Peroxisome proliferator-activated receptor-γ agonist pioglitazone ameliorates white matter lesion and cognitive impairment in hypertensive rats

Cerebral Perfusion Characteristics and Dynamic Brain Structural Changes in Stroke-Prone Renovascular Hypertensive Rats: A Preclinical Model for Cerebral Small Vessel Disease

Hypertension is a leading cause of cerebral small vessel disease (CSVD) and vascular dementia in elderly individuals. We aimed to assess cerebral perfusion and dynamic changes in brain structure in stroke-prone renovascular hypertensive rats (RHRSPs) with different durations of hypertension and to investigate whether they have pathophysiological features similar to those of humans with CSVD. The RHRSP model was established using the two-kidney, two-clip (2k2c) method, and the Morris water maze (MWM) test, MRI, immunohistochemistry, and biochemical analysis were performed at multiple time points for up to six months following the 2k2c operation. Systolic blood pressure was significantly greater in the RHRSP group than in the sham-operated group at week 4 post-surgery and continued to increase over time, leading to cognitive decline by week 20. Arterial spin labeling revealed cerebral hypoperfusion in the RHRSP group at 8 weeks, accompanied by vascular remodeling and decreased vessel density. Diffusion tensor imaging and Luxol fast blue staining indicated that white matter disintegration and demyelination gradually progressed in the corpus callosum and that myelin basic protein levels decreased. Eight weeks after surgery, blood-brain barrier (BBB) leakage into the corpus callosum was observed. The albumin leakage area was negatively correlated with the myelin sheath area (r=-0.88, p<0.001). RNA-seq analysis revealed downregulation of most angiogenic genes and upregulation of antiangiogenic genes in the corpus callosum of RHRSPs 24 weeks after surgery. RHRSPs developed cerebral hypoperfusion, BBB disruption, spontaneous white matter damage, and cognitive impairment as the duration of hypertension increased. RHRSPs share behavioral and neuropathological characteristics with CSVD patients, making them suitable animal models for preclinical trials related to CSVD.

Regional contribution of vascular dysfunction in white matter dementia: clinical and neuropathological insights

The maintenance of adequate blood supply and vascular integrity is fundamental to ensure cerebral function. A wide range of studies report vascular dysfunction in white matter dementias, a group of cerebral disorders characterized by substantial white matter damage in the brain leading to cognitive impairment. Despite recent advances in imaging, the contribution of vascular-specific regional alterations in white matter dementia has been not extensively reviewed. First, we present an overview of the main components of the vascular system involved in the maintenance of brain function, modulation of cerebral blood flow and integrity of the blood-brain barrier in the healthy brain and during aging. Second, we review the regional contribution of cerebral blood flow and blood-brain barrier disturbances in the pathogenesis of three distinct conditions: the archetypal white matter predominant neurocognitive dementia that is vascular dementia, a neuroinflammatory predominant disease (multiple sclerosis) and a neurodegenerative predominant disease (Alzheimer's). Finally, we then examine the shared landscape of vascular dysfunction in white matter dementia. By emphasizing the involvement of vascular dysfunction in the white matter, we put forward a hypothetical map of vascular dysfunction during disease-specific progression to guide future research aimed to improve diagnostics and facilitate the development of tailored therapies.

Pathogenesis and research progress in leukoaraiosis

Leukoaraiosis is a common imaging marker of cerebral small vessel disease. In recent years, with the continuous advances in brain imaging technology, the detection rate of leukoaraiosis is higher and its clinical subtypes are gradually gaining attention. Although leukoaraiosis has long been considered an incidental finding with no therapeutic necessity, there is now growing evidence linking it to, among other things, cognitive impairment and a high risk of death after stroke. Due to different research methods, some of the findings are inconsistent and even contradictory. Therefore, a comprehensive and in-depth study of risk factors for leukoaraiosis is of great clinical significance. In this review, we summarize the literature on leukoaraiosis in recent years with the aim of elucidating the disease in terms of various aspects (including pathogenesis, imaging features, and clinical features, etc.).

