Murine experimental models of amyotrophic lateral sclerosis: an update.

INTRODUCTION: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease whose aetiology is unknown. It is characterised by upper and lower motor neuron degeneration. Approximately 90% of cases of ALS are sporadic, whereas the other 10% are familial. Regardless of whether the case is familial o sporadic, patients will develop progressive weakness, muscle atrophy with spasticity, and muscle contractures. Life expectancy of these patients is generally 2 to 5 years after diagnosis. DEVELOPMENT: In vivo models have helped to clarify the aetiology and pathogenesis of ALS, as well as the mechanisms of the disease. However, as these mechanisms are not yet fully understood, experimental models are essential to the continued study of the pathogenesis of ALS, as well as in the search for possible therapeutic targets. Although 90% of cases are sporadic, most of the models used to study ALS pathogenesis are based on genetic mutations associated with the familial form of the disease; the pathogenesis of sporadic ALS remains unknown. Therefore, it would be critical to establish models based on the sporadic form. CONCLUSIONS: This article reviews the main genetic and sporadic experimental models used in the study of this disease, focusing on those that have been developed using rodents.

Exonic variants of the P2RX7 gene in familial multiple sclerosis.

INTRODUCTION: Several studies have analysed the presence of P2RX7 variants in patients with MS, reporting diverging results. METHODS: Our study analyses P2RX7 variants detected through whole-exome sequencing (WES). RESULTS: We analysed P2RX7, P2RX4, and CAMKK2 gene variants detected by whole-exome sequencing in all living members (n = 127) of 21 families including at least 2 individuals with multiple sclerosis. P2RX7 gene polymorphisms previously associated with autoimmune disease. Although no differences were observed between individuals with and without multiple sclerosis, we found greater polymorphism of gain-of-function variants of P2RX7 in families with individuals with multiple sclerosis than in the general population. Copresence of gain-of-function and loss-of-function variants was not observed to reduce the risk of presenting the disease. Three families displayed heterozygous gain-of-function SNPs in patients with multiple sclerosis but not in healthy individuals. We were unable to determine the impact of copresence of P2RX4 and CAMKK2 variants with P2RX7 variants, or the potential effect of the different haplotypes described in the gene. No clinical correlations with other autoimmune diseases were observed in our cohort. CONCLUSIONS: Our results support the hypothesis that the disease is polygenic and point to a previously unknown mechanism of genetic predisposition to familial forms of multiple sclerosis. P2RX7 gene activity can be modified, which suggests the possibility of preventive pharmacological treatments for families including patients with familial multiple sclerosis.

Variant rs4149584 (R92Q) of the TNFRSF1A gene in patients with familial multiple sclerosis.

INTRODUCTION: Genomic studies have identified numerous genetic variants associated with susceptibility to multiple sclerosis (MS); however, each one explains only a small percentage of the risk of developing the disease. These variants are located in genes involved in specific pathways, which supports the hypothesis that the risk of developing MS may be linked to alterations in these pathways, rather than in specific genes. We analyzed the role of the TNFRSF1A gene, which encodes one of the TNF-α receptors involved in a signaling pathway previously linked to autoimmune disease. METHODS: We included 138 individuals from 23 families including at least 2 members with MS, and analyzed the presence of exonic variants of TNFRSF1A through whole-exome sequencing. We also conducted a functional study to analyze the pathogenic mechanism of variant rs4149584 (-g.6442643C > G, NM_001065.4:c.362 G > A, R92Q) by plasmid transfection into human oligodendroglioma (HOG) cells, which behave like oligodendrocyte lineage cells; protein labeling was used to locate the protein within cells. We also analyzed the ability of transfected HOG cells to proliferate and differentiate into oligodendrocytes. RESULTS: Variant rs4149584 was found in 2 patients with MS (3.85%), one patient with another autoimmune disease (7.6%), and in 5 unaffected individuals (7.46%). The 2 patients with MS and variant rs4149584 were homozygous carriers and belonged to the same family, whereas the remaining individuals presented the variant in heterozygosis. The study of HOG cells transfected with the mutation showed that the protein does not reach the cell membrane, but rather accumulates in the cytoplasm, particularly in the endoplasmic reticulum and near the nucleus; this suggests that, in the cells presenting the mutation, TNFRSF1 does not act as a transmembrane protein, which may alter its signaling pathway. The study of cell proliferation and differentiation found that transfected cells continue to be able to differentiate into oligodendrocytes and are probably still capable of producing myelin, although they present a lower rate of proliferation than wild-type cells. CONCLUSIONS: Variant rs4149584 is associated with risk of developing MS. We analyzed its functional role in oligodendrocyte lineage cells and found an association with MS in homozygous carriers. However, the associated molecular alterations do not influence the differentiation into oligodendrocytes; we were therefore unable to confirm whether this variant alone is pathogenic in MS, at least in heterozygosis.

