Characterization of a cerebral palsy‐like model in rats: Analysis of gait pattern and of brain and spinal cord motor areas

Perinatal anoxia associated with sensorimotor restriction causes muscle atrophy and microglial activation: Meta-analysis of preclinical studies with implications for cerebral palsy

Several experimental cerebral palsy models have been created to investigate cellular and molecular mechanisms involved in this condition and develop new therapeutic strategies. The model that has come closest to a motor phenotype similar to cerebral palsy is the one that combines perinatal anoxia with hindlimb sensorimotor restriction, as it induces visible changes at the peripheral and central levels. This systematic review with meta-analysis presents the impact of the cerebral palsy model that associates perinatal anoxia with hindlimb sensorimotor restriction on the nervous, muscular and skeletal systems. Studies with perinatal anoxia associated with sensorimotor restriction and which evaluated outcomes related to skeletal, muscle, or nervous tissue were recovered from the databases: Embase, PubMed, Scopus, and Web of Science. The methodological and quantitative assessment was performed after eligibility screening (PROSPERO - ID: CRD42023477770). After screening of 4,641 articles, 21 studies with a moderate quality of evidence were chosen to be included in this review and 11 articles were included in the meta-analysis. The results of the meta-analysis reported a significant reduction in the media area of the soleus muscle fibers, increased number of glia cells and glia/neuron index in the somatosensory cortex, increased microglial activation in the hippocampus, and no changes in the corpus callosum thickness or neuron cells. The combination of perinatal anoxia and sensorimotor restriction entails muscle deficits and excessive activation of glial cells in brain areas. These results contribute to a methodological refinement of cerebral palsy models and favor new studies proposed for methodological elucidation in animal experimentation.

Evaluation of developmental milestones and of brain measurements in rats exposed to the pesticide pyriproxyfen in prenatal period

Pyriproxyfen is a pesticide used in Brazil to control the Aedes aegypti mosquito, vector of arboviruses like Zika and dengue. However, this pesticide is structurally similar to retinoic acid, a metabolite of vitamin A that regulates neuronal differentiation and hindbrain development during the embryonic period. Due to the similarity between pyriproxyfen and retinoic acid, studies indicate that this pesticide may have cross-reactivity with retinoid receptors. Thus, pregnant exposure to pyriproxyfen could interfere in the nervous system development of the fetal. In this context, the present study evaluated whether prenatal exposure to pyriproxyfen affects neonatal development and brain structure in rats. Wistar rat pups were divided in three experimental groups: (1) negative control (CT-)-offspring of rats that drink potable water during pregnancy; (2) pyriproxyfen (PIR)-offspring of rats exposed to Sumilarv® prenatally, a pesticide that has pyriproxyfen as active ingredient; and (3) positive control (CT+)-offspring of rats exposed to an excess of vitamin A prenatally. Only vitamin A treated-pregnant showed lower weight gain, but gestation length was similar among pregnant that received potable water, water containing vitamin A and water containing Sumilarv. In relation to the offspring, PIR group exhibits a delayed front-limb suspension response but performed early the negative geotaxis reflex. On the other hand, CT+ group exhibited lower body weight in the 1st postnatal day, delayed audio startle response, but performed early the eyelids opening and hindlimb placing response. A reduction in the maximum brain width was observed both in PIR and CT+ groups, but a reduction in the number of neurons in the M1 cortex was showed only in CT+ group. The number of glial cells in this brain area was similar between the three experimental groups studied. Although prenatal exposure to pyriproxyfen did not alter neonatal milestones in the same way as vitamin A in excess, both substances caused a reduction in the maximum width of the brain, suggesting that this pesticide can produce neurotoxic effects during the embryonic period.

Acrobatic training prevents motor deficits and neuronal loss in male and female rats following chronic cerebral hypoperfusion

BACKGROUND

Chronic cerebral hypoperfusion in vascular dementia leads to memory and motor deficits; Physical exercise improves these aspects and promotes neuroprotection. Sexual dimorphism may significantly influence both ischemic and exercise outcomes.

AIMS

The aim of this study was to investigate the effects of 2VO (Two-Vessel occlusion) and the acrobatic training on motor function, functional performance, and tissue loss in male and female rats.