Mesenchymal Stem Cells Improve Cognitive Impairment and Reduce Aβ Deposition via Promoting AQP4 Polarity and Relieving Neuroinflammation in Rats With Chronic Hypertension-Induced Cerebral Small-Vessel Disease

Cerebral small-vessel disease (CSVD) is the main cause of vascular cognitive impairment (VCI), and the accumulation of amyloid β-protein (Aβ) may be significantly involved in CSVD-induced VCI. The imbalance between Aβ production and clearance is believed to be an important pathological mechanism of Aβ deposition in Alzheimer disease. In this study, we aimed to disclose the roles of aquaporin 4 (AQP4) and neuroinflammation in CSVD, which were the key factors for Aβ clearance and production, respectively, and the effect of mesenchymal stem cells (MSCs) on Aβ deposition and these two factors. The stroke-prone renovascular hypertensive (RHRSP) rats were grouped and received MSC and MSC + AS1517499 (an inhibitor of pSTAT6). The latter was used to explore the underlying mechanism. The cognitive function, white matter lesions, Aβ expression, expression, and polarity of AQP4, neuroinflammation and the STAT6 pathway were investigated. Compared with sham-operated rats, RHRSP rats showed spatial cognitive impairment, white matter lesions and Aβ deposition. Moreover, AQP4 polarity disorder and neuroinflammatory activation were found, which were linked to Aβ deposition. Treatment with MSCs markedly improved cognitive tasks and reduced Aβ deposition but failed to reduce white-matter lesions. Furthermore, MSCs not only promoted AQP4 polarity but also alleviated neuroinflammation probably through the STAT6 pathway. The present study demonstrated that Aβ deposition, AQP4 polarity disorder and neuroinflammation might be involved in CSVD and the regulatory effects of MSCs on them suggested potential therapeutic value for CSVD.

Peroxisome proliferator-activator receptor γ and psoriasis, molecular and cellular biochemistry

The pathophysiology of psoriasis is complex and has not been completely elucidated. Better understanding of the pathogenesis may contribute to further improvement of our therapeutic strategies controlling psoriasis. Emerging evidence points to a causative relationship between altered activity of peroxisome proliferator-activated receptor γ (PPARγ) and psoriasis. The present review focuses on deeper understanding of the possible role of PPARγ in the pathogenesis of psoriasis and the potential of PPARγ agonist to improve the treatment of psoriasis. PPARγ is decreased in psoriasis. PPARγ possibly has effects on the multiple aspects of the pathogenesis of psoriasis, including abnormal lipid metabolism, insulin resistance, immune cells, pro-inflammatory cytokines, keratinocytes, angiogenesis, oxidative stress, microRNAs and nuclear factor kappa B. As defective activation of PPARγ is involved in psoriasis development, PPARγ agonists may be promising agents for treatment of psoriasis. Pioglitazone appears an effective and safe option in the treatment of patients with psoriasis, but there are still concerns about its potential side effects. Research effort has recently been undertaken to explore the PPARγ-activating potential of natural products. Among them some have been studied clinically or preclinically for treatment of psoriasis with promising results.

Precocious White Matter Inflammation and Behavioural Inflexibility Precede Learning and Memory Impairment in the TgAPP21 Rat Model of Alzheimer Disease

Neuroinflammation and behavioural inflexibility are both common in late adulthood but far more profound in Alzheimer disease (AD). To investigate the relationship between ageing, AD, neuroinflammation, and behavioural flexibility, male wild-type Fischer 344 (Wt) and the transgenic APP21 (TgAPP21) rats were aged to 4, 8, 13, and 22 months and evaluated for neuroinflammation and cognitive impairment. TgAPP21 rats overexpress a pathogenic variant of the human amyloid precursor protein (hAPP; Swedish and Indiana mutations) but do not spontaneously develop overt pathology related to AD. In both genotypes, learning and memory were similarly impaired in older rats. However, at 8 months of age, TgAPP21 rats demonstrated behavioural inflexibility in set shifting, reversal, and the Morris water maze, while Wt rats showed inflexibility at 13 and 22 months of age. This early inflexibility in TgAPP21 rats was accompanied by a precocious increase in microglia activation within the corpus callosum; 8- and 13-month-old TgAPP21 rats had similar levels of microglia activation as 13- and 22-month-old Wt rats, respectively. However, while neuroinflammation within the white matter continued to progress with age, behavioural inflexibility peaked in 8-month-old TgAPP21 rats; in older TgAPP21 rats, memory and learning impairments masked inflexibility. These findings suggest that the behavioural inflexibility and white matter inflammation seen in normal ageing are accelerated in AD and may precede impairments of learning and memory.

