Publication Date

2009

Document Type

Thesis

Committee Members

Yanfang Chen (Advisor), Khalid Elased (Committee Member), Mariana Morris (Committee Member)

Degree Name

Master of Science (MS)

Abstract

Type 2 diabetes mellitus is a major risk factor for ischemic stroke. Also diabetes is associated with poor outcome after stroke. Underlying mechanisms are however not fully understood. Alteration in the expression of the SDF-1a/CXCR4 axis, which is important for ischemic tissue repair, can be a probable cause. In this study, we have determined the expression of SDF-1a/CXCR4 in the brains of type II diabetic mice at basal and in response to ischemic stroke and have investigated a method for overexpression of SDF-1a in the brains of the diabetic mice. Adult male C57BLKS/J mice (db/db) of age 8 weeks were used as the murine model for type II diabetes and their age matched lean littermates served as controls (db/+). Microvascular density was first determined in the cerebral cortex of db/db diabetic mice by immunohistochemical analysis. Focal cerebral ischemia was induced by middle cerebral artery occlusion surgery (MCAO) in type 2 diabetic db/db mice and their controls. 48 hours after surgery, volume of ischemic damage was determined by TTC staining. The expression of SDF-1a and CXCR4 in the ischemic and non ischemic sides of brains of both the groups were determined using western blot and real time RT PCR. The db/db diabetic mice were injected with the vector, adeno associated virus 9 (AAV-SDF-1a) in the brain striatum and the overexpression of SDF-1a was determined by immunohistochemical analysis. Double immunohistochemistry was used to determine the localization of SDF-1a in brain after injection of the vector. The microvascular density in the cerebral cortex was reduced in db/db mice as compared with db/+ mice (p<0.05). Volume of ischemic damage was significantly increased in db/db mice after focal cerebral ischemia (p< 0.01). The levels of SDF-1a expression in both ischemic and non ischemic side of brain were reduced in db/db mice as compared with those in db/+ mice at mRNA (p< 0.01) and protein level (p< 0.01). The amount of CXCR4 expression was significantly reduced only in the ischemic side of the brains of db/db mice at protein level (p=0.001) and at m-RNA level (p=0.001). But in the non ischemic side, the expression of CXCR4 did not show any significant difference between the two groups. Immunohistochemical analysis showed overexpression of SDF-1a in the striatum receiving the microinjection of AAV-SDF-1a and double immunohistochemistry showed SDF-1a to be localized in the glial cells of the cerebral striatum after microinjection. The results indicate that microvascular density is reduced and ischemia induced cerebral damage is enlarged in diabetes which may be linked to the impaired expression of hypoxia regulated SDF-1a/CXCR4 axis after ischemic stroke in diabetes and vector mediated over expression of SDF-1a in the brain can be a novel therapeutic technique for treating ischemic stroke in diabetics.

Page Count

75

Department or Program

Department of Pharmacology and Toxicology

Year Degree Awarded

2009

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