METHODS

Male and female rats were randomly divided into 4 groups: sham acrobatic, sham sedentary, 2VO acrobatic and 2VO sedentary. After 45 days of 2VO surgery, the animals received 4 weeks of acrobatic training. At the end, open field, beam balance and horizontal ladder tests were performed. Brain samples were taken for histological and morphological evaluation.

RESULTS

Spontaneous motor activity in the open field was not affected by 2VO, on the other hand, an impairment in forelimb placement was observed after 2VO and acrobatic training prevented errors and improved hindlimb placement. Neuronal loss was found in the motor cortex and striatum after 2VO, especially in females, which was prevented by acrobatic training.

CONCLUSION

Mild motor damage was found in animals after 2VO when refined movement was evaluated, probably associated to neuronal death in the motor cortex and striatum. The acrobatic exercise showed a neuroprotective effect, promoting neuronal survival and attenuating the motor deficit.

Neuroinflammation, blood-brain barrier dysfunction, hippocampal atrophy and delayed neurodevelopment: Contributions for a rat model of congenital Zika syndrome

The congenital Zika syndrome (CZS) has been characterized as a set of several brain changes, such as reduced brain volume and subcortical calcifications, in addition to cognitive deficits. Microcephaly is one of the possible complications found in newborns exposed to Zika virus (ZIKV) during pregnancy, although it is an impacting clinical sign. This study aimed to investigate the consequences of a model of congenital ZIKV infection by evaluating the histopathology, blood-brain barrier, and neuroinflammation in pup rats 24 h after birth, and neurodevelopment of the offspring. Pregnant rats were inoculated subcutaneously with ZIKV-BR at the dose 1 × 107 plaque-forming unit (PFU mL-1) of ZIKV isolated in Brazil (ZIKV-BR) on gestational day 18 (G18). A set of pups, 24 h after birth, was euthanized. The brain was collected and later evaluated for the histopathology of brain structures through histological analysis. Additionally, analyses of the blood-brain barrier were conducted using western blotting, and neuroinflammation was assessed using ELISA. Another set of animals was evaluated on postnatal days 3, 6, 9, and 12 for neurodevelopment by observing the developmental milestones. Our results revealed hippocampal atrophy in ZIKV animals, in addition to changes in the blood-brain barrier structure and pro-inflammatory cytokines expression increase. Regarding neurodevelopment, a delay in important reflexes during the neonatal period in ZIKV animals was observed. These findings advance the understanding of the pathophysiology of CZS and contribute to enhancing the rat model of CZS.

Resistance exercise was safe for the pregnancy and offspring's development and partially protected rats against early life stress-induced effects

Promising evidence points to gestational physical exercise as the key to preventing various disorders that affect the offspring neurodevelopment, but there are no studies showing the impact of resistance exercise on offspring health. Thus, the aim of this study was to investigate whether resistance exercise during pregnancy is able to prevent or to alleviate the possible deleterious effects on offspring, caused by early life-stress (ELS). Pregnant rats performed resistance exercise throughout the gestational period:they climbed a sloping ladder with a weight attached to their tail, 3 times a week. Male and female pups, on the day of birth (P0), were divided into 4 experimental groups: 1) rats of sedentary mothers (SED group); 2) rats of exercised mothers (EXE group); 3) rats of sedentary mothers and submitted to maternal separation (ELS group) and 4) rats of exercised mothers and submitted to MS (EXE + ELS group). From P1 to P10, pups from groups 3 and 4 were separated from their mothers for 3 h/day. Maternal behavior was assessed. From P30, behavioral tests were performed and on P38 the animals were euthanized and prefrontal cortex samples were collected. Oxidative stress and tissue damage analysis by Nissl staining were performed. Our results demonstrate that male rats are more susceptible to ELS than females, showing impulsive and hyperactive behavior similar to that seen in children with ADHD. This behavior was attenuated by the gestational resistance exercise. Our results demonstrate, for the first time, that resistance exercise performed during pregnancy seems to be safe for the pregnancy and offspring's neurodevelopment and are effective in preventing ELS-induced damage only in male rats. Interestingly, resistance exercise during pregnancy improved maternal care and it is reasonable to propose that this finding may be related to the protective role on the animals neurodevelopment, observed in our study.

