We investigated the effect of treatment with intranasal transforming growth factor-β1 (TGF-β1) on neurogenesis in the adult mouse SVZ following focal ischemia. The modified Neurological Severity Scores (NSS) test was used to evaluate neurological function, and infarct volumes were determined from hematoxylin-stained sections. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) labeling was performed at 7 days after middle cerebral artery occlusion (MCAO). Immunohistochemistry was used to detect bromodeoxyuridine (BrdU) and neuron- or glia-specific markers for identifying neurogenesis in the SVZ at 7, 14, 21, 28 days after MCAO.ResultsIntranasal treatment of TGF-β1 shows significant improvement in neurological function and reduction of infarct volume compared with control animals. TGF-β1 treated mice had significantly less TUNEL-positive cells in the ipsilateral striatum than that in control groups. The number of BrdU-incorporated cells in the SVZ and striatum was significantly increased in the TGF-β1 treated group compared with control animals at each time point. In addition, numbers of BrdU- labeled cells coexpressed with the migrating neuroblast marker doublecortin (DCX) and the mature neuronal marker neuronal nuclei (NeuN) were significantly increased after intranasal delivery of TGF-β1, while only a few BrdU labeled cells co-stained with glial fibrillary acidic protein (GFAP).ConclusionIntranasal administration of TGF-β1 reduces infarct volume, improves functional recovery and enhances neurogenesis in mice after stroke. Intranasal TGF-β1 may have therapeutic potential for cerebrovascular disorders.

Plasma fibrinogen is associated with cognitive decline and risk for dementia in patients with mild cognitive impairment

This study was aimed to investigate the relationship between plasma fibrinogen level and risk for cognitive decline and dementia in patients with mild cognitive impairment (MCI). Elderly patients with suspected cognitive impairment were screened and evaluated periodically. One hundred and eighty‐five patients who met the criteria for MCI were enrolled. Blood coagulation functions and plasma fibrinogen levels were measured at baseline. Hyperfibrinogenaemia was defined as plasma fibrinogen ≥3.0 g/l. Global cognitive function was assessed serially with Mini‐Mental State Examination (MMSE). The enrolled patients were followed for 2 years to observe if dementia was developed. There were 185 patients diagnosed as MCI, of which 17 (9.2%) deceased, 15 (8.1%) lost to follow‐up, and 68 (36.8%) developed dementia during follow‐up. Mean of MMSE score of the enrolled patients declined significantly during follow‐up (22.0 ± 3.0 vs. 18.1 ± 5.8, p < 0.001). Patients with hyperfibrinogenaemia at baseline had greater MMSE decrement during follow‐up than patients with normal fibrinogen level (−5.4 ± 5.4 vs. −3.5 ± 4.5, p < 0.05). Linear regression indicated that plasma fibrinogen level was associated with cognitive decline (R = 0.17, p < 0.05). Patients with hyperfibrinogenaemia had an increased risk for dementia and vascular dementia compared with patients with normal level of plasma fibrinogen (log rank test, p < 0.05). There was a trend that hyperfibrinogenaemia also increased risk for dementia of Alzheimers type (p = 0.061). It can be concluded that plasma fibrinogen level may be associated with cognitive decline, and hyperfibrinogenaemia may increase risk for dementia in patients with MCI.

Angiotensin-converting enzyme insertion/deletion polymorphism contributes to ischemic stroke risk: a meta-analysis of 50 case-control studies.

Background Many studies have investigated the association between the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and risk of ischemic stroke. However, the evidence is inadequate to draw robust conclusions because most studies were generally small and conducted in heterogeneous populations. To shed light on these inconclusive findings, we conducted a large meta-analysis of studies relating the ACE I/D polymorphism to the risk of ischemic stroke. Methods Relevant studies were identified by searching PubMed and Embase through February 2012 and by reviewing the references of retrieved articles. We included studies that reported odds ratio (OR) with 95% confidence interval (CI) for the association between this polymorphism and ischemic stroke risk. Results Fifty independent publications, with 10 070 stroke cases and 22 103 controls, were included. The results indicated that the DD homozygote carriers had a 37% higher risk of ischemic stroke when compared with the homozygotes II and heterozygote ID [odds ratio (OR) = 1.37, 95% confidence interval (CI): 1.22–1.53]. Subgroup analyses indicated that this higher risk was more pronounced among Asians, hospital-based studies, and small vessel disease (SVD). Potential publication bias may exist, but correction for this bias using a formal statistical method did not materially alter the combined risk estimate. Conclusion The results of our meta-analysis indicate that the D allele of ACE I/D polymorphism is a low-penetrance susceptibility marker of ischemic stroke.

Intranasal delivery of nerve growth factor attenuates aquaporins-4-induced edema following traumatic brain injury in rats.

Traumatic brain injury (TBI) remains the leading cause of injury-related death and disability. Brain edema, one of the most major complications of TBI, contributes to elevated intracranial pressure, and poor prognosis following TBI. Nerve growth factor (NGF) appears to be a viable strategy to treat brain edema and TBI. Unfortunately, due to its poor blood-brain barrier (BBB) permeability, the clinical application of NGF has been greatly limited. We previously demonstrated that intranasal NGF could bypass the BBB and distribute throughout the brain. Here we further studied whether intranasal NGF could attenuate TBI-induced brain edema and its putative mechanisms. TBI was produced by a modified weight-drop model. We found that intranasal administration of NGF (5μg/d) attenuated the brain edema, as assayed by hemisphere water content, at 12h, 24h and 72h after TBI induction. This attenuation was associated with a prominent decrease of the content of aquaporin-4, which plays a pivotal role in the formation of brain edema. By the use of RT-PCR and ELISA, we showed that intranasal NGF markedly inhibited the transcription and expression of pro-inflammatory cytokines including IL-1β and TNF-α. An electrophoretic mobility shift assay (EMSA) displayed a significant activation of nuclear factor-κB following TBI, which was, however, much lowered in the NGF-treated rats. Furthermore, upon intranasal NGF supplementation, mitochondria-mediated apoptosis following TBI was minimized, as indicated by upregulation of Bcl-2 and downregulation of caspase-3. Collectively, our findings suggested that intranasal NGF may be a promising strategy to treat brain edema and TBI.

