Targeted Gene Therapy for Ischemic Stroke - Gene Delivery and Therapy for Neurological Disorders - page 191

Chapter 8

Targeted Gene Therapy for Ischemic Stroke

Fanxia Shen and Hua Su

Abstract

Exogenous delivery of angiogenic and neuroprotective genes has been shown to enhance innate
compensatory responses after ischemic injury. However, there are certain barriers in translating gene-
based therapy to the clinical setting. For example, systemic delivery of genes into the brain is prevented by
the blood-brain barrier (BBB); intraventricular delivery results in nonspecifi c distribution and gene expres-
sion; and stereotactic injection of vectors into the ischemic penumbra requires an invasive procedure that
can cause additional damage. This chapter describes an adeno-associated viral (AAV) vector with two pri-
mary attributes that have the potential to overcome these problems. First, the vector contains hypoxia
response elements (HREs) that restrict therapeutic gene expression to ischemic tissue. Second, AAV sero-
type 9 (AAV9) effectively penetrates the BBB, enabling intravenous administration. This chapter also
illustrates the methods of constructing AAV vectors with hypoxia-inducible gene expression, generating
the mouse permanent distal middle cerebral artery occlusion (pMCAO) model, standard assays to analyze
brain injury and gene transfer, and effective behavior tests for the pMCAO model.

Key words Adeno-associated viral vector serotype 9, Hypoxia response, Gene transfer, Ischemia,
Intravenous delivery, Permanent distal middle cerebral artery occlusion, Target gene expression in
ischemic brain

1 Introduction

Stroke is a leading cause of serious long-term disability in the
United States. The delivery of angiogenic and neuroprotective
genes or microRNA into the brain has been shown to attenuate
ischemic injury and promote functional recovery [ 1 - 8 ]. However,
effective and safe delivery of the therapeutic genes into the ischemic
brain is a challenge. Here, we will describe a noninvasive method of
gene delivery to achieve targeted gene expression in ischemic brain
tissues. The method employs adeno-associated virus serotype 9
(AAV9) to facilitate the penetration of the blood-brain barrier
(BBB) and hypoxia response element (HRE) to render the gene
expression only in ischemic tissues.
Since uncontrolled expression of transgenes, such as angiogenic
genes, can cause unwanted side effects [ 9 - 11 ], it is important to