Should we expect neurological symptoms in the SARS-CoV-2 epidemic? / ¿Es esperable que haya cuadros neurológicos por la pandemia por SARS-CoV-2?

INTRODUCTION: There is growing evidence that SARS-CoV-2 can gain access to the central nervous system (CNS). We revise the literature on coronavirus infection of the CNS associated with neurological diseases. DEVELOPMENT: Neurological symptoms were rarely reported in the SARS-CoV and MERS-CoV epidemics, although isolated cases were described. There are also reports of cases of neurological symptoms associated with CoV-OC43 and CoV-229E infection. The presence of neurological lesions, especially demyelinating lesions in the mouse hepatitis virus model, may explain the mechanisms by which coronaviruses enter the CNS, particularly those related with the immune response. This may explain the presence of coronavirus in patients with multiple sclerosis. We review the specific characteristics of SARS-CoV-2 and address the question of whether the high number of cases may be associated with greater CNS involvement. CONCLUSION: Although neurological symptoms are not frequent in coronavirus epidemics, the high number of patients with SARS-CoV-2 infection may explain the presence of the virus in the CNS and increase the likelihood of early- or delayed-onset neurological symptoms. Follow-up of patients affected by the SARS-CoV-2 epidemic should include careful assessment of the CNS.

Experimental models of demyelination and remyelination. / Modelos experimentales de desmielinización-remielinización.

INTRODUCTION: Experimental animal models constitute a useful tool to deepen our knowledge of central nervous system disorders. In the case of multiple sclerosis, however, there is no such specific model able to provide an overview of the disease; multiple models covering the different pathophysiological features of the disease are therefore necessary. DEVELOPMENT: We reviewed the different in vitro and in vivo experimental models used in multiple sclerosis research. Concerning in vitro models, we analysed cell cultures and slice models. As for in vivo models, we examined such models of autoimmunity and inflammation as experimental allergic encephalitis in different animals and virus-induced demyelinating diseases. Furthermore, we analysed models of demyelination and remyelination, including chemical lesions caused by cuprizone, lysolecithin, and ethidium bromide; zebrafish; and transgenic models. CONCLUSIONS: Experimental models provide a deeper understanding of the different pathogenic mechanisms involved in multiple sclerosis. Choosing one model or another depends on the specific aims of the study.

Human recombinant erythropoietin reduces sensorimotor dysfunction and cognitive impairment in rat models of chronic kidney disease. / La eritropoyetina humana recombinante reduce la disfunción sensoriomotora y el deterioro cognitivo en ratas con enfermedad renal crónica.

INTRODUCTION: Chronic kidney disease (CKD) can cause anaemia and neurological disorders. Recombinant human erythropoietin (rHuEPO) is used to manage anaemia in CKD. However, there is little evidence on the effects of rHuEPO on behaviour and cognitive function in CKD. This study aimed to evaluate the impact of rHuEPO in sensorimotor and cognitive functions in a CKD model. METHODS: Male Wistar rats were randomly assigned to 4 groups: control and CKD, with and without rHuEPO treatment (1050 IU per kg body weight, once weekly for 4 weeks). The Morris water maze, open field, and adhesive removal tests were performed simultaneously to kidney damage induction and treatment. Markers of anaemia and renal function were measured at the end of the study. RESULTS: Treatment with rHuEPO reduced kidney damage and corrected anaemia in rats with CKD. We observed reduced sensorimotor dysfunction in animals with CKD and treated with rHuEPO. These rats also completed the water maze test in a shorter time than the control groups. CONCLUSIONS: rHuEPO reduces kidney damage, corrects anemia, and reduces sensorimotor and cognitive dysfunction in animals with CKD.

NG2 and GFAP co-expression after differentiation in cells transfected with mutant GFAP and in undifferentiated glioma cells. / Coexpresión de NG2/GFAP tras la diferenciación en células transfectadas con las mutaciones de GFAP y en células procedentes de gliomas indiferenciados.