Rethinking pioglitazone as a cardioprotective agent: a new perspective on an overlooked drug

Since 1985, the thiazolidinedione pioglitazone has been widely used as an insulin sensitizer drug for type 2 diabetes mellitus (T2DM). Although fluid retention was early recognized as a safety concern, data from clinical trials have not provided conclusive evidence for a benefit or a harm on cardiac function, leaving the question unanswered. We reviewed the available evidence encompassing both in vitro and in vivo studies in tissues, isolated organs, animals and humans, including the evidence generated by major clinical trials. Despite the increased risk of hospitalization for heart failure due to fluid retention, pioglitazone is consistently associated with reduced risk of myocardial infarction and ischemic stroke both in primary and secondary prevention, without any proven direct harm on the myocardium. Moreover, it reduces atherosclerosis progression, in-stent restenosis after coronary stent implantation, progression rate from persistent to permanent atrial fibrillation, and reablation rate in diabetic patients with paroxysmal atrial fibrillation after catheter ablation. In fact, human and animal studies consistently report direct beneficial effects on cardiomyocytes electrophysiology, energetic metabolism, ischemia–reperfusion injury, cardiac remodeling, neurohormonal activation, pulmonary circulation and biventricular systo-diastolic functions. The mechanisms involved may rely either on anti-remodeling properties (endothelium protective, inflammation-modulating, anti-proliferative and anti-fibrotic properties) and/or on metabolic (adipose tissue metabolism, increased HDL cholesterol) and neurohormonal (renin–angiotensin–aldosterone system, sympathetic nervous system, and adiponectin) modulation of the cardiovascular system. With appropriate prescription and titration, pioglitazone remains a useful tool in the arsenal of the clinical diabetologist.

Neurovascular unit dysregulation, white matter disease, and executive dysfunction: the shared triad of vascular cognitive impairment and Alzheimer disease

Executive dysfunction is the most important predictor for loss of independence in dementia. As executive function involves the coordination of distributed cerebral functions, executive function requires healthy white matter. However, white matter is highly vulnerable to cerebrovascular insults, with executive dysfunction being a core feature of vascular cognitive impairment (VCI). At the same time, cerebrovascular pathology, white matter disease, and executive dysfunction are all increasingly recognized as features of Alzheimer disease (AD). Recent studies have characterized the crucial role of glial cells in the pathological changes observed in both VCI and AD. In comorbid VCI and AD, the glial cells of the neurovascular unit (NVU) emerge as important therapeutic targets for the preservation of white matter integrity and executive function. Our synthesis from current research identifies dysregulation of the NVU, white matter disease, and executive dysfunction as a fundamental triad that is common to both VCI and AD. Further study of this triad will be critical for advancing the prevention and management of dementia.

Rosiglitazone attenuates cell apoptosis through antioxidative and anti-apoptotic pathways in the hippocampi of spontaneously hypertensive rats

Oxidative stress serves an important role in hypertensive brain damage. Peroxisome proliferator‑activated receptor γ (PPAR‑γ) agonists possess antioxidative and anti‑apoptotic effects. The present study verified the possibility that rosiglitazone serves a neuroprotective role by alleviating oxidative stress and cell apoptosis in the hippocampi of spontaneously hypertensive rats (SHRs). SHRs and age‑matched Wistar‑Kyoto (WKY; both 56 weeks old) rats received gavage administration of vehicle or rosiglitazone (5 mg/kg/day) for eight weeks. Systolic blood pressure (SBP) was measured by the indirect tail‑cuff method. The expression ratio of activated astrocytes was analyzed by glial fibrillary acidic protein immunohistochemistry. PPAR‑γ, inducible nitric oxide synthase (iNOS), gp47phox, B‑cell lymphoma 2 (Bcl‑2), Bcl‑2‑associated X protein (Bax) and caspase‑3 expression were investigated by quantitative polymerase chain reaction and western blot analysis. The number of apoptotic cells in the hippocampus of four groups was detected using the terminal deoxynucleotidyl transferase‑mediated dUTP end‑labeling (TUNEL) method. Compared with the WKY group, the SHR group exhibited decreased Bcl‑2 and PPAR‑γ expression, increased SBP, increased ratio of activated astrocytes and TUNEL‑positive cells, increased expression of iNOS, gp47phox, caspase‑3 and Bax. Rosiglitazone administration increased Bcl‑2 and PPAR‑γ expression, decreased the ratio of activated astrocytes and TUNEL‑positive cells, decreased iNOS, gp47phox, caspase‑3 and Bax expression in the hippocampi of SHRs. However, rosiglitazone did not significantly decreased SBP in the SHR group. Therefore, rosiglitazone exerts neuroprotective effect through antioxidative and anti‑apoptotic pathways, which was independent of blood pressure control.