Down-regulation of IGF-1/IGF-1R in hippocampus of rats with vascular dementia

Insulin-like growth factor-1 (IGF-1) has been demonstrated to have neuroprotective effects, but little is known concerning its role in vascular dementia (VaD). This study aimed to evaluate expression of IGF-1 signaling in hippocampus in rat model of VaD, and probe the underlying mechanisms. Permanent occlusion of bilateral common carotid arteries (2-VO) was used as VaD model. Learning and memory functions were declined significantly in 2-VO rats, and these impairments were further deteriorated with the prolongation of 2-VO treatment. IGF-1, IGF-1 receptor (IGF-1R), total Akt and phosphorylated Akt (p-Akt) were all measured at 1, 2 and 4 months following 2-VO injury. Compared with controls, IGF-1, IGF-1 mRNA and p-Akt expression were significantly decreased in hippocampus of 2-VO rats. However, changes of IGF-1R and total Akt levels were not significant. These results suggest that down-regulation of IGF-1 and p-Akt may contribute to the impairments of learning and memory functions after 2-VO. IGF-1/IGF-1R signaling system may involved in the onset and development of VaD.

Effects of repetitive transcranial magnetic stimulation on motor recovery and motor cortex excitability in patients with stroke: a randomized controlled trial.

Repetitive transcranial magnetic stimulation (rTMS) changes the excitability of the motor cortex and thereby has the potential to enhance motor recovery after stroke. This randomized, sham‐controlled, double‐blind study was to compare the effects of high‐frequency versus low‐frequency rTMS on motor recovery during the early phase of stroke and to identify the neurophysiological correlates of motor improvements.

Variant recurrent risk among stroke patients with different CYP2C19 phenotypes and treated with clopidogrel

Abstract Polymorphisms of CYP2C19 have been associated with variant risk of subsequent cardiovascular events in survivors of myocardial infarction (MI) receiving clopidogrel. This study evaluated the impacts of CYP2C19 polymorphisms on stroke recurrence and other vascular events in a cohort of Chinese patients receiving clopidogrel. From Nanjing Stroke Registry Program, 625 consecutive patients with ischemic stroke were enrolled between May 2008 and April 2010. CYP2C19 variants (*2, *3, and *17) were genotyped. Clinical outcomes were determined with three monthly follow-up. The primary endpoint was a composite of vascular death, non-fatal ischemic stroke, and non-fatal MI. The second endpoint was bleeding events. The median exposure to clopidogrel was 13.2 (interquartile range, 8.9–18.0) months. Primary endpoint was observed in 85 (13.6%) patients and secondary endpoint in 13 (2.1%) patients. Frequencies of CYP2C19*1, *2, *3, and *17 alleles were 61.2, 34.0, 3.8, and 1.0%, respectively, in this patient cohort. CYP2C19 loss-of-function allele (*2 and *3, LOF) carriers were observed with higher risk of subsequent vascular events compared with non-carriers (17.2 versus 8.1%, HR = 2.16, 95% CI: 1.31–3.56, p = 0.003). After adjusted for age, sex, major cardiovascular risk factors, and drug agent, CYP2C19 LOF carrier was independently associated with primary endpoint (HR = 2.31, 95% CI: 1.39–3.84, p = 0.001). No significant association between CYP2C19 gain-of-function (*17, GOF) and clinical events was detected. In Chinese stroke survivors treated with clopidogrel, carriers of CYP2C19 LOF allele may have increased risk of recurrence.

Chinese Guidelines for Endovascular Management of Ischemic Cerebrovascular Diseases

Endovascular technology was initially applied in treating peripheral vascular disease and was further developed in managing coronary artery disease. During the latest two decades, it has been introduced into the arena of cerebrovascular diseases, which has garnered attention and research interests.

Co-culturing improves the OGD-injured neuron repairing and NSCs differentiation via Notch pathway activation

Neural stem cell (NSC) transplantation for ischemic stroke is expected to repair the neuronal injury and replace the lost neurons through cell-cell cross talk between injured neurons and the transplanted NSCs. Here, we set up an in vitro co-culturing system of oxygen-glucose deprivation (OGD) injured neurons and NSCs to investigate the neuronal repairing effect and effects on NSCs differentiation. We focused on the Notch1 pathway as a possible mediator of these effects. OGD-injured neurons induced increased activation of Notch1 in co-cultured NSCs, through the up-regulations of the DLL1, the Notch1 intracellular domain (NICD) and the down-stream genes Hes1/5. When the NSCs were pre-treated with the Notch pathway inhibitor DAPT, the activation of Notch1 was blocked, lower NSCs differentiation was detected and the neurotrophic effect was also abolished. As shown by the novel co-culturing system, the NSCs co-cultured with OGD injured neurons were induced to differentiate through the Notch1 pathway activation; and these induced NSCs showed greater potential to support both the repair of injured neurons and form new neurons.