INTRODUCTION: Alexander disease is a rare disorder caused by mutations in the gene coding for glial fibrillary acidic protein (GFAP). In a previous study, differentiation of neurospheres transfected with these mutations resulted in a cell type that expresses both GFAP and NG2. OBJECTIVE: To determine the effect of molecular marker mutations in comparison to undifferentiated glioma cells simultaneously expressing GFAP and NG2. METHODS: We used samples of human glioblastoma (GBM) and rat neurospheres transfected with GFAP mutations to analyse GFAP and NG2 expression after differentiation. We also performed an immunocytochemical analysis of neuronal differentiation for both cell types and detection of GFAP, NG2, vimentin, Olig2, and caspase-3 at 3 and 7 days from differentiation. RESULTS: Both the cells transfected with GFAP mutations and GBM cells showed increased NG2 and GFAP expression. However, expression of caspase-3-positive cells was found to be considerably higher in transfected cells than in GBM cells. CONCLUSIONS: Our results suggest that GFAP expression is not the only factor associated with cell death in Alexander disease. Caspase-3 expression and the potential role of NG2 in increasing resistance to apoptosis in cells co-expressing GFAP and NG2 should be considered in the search for new therapeutic strategies for the disease.

Neuroprotective effects of phytochemicals on dopaminergic neuron cultures. / Efecto neuroprotector de fitoquímicos en cultivo de neuronas dopaminérgicas.

INTRODUCTION: Parkinson's disease is a progressive neurodegenerative disorder characterised by a loss of dopaminergic neurons in the substantia nigra pars compacta, which results in a significant decrease in dopamine levels and consequent functional motor impairment. DEVELOPMENT: Although its aetiology is not fully understood, several pathogenic mechanisms, including oxidative stress, have been proposed. Current therapeutic approaches are based on dopamine replacement drugs; these agents, however, are not able to stop or even slow disease progression. Novel therapeutic approaches aimed at acting on the pathways leading to neuronal dysfunction and death are under investigation. CONCLUSIONS: In recent years, such natural molecules as polyphenols, alkaloids, and saponins have been shown to have a neuroprotective effect due to their antioxidant and anti-inflammatory properties. The aim of our review is to analyse the most relevant studies worldwide addressing the benefits of some phytochemicals used in in vitro models of Parkinson's disease.

Myelin changes in Alexander disease. / La alteración de la mielina en la enfermedad de Alexander.

INTRODUCTION: Alexander disease (AxD) is a type of leukodystrophy. Its pathological basis, along with myelin loss, is the appearance of Rosenthal bodies, which are cytoplasmic inclusions in astrocytes. Mutations in the gene coding for GFAP have been identified as a genetic basis for AxD. However, the mechanism by which these variants produce the disease is not understood. DEVELOPMENT: The most widespread hypothesis is that AxD develops when a gain of function mutation causes an increase in GFAP. However, this mechanism does not explain myelin loss, given that experimental models in which GFAP expression is normal or mutated do not exhibit myelin disorders. This review analyses other possibilities that may explain this alteration, such as epigenetic or inflammatory alterations, presence of NG2 (+) - GFAP (+) cells, or post-translational modifications in GFAP that are unrelated to increased expression. CONCLUSIONS: The different hypotheses analysed here may explain the myelin alteration affecting these patients, and multiple mechanisms may coexist. These theories raise the possibility of designing therapies based on these mechanisms.

Vitamin D and remyelination in multiple sclerosis. / Vitamina D y remielinización en la esclerosis múltiple.

INTRODUCTION: Several studies have found an association between multiple sclerosis and vitamin D (VD) deficiency, which suggests that VD may play a role in the immune response. However, few studies have addressed its role in remyelination. DEVELOPMENT: The VD receptor and the enzymes transforming VD into metabolites which activate the VD receptor are expressed in central nervous system (CNS) cells, which suggests a potential effect of VD on the CNS. Both in vitro and animal model studies have shown that VD may play a role in myelination by acting on factors that influence the microenvironment which promotes both proliferation and differentiation of neural stem cells into oligodendrocyte progenitor cells and oligodendrocytes. It remains unknown whether the mechanisms of internalisation of VD in the CNS are synergistic with or antagonistic to the mechanisms that facilitate the entry of VD metabolites into immune cells. CONCLUSIONS: VD seems to play a role in the CNS and our hypothesis is that VD is involved in remyelination. Understanding the basic mechanisms of VD in myelination is necessary to manage multiple sclerosis patients with VD deficiency.

