Distinguishing Distinct Neural Systems for Proximal vs Distal Upper Extremity Motor Control After Acute Stroke.

BACKGROUND AND OBJECTIVES: The classic and singular pattern of distal greater than proximal upper extremity motor deficits after acute stroke does not account for the distinct structural and functional organization of circuits for proximal and distal motor control in the healthy CNS. We hypothesized that separate proximal and distal upper extremity clinical syndromes after acute stroke could be distinguished and that patterns of neuroanatomical injury leading to these 2 syndromes would reflect their distinct organization in the intact CNS. METHODS: Proximal and distal components of motor impairment (upper extremity Fugl-Meyer score) and strength (Shoulder Abduction Finger Extension score) were assessed in consecutively recruited patients within 7 days of acute stroke. Partial correlation analysis was used to assess the relationship between proximal and distal motor scores. Functional outcomes including the Box and Blocks Test (BBT), Barthel Index (BI), and modified Rankin scale (mRS) were examined in relation to proximal vs distal motor patterns of deficit. Voxel-based lesion-symptom mapping was used to identify regions of injury associated with proximal vs distal upper extremity motor deficits. RESULTS: A total of 141 consecutive patients (49% female) were assessed 4.0 ± 1.6 (mean ± SD) days after stroke onset. Separate proximal and distal upper extremity motor components were distinguishable after acute stroke (p = 0.002). A pattern of proximal more than distal injury (i.e., relatively preserved distal motor control) was not rare, observed in 23% of acute stroke patients. Patients with relatively preserved distal motor control, even after controlling for total extent of deficit, had better outcomes in the first week and at 90 days poststroke (BBT, ρ = 0.51, p < 0.001; BI, ρ = 0.41, p < 0.001; mRS, ρ = 0.38, p < 0.001). Deficits in proximal motor control were associated with widespread injury to subcortical white and gray matter, while deficits in distal motor control were associated with injury restricted to the posterior aspect of the precentral gyrus, consistent with the organization of proximal vs distal neural circuits in the healthy CNS. DISCUSSION: These results highlight that proximal and distal upper extremity motor systems can be selectively injured by acute stroke, with dissociable deficits and functional consequences. Our findings emphasize how disruption of distinct motor systems can contribute to separable components of poststroke upper extremity hemiparesis.

Domain-Specific Outcome Measures in Clinical Trials of Therapies Promoting Stroke Recovery: A Suggested Blueprint.

Different deficits recover to different degrees and with different time courses after stroke, indicating that plasticity differs across the brain's neural systems after stroke. To capture these differences, domain-specific outcome measures have received increased attention. Such measures have potential advantages over global outcome scales, which combine recovery across many domains into a single score and so blur the ability to capture individual measures of stroke recovery. Use of a global end point to rate disability can overlook substantial recovery in specific domains, such as motor or language, and may not differentiate between good and poor recovery for specific neurological domains. In light of these points, a blueprint is proposed for using domain-specific outcome measures in stroke recovery trials. Key steps include selecting a domain in the context of preclinical data, picking a domain-specific clinical trial end point, anchoring inclusion criteria to this end point, scoring this end point both before and after treatment, and then pursuing regulatory approval on the basis of the domain-specific results. This blueprint is intended to foster clinical trials that, by using domain-specific end points, are able to demonstrate favorable results in clinical trials of therapies that promote stroke recovery.

Association of Modified Rankin Scale With Recovery Phenotypes in Patients With Upper Extremity Weakness After Stroke.

