The Effect of an NgR1 Antagonist on the Neuroprotection of Cortical Axons After Cortical Infarction in Rats

Cell-to-Cell Interactions Mediating Functional Recovery after Stroke

Ischemic damage in brain tissue triggers a cascade of molecular and structural plastic changes, thus influencing a wide range of cell-to-cell interactions. Understanding and manipulating this scenario of intercellular connections is the Holy Grail for post-stroke neurorehabilitation. Here, we discuss the main findings in the literature related to post-stroke alterations in cell-to-cell interactions, which may be either detrimental or supportive for functional recovery. We consider both neural and non-neural cells, starting from astrocytes and reactive astrogliosis and moving to the roles of the oligodendrocytes in the support of vulnerable neurons and sprouting inhibition. We discuss the controversial role of microglia in neural inflammation after injury and we conclude with the description of post-stroke alterations in pyramidal and GABAergic cells interactions. For all of these sections, we review not only the spontaneous evolution in cellular interactions after ischemic injury, but also the experimental strategies which have targeted these interactions and that are inspiring novel therapeutic strategies for clinical application.

Lentiviral vector delivery of short hairpin RNA to NgR1 promotes nerve regeneration and locomotor recovery in injured rat spinal cord

Nogo receptor 1 (NgR1) is a high-affinity receptor of myelin-associated inhibitors (MAIs), and suppresses neurogenesis. Lentiviral vector are commonly used to alter the expression of targeted genes. However, little is known about the potential function of lentiviral vector harboring NgR1 shRNA (LV-NgR1 shRNA) on neurogenesis in spinal cord injury (SCI). In this study, the rats were randomly divided into three groups: including the LN (LV-NgR1 shRNA injection), LC (LV-control shRNA injection) and Sham (laminectomy only). Eight weeks post-injection of LV, spinal cords were examined by histology for changes in cavity size and by immunohistochemistry for changes in expression of NgR1, cell apoptosis, astrocytes, neurons and myelination. Motor function was assessed using the Basso, Beattie and Bresnahan (BBB) locomotor scale. Animals that received LV-NgR1 shRNA remarkably improved the motor function. These animals also showed an increase in levels of nerve fibers, synapses and myelination, a decrease in levels of lesion cavity and cell apoptosis at 8 weeks post-treatment. These findings give evidence that NgR1 may be a promising target for SCI treatment.

The Involvement of the Myelin-Associated Inhibitors and Their Receptors in CNS Plasticity and Injury

The limited capacity for the central nervous system (CNS) to repair itself was first described over 100 years ago by Spanish neuroscientist Ramon Y. Cajal. However, the exact mechanisms underlying this failure in neuronal regeneration remain unclear and, as such, no effective therapeutics yet exist. Numerous studies have attempted to elucidate the biochemical and molecular mechanisms that inhibit neuronal repair with increasing evidence suggesting that several inhibitory factors and repulsive guidance cues active during development actually persist into adulthood and may be contributing to the inhibition of repair. For example, in the injured adult CNS, there are various inhibitory factors that impede the outgrowth of neurites from damaged neurons. One of the most potent of these neurite outgrowth inhibitors is the group of proteins known as the myelin-associated inhibitors (MAIs), present mainly on the membranes of oligodendroglia. Several studies have shown that interfering with these proteins can have positive outcomes in CNS injury models by promoting neurite outgrowth and improving functional recovery. As such, the MAIs, their receptors, and downstream effectors are valid drug targets for the treatment of CNS injury. This review will discuss the current literature on MAIs in the context of CNS development, plasticity, and injury. Molecules that interfere with the MAIs and their receptors as potential candidates for the treatment of CNS injury will additionally be introduced in the context of preclinical and clinical trials.