Insulin-like growth factor-I receptors in normal appearing white matter and chronic plaques in multiple sclerosis

Preclinical studies suggest that insulin-like growth factor-I (IGF-I) plays an important role in oligodendrocyte survival and myelination. We used human recombinant [125I]IGF-I to study IGF-I receptors in post-mortem brain tissue from patients with multiple