Unilateral cerebral ischemia inhibits optomotor responses of the ipsilateral eye in mice

Unilateral cerebral ischemia induces morphological changes in the layer V projection neurons of the contralateral hemisphere

Decreased blood flow to the brain causes stroke and damage to neuronal networks. Neuronal damage occurs not only in the infarct core but also in areas away from the infarcts. This study was aimed to assess alterations of the cortical projection neurons that were distantly connected with the infarcts. Unilateral cortical ischemia was generated by middle cerebral artery occlusion in the right somatosensory cortex. Pre-labeled thalamocortical neurons disappeared, whereas contralateral callosal projection neurons survived 48 h post-ischemia. The unilateral ischemia increased the total length, segment length and the spine volume of dendrites from layer V callosal neurons in the homotopic cortex of the contralateral hemisphere. The morphological remolding of the contralateral cortical neurons cannot be reproduced by the spinal cord hemisection that cuts axons of corticospinal projection neurons of layer V. The data suggest that the retrograde degeneration of axons may not account for the early morphological changes in the contralateral cortex. We hypothesize that the loss of innervations from the ischemic cortex may bring in adaptive changes to the connected neurons, and adult cortical neurons can adjust their morphology to meet the reduction of synaptic inputs. This study may improve our understanding of the re-organization of cortical circuits following focal cerebral ischemia and help the development of new treatments designed to minimize the disability associated with stroke.

Stem Cells as Drug-like Biologics for Mitochondrial Repair in Stroke

Stroke is a devastating condition characterized by widespread cell death after disruption of blood flow to the brain. The poor regenerative capacity of neural cells limits substantial recovery and prolongs disruptive sequelae. Current therapeutic options are limited and do not adequately address the underlying mitochondrial dysfunction caused by the stroke. These same mitochondrial impairments that result from acute cerebral ischemia are also present in retinal ischemia. In both cases, sufficient mitochondrial activity is necessary for cell survival, and while astrocytes are able to transfer mitochondria to damaged tissues to rescue them, they do not have the capacity to completely repair damaged tissues. Therefore, it is essential to investigate this mitochondrial transfer pathway as a target of future therapeutic strategies. In this review, we examine the current literature pertinent to mitochondrial repair in stroke, with an emphasis on stem cells as a source of healthy mitochondria. Stem cells are a compelling cell type to study in this context, as their ability to mitigate stroke-induced damage through non-mitochondrial mechanisms is well established. Thus, we will focus on the latest preclinical research relevant to mitochondria-based mechanisms in the treatment of cerebral and retinal ischemia and consider which stem cells are ideally suited for this purpose.

The brain and eye: Treating cerebral and retinal ischemia through mitochondrial transfer

Stroke remains a devastating disease with limited treatment options, despite our growing understanding of its pathology. While ischemic stroke is traditionally characterized by a blockage of blood flow to the brain, this may coincide with reduced blood circulation to the eye, resulting in retinal ischemia, which may in turn lead to visual impairment. Although effective treatment options for retinal ischemia are similarly scarce, new evidence suggests that deleterious changes to mitochondrial structure and function play a major role in both cerebral and retinal ischemia pathologies. Prior studies establish that astrocytes transfer healthy mitochondria to ischemic neurons following stroke; however, this alone is not enough to significantly mitigate the damage caused by primary and secondary cell death. Thus, stem cell-based regenerative medicine targeting amelioration of ischemia-induced mitochondrial dysfunction via the transfer of functional mitochondria to injured neural cells represents a promising approach to improve stroke outcomes for both cerebral and retinal ischemia. In this review, we evaluate recent laboratory evidence supporting the remedial capabilities of mitochondrial transfer as an innovative stroke treatment. In particular, we examine exogenous stem cell transplants in their potential role as suppliers of healthy mitochondria to neurons, brain endothelial cells, and retinal cells.

Impact statement

Stroke constitutes a global health crisis, yet potent, applicable therapeutic options remain effectively inaccessible for many patients. To this end, stem cell transplants stand as a promising stroke treatment and as an emerging subject of research for cell-based regenerative medicine. This is the first review to synthesize the implications of stem cell-derived mitochondrial transfer in both the brain and the eye. As such, this report carries fresh insight into the commonalities between the two stroke-affected organs. We present the findings of this developing area of research inquiry with the hope that our evaluation may advance the use of stem cell transplants as viable therapeutic alternatives for ischemic stroke and related disorders characterized by mitochondrial dysfunction. Such lab-to-clinic translational advancement has the potential to save and improve the ever increasing millions of lives affected by stroke.

Eye Opener in Stroke

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Retinal ischemia is a major cause of visual impairment in stroke patients, but our incomplete understanding of its pathology may contribute to a lack of effective treatment. Here, we investigated the role of mitochondrial dysfunction in retinal ischemia and probed the potential of mesenchymal stem cells (MSCs) in mitochondrial repair under such pathological condition.