Confused Connections? Targeting White Matter to Address Treatment Resistant Schizophrenia

Despite development of comprehensive approaches to treat schizophrenia and other psychotic disorders and improve outcomes, there remains a proportion (approximately one-third) of patients who are treatment resistant and will not have remission of psychotic symptoms despite adequate trials of pharmacotherapy. This level of treatment response is stable across all stages of the spectrum of psychotic disorders, including early phase psychosis and chronic schizophrenia. Our current pharmacotherapies are beneficial in decreasing positive symptomology in most cases, however, with little to no impact on negative or cognitive symptoms. Not all individuals with treatment resistant psychosis unfortunately, even benefit from the potential pharmacological reductions in positive symptoms. The existing pharmacotherapy for psychosis is targeted at neurotransmitter receptors. The current first and second generation antipsychotic medications all act on dopamine type 2 receptors with the second generation drugs also interacting significantly with serotonin type 1 and 2 receptors, and with varying pharmacodynamic profiles overall. This focus on developing dopaminergic/serotonergic antipsychotics, while beneficial, has not reduced the proportion of patients experiencing treatment resistance to date. Another pharmacological approach is imperative to address treatment resistance both for response overall and for negative symptoms in particular. There is research suggesting that changes in white matter integrity occur in schizophrenia and these may be more associated with cognition and even negative symptomology. Here we review the evidence that white matter abnormalities in the brain may be contributing to the symptomology of psychotic disorders. Additionally, we propose that white matter may be a viable pharmacological target for pharmacoresistant schizophrenia and discuss current treatments in development for schizophrenia that target white matter.

Mineralocorticoid receptor antagonism prevents obesity-induced cerebral artery remodeling and reduces white matter injury in rats

OBJECTIVE

Midlife obesity is a risk factor for dementia development. Obesity has also been linked to hyperaldosteronism, and this can be modeled in rats by high fat (HF) feeding from weaning. Aldosterone, or activation of the mineralocorticoid receptor (MR) causes cerebrovascular injury in lean hypertensive rats. We hypothesized that rats fed a HF diet would show inward middle cerebral artery (MCA) remodeling that could be prevented by MR antagonism. We further proposed that the cerebral artery remodeling would be associated with white mater injury.

METHODS

Three-week-old male Sprague-Dawley rats were fed a HF diet ± the MR antagonist canrenoic acid (Canr) for 17 weeks. Control rats received normal chow (control NC). MCA structure was assessed by pressure myography.

RESULTS

The MCAs from HF fed rats had smaller lumens and thicker walls when compared to arteries from control NC rats; Canr prevented the MCA remodeling associated with HF feeding. HF feeding increased the mRNA expression of markers of cell proliferation and vascular inflammation in cerebral arteries and Canr treatment prevented this. White mater injury was increased in the rats fed the HF diet and this was reduced by Canr treatment. The expression of doublecortin, a marker of new and immature neurons was reduced in HF fed rats, and MR antagonism normalized this.

CONCLUSIONS

These data suggest that HF feeding leads to MR dependent remodeling of the MCA and this is associated with markers of dementia development.

Machine learning shows association between genetic variability in PPARG and cerebral connectivity in preterm infants

Preterm birth affects 11% of births globally; 35% of infants develop long-term neurocognitive problems, and prematurity leads to the loss of 75 million disability adjusted life years per annum worldwide. Imaging studies have shown that these infants have extensive alterations in brain development, but little is known about the molecular or cellular mechanisms involved. This imaging genetics study found a strong association between abnormal cerebral connectivity and variability in the PPARG gene, implicating PPARG signaling in abnormal white-matter development in preterm infants and suggesting a tractable new target for therapeutic research.

