Color-Coded Microspheres and Histological Analysis for Cerebral Mapping: An Experimental Model

Abstract

Background: The integration of histology and microcirculation in real time through specific regions of the brain is a challenging concept that has not been reported before. This study describes for first time a brain-mapping model that superimposes regional microvascular blood flow (RMBF) analysis with immunohistochemistry analysis in an experimental ovine model. Methods: Five Merino sheep were instrumented, ventilated and cardiovascularly supported according to local guidelines. Two ultrasound catheter sheaths were inserted into the right internal jugular vein for the introduction of an intracardiac echocardiography probe and transeptal catheter, as previously described. For the analysis of RMBF, color-coded microspheres were injected into the left atrium while a reference blood sample was extracted from the femoral artery. After euthanasia and fixation with formalin, the brain was used as proof of principle and the endpoint for determination of microcirculation and histology analysis at different time points. An antero-posterior slicing strategy of the sheep brain differentiated even-numbered from odd-numbered slices. For the histology analysis, immunohistochemistry applied to odd-numbered slices used amyloid precursor protein (APP) antibodies and hematoxylin-eosin staining. Simultaneously, even-numbered slices were dedicated for cytometric quantification of RMBF. Results: Homogeneous allocation of microspheres to different regions of the brain over time with no statistical difference between slices and RMBF count was found. In addition, immunohistochemistry showed baseline staining, confirming a state of normal cerebral perfusion. Conclusions: This study has demonstrated the feasibility and reproducibility of a brain-mapping model that superimposes RMBF data and immunohistochemistry data over time, establishing a new experimental model. J Neurol Res. 2014;4(1):7-14 doi: http://dx.doi.org/ 10.14740 / jnr256w