Histological changes in the rat brain and spinal cord following prolonged intracerebroventricular infusion of cerebrospinal fluid from amyotrophic lateral sclerosis patients are similar to those caused by the disease. / La infusión intracerebroventricular prolongada de líquido cefalorraquídeo procedente de pacientes con esclerosis lateral amiotrófica provoca cambios histológicos en el cerebro y la médula espinal de la rata similares a los hallados en la enfermedad.

INTRODUCTION: Cerebrospinal fluid (CSF) from amyotrophic lateral sclerosis (ALS) patients induces cytotoxic effects in in vitro cultured motor neurons. MATERIAL AND METHODS: We selected CSF with previously reported cytotoxic effects from 32 ALS patients. Twenty-eight adult male rats were intracerebroventricularly implanted with osmotic mini-pumps and divided into 3 groups: 9 rats injected with CSF from non-ALS patients, 15 rats injected with cytotoxic ALS-CSF, and 4 rats injected with a physiological saline solution. CSF was intracerebroventricularly and continuously infused for periods of 20 or 43days after implantation. We conducted clinical assessments and electromyographic examinations, and histological analyses were conducted in rats euthanised 20, 45, and 82days after surgery. RESULTS: Immunohistochemical studies revealed tissue damage with similar characteristics to those found in the sporadic forms of ALS, such as overexpression of cystatinC, transferrin, and TDP-43 protein in the cytoplasm. The earliest changes observed seemed to play a protective role due to the overexpression of peripherin, AKTpan, AKTphospho, and metallothioneins; this expression had diminished by the time we analysed rats euthanised on day 82, when an increase in apoptosis was observed. The first cellular changes identified were activated microglia followed by astrogliosis and overexpression of GFAP and S100B proteins. CONCLUSION: Our data suggest that ALS could spread through CSF and that intracerebroventricular administration of cytotoxic ALS-CSF provokes changes similar to those found in sporadic forms of the disease.

Cerebrospinal fluid cytotoxicity does not affect survival in amyotrophic lateral sclerosis.

OBJECTIVES: Cerebrospinal fluid (CSF) from some patients with amyotrophic lateral sclerosis (ALS) has been demonstrated to significantly reduce the neuronal viability of primary cell cultures of motor neurons. We aimed to study the potential clinical consequences associated with the cytotoxicity of CSF in a cohort of patients with ALS. METHODS: We collected CSF from thirty-one patients with ALS. We analysed cytotoxicity by incubating it into the primary cultures of motor cortex neurons. Neural viability was quantified after 24 hours using the colorimetric MTT reduction assay. All patients were followed up from the moment of diagnosis to death, and a complete evaluation during disease progression and survival was performed, including gastrostomy and respiratory assistance. RESULTS: Twenty-one patients (67.7%) presented a cytotoxic CSF. There were no significant differences between patients with and without cytotoxicity regarding mean time from symptom onset to the diagnosis, from the diagnosis to death, from the diagnosis to respiratory assistance with BIPAP, from diagnosis to gastrostomy and from the onset of symptoms to death. In Cox regression analysis, bulbar onset, but not cytotoxicity, gender or age at onset, was associated with a lower risk of survival. CONCLUSIONS: Cerebrospinal fluid cytotoxicity was not associated with differential survival rates. This suggests that the presence of cytotoxicity in CSF, measured through neuronal viability in primary cultures of motor cortex neurons, could reflect different mechanisms of the disease, but it does not predict disease outcome.

Effect of axotomy and 17ß-estradiol on P2X7 receptor expression pattern in the hypoglossal nucleus of ovariectomized mice.