Preterm infants show abnormal structural and functional brain development, and have a high risk of long-term neurocognitive problems. The molecular and cellular mechanisms involved are poorly understood, but novel methods now make it possible to address them by examining the relationship between common genetic variability and brain endophenotype. We addressed the hypothesis that variability in the Peroxisome Proliferator Activated Receptor (PPAR) pathway would be related to brain development. We employed machine learning in an unsupervised, unbiased, combined analysis of whole-brain diffusion tractography together with genomewide, single-nucleotide polymorphism (SNP)-based genotypes from a cohort of 272 preterm infants, using Sparse Reduced Rank Regression (sRRR) and correcting for ethnicity and age at birth and imaging. Empirical selection frequencies for SNPs associated with cerebral connectivity ranged from 0.663 to zero, with multiple highly selected SNPs mapping to genes for PPARG (six SNPs), ITGA6 (four SNPs), and FXR1 (two SNPs). SNPs in PPARG were significantly overrepresented (ranked 7–11 and 67 of 556,000 SNPs; P < 2.2 × 10⁻⁷), and were mostly in introns or regulatory regions with predicted effects including protein coding and nonsense-mediated decay. Edge-centric graph-theoretic analysis showed that highly selected white-matter tracts were consistent across the group and important for information transfer (P < 2.2 × 10⁻¹⁷); they most often connected to the insula (P < 6 × 10⁻¹⁷). These results suggest that the inhibited brain development seen in humans exposed to the stress of a premature extrauterine environment is modulated by genetic factors, and that PPARG signaling has a previously unrecognized role in cerebral development.

Peroxisome proliferator-activated receptor γ (PPARγ): A master gatekeeper in CNS injury and repair

Peroxisome proliferator-activated receptor γ (PPARγ) is a widely expressed ligand-modulated transcription factor that governs the expression of genes involved in inflammation, redox equilibrium, trophic factor production, insulin sensitivity, and the metabolism of lipids and glucose. Synthetic PPARγ agonists (e.g. thiazolidinediones) are used to treat Type II diabetes and have the potential to limit the risk of developing brain injuries such as stroke by mitigating the influence of comorbidities. If brain injury develops, PPARγ serves as a master gatekeeper of cytoprotective stress responses, improving the chances of cellular survival and recovery of homeostatic equilibrium. In the acute injury phase, PPARγ directly restricts tissue damage by inhibiting the NFκB pathway to mitigate inflammation and stimulating the Nrf2/ARE axis to neutralize oxidative stress. During the chronic phase of acute brain injuries, PPARγ activation in injured cells culminates in the repair of gray and white matter, preservation of the blood-brain barrier, reconstruction of the neurovascular unit, resolution of inflammation, and long-term functional recovery. Thus, PPARγ lies at the apex of cell fate decisions and exerts profound effects on the chronic progression of acute injury conditions. Here, we review the therapeutic potential of PPARγ in stroke and brain trauma and highlight the novel role of PPARγ in long-term tissue repair. We describe its structure and function and identify the genes that it targets. PPARγ regulation of inflammation, metabolism, cell fate (proliferation/differentiation/maturation/survival), and many other processes also has relevance to other neurological diseases. Therefore, PPARγ is an attractive target for therapies against a number of progressive neurological disorders.

High Serum Levels of Malondialdehyde and 8-OHdG are both Associated with Early Cognitive Impairment in Patients with Acute Ischaemic Stroke

Post-stroke cognitive impairment (PSCI) is an increasingly prevalent sequel after stroke that may associate with poor functional outcome and increased risk of recurrent stroke. We aimed to explore the relationship between oxidative stress biomarkers and the presence of PSCI. 193 first-ever acute ischaemic stroke patients were consecutively enrolled in the current study. The oxidative stress biomarkers malondialdehyde (MDA) and 8-hydroxydeoxyquanosine (8-OHdG) were measured within 24 h after admission. Cognition function was evaluated by the Mini-Mental State Examination (MMSE) at 1 month after stroke. Serum levels of 8-OHdG and MDA were both significantly higher in the PSCI (p < 0.001) compared with the non-PSCI group. Both the serum levels of both 8-OHdG and MDA were negatively correlated with the MMSE score. Receiver operating characteristic curve analysis was used to evaluate 8-OHdG and MDA as markers of a high risk of PSCI and produced area under curve values of 0.700 and 0.793. Adjusted logistic regression showed that serum 8-OHdG and MDA levels remained as independent markers of PSCI. High serum levels of malondialdehyde and 8-OHdG are associated with the presence of PSCI at 1 month after stroke.