Vitamin D supplementation combined with aerobic physical exercise restores the cell density in hypothalamic nuclei of rats exposed to monosodium glutamate

BACKGROUND & AIMS

In view of the increase in the prevalence of obesity and metabolic syndrome in childhood and adolescence, this study proposed the early and combined use of treatments to restore brain areas related to satiety. The vitamin D supplementation, aerobic exercise and the combination of these interventions on the structure of arcuate (ARC) and ventromedial (VMH) nuclei of hypothalamus were investigated in monosodium glutamate (MSG)-treated rats.

METHODS

Wistar rats were separated into five groups: Control group (CT); Obese group injected with MSG (OB); Obese group supplemented with vitamin D (OBvd); Obese group submitted to forced swimming training (OBexe) and Obese group treated with vitamin D supplementation and forced swimming training (OBvd + exe).

RESULTS

In the OB group, the visceral fat weight was significantly higher, there was a reduction in the number of glial cells in the ARC nucleus and also in the number of neurons in the ARC and VMH nuclei. Aerobic exercise was able to reduce the visceral fat weight in the OBexe group. The combination of treatments used in the OBvd + exe group reversed the loss of neurons and glial cells produced by MSG in the ARC nucleus. All treated groups exhibited a higher number of neurons in VMH nucleus, but an increase in the glial cells were observed only in the OBexe and OBvd + exe groups.

CONCLUSIONS

The effectiveness of obesity treatment can be favored through the early and combined use of vitamin D supplementation and aerobic exercise, since these therapies are able to restore brain nuclei involved in the control of food intake.

Gait analysis with muscular fibrosis and treatment with Alpinia zerumbet essential oil in immobilized rats

The analysis of gait in animals is important for understanding movement disorders in various human pathologies, especially those that develop muscle fibrosis. In the search for treatment alternatives for this problem, essential oils have been studied. Among them, research involving the essential oil of Alpinia zerumbet (EOAz) has been shown to promote relaxation and improve muscle function. Therefore, this study aimed to evaluate the effect of EOAz on gait with muscle fibrosis in immobilized rats. 30 rats (Wistar) were divided into five groups of six animals each: control group (without fibrosis and without treatment), immobilization group (with fibrosis and without treatment), and EOAz treatment groups (with fibrosis and with treatment). The animals were immobilized for 15 days with an ankle plantar flexion orthosis. After this period, they were treated with the oil cutaneously for 30 days. The analysis of behavioral tests before treatment indicated a significant increase in the means of the immobilized groups about to with concerning the control. We conclude that EOAz was effective in improving gait after inducing muscle fibrosis in immobilized rats. Studies are needed to assess the oil's effectiveness in the treatment of muscle fibrosis in human pathologies.

Locomotion is impacted differently according to the perinatal brain injury model: Meta-analysis of preclinical studies with implications for cerebral palsy

BACKGROUND

Different approaches to reproduce cerebral palsy (CP) in animals, contribute to the knowledge of the pathophysiological mechanism of this disease and provide a basis for the development of intervention strategies. Locomotion and coordination are the main cause of disability in CP, however, few studies highlight the quantitative differences of CP models, on locomotion parameters, considering the methodologies to cause brain lesions in the perinatal period.

METHODS

Studies with cerebral palsy animal models that assess locomotion parameters were systematically retrieved from Medline/PubMed, SCOPUS, LILACS, and Web of Science. Methodological evaluation of included studies and quantitative assessment of locomotion parameters were performed after eligibility screening.

RESULTS

CP models were induced by hypoxia-ischemia (HI), Prenatal ischemia (PI), lipopolysaccharide inflammation (LPS), intraventricular haemorrhage (IVH), anoxia (A), sensorimotor restriction (SR), and a combination of different models. Overall, 63 studies included in qualitative synthesis showed a moderate quality of evidence. 16 studies were included in the quantitative meta-analysis. Significant reduction was observed in models that combined LPS with HI related to distance traveled (SMD -7.24 95 % CI [-8.98, -5.51], Z = 1.18, p < 0.00001) and LPS with HI or anoxia with sensory-motor restriction (SMD -6.01, 95 % CI [-7.67, -4.35], Z = 7.11), or IVH (SMD -4.91, 95 % CI [-5.84, -3.98], Z = 10.31, p < 0.00001) related to motor coordination.

