Dinko Mitrečić

Impaired blood-brain and blood-spinal cord barriers in mutant SOD1-linked ALS rat.

Blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) impairment is an additional accident occurring during the amyotrophic lateral sclerosis (ALS) progression. In this work, we aimed to decipher if BBB/BSCB leakage appeared before critical detrimental events and could serve as a marker preceding clinical symptoms. Three different BBB leakage markers: Evans blue, IgG and hemosiderin, were used to look at the SOD1-linked ALS rat model at presymptomatic and symptomatic stages. Although IgG and hemosiderin could be detected at presymptomatic stage, Evans blue extravasation which fits best with BBB/BSCB impairment could only be seen at symptomatic stages. BBB/BSCB impairment was further substantiate by showing at symptomatic stages decreased mRNA expression of ZO-1 and occludin as well as agrin, a basal membrane constituent. Electron microscopic data substantiate a toxic environment around endothelial cell and peri-vascular swollen astrocyte end-feet showing oedema-linked BBB opening.

Distribution, differentiation, and survival of intravenously administered neural stem cells in a rat model of amyotrophic lateral sclerosis.

The transplantation of neural stem cells (NSCs) is a challenging therapeutic strategy for the treatment of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). To provide insight into the potential of the intravenous delivery of NSCs, we evaluated the delivery of NSCs marked with green fluorescent protein to the central nervous system (CNS) via intravenous tail vein injections in an ALS model. The injected cell fates were followed 1, 3, and 7 days after transplantation. The highest efficiency of cell delivery to the CNS was found in symptomatic ALS (up to 13%), moderate in presymptomatic ALS (up to 6%), and the lowest in wild-type animals (up to 0.3%). NSCs injected into ALS animals preferentially colonized the motor cortex, hippocampus, and spinal cord, and their differentiation was characterized by a decrease of nestin expression and the appearance of MAP2-, GFAP-, O4-, and CD68-positive cells. Tumor necrosis factor (TNF) administration increased the CNS delivery of transplanted cells in wild-type and presymptomatic, but not ALS symptomatic animals. Moreover, a TNF-related increase in NSC differentiation and survival was detected. Apoptosis was detected as the main cause of the loss of transplanted cells and it was influenced by TNF. Although 3 days after TNF treatment cell death was accelerated, TNF slowed down apoptosis after 7 days. This study provides elementary facts about the process occurring after NSCs leave the blood stream and enter the nervous tissue affected by inflammation/degeneration, which should help facilitate the planning of future bench-to-bedside translational projects.

Brain and spinal cord affected by amyotrophic lateral sclerosis induce differential growth factors expression in rat mesenchymal and neural stem cells

C. Nicaise, D. Mitrecic and R. Pochet (2011) Neuropathology and Applied Neurobiology37, 179–188
Brain and spinal cord affected by amyotrophic lateral sclerosis induce differential growth factors expression in rat mesenchymal and neural stem cells

In Vivo Morphological Changes in Animal Models of Amyotrophic Lateral Sclerosis and Alzheimer's‐Like Disease: MRI Approach

Magnetic resonance imaging (MRI) is the only noninvasive technique that provides structural information on both cell loss and metabolic changes. After reviewing all the results obtained in clinical studies, reliable biomarkers in neurological diseases are still lacking. Diffusional MRI, MR spectroscopy, and the assessment of regional atrophy are promising approaches, but they cannot be simultaneously used on a single patient. Thus, for further research progress, reliable animal models are needed. To this aim, we have used the clinical MRI to assess neurodegenerative processes in the hSOD‐1G93A ALS rat model and in the trimethyltin (TMT)‐treated model of Alzheimers‐like disease. T2‐weighted (T2W) hyperintensive neurodegenerative foci were found in the brainstem of the ALS rat with apparent lateral ventricle dilation (T1W—hypointensity vs. T2W—hyperintensity). Degenerative processes in these areas were also confirmed by confocal images of GFAP‐positive astrogliosis. MRI after i.v.i. of magnetic anti‐CD4 antibodies indicated an accumulation of inflammatory cells near dilated ventricles. TMT‐treated rats also revealed the dilation of lateral ventricles. Expected deterioration in the hippocampus was not observed by clinical MRI, but immunocytochemistry could reveal significant redistribution of macro‐ and microglia in this structure. In both models, Gd‐DTPA contrast revealed a compromised blood brain barrier that may serve as the passage for inflammatory immune cells in the vicinity of dilated lateral ventricles. Moreover, in both models the midbrain region of the dorsal hippocampus was the target of BBB compromise, thus revealing a potentially vulnerable point that can be the primary target of neurodegeneration in the central nervous system. Anat Rec, 292:1882–1892, 2009.

