Non-paretic Forelimb Training Does Not Interfere with Recovery of Paretic Forelimb Strength After Experimental Middle Cerebral Artery Occlusion

Humans often compensate with their unimpaired (non-paretic) forelimb after surviving a stroke. Research in rats suggests that this can be maladaptive after focal motor cortical strokes. Forelimb weakness is understudied in rodent models of stroke. The purpose of the study is to determine whether behavioral experience with the non-paretic forelimb differentially affects paretic forelimb strength recovery after ischemic injury caused by middle cerebral artery occlusion (MCAo). Because behavioral manipulations can influence patterns of neural connectivity post-stroke, the present study also examined how training with non-paretic limb influenced corticostriatal projections. After training to proficiency with the preferred forelimb on the Isometric Pull Task, rats underwent MCAo in the hemisphere contralateral to this limb. One week after MCAo, rats were probed for initial impairment level and then assigned to either Non-Paretic Limb Training (NPT) or non-training control conditions for 14 days. Paretic limb performance was probed one day later. All rats then received six weeks of Rehabilitative Training (RT). The anterograde tract tracer BDA was then injected into the lesioned hemisphere. Training with the non-paretic limb (NPT) does not interfere with paretic limb recovery on the Isometric Pull Task, increase reliance on the impaired forelimb, or influence ipsi corticostriatal axon quantities after MCAo. Compensatory use of the non-paretic forelimb after strokes involving subcortical damage or cortical damage primarily in the somatosensory region may not be maladaptive for strength. Understanding how behavioral recovery varies with lesion locus could influence clinical management of patients

Nitric Oxide Facilitates Delivery and Mediates Improved Outcome of Autologous Bone Marrow Mononuclear Cells in a Rodent Stroke Model

Bone marrow mononuclear cells (MNC) represent an investigational treatment for stroke. The objective of this study was to determine the relevance of vasoactive mediators, generated in response to MNC injection, as factors regulating cerebral perfusion (CP), the biodistribution of MNC, and outcome in stroke.Long Evans rats underwent transient middle cerebral artery occlusion. MNC were extracted from the bone marrow at 22 hrs and injected via the internal carotid artery or the femoral vein 2 hours later. CP was measured with MRI or continuous laser Doppler flowmetry. Serum samples were collected to measure vasoactive mediators. Animals were treated with the Nitric Oxide (NO) inhibitor, L-NAME, to establish the relevance of NO-signaling to the effect of MNC. Lesion size, MNC biodistribution, and neurological deficits were assessed.CP transiently increased in the peri-infarct region within 30 min after injecting MNC compared to saline or fibroblast control. This CP increase corresponded temporarily to serum NO elevation and was abolished by L-NAME. Pre-treatment with L-NAME reduced brain penetration of MNC and prevented MNC from reducing infarct lesion size and neurological deficits.NO generation in response to MNC may represent a mechanism underlying how MNC enter the brain, reduce lesion size, and improve outcome in ischemic stroke

Behavioral experience effects on forelimb strength recovery and corticostriatal axonal plasticity after experimental middle cerebral artery occlusion

The overarching goal of this dissertation project is to test how behavioral experiences with the paretic and non-paretic forelimbs influence recovery of paretic forelimb strength and corticostriatal projections after strokes caused by occlusion of the middle cerebral artery. In order to accomplish this goal, we pursued the following specific aims: 1) to establish a model that characterizes paretic forelimb weakness using an automated skilled reaching task after middle cerebral artery occlusion (MCAo) in the rat, 2) to test the effects of skilled rehabilitative strength training on paretic forelimb recovery and corticostriatal axonal plasticity after MCAo, and 3) to test whether training with the non-paretic forelimb interferes with recovery of the paretic forelimb and its effects on axonal plasticity after MCAo. The results from the study assessing the first aim are described in chapter 2. We found that the Isometric Pull Task, an automated skilled reaching task, detects forelimb weakness after experimental MCAo. Furthermore, we found that the intraluminal suture MCAo model consistently produces large infarcts damaging somatosensory cortex and striatum. The results for the second aim are described in chapter 3, where we show that daily rehabilitative training with the paretic forelimb for six weeks on the Isometric Pull Task improves paretic forelimb strength after MCAo. We also found that rehabilitative training reduces contralesional striatal axon projections but does not affect contralesional cortical or ipsilesional striatal axon projections that originate from cortex of the lesioned hemisphere. The results for the third aim are described in chapter 4, where we show that 14 days of non-paretic forelimb training post-MCAo on the Isometric Pull Task does not reduce the efficacy of rehabilitative training. These findings suggest that compensating with the intact body side early after stroke may not always be detrimental to recovery and may depend on infarct locus. We also show that non-paretic limb use after MCAo does not influence corticostriatal axonal plasticity. These findings are consistent with the lack of behavioral effect of non-paretic limb training. We finish in chapter 5 by summarizing the results and discussing the implications and potential future direction of this work.Psycholog

Cryopreservation of Bone Marrow Mononuclear Cells Alters Their Viability and Subpopulation Composition but Not Their Treatment Effects in a Rodent Stroke Model

The systemic administration of autologous bone marrow (BM) derived mononuclear cells (MNCs) is under investigation as a novel therapeutic modality for the treatment of ischemic stroke. Autologous applications raise the possibility that MNCs could potentially be stored as a banked source. There have been no studies that investigate the effects of cryopreservation of BM-MNCs on their functional abilities in stroke models. In the present study, C57BL/6 mice were subjected to middle cerebral artery occlusion (MCAo) for 60 minutes and then divided into two treatment groups: fresh MNCs versus cryopreserved MNCs. BM-MNCs were collected at 22 hours after MCAo and were stored in liquid nitrogen for 12 months in cryopreserved MNCs group. BM-MNCs cellular viability, composition, and phenotype of the various subpopulations of mice BM-MNCs were evaluated by flow cytometry, and the behavioral recovery of stroke animals was tested with freshly harvested MNCs versus cryopreserved MNCs by corner test and ladder rung test. We found that long-term cryopreservation negatively impacts the cellular viability of bone marrow MNCs. Cryopreservation also alters the cellular composition of various subpopulations within the MNCs. However, despite the changes observed in cryopreserved cells, both fresh and frozen MNCs have similar beneficial effect on behavioral and histological outcomes

Details of different behavioral tests and scores.

<p>Details of different behavioral tests and scores.</p

L-NAME inhibits the beneficial effect of MNCs.

<p>(A) Chronic infarct cavity at 28 days after stroke in animals treated with saline or MNCs. Animals at 24 hrs after stroke received saline followed by IV MNCs (10 million cells), or L-NAME followed by IV MNCs (10 million cells), or saline only. Lesion size was reduced by MNCs at 28 days after stroke. However, pre-treatment with L-NAME before MNC infusion abolished this reduction in lesion size (§p<0.05 compared with saline). The lesion size was calculated as a percent of the contralateral cortex N = 8 per group. (B) Neurological deficits serially evaluated after stroke in animals treated with saline IP followed by IV infusion of MNCs or L-NAME IP followed by IV infusion of MNCs. At 28 days, animals treated with saline followed by MNCs showed a significant reduction in deficits compared with animals treated with L-NAME+MNCs or compared with animals treated with saline only (§p<0.05). The x-axis represents the time in days after stroke. Baseline refers to the time point before stroke. N = 8 per group.</p

Illustration of a pulmonary artery of an animal pre-treated with L-NAME or Saline before IV MNC administration.

<p>Arrows point toward Q tracker labeled MNCs.</p