CONCLUSION

The combination of different approaches to reproduce CP in animals causes greater deficits in locomotion and motor coordination from the early stages of life to adulthood. These findings contribute to methodological refinement, reduction, and replacement in animal experimentation, favoring translational purposes.

Effects of Scalp Acupuncture on Functional Deficits Induced by Early Sensorimotor Restriction

The aim of this study was to investigate the effects of scalp acupuncture and electrostimulation, combined or not, in a disuse model consisted of early sensorimotor restriction in rats. Male Wistar pups received sensorimotor restriction from the second postnatal day (P2) until P28. Animals were divided into five different groups (n = 6): control (CT), sensorimotor restricted (SR), acupuncture (AC), electrostimulation (EL), and electroacupuncture (AC+EL). Experimental animals received sham, acupuncture, or electrical stimulation, combined or not, of two scalp regions for 7 days (P29-P35). Before treatment period (P29) and after treatment (P36), animals were evaluated with the narrow suspended bar, horizontal ladder, and stride length tests. SR animals had worse performance in the narrow suspended and horizontal ladder tasks compared with SR animals at P29 (p ≤ 0.005). Significant improvements were observed in both tasks in AC, EL, and EL+AC groups comparing P29 and P36 (p < 0.001). Also, at P35, all treated animals performed significantly better motor tasks compared with SR group (p < 0.05). There was no difference between treated groups. Finally, acupuncture and electrical stimulation, combined or not, have beneficial effect on motor performance following early developmental disuse.

Neonatal hypoxia-ischemia caused mild motor dysfunction, recovered by acrobatic training, without affecting morphological structures involved in motor control in rats

The aim of this study was to evaluated motor function and morphological aspects of the components involved in motor control (sensorimotor cortex, spinal cord, sciatic nerve, neuromuscular junctions and skeletal muscle) in male Wistar rats exposed to a model of neonatal hypoxic-ischemic encephalopathy (HIE) and the possible influence of different physical exercise protocols - treadmill and acrobatic. Male Wistar rats at the 7^th post-natal day (PND) were submitted to the HIE model and from the 22^nd until 60^th PND the exercise protocols (treadmill or acrobatic training) were running. After the training, the animals were evaluated in Open Field, Ladder Rung Walking and Rotarod tasks and after samples of the motor control components were collected. Our results evidenced that the acrobatic training reversed the hyperactivity and anxiety, caused locomotion improvement and decreased brain atrophy in HIE animals. We did not find morphological differences on sensorimotor cortex, spinal cord, sciatic nerve, neuromuscular junctions and skeletal muscle in the animals submitted to HIE model. These intriguing data support the statement of the Rice-Vannucci model does not seem to reproduce, in structures involved in control function, the damage found in humans that suffer HIE. Regarding the protocols of exercise, we proposed that the acrobatic exercise could be a good therapeutic option especially in children affected by neonatal HIE and can be responsible for good results in cognitive and motor aspects.

Synaptophysin and caspase-3 expression on lumbar segments of spinal cord after sensorimotor restriction during early postnatal period and treadmill training

The purpose of the current study was to investigate whether locomotor stimulation training could have beneficial effects on spinal cord plasticity consequent to sensorimotor restriction (SR). Male Wistar rats were exposed to SR from postnatal day 2 (P2) to P28. Control and experimental rats underwent locomotor stimulation training in a treadmill from P31 to P52. The intensity of the synaptophysin and caspase-3 immunoreaction was determined on ventral horn of spinal cord. The synaptophysin immunoreactivity was lower in the ventral horn of sensorimotor restricted rats compared to controls animals and was accompanied by an increased caspase-3 immunoreactivity. Those alterations were reversed at the end of the training period. Our results suggest that immobility affects the normal developmental process that spinal cord undergoes in early postnatal life influencing both pro-apoptotic and synapse markers. Also, we demonstrated that this phenomenon was reversed by 3 weeks of treadmill training.