Focal Malonate Injection Into the Internal Capsule of Rats as a Model of Lacunar Stroke

Abstract

Background: Stroke is the first cause of disability in adults in western countries. Infarct of the internal capsule (IC) may be related to motor impairment and poor prognosis in stroke patients. Functional deficits due to medium-sized infarcts are difficult to predict, except if the specific site of the lesion is taken into account. None of the few pre-clinical models recapitulating this type of stroke has shown clear, reproducible, and long-lasting sensorimotor deficits. Here, we developed a rat model of lacunar infarction within the IC, key structure of the sensorimotor pathways, by precise injection of malonate.Methods: The mitochondrial toxin malonate was injected during stereotactic surgery into the IC of rat brains. Rats were divided in three groups: two groups received malonate solution at 1.5M (n = 12) or at 3M (n = 10) and a sham group (n = 5) received PBS. Three key motor functions usually evaluated following cerebral lesion in the clinic strength, target reaching, and fine dexterity were assessed in rats by a forelimb grip strength test, a skilled reaching task (staircase) for reaching and dexterity, and single pellet retrieval task. Sensorimotor functions were evaluated by a neurological scale. Live brain imaging, using magnetic resonance (MRI), and post-mortem immunohistochemistry in brain slices were performed to characterize the lesion site after malonate injection.Results: Intracerebral injection of malonate produced a 100% success rate in inducing a lesion in the IC. All rats receiving the toxin, regardless the dose injected, had similar deficits in strength and dexterity of the contralateral forepaw, and showed significant neurological impairment. Additionally, only partial recovery was observed with respect to strength, while no recovery was observed for dexterity and neurological deficit. MRI and immunostaining show volume size and precise location of the lesion in the IC, destruction of axonal structures and Wallerian degeneration of fibers in the area above the injection site.Conclusions: This pre-clinical model of lacunar stroke induces a lesion in the IC with measurable and reproducible sensorimotor deficits, and limited recovery with stabilization of performance 2 weeks post-injury. Future therapies in stroke may be successfully tested in this model.

A Reproducible New Model of Focal Ischemic Injury in the Marmoset Monkey: MRI and Behavioural Follow-Up

“…In line with our experience in rats [17], [22], the malonate model was highly reproducible and survivable. However, we report here the death of five marmosets due to respiratory failure during surgery (n=3) and extensive oedema (n=2).…”

“…Cell death occurs through necrosis and apoptosis due to the synergistic effects of energy failure and subsequent excitotoxicity leading to brain damage similar to that observed after an ischemic insult in humans [16]- [22]. This approach has been previously validated in rats by our team, and has proven to be a survivable procedure that leads to long-term functional deficits whether the lesion involves the cortex and striatum or the internal capsule [17], [22], thus suitable for testing of stem cellbased therapies [18], [21]. However, a major limitation of the rodent model in the context of post-stroke therapy testing is the total absence of measurable dexterity recovery [17], [22].…”

“…This approach has been previously validated in rats by our team, and has proven to be a survivable procedure that leads to long-term functional deficits whether the lesion involves the cortex and striatum or the internal capsule [17], [22], thus suitable for testing of stem cellbased therapies [18], [21]. However, a major limitation of the rodent model in the context of post-stroke therapy testing is the total absence of measurable dexterity recovery [17], [22]. In addition, the anatomy of brain structures involved in motor control, particularly the basal ganglia and subcortical motor loops, are dissimilar to the human brain.…”

Neurofunctional and neuroimaging readouts for designing a preclinical stem-cell therapy trial in experimental stroke

“…The test must be quantitative, allow repetition and it must reveal long term and stable deficits with enough sensitivity to show an improvement in treated vs non-treated subjects (26,27). The staircase test, a skilled reaching task that assesses forelimb function, fulfills these criteria for the long-term evaluation of motor recovery in stroke-induced rats (28,29). However, the optimal frequency of testing, the timescale and side bias modifications in time still remained to be determined (30)(31)(32)(33).…”

Adamts18 modulates the development of the aortic arch and common carotid artery

“…The polyethylene thread was removed 90 min after placement. Motor function and reflexes of the ischemic mice were evaluated using a neurological severity scoring system (NSS), as described previously (Cirillo et al, 2018). All treated mice were sacrificed at 48 h, and all brain tissues were separated and freezed.…”