Relevance Of Sham Control Group In Preclinical Animal Studies Of Cerebral Ischemia

BackgroundIn experimental animal studies, control sham groups are essential to reduce the influence of the surgical intervention on the analysis. The intraluminal filament procedure is one of the most common models of middle cerebral artery occlusion (MCAO) used in the study of cerebral ischemia. However, in these studies, the sham group has not usually been included in the experimental design because of the assumption that the surgical procedure required to access the middle cerebral artery does not affect brain tissue, or that the results obtained from this group are not relevant. ObjectivesIn this study, we aimed to evaluate the relevance of the sham group by analyzing and comparing the brain protein profile of a sham and an ischemic group subjected to the surgical intraluminal filament occlusion of the middle cerebral artery. Material and MethodsThree randomized experimental groups were tested: control group (healthy animals), sham group, and ischemic group. Twenty-four hours after the interventional procedure, the brain tissue was evaluated by magnetic resonance imaging (MRI). After animal perfusion, the brain is removed for proteomic analysis by liquid chromatography-mass spectrometry (LC-MS/MS) using both a qualitative analysis by data-dependent acquisition (DDA) mode and a quantitative analysis, using a sequential window acquisition of all theoretical mass spectra (SWATH-MS) method on a hybrid quadrupole time-of-flight mass spectrometer. ResultsMRI results showed that only animals subjected to cerebral ischemia had ischemic injury. In the sham group 137 dysregulated proteins were detected compared to the 65 in the ischemic group. Moreover, a comparative study of both protein profiles showed the existence of a pool of 17 that appeared dysregulated in both sham and ischemic animals. These results indicate that the surgical procedure required for intraluminal occlusion of the MCA induce changes on brain protein expression that are not associated with the ischemic lesion. ConclusionThis study highlights the importance of including a sham group in the experimental model design to guarantee that the therapeutic target under study is not affected by the surgical intervention.