BACKGROUND AND OBJECTIVES: Precise measurement of outcomes is essential for stroke trials and clinical care. Prior research has highlighted conceptual differences between global outcome measures such as the modified Rankin Scale (mRS) and domain-specific measures (e.g., motor, sensory, language or cognitive function). This study related motor phenotypes to the mRS, specifically aiming to determine whether mRS levels distinguish motor impairment and function phenotypes, and to compare mRS outcomes to meaningful changes in impairment and function from acute to subacute recovery after stroke. METHODS: Patients with upper extremity weakness after ischemic stroke were assessed with a battery of impairment and functional measures within the first week and at 90 days after stroke. Impairment and functional outcomes were examined in relation to 90-day mRS scores. Clinically meaningful changes in motor impairment, activities of daily living, and mobility were examined in relation to 90-day mRS score. RESULTS: In this cohort of 73 patients with stroke, impairment and functional outcomes were associated with 90-day mRS scores but showed substantial variability within individual mRS levels: within mRS level 2, upper extremity impairment ranged from near hemiplegia (with an upper extremity Fugl-Meyer score 8) to no deficits (upper extremity Fugl-Meyer score 66). Overall, there were few differences in impairment and functional outcomes between adjacent mRS levels. While some outcome measures were significantly different between mRS levels 3 and 4 (Nine-Hole Peg, Leg Motor, gait velocity, Timed Up and Go, NIH Stroke Scale, and Barthel Index), none of the outcome measures differed between mRS levels 1 and 2. Fugl-Meyer and grip strength were not different between any adjacent mRS levels. A substantial number of patients experienced clinically meaningful changes in impairment and function in the first 90 days after stroke but did not achieve good mRS outcome (mRS score ≤ 2). DISCUSSION: The mRS broadly relates to domain-specific outcomes after stroke, confirming its established value in stroke trials, but it does not precisely distinguish differences in impairment and function, nor does it sufficiently capture meaningful clinical changes across impairment, activities of daily living status, and mobility. These findings underscore the potential utility of incorporating detailed phenotypic measures along with the mRS in future stroke trials.

Cognitive Demands Influence Upper Extremity Motor Performance During Recovery From Acute Stroke.

OBJECTIVE: To test the hypothesis that cognitive demands influence motor performance during recovery from acute stroke, we tested patients with acute stroke on 2 motor tasks with different cognitive demands and related task performance to cognitive impairment and neuroanatomic injury. METHODS: We assessed the contralesional and ipsilesional upper extremities of a cohort of 50 patients with weakness after unilateral acute ischemic stroke at 3 time points with 2 tasks: the Box & Blocks Test, a task with greater cognitive demand, and Grip Strength, a simple and ballistic motor task. We compared performance on the 2 tasks, related motor performance to cognitive dysfunction, and used voxel-based lesion symptom mapping to determine neuroanatomic sites associated with motor performance. RESULTS: Consistent across contralesional and ipsilesional upper extremities and most pronounced immediately after stroke, Box & Blocks scores were significantly more impaired than Grip Strength scores. The presence of cognitive dysfunction significantly explained up to 33% of variance in Box & Blocks performance but was not associated with Grip Strength performance. While Grip Strength performance was associated with injury largely restricted to sensorimotor regions, Box & Blocks performance was associated with broad injury outside sensorimotor structures, particularly the dorsal anterior insula, a region known to be important for complex cognitive function. CONCLUSIONS: Together, these results suggest that cognitive demands influence upper extremity motor performance during recovery from acute stroke. Our findings emphasize the integrated nature of motor and cognitive systems and suggest that it is critical to consider cognitive demands during motor testing and neurorehabilitation after stroke.

Extracellular vesicles derived from bone marrow mesenchymal stem cells enhance myelin maintenance after cortical injury in aged rhesus monkeys.

Cortical injury, such as stroke, causes neurotoxic cascades that lead to rapid death and/or damage to neurons and glia. Axonal and myelin damage in particular, are critical factors that lead to neuronal dysfunction and impair recovery of function after injury. These factors can be exacerbated in the aged brain where white matter damage is prevalent. Therapies that can ameliorate myelin damage and promote repair by targeting oligodendroglia, the cells that produce and maintain myelin, may facilitate recovery after injury, especially in the aged brain where these processes are already compromised. We previously reported that a novel therapeutic, Mesenchymal Stem Cell derived extracellular vesicles (MSC-EVs), administered intravenously at both 24 h and 14 days after cortical injury, reduced microgliosis (Go et al. 2019), reduced neuronal pathology (Medalla et al. 2020), and improved motor recovery (Moore et al. 2019) in aged female rhesus monkeys. Here, we evaluated the effect of MSC-EV treatment on changes in oligodendrocyte maturation and associated myelin markers in the sublesional white matter using immunohistochemistry, confocal microscopy, stereology, qRT-PCR, and ELISA. Compared to vehicle control monkeys, EV-treated monkeys showed a reduction in the density of damaged oligodendrocytes. Further, EV-treatment was associated with enhanced myelin maintenance, evidenced by upregulation of myelin-related genes and increases in actively myelinating oligodendrocytes in sublesional white matter. These changes in myelination correlate with the rate of motor recovery, suggesting that improved myelin maintenance facilitates this recovery. Overall, our results suggest that EVs act on oligodendrocytes to support myelination and improves functional recovery after injury in the aged brain. SIGNIFICANCE: We previously reported that EVs facilitate recovery of function after cortical injury in the aged monkey brain, while also reducing neuronal pathology (Medalla et al. 2020) and microgliosis (Go et al. 2019). However, the effect of injury and EVs on oligodendrocytes and myelination has not been characterized in the primate brain (Dewar et al. 1999; Sozmen et al. 2012; Zhang et al. 2013). In the present study, we assessed changes in myelination after cortical injury in aged monkeys. Our results show, for the first time, that MSC-EVs support recovery of function after cortical injury by enhancing myelin maintenance in the aged primate brain.