A preliminary longitudinal study of white matter alteration in cocaine use disorder subjects

BACKGROUND

Previous diffusion tensor imaging (DTI) studies have consistently shown that subjects with cocaine use disorder (CocUD) had altered white matter microstructure in the corpus callosum. It is believed that these alterations are due to preexisting factors, chronic cocaine use, or both. However, there is no published longitudinal DTI study on human cocaine users yet which could shed light on the relationship between cocaine use and DTI findings.

METHODS

This study used a longitudinal design and DTI to test if the white matter microstructure shows quicker alteration in CocUD subjects than controls. DTI data were acquired from eleven CocUD subjects who participated a treatment study and eleven non-drug-using controls at baseline (Scan 1) and after ten weeks (Scan 2). The baseline fractional anisotropy (FA), a general measure of white matter microstucture, and the change in FA (ΔFA, equals Scan 1 FA minus Scan 2 FA) were both compared between groups.

RESULTS

The two groups did not show a difference in FA at baseline. The CocUD subjects had significantly greater ΔFA than the controls in the left splenium of the corpus callosum. In CocUD subjects, greater ΔFA in this region was associated with shorter lifetime cocaine use and greater number of positive cocaine urine samples collected during the treatment.

CONCLUSION

The finding in the left splenium is consistent with previous animal studies and provide indirect evidence about the effects of chronic cocaine use on white matter alterations. The subject sample size is small, therefore the results should be treated as preliminary.

Multiple Factors Involved in the Pathogenesis of White Matter Lesions

White matter lesions (WMLs), also known as leukoaraiosis (LA) or white matter hyperintensities (WMHs), are characterized mainly by hyperintensities on T2-weighted or fluid-attenuated inversion recovery (FLAIR) images. With the aging of the population and the development of imaging technology, the morbidity and diagnostic rates of WMLs are increasing annually. WMLs are not a benign process. They clinically manifest as cognitive decline and the subsequent development of dementia. Although WMLs are important, their pathogenesis is still unclear. This review elaborates on the advances in the understanding of the pathogenesis of WMLs, focusing on anatomy, cerebral blood flow autoregulation, venous collagenosis, blood brain barrier disruption, and genetic factors. In particular, the attribution of WMLs to chronic ischemia secondary to venous collagenosis and cerebral blood flow autoregulation disruption seems reasonable. With the development of gene technology, the effect of genetic factors on the pathogenesis of WMLs is gaining gradual attention.

Cerebral small vessel disease and post-stroke cognitive impairment

Cerebral small vessel disease (CSVD) refers to a group of pathological processes with multifarious etiologies that affect the small arteries, arterioles, venules, and capillaries of the brain. Features seen on neuroimaging include white matter hyperintensities, lacunar infarction, cerebral microbleeds, brain atrophy, microinfarcts and enlarged perivascular spaces (EPVS). CSVD gives rise to one in five strokes worldwide and is a leading cause of cognitive impairment and dementia, especially in the elderly. Post-stroke cognitive impairment (PSCI) is one of the most common subtypes of cognitive impairment. The underlying mechanisms of PSCI are not known in detail. A growing body of evidence has been suggesting that CSVD plays an important role in the pathogenesis of PSCI. This article reviews the advances in research on the relationship between CSVD and PSCI.

Type 2 Diabetes, Cognition, and Dementia in Older Adults: Toward a Precision Health Approach

IN BRIEF There has been a concurrent dramatic rise in type 2 diabetes and dementia in the United States, and type 2 diabetes shares common genetic and environmental risk factors and underlying pathology with both vascular and Alzheimer's dementias. Given the ability to identify this at-risk population and a variety of potential targeted treatments, type 2 diabetes represents a promising focus for a precision health approach to reduce the impact of cognitive decline and dementia in older adults.

Is Immunomodulation a Principal Mechanism Underlying How Cell-Based Therapies Enhance Stroke Recovery?

