1. ^*Research Center for Developmental Medicine and Biology, University of Auckland, Auckland, New Zealand
2. ^†Department of Molecular Medicine, Faculty of Medicine and Health Sciences, University of Auckland, Auckland, New Zealand
3. ^‡Department of Anatomy and Radiology, Faculty of Medicine and Health Sciences, University of Auckland, Auckland, New Zealand

Correspondence: Dr. Jian Guan, Research Center for Developmental Medicine and Biology, Department of Pediatrics, Faculty of Medicine and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.

Received 11 October 2000; Revised 20 December 2000; Accepted 20 December 2000.

Abstract

Insulin-like growth factor-1 (IGF-1) is known to be important for oligodendrocyte survival and myelination. In the current study, the authors examined the hypothesis that exogenous IGF-1 could reduce postischemic white matter injury. Bilateral brain injury was induced in near-term fetal sheep by 30 minutes of reversible carotid artery occlusion. Ninety minutes after ischemia, either vehicle (n = 8) or a single dose of 3 g IGF-1 (n = 9) was infused intracerebroventricularly over 1 hour. White matter changes were assessed after 4 days recovery in the parasagittal intragyral white matter and underlying corona radiata. Proteolipid protein (PLP) mRNA staining was used to identify bioactive oligodendrocytes. Glial fibrillary acidic protein (GFAP) and isolectin B-4 immunoreactivity were used to label astrocytes and microglia, respectively. Myelin basic protein (MBP) density and the area of the intragyral white matter tracts were determined by image analysis. Insulin-like growth factor-1 treatment was associated with significantly reduced loss of oligodendrocytes in the intragyral white matter (P < 0.05), with improved MBP density (P < 0.05), reduced tissue swelling, and increased numbers of GFAP and isolectin B-4 positive cells compared with vehicle treatment. After ischemia there was a close association of PLP mRNA labeled cells with reactive astrocytes and macrophages/microglia. In conclusion, IGF-1 can prevent delayed, postischemic oligodendrocyte cell loss and associated demyelination.