A double-blind, randomized, controlled study of two dose strengths of dalfampridine extended release on walking deficits in ischemic stroke.

BACKGROUND: Stroke-induced ischemia affects both cortex and underlying white matter. Dalfampridine extended release tablets (D-ER) enhance action potential conduction in demyelinated axons, which may positively affect post-stroke recovery. OBJECTIVE: Based on promising preliminary data, we compared efficacy of D-ER administered at 7.5 mg or 10 mg with placebo on post-stroke ambulation. Primary study outcome (response) was a ≥20% increase on the 2-minute walk test (2 MinWT) at 12 weeks after first drug administration. METHODS: This was a multicenter, randomized, placebo-controlled, 3-arm, parallel-group, safety and efficacy trial. After obtaining baseline measures of 2 MinWT, Walk-12, and Timed Up and Go, subjects entered a 2-week, single-blind placebo run-in period and were randomized 1:1:1 to receive 7.5 mg D-ER, 10 mg D-ER, or placebo, dosed twice-daily for 12 weeks. Follow-up evaluations occurred at weeks 14 and 16 when subjects were off study drug. RESULTS: The study was terminated early with 377 of planned 540 patients enrolled, due to no treatment effect. At week 12, mean increase in distances walked in 2 minutes were similar among the 3 study groups (14.9±40.0 feet; 19.4±39.6 feet; and 20.4±38.3 feet for placebo, 7.5 mg D-ER, and 10 mg D-ER, respectively). The proportion of subjects who showed ≥20% improvement on 2 MinWT at week 12 was 13.5%, 14.0%, and 19.0%, for placebo, 7.5 mg D-ER, and 10 mg D-ER, respectively; these were nonsignificant changes from baseline for all groups. CONCLUSIONS: D-ER at either a 7.5-mg or 10-mg dose did not significantly increase performance on the 2 MinWT in stroke survivors with gait impairment, although this study was terminated early before full enrollment. (Clinical Trial # NCT02271217).

Extracellular vesicles from mesenchymal stem cells reduce microglial-mediated neuroinflammation after cortical injury in aged Rhesus monkeys.

Cortical injury, such as injuries after stroke or age-related ischemic events, triggers a cascade of degeneration accompanied by inflammatory responses that mediate neurological deficits. Therapeutics that modulate such neuroinflammatory responses in the aging brain have the potential to reduce neurological dysfunction and promote recovery. Extracellular vesicles (EVs) from mesenchymal stem cells (MSCs) are lipid-bound, nanoscale vesicles that can modulate inflammation and enhance recovery in rodent stroke models. We recently assessed the efficacy of intravenous infusions of MSC-EVs (24-h and 14-days post-injury) as a treatment in aged rhesus monkeys (Macaca mulatta) with cortical injury that induced impairment of fine motor function of the hand. Aged monkeys treated with EVs after injury recovered motor function more rapidly and more fully than aged monkeys given a vehicle control. Here, we describe EV-mediated inflammatory changes using histological assays to quantify differences in markers of neuroinflammation in brain tissue between EV and vehicle-treated aged monkeys. The activation status of microglia, the innate macrophages of the brain, is critical to cell fate after injury. Our findings demonstrate that EV treatment after injury is associated with greater densities of ramified, homeostatic microglia, along with reduced pro-inflammatory microglial markers. These findings are consistent with a phenotypic switch of inflammatory hypertrophic microglia towards anti-inflammatory, homeostatic functions, which was correlated with enhanced functional recovery. Overall, our data suggest that EVs reduce neuroinflammation and shift microglia towards restorative functions. These findings demonstrate the therapeutic potential of MSC-derived EVs for reducing neuroinflammation after cortical injury in the aged brain.

