Exact location of sensorimotor cortex injury after photochemical modulation; evidence of stroke based on stereological and morphometric studies in mice

The integrity of the structural cerebral cortex is disrupted after stroke either at the macroscopic or microscopic levels. Therefore, many attempts have been gathered to circumvent stroke-associated problems in the brain tissue. The current study was aimed to design an animal model of photochemical stroke using rose bengal (RB) plus laser irradiation (L) after 10, 15, and 20 min (´) and evaluate its effect on the cerebral tissue using unbiased stereological quantitative methods and morphometric histological analysis. Photochemical stroke was induced by intraperitoneal injection of RB dye and further activation through the exposure of the right sensorimotor cortex with the green laser radiation (100 mW; 532 nm). Mice were randomly allocated into 4 groups (each in 15) as follows: control (10 μg/gbw RB), RB + 10'L, RB + 15'L, and RB + 20'L. Target irradiation site was adjusted to 2 mm lateral to the bregma. Vernier caliper morphometric evaluation, cresyl violet staining, and unbiased stereological assays including Cavalier's principle and point counting techniques were used to monitor the pathological changes and lesion volume on days 1, 3, and 7 after the ischemia induction. Our data showed that the mean diameter of the lesion site and lesion infarct volume in the group RB + 20'L) was significantly increased relative to the other groups (P < 0.05). Notably, the lesion volume and diameter in the group RB + 15'L was larger compared with the group RB + 10'L and control mice (P < 0.05). Data showed an increased acute inflammatory response such as hyperemia and edema 3 days after ischemic induction while the intensity of acute changes and lesion volume were reduced and replaced with necrotic and chronic pathological changes including astrogliosis on day 7. It is concluded that the laser irradiation of RB-injected mice at a distinct time period could induce the magnificent degenerative effects on the cerebral cortex which is similar to the stroke condition.

Loss of selective wrist muscle activation in post-stroke patients

Purpose: Loss of selective muscle activation after stroke contributes to impaired arm function, is difficult to quantify and is not systematically assessed yet. The aim of this study was to describe and validate a technique for quantification of selective muscle activation of wrist flexor and extensor muscles in a cohort of post-stroke patients. Patterns of selective muscle activation were compared to healthy volunteers and test-retest reliability was assessed.Materials and methods: Activation Ratios describe selective activation of a muscle during its expected optimal activation as agonist and antagonist. Activation Ratios were calculated from electromyography signals during an isometric maximal torque task in 31 post-stroke patients and 14 healthy volunteers. Participants with insufficient voluntary muscle activation (maximal electromyography signal <3SD higher than baseline) were excluded.Results: Activation Ratios at the wrist were reliably quantified (Intraclass correlation coefficients 0.77-0.78). Activation Ratios were significantly lower in post-stroke patients compared to healthy participants (p < 0.05).Conclusion: Activation Ratios allow for muscle-specific quantification of selective muscle activation at the wrist in post-stroke patients. Loss of selective muscle activation may be a relevant determinant in assigning and evaluating therapy to improve functional outcome.Implications for RehabilitationLoss of selective muscle activation after stroke contributes to impaired arm function, is difficult to quantify and is not systematically assessed yet.The ability for selective muscle activation is a relevant determinant in assigning and evaluating therapy to improve functional outcome, e.g., botulinum toxin.Activation Ratios allow for reliable and muscle-specific quantification of selective muscle activation in post-stroke patients.

Ischemic stroke and repair: current trends in research and tissue engineering treatments

Stroke, the third leading cause of mortality, is usually associated with severe disabilities, high recurrence rate and other poor outcomes. Currently, there are no long-term effective treatments for stroke. Cell and cytokine therapies have been explored previously. However, the therapeutic outcomes are often limited by poor survival of transplanted cells, uncontrolled cell differentiation, ineffective engraftment with host tissues and non-sustained delivery of growth factors. A tissue-engineering approach provides an alternative for treating ischemic stroke. The key design considerations for the tissue engineering approach include: choice of scaffold materials, choice of cells and cytokines and delivery methods. Here, we review current cell and biomaterial based therapies available for ischemic stroke, with a special focus on tissue-engineering strategies for regeneration of stroke-affected neuronal tissue.

Measuring anisotropic muscle stiffness properties using elastography

Physiological and pathological changes to the anisotropic mechanical properties of skeletal muscle are still largely unknown, with only a few studies quantifying changes in vivo. This study used the noninvasive MR elastography (MRE) technique, in combination with diffusion tensor imaging (DTI), to measure shear modulus anisotropy in the human skeletal muscle in the lower leg. Shear modulus measurements parallel and perpendicular to the fibre direction were made in 10 healthy subjects in the medial gastrocnemius, soleus and tibialis anterior muscles. The results showed significant differences in the medial gastrocnemius (μ‖ = 0.86 ± 0.15 kPa; μ⊥ = 0.66 ± 0.19 kPa, P < 0.001), soleus (μ‖ = 0.83 ± 0.22 kPa; μ⊥ = 0.65 ± 0.13 kPa, P < 0.001) and the tibialis anterior (μ‖ = 0.78 ± 0.24 kPa; μ⊥ = 0.66 ± 0.16 kPa, P = 0.03) muscles, where the shear modulus measured in the direction parallel is greater than that measured in the direction perpendicular to the muscle fibres. No significant differences were measured across muscle groups. This study provides the first direct estimates of the anisotropic shear modulus in the triceps surae muscle group, and shows that the technique may be useful for the probing of mechanical anisotropy changes caused by disease, aging and injury.

Measuring changes in muscle stiffness after eccentric exercise using elastography

Muscle stiffness has been reported to increase following eccentric muscle exercise, but to date only indirect methods have been used to measure it. This study aimed to use Magnetic Resonance Elastography (MRE), a noninvasive imaging technique, to assess the time-course of passive elasticity changes in the medial gastrocnemius and soleus muscles before and after a bout of eccentric exercise. Shear storage modulus (G') and loss modulus (G'') measurements were made in eight healthy subjects for both muscles in vivo before, one hour after, 48 hours after and 1 week after eccentric exercise. The results show a 21% increase in medial gastrocnemius storage modulus following eccentric exercise with a peak occurring ~48 hours after exercise (before exercise 1.15 ± 0.23 kPa, 48 hours after 1.38 ± 0.27 kPa). No significant changes in soleus muscle storage modulus were measured for the exercise protocol used in this study, and no significant changes in loss modulus were observed. This study provides the first direct measurements in skeletal muscle before and after eccentric exercise damage and suggests that MRE can be used to detect the time course of changes to muscle properties.

Neuroregenerative strategies in the brain: emerging significance of bone morphogenetic protein 7 (BMP7)

Every year thousands of people suffer from brain injuries and stroke, and develop motor, sensory, and cognitive problems as a result of neuronal loss in the brain. Unfortunately, the damaged brain has a limited ability to enact repair and current modes of treatment are not sufficient to offset the damage. An extensive list of growth factors, neurotrophic factors, cytokines, and drugs has been explored as potential therapies. However, only a limited number of them may actually have the potential to effectively offset the brain injury or stroke-related problems. One of the treatments considered for future brain repair is bone morphogenetic protein 7 (BMP7), a factor currently used in patients to treat non-neurological diseases. The clinical application of BMP7 is based on its neuroprotective role in stroke animal models. This paper reviews the current approaches considered for brain repair and discusses the novel convergent strategies by which BMP7 potentially can induce neuroregeneration.