The objective of the study was to examine whether axotomy and 17ß-estradiol affects P2X7 receptor expression and distribution in the hypoglossal nucleus. The left hypoglossal nerve of ovariectomized mice was cut and animals received a single injection of 17ß-estradiol (25 µg/100g b.w. in 20% (2-hydroxypropyl)-ß-cyclodextrin) or vehicle one hour after axotomy. Mice were sacrificed on day 4 following surgery. The area fraction of P2X7 receptor immunoreactive structures and of CD11b immunolabeled microglia, P2X7 protein concentration, and the immunoreactivity pattern of estrogen receptor (ER) alpha/beta were analyzed on both sides of the hypoglossal nucleus. Following axotomy the area fraction of P2X7 immunoreactive neurons showed a decreasing tendency, while the area fraction of P2X7 immunolabeled microglia increased significantly on the axotomized side compared with the control side in mice injected with vehicle. In animals treated with 17ß-estradiol the decrease in area fraction of neural and the increase in area fraction of microglial P2X7 immunostaining on the axotomized side were significantly enhanced compared with animals injected with vehicle. The P2X7 immunoreactivity pattern on the control side of the nucleus remained unchanged after 17ß-estradiol injection. Semi-quantitative Western blots revealed no significant difference in P2X7 protein concentration comparing the axotomized side with the control side in either experimental group. The CD11b immunoreactive microglia area fraction increased significantly following axotomy, but was not affected by 17ß-estradiol. Neither ER alpha, nor beta colocalized with CD11b. Our results suggest that axotomy induces cell-type specific changes in P2X7 receptor expression, which may be directly regulated by 17ß-estradiol through ER alpha or beta in neurons, but not in activated microglia.

Astrocytes in neurodegenerative diseases (I): function and molecular description.

INTRODUCTION: Astrocytes have been considered mere supporting cells in the CNS. However, we now know that astrocytes are actively involved in many of the functions of the CNS and may play an important role in neurodegenerative diseases. DEVELOPMENT: This article reviews the roles astrocytes play in CNS development and plasticity; control of synaptic transmission; regulation of blood flow, energy, and metabolism; formation of the blood-brain barrier; regulation of the circadian rhythms, lipid metabolism and secretion of lipoproteins; and in neurogenesis. Astrocyte markers and the functions of astrogliosis are also described. CONCLUSION: Astrocytes play an active role in the CNS. A good knowledge of astrocytes is essential to understanding the mechanisms of neurodegenerative diseases.

Cellular changes in motor neuron cell culture produced by cytotoxic cerebrospinal fluid from patients with amyotrophic lateral sclerosis.

INTRODUCTION: The neurotoxic effects of cerebrospinal fluid (CSF) from patients with amyotrophic lateral sclerosis (ALS) have been reported by various authors who have attributed this neurotoxicity to the glutamate in CSF-ALS. MATERIAL AND METHODS: Cultures of rat embryonic cortical neurons were exposed to CSF from ALS patients during an incubation period of 24 hours. Optical microscopy was used to compare cellular changes to those elicited by exposure to 100µm glutamate, and confocal microscopy was used to evaluate immunohistochemistry for caspase-3, TNFα, and peripherin. RESULTS: In the culture exposed to CSF-ALS, we observed cells with nuclear fragmentation and scarce or null structural modifications to the cytoplasmic organelles or to plasma membrane maintenance. This did not occur in the culture exposed to glutamate. The culture exposed to CSF-ALS also demonstrated increases in caspase-3, TNFα, and in peripherin co-locating with caspase-3, but not with TNFα, suggesting that TNFα may play an early role in the process of apoptosis. CONCLUSIONS: CFS-ALS cytotoxicity is not related to glutamate. It initially affects the nucleus without altering the cytoplasmic membrane. It causes cytoplasmic apoptosis that involves an increase in caspase-3 co-located with peripherin, which is also overexpressed.

[Cell therapy in amyotrophic lateral sclerosis: science and controversy]. / Terapia celular en la esclerosis lateral amiotrófica: ciencia y controversia.

Stem cell therapy is seen as a possible alternative for the treatment of different degenerative diseases, among which includes amyotrophic lateral sclerosis (ALS). Despite there being basic research works with this therapy in ALS, the mechanism of action of the implanted cells are still unclear. It is also unclear which type of cells to use (bone marrow, fat, dental pulp, etc.), or the most ideal administration route. Furthermore, clinical trials with mesenchymal stem cells are not very conclusive, therefore it has not been convincingly established as an alternative therapy in ALS or any other neurodegenerative disease. Despite the scientific evidence, several clinical trials have been conducted in the last few years that offer stem cell treatments for neurodegenerative diseases, giving rise to what is known as "cellular tourism". This phenomenon has set off alarms and reactions in the scientific community. The application of these therapies must be performed following the good clinical practice guidelines in research, evidence based methodology and international ethical and scientific recommendations.