Corticospinal Tract Injury Estimated From Acute Stroke Imaging Predicts Upper Extremity Motor Recovery After Stroke.

Background and Purpose- Injury to the corticospinal tract (CST) has been shown to have a major effect on upper extremity motor recovery after stroke. This study aimed to examine how well CST injury, measured from neuroimaging acquired during the acute stroke workup, predicts upper extremity motor recovery. Methods- Patients with upper extremity weakness after ischemic stroke were assessed using the upper extremity Fugl-Meyer during the acute stroke hospitalization and again at 3-month follow-up. CST injury was quantified and compared, using 4 different methods, from images obtained as part of the stroke standard-of-care workup. Logistic and linear regression were performed using CST injury to predict ΔFugl-Meyer. Injury to primary motor and premotor cortices were included as potential modifiers of the effect of CST injury on recovery. Results- N=48 patients were enrolled 4.2±2.7 days poststroke and completed 3-month follow-up (median 90-day modified Rankin Scale score, 3; interquartile range, 1.5). CST injury distinguished patients who reached their recovery potential (as predicted from initial impairment) from those who did not, with area under the curve values ranging from 0.70 to 0.8. In addition, CST injury explained ≈20% of the variance in the magnitude of upper extremity recovery, even after controlling for the severity of initial impairment. Results were consistent when comparing 4 different methods of measuring CST injury. Extent of injury to primary motor and premotor cortices did not significantly influence the predictive value that CST injury had for recovery. Conclusions- Structural injury to the CST, as estimated from standard-of-care imaging available during the acute stroke hospitalization, is a robust way to distinguish patients who achieve their predicted recovery potential and explains a significant amount of the variance in poststroke upper extremity motor recovery.

Cell based therapy reduces secondary damage and increases extent of microglial activation following cortical injury.

Cortical injury elicits long-term cytotoxic and cytoprotective mechanisms within the brain and the balance of these pathways can determine the functional outcome for the individual. Cytotoxicity is exacerbated by production of reactive oxygen species, accumulation of iron, and peroxidation of cell membranes and myelin. There are currently no neurorestorative treatments to aid in balancing the cytotoxic and cytoprotective mechanisms following cortical injury. Cell based therapies are an emerging treatment that may function in immunomodulation, reduction of secondary damage, and reorganization of surviving structures. We previously evaluated human umbilical tissue-derived cells (hUTC) in our non-human primate model of cortical injury restricted to the hand area of primary motor cortex. Systemic hUTC treatment resulted in significantly greater recovery of fine motor function compared to vehicle controls. Here we investigate the hypothesis that hUTC treatment reduces oxidative damage and iron accumulation and increases the extent of the microglial response to cortical injury. To test this, brain sections from these monkeys were processed using immunohistochemistry to quantify oxidative damage (4-HNE) and activated microglia (LN3), and Prussian Blue to quantify iron. hUTC treated subjects exhibited significantly reduced oxidative damage in the sublesional white matter and iron accumulation in the perilesional area as well as a significant increase in the extent of activated microglia along white matter pathways. Increased perilesional iron accumulation was associated with greater perilesional oxidative damage and larger reconstructed lesion volume. These findings support the hypothesis that systemic hUTC administered 24 h after cortical damage decreases the cytotoxic response while increasing the extent of microglial activation.

Cell based therapy enhances activation of ventral premotor cortex to improve recovery following primary motor cortex injury.