Transplantation of stem cell-derived astrocytes for the treatment of amyotrophic lateral sclerosis and spinal cord injury.

Neglected for years, astrocytes are now recognized to fulfill and support many, if not all, homeostatic functions of the healthy central nervous system (CNS). During neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and spinal cord injury (SCI), astrocytes in the vicinity of degenerating areas undergo both morphological and functional changes that might compromise their intrinsic properties. Evidence from human and animal studies show that deficient astrocyte functions or loss-of-astrocytes largely contribute to increased susceptibility to cell death for neurons, oligodendrocytes and axons during ALS and SCI disease progression. Despite exciting advances in experimental CNS repair, most of current approaches that are translated into clinical trials focus on the replacement or support of spinal neurons through stem cell transplantation, while none focus on the specific replacement of astroglial populations. Knowing the important functions carried out by astrocytes in the CNS, astrocyte replacement-based therapies might be a promising approach to alleviate overall astrocyte dysfunction, deliver neurotrophic support to degenerating spinal tissue and stimulate endogenous CNS repair abilities. Enclosed in this review, we gathered experimental evidence that argue in favor of astrocyte transplantation during ALS and SCI. Based on their intrinsic properties and according to the cell type transplanted, astrocyte precursors or stem cell-derived astrocytes promote axonal growth, support mechanisms and cells involved in myelination, are able to modulate the host immune response, deliver neurotrophic factors and provide protective molecules against oxidative or excitotoxic insults, amongst many possible benefits. Embryonic or adult stem cells can even be genetically engineered in order to deliver missing gene products and therefore maximize the chance of neuroprotection and functional recovery. However, before broad clinical translation, further preclinical data on safety, reliability and therapeutic efficiency should be collected. Although several technical challenges need to be overcome, we discuss the major hurdles that have already been met or solved by targeting the astrocyte population in experimental ALS and SCI models and we discuss avenues for future directions based on latest molecular findings regarding astrocyte biology.

Expression analysis of genes involved in TLR2-related signaling pathway: Inflammation and apoptosis after ischemic brain injury

Toll-like receptor 2 (TLR2) is involved in innate immunity in the brain and in the cascade of events after ischemic stroke. The aim of this study was to get an insight into the expression of genes related to TLR2 signaling pathway and associated with inflammation and apoptosis in the later stages of brain response after ischemic injury. Middle cerebral artery occlusion was performed on both wild-type and TLR2(-/-) mice followed by real-time PCR to measure the relative expression of selected genes. In TLR2(-/-) mice expression of genes involved in proinflammatory response was decreased after cerebral ischemia. Tnf was the most prominent cytokine active in the late phase of recovery. Contrary to proinflammatory genes, the expression of Casp8, as a hallmark of apoptosis, was increased in TLR2(-/-) mice, in particular in the late phase of recovery.

Current Advances in Intravascular Administration of Stem Cells for Neurological Diseases: A New Dose of Rejuvenation Injected

Selection of the appropriate administration route is one of the critical steps in a successful therapeutic process. From its beginning, stem cell-based rejuvenation of the central nervous system has been based on intraparenchymal cell transplantation. However, a high invasiveness of the procedure and a focal cell delivery can not be justified for any pathological conditions. This review analyses, compares, and comments on observed differences between the intraparenchymal and intravascular administration route for neurological diseases. A special emphasis has been given to the reported obstacles and specific recommendations have been made. More significant success with intravascular delivery of stem cells for neurological diseases can be achieved with smaller cells, use of dilatators of lung vasculature, blocking of endothelial receptors, less aggressive pretreatment of cells, and permeabilization of the blood-brain barrier. If these requirements are met, intravascular administration represents one of the major options for delivery of stem cells to the aging brain, with obvious advantages over direct intraparenchymal injection.