[Molecular aspects of hepatic encephalopathy]. / Aspectos moleculares de la encefalopatía hepática.

INTRODUCTION: Liver fibrosis and its end stage, cirrhosis, is an enormous worldwide health problem. Hepatic encephalopathy (HE) or portal-systemic encephalopathy continues to be a major clinical problem of long-term cirrhosis. In this review we emphasise the molecular basis of HE and the involvement of oxidative stress in the development of this disease. BACKGROUND: Several studies suggest that the pathogenesis of HE could be multifactorial and have implicated different factors, such as alterations in blood brain barrier, substances; such as ammonia and manganese, neurotransmission disorders such as dopamine, glutamate and GABA. DEVELOPMENT: HE is a severe complication of both acute and chronic liver failure. Neuropathologically, it is characterized by astrocyte changes known as Alzheimer type II astrocytosis. In addition, astrocytes manifest altered expression of astrocyte-specific proteins, such as, glial fibrillary acidic protein, glutamine synthetase, monoamine oxidase and peripheral type benzodiazepine receptors. CONCLUSIONS: HE is a complex neuropsychiatric syndrome associated with liver failure. These alterations are products of increases in oxidative stress in brain due to neurotoxin activity. The main strategy for HE treatment is directed at ammonia reduction, which can be achieved either by decreasing its absorption/production or increasing its removal.

IGF-I stimulates neurogenesis in the hypothalamus of adult rats.

In the brain of adult rats neurogenesis persists in the subventricular zone of the lateral ventricles and in the dentate gyrus of the hippocampus. By contrast, low proliferative activity was observed in the hypothalamus. We report here that, after intracerebroventricular treatment with insulin-like growth factor I (IGF-I), cell proliferation significantly increased in both the periventricular and the parenchymal zones of the whole hypothalamus. Neurons, astrocytes, tanycytes, microglia and endothelial cells of the local vessels were stained with the proliferative marker 5-bromo-2'-deoxyuridine (BrdU) in response to IGF-I. Conversely, we never observed BrdU-positive ciliated cubic ependymal cells. Proliferation was intense in the subventricular area of a distinct zone of the mid third ventricle wall limited dorsally by ciliated cubic ependyma and ventrally by tanycytic ependyma. In this area, we saw a characteristic cluster of proliferating cells. This zone of the ventricular wall displayed three cell layers: ciliated ependyma, subependyma and underlying tanycytes. After IGF-I treatment, proliferating cells were seen in the subependyma and in the layer of tanycytes. In the subependyma, proliferating glial fibrillary acidic protein-positive astrocytes contacted the ventricle by an apical process bearing a single cilium and there were many labyrinthine extensions of the periventricular basement membranes. Both features are typical of neurogenic niches in other brain zones, suggesting that the central overlapping zone of the rat hypothalamic wall could be considered a neurogenic niche in response to IGF-I.

Proliferation in the human ipsilateral subventricular zone after ischemic stroke.

BACKGROUND: It is uncertain whether neurogenesis occurs in humans after stroke. We studied the morphologic changes that occurred in the subventricular zone (SVZ) in patients who died following an acute ischemic stroke. METHODS: We examined coronal brain slices from patients who died after a first-ever cerebral nonlacunar infarction in the middle cerebral artery territory. We evaluated the morphologic changes in the ipsilateral and contralateral SVZ by light and electron microscopy. Using immunochemistry with Ki-67 and PCNA, we detected cell proliferation. We used Tuj-1 for immature neurons and PSA-NCAM for migrating cells. RESULTS: The study included 7 patients with a mean age of 82 +/- 5 (mean +/- SD) years; 4 were men. They died a mean of 10 +/- 5 days after the ischemic stroke. Brain samples were obtained a mean of 4 +/- 2 hours after death. In comparison with the contralateral SVZ, the following changes were observed in the ipsilateral SVZ: an increase in the width of the gap and ribbon layers, as well as in the cell density of the ribbon layer, an enlargement of the cytoplasmic volume of astrocytes, and an increase of Ki-67-positive cells. In the ipsilateral SVZ, mitoses and cells that stained for either Tuj-1 or PSA-NCAM markers were observed more frequently than in the contralateral SVZ. CONCLUSION: We found unequivocal evidence of active cell proliferation in the ipsilateral subventricular zone following an acute ischemic stroke in our patients.