Stroke results in enduring damage to the brain which is accompanied by innate neurorestorative processes, such as reorganization of surviving circuits. Nevertheless, patients are often left with permanent residual impairments. Cell based therapy is an emerging therapeutic that may function to enhance the innate neurorestorative capacity of the brain. We previously evaluated human umbilical tissue-derived cells (hUTC) in our non-human primate model of cortical injury limited to the hand area of primary motor cortex. Injection of hUTC 24 h after injury resulted in significantly enhanced recovery of fine motor function compared to vehicle treated controls (Moore et al., 2013). These monkeys also received an injection of Bromodeoxyuridine (BrdU) 8 days after cortical injury to label cells undergoing replication. This was followed by 12 weeks of behavioral testing, which culminated 3 h prior to perfusion in a final behavioral testing session using only the impaired hand. In this session, the neuronal activity initiating hand movements leads to the upregulation of the immediate early gene c-Fos in activated cells. Following perfusion-fixation of the brain, sections were processed using immunohistochemistry to label c-Fos activated cells, pre-synaptic vesicle protein synaptophysin, and BrdU labeled neuroprogenitor cells to investigate the hypothesis that hUTC treatment enhanced behavioral recovery by facilitating reorganization of surviving cortical tissues. Quantitative analysis revealed that c-Fos activated cells were significantly increased in the ipsi- and contra-lesional ventral premotor but not the dorsal premotor cortices in the hUTC treated monkeys compared to placebo controls. Furthermore, the increase in c-Fos activated cells in the ipsi- and contra-lesional ventral premotor cortex correlated with a decrease in recovery time and improved grasp topography. Interestingly, there was no difference between treatment groups in the number of synaptophysin positive puncta in either ipsi- or contra-lesional ventral or dorsal premotor cortices. Nor was there a significant difference in the density of BrdU labeled cells in the subgranular zone of the hippocampus or the subventricular zone of the lateral ventricle. These findings support the hypothesis that hUTC treatment enhances the capacity of the brain to reorganize after cortical injury and that bilateral plasticity in ventral premotor cortex is a critical locus for this recovery of function. This reorganization may be accomplished through enhanced activation of pre-existing circuits within ventral premotor, but it could also reflect ventral premotor projections to the brainstem or spinal cord.

Inosine enhances recovery of grasp following cortical injury to the primary motor cortex of the rhesus monkey.

BACKGROUND: Inosine, a naturally occurring purine nucleoside, has been shown to stimulate axonal growth in cell culture and promote corticospinal tract axons to sprout collateral branches after stroke, spinal cord injury and TBI in rodent models. OBJECTIVE: To explore the effects of inosine on the recovery of motor function following cortical injury in the rhesus monkey. METHODS: After being trained on a test of fine motor function of the hand, monkeys received a lesion limited to the area of the hand representation in primary motor cortex. Beginning 24 hours after this injury and continuing daily thereafter, monkeys received orally administered inosine (500 mg) or placebo. Retesting of motor function began on the 14th day after injury and continued for 12 weeks. RESULTS: During the first 14 days after surgery, there was evidence of significant recovery within the inosine-treated group on measures of fine motor function of the hand, measures of hand strength and digit flexion. While there was no effect of treatment on the time to retrieve a reward, the treated monkeys returned to asymptotic levels of grasp performance significantly faster than the untreated monkeys. Additionally, the treated monkeys evidenced a greater degree of recovery in terms of maturity of grasp pattern. CONCLUSION: These findings demonstrate that inosine can enhance recovery of function following cortical injury in monkeys.

An optimized dosing regimen of cimaglermin (neuregulin 1ß3, glial growth factor 2) enhances molecular markers of neuroplasticity and functional recovery after permanent ischemic stroke in rats.

Cimaglermin (neuregulin 1ß3, glial growth factor 2) is a neuregulin growth factor family member in clinical development for chronic heart failure. Previously, in a permanent middle cerebral artery occlusion (pMCAO) rat stroke model, systemic cimaglermin treatment initiated up to 7 days after ischemia onset promoted recovery without reduced lesion volume. Presented here to extend the evidence are two studies that use a rat stroke model to evaluate the effects of cimaglermin dose level and dose frequency initiated 24 hr after pMCAO. Forelimb- and hindlimb-placing scores (proprioceptive behavioral tests), body-swing symmetry, and infarct volume were compared between treatment groups (n = 12/group). Possible mechanisms underlying cimaglermin-mediated neurologic recovery were examined through axonal growth and synapse formation histological markers. Cimaglermin was evaluated over a wider dose range (0.02, 0.1, or 1.0 mg/kg) than doses previously shown to be effective but used the same dosing regimen (2 weeks of daily intravenous administration, then 1 week without treatment). The dose-frequency study used the dose-ranging study's most effective dose (1.0 mg/kg) to compare daily, once per week, and twice per week dosing for 3 weeks (then 1 week without treatment). Dose- and frequency-dependent functional improvements were observed with cimaglermin without reduced lesion volume. Cimaglermin treatment significantly increased growth-associated protein 43 expression in both hemispheres (particularly somatosensory and motor cortices) and also increased synaptophysin expression. These data indicate that cimaglermin enhances recovery after stroke. Immunohistochemical changes were consistent with axonal sprouting and synapse formation but not acute neuroprotection. Cimaglermin represents a potential clinical development candidate for ischemic stroke treatment.

Use of Anisotropy, 3D Segmented Atlas, and Computational Analysis to Identify Gray Matter Subcortical Lesions Common to Concussive Injury from Different Sites on the Cortex.

Traumatic brain injury (TBI) can occur anywhere along the cortical mantel. While the cortical contusions may be random and disparate in their locations, the clinical outcomes are often similar and difficult to explain. Thus a question that arises is, do concussions at different sites on the cortex affect similar subcortical brain regions? To address this question we used a fluid percussion model to concuss the right caudal or rostral cortices in rats. Five days later, diffusion tensor MRI data were acquired for indices of anisotropy (IA) for use in a novel method of analysis to detect changes in gray matter microarchitecture. IA values from over 20,000 voxels were registered into a 3D segmented, annotated rat atlas covering 150 brain areas. Comparisons between left and right hemispheres revealed a small population of subcortical sites with altered IA values. Rostral and caudal concussions were of striking similarity in the impacted subcortical locations, particularly the central nucleus of the amygdala, laterodorsal thalamus, and hippocampal complex. Subsequent immunohistochemical analysis of these sites showed significant neuroinflammation. This study presents three significant findings that advance our understanding and evaluation of TBI: 1) the introduction of a new method to identify highly localized disturbances in discrete gray matter, subcortical brain nuclei without postmortem histology, 2) the use of this method to demonstrate that separate injuries to the rostral and caudal cortex produce the same subcortical, disturbances, and 3) the central nucleus of the amygdala, critical in the regulation of emotion, is vulnerable to concussion.

Recovery of fine motor performance after ischemic damage to motor cortex is facilitated by cell therapy in the rhesus monkey.

We investigated the efficacy on recovery of function following controlled cortical ischemia in the monkey of the investigational cell drug product, CNTO 0007. This drug contains a cellular component, human umbilical tissue-derived cells, in a proprietary thaw and inject formulation. Results demonstrate significantly better recovery of motor function in the treatment group with no difference between groups in the volume or surface area of ischemic damage, suggesting that the cells stimulated plasticity.

Dalfampridine improves sensorimotor function in rats with chronic deficits after middle cerebral artery occlusion.

BACKGROUND AND PURPOSE: Stroke survivors often have permanent deficits that are only partially addressed by physical therapy. This study evaluated the effects of dalfampridine, a potassium channel blocker, on persistent sensorimotor deficits in rats with treatment initiated 4 or 8 weeks after stroke. METHODS: Rats underwent permanent middle cerebral artery occlusion. Sensorimotor function was measured using limb-placing and body-swing symmetry tests, which normally show a partial recovery from initial deficits that plateaus ≈4 weeks after permanent middle cerebral artery occlusion. Dalfampridine was administered starting at 4 or 8 weeks after permanent middle cerebral artery occlusion in 2 blinded, vehicle-controlled studies. Plasma samples were collected and brain tissue was processed for histologic assessment. RESULTS: Dalfampridine treatment (0.5-2.0 mg/kg) improved forelimb- and hindlimb-placing responses and body-swing symmetry in a reversible and dose-dependent manner. Plasma dalfampridine concentrations correlated with dose. Brain infarct volumes showed no differences between treatment groups. CONCLUSIONS: Dalfampridine improves sensorimotor function in the rat permanent middle cerebral artery occlusion model. Dalfampridine extended-release tablets (prolonged release fampridine outside the United States) are used to improve walking in patients with multiple sclerosis, and these preclinical data provide a strong rationale for examining the potential of dalfampridine to treat chronic stable deficits in stroke patients. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT01605825.