Toward the Treatments with Neural Stem Cells: Experiences from Amyotrophic Lateral Sclerosis

Common pathological features of neurodegenerative diseases are progressive dysfunction and neuronal death. In amyotrophic lateral sclerosis (ALS), motor neurons are selectively affected, leading to death because of paralysis. The main therapeutic goal in neurodegenerative diseases is to diminish neural dysfunction and to replace non‐functional cells with the new ones. “Cell‐oriented” treatment strategies include isolation of neural stem cells (NSC), their controlled differentiation, and cellular injections targeting the affected region. Beneficial effects of injected cells result from the combination of cell replacement and secretion of the growth factors. Here, we summarize the current state of isolation and differentiation of NSC, and emphasize the embryo tail bud as a particular region where neuroepithelium differentiates from undifferentiated mesenchymal cells over the course of normal development. The possibility to obtain cells from autologous mesenchyme capable of integrating into affected regions represents a major challenge whose achievement should circumvent the pitfall of the immune reaction against transplanted cells. We also present our own results: when intravenously injected in symptomatic ALS rats, NSC migrated to the motor cortex and continued to differentiate. Thus, we illustrate that the use of NSC in rodent models of ALS may represent a paradigm for other neurodegenerative diseases. Anat Rec, 292:1962–1967, 2009.

Increased expression and colocalization of GAP43 and CASP3 after brain ischemic lesion in mouse

GAP43 is a protein involved in neurite outgrowth during development and axon regeneration reflecting its presynaptic localization in developing neurons. Recently, it has been demonstrated that GAP43 is a ligand of CASP3 involved in receptor endocytosis and is also localized post-synaptically. In this study, by using a transgenic mouse strain carrying a bioluminescent reporter for GAP43 combined with an in vivo bioluminescence assay for CASP3, we demonstrated that one day after brain ischemic lesion and, even more pronounced, four days after stroke, expression of both CASP3 and Gap43 in neurons increased more than 40 times. The in vivo approach of CASP3 and GAP43 colocalization imaging was further validated and quantified by immunofluorescence. Importantly, in 82% of GAP43 positive cells, colocalization with CASP3 was present. These findings suggested that one and four days after stroke CASP3 expression, not necessarily associated with neuronal death, increased and suggested that CASP3 and GAP43 might be part of a common molecular pathway involved in early response to ischemic events occurring after onset of stroke.

Murine neural crest stem cells and embryonic stem cell-derived neuron precursors survive and differentiate after transplantation in a model of dorsal root avulsion

Spinal root avulsion results in paralysis and sensory loss, and is commonly associated with chronic pain. In addition to the failure of avulsed dorsal root axons to regenerate into the spinal cord, avulsion injury leads to extensive neuroinflammation and degeneration of second‐order neurons in the dorsal horn. The ultimate objective in the treatment of this condition is to counteract degeneration of spinal cord neurons and to achieve functionally useful regeneration/reconnection of sensory neurons with spinal cord neurons. Here we compare survival and migration of murine boundary cap neural crest stem cells (bNCSCs) and embryonic stem cells (ESCs)‐derived, predifferentiated neuron precursors after their implantation acutely at the junction between avulsed dorsal roots L3–L6 and the spinal cord. Both types of cells survived transplantation, but showed distinctly different modes of migration. Thus, bNCSCs migrated into the spinal cord, expressed glial markers and formed elongated tubes in the peripheral nervous system (PNS) compartment of the avulsed dorsal root transitional zone (DRTZ) area. In contrast, the ESC transplants remained at the site of implantation and differentiated to motor neurons and interneurons. These data show that both stem cell types successfully survived implantation to the acutely injured spinal cord and maintained their differentiation and migration potential. These data suggest that, depending on the source of neural stem cells, they can play different beneficial roles for recovery after dorsal root avulsion. Copyright