Inflammation within the brain and in peripheral tissues contributes to brain injury following ischemic stroke. Therapeutic modulation of the inflammatory response has been actively pursued as a novel stroke treatment approach for decades, without success. In recent years, extensive studies support the high potential for cell-based therapies to become a new treatment modality for stroke and other neurological disorders. In this review, we explore different types of cellular therapies and discuss how they modulate central and peripheral inflammatory processes after stroke. Apart from identifying potential targets for cell therapy, we also discuss paracrine and immunomodulatory mechanisms of cell therapy.

Rodent Models of Vascular Cognitive Impairment

Vascular cognitive impairment dementia (VCID), which is an increasingly important cause of dementia in the elderly, lacks effective treatments. Many different types of vascular disease are included under the diagnosis of VCID, including large vessel disease with multiple strokes and small vessel disease with lacunar infarcts and white matter disease. Animal models have been developed to study the multiple forms of VCID. Because of its progressive course, small vessel disease (SVD) is thought to be the optimal form of VCID for treatment. One theory is that the pathophysiology involves hypoxic hypoperfusion resulting in injury to the white matter and neuronal death. Bilateral occlusion of the common carotid arteries (BCAO) in a normotensive rat, which reduces cerebral blood flow, induces hypoxia with white matter damage; this model has been used to test drugs to block the injury. Another model is the spontaneously hypertensive/stroke prone rat (SHR/SP). Hypertension leads to small vessel disease resulting in progressive damage to the white matter, cortex, and hippocampus. Bilateral carotid artery stenosis (BCAS) with coils or ameroid constrictors produces a slower development of changes than BCAO, avoiding the acute ischemia. A few studies have been done with the two-clip, two-vessel occlusion renal model for induction of hypertension. There are benefits and drawbacks to each of these models with the model selected depending on the type of vascular damage that is to be studied. This review describes the most commonly used models, and the drugs that have been used to reduce the damage.

The molecular mechanisms of action of PPAR-γ agonists in the treatment of corneal alkali burns (Review)

Corneal alkali burns (CAB) are characterized by injury-induced inflammation, fibrosis and neovascularization (NV), and may lead to blindness. This review evaluates the current knowledge of the molecular mechanisms responsible for CAB. The processes of cytokine production, chemotaxis, inflammatory responses, immune response, cell signal transduction, matrix metalloproteinase production and vascular factors in CAB are discussed. Previous evidence indicates that peroxisome proliferator-activated receptor γ (PPAR-γ) agonists suppress immune responses, inflammation, corneal fibrosis and NV. This review also discusses the role of PPAR-γ as an anti-inflammatory, anti-fibrotic and anti-angiogenic agent in the treatment of CAB, as well as the potential role of PPAR-γ in the pathological process of CAB. There have been numerous studies evaluating the clinical profiles of CAB, and the aim of this systematic review was to summarize the evidence regarding the treatment of CAB with PPAR-γ agonists.

Spontaneous white matter lesion in brain of stroke-prone renovascular hypertensive rats: a study from MRI, pathology and behavior

Hypertension is considered one of the most important controllable risk factors for white matter lesion (WML). Our previous work found that stroke-prone renovascular hypertensive rats (RHRSP) displayed a high rate of WML. This study aimed to investigate the WML in RHRSP from MRI, pathology and behavior. RHRSP model was established by two-kidney, two-clipmethod and kept for 20 weeks. WML was decteted by magnetic resonance imaging (MRI) and loyez staining. Cognition was tested by morris water maze (MWM). Vascular changes were observed by HE staining on brain and carotid sections. Ultrastucture of blood brain barrier (BBB) were observed by transmission electron microscope. Immunofluorescence was used to detect albumin leakage and cell proliferation. T(2)-weighted MRI scans of RHRSP displayed diffuse, confluent white-matter hyperintensities. Pathological examination of the same rat showed marked vacuoles, disappearence of myelin and nerve fibers in white matter, supporting the neuroimaging findings. Spatial learning and memory impairment were observed in RHRSP. The small arteries in brain exhibited fibrinoid necrosis, hyalinosis and vascular remodeling. BBB disruption and plasma albumin leakage into vascular wall was observed in RHRSP. Increased cell proliferation in subventricular zone was seen in RHRSP. RHRSP demonstrated spontaneous WML and cognitive impairment. Hypertensive small vessel lesions and BBB disruption might paly causative factors for the onset and development of WML. The characteristic features of WML in RHRSP suggested it a valid animal model for WML.