A non-brain penetrant PDE5A inhibitor improves functional recovery after stroke in rats.

PURPOSE: Phosphodiesterase 5A (PDE5A) inhibitors improve functional recovery in experimental models of stroke in rats when treatment is delayed and without effect on infarct volume. PDE5A is expressed to only a very limited extent in forebrain tissues, raising the possibility that the locus of effect for the inhibitors is outside the brain. To start to address this question, we determined whether PDE5A inhibitors must have the ability to cross the blood brain barrier to improve recovery. METHOD: After permanent middle cerebral artery occlusion in rats, PF-5 and UK-489,791, PDE5A inhibitors that do or do not pass the blood brain barrier, were administered starting 24 h after occlusion and continued for 1 week. Motor function was assessed at intervals to 28 days using body swing and limb placement measures. RESULTS: Both PF-5 and UK-489,791 produced improvement in motor scores over 28 days that were significantly greater than in vehicle treated animals. There was no difference in efficacy between the two PDE5A inhibitors. CONCLUSIONS: Brain penetrability appears not to be critical to the ability of a PDE5A inhibitor to improve functional recovery after experimental stroke in rats. This finding is discussed with regard to the cellular target(s) for PDE5A inhibitors mediating this effect.

Recovery from ischemia in the middle-aged brain: a nonhuman primate model.

Studies of recovery from stroke mainly utilize rodent models and focus primarily on young subjects despite the increased prevalence of stroke with age and the fact that recovery of function is more limited in the aged brain. In the present study, a nonhuman primate model of cortical ischemia was developed to allow the comparison of impairments in young and middle-aged monkeys. Animals were pretrained on a fine motor task of the hand and digits and then underwent a surgical procedure to map and lesion the hand-digit representation in the dominant motor cortex. Animals were retested until performance returned to preoperative levels. To assess the recovery of grasp patterns, performance was videotaped and rated using a scale adapted from human occupational therapy. Results demonstrated that the impaired hand recovers to baseline in young animals in 65-80 days and in middle-aged animals in 130-150 days. However, analysis of grasp patterns revealed that neither group recover preoperative finger thumb grasp patterns, rather they develop compensatory movements.

Glial growth factor 2 promotes functional recovery with treatment initiated up to 7 days after permanent focal ischemic stroke.

Neuregulins are a family of growth factors essential for normal cardiac and nervous system development. The EGF-like domain of neuregulins contains the active site which binds and activates signaling cascades through ErbB receptors. A neuregulin-1 gene EGF-like fragment demonstrated neuroprotection in the transient middle cerebral artery occlusion (MCAO) stroke model and drastically reduced infarct volume (Xu et al., 2004). Here we use a permanent MCAO rat model to initially compare two products of the neuregulin-1 gene and also assess levels of recovery with acute versus delayed time to treatment. In the initial study full-length glial growth factor 2 (GGF2) and an EGF-like domain fragment were compared with acute intravenous delivery. In a second study GGF2 only was delivered starting at 24h, 3 days or 7 days after permanent ischemia was induced. In both studies daily intravenous administration continued for 10 days. Recovery of neurological function was assessed using limb placing and body swing tests. GGF2 had similar functional improvements compared to the EGF-like domain fragment at equimolar doses, and a higher dose of GGF2 demonstrated more robust functional improvements compared to a lower dose. GGF2 improved sensorimotor recovery with all treatment paradigms, even enhancing recovery of function with a delay of 7 days to treatment. Histological assessments did not show any associated reduction in infarct volume at either 48 h or 21 days post-ischemic event. Neurorestorative effects of this kind are of great potential clinical importance, given the difficulty of delivering neuroprotective therapies within a short time after an ischemic event in human patients. If confirmed by additional work including additional data on mechanism(s) of improved outcome with verification in other stroke models, one can make a compelling case to bring GGF2 to clinical trials as a neurorestorative approach to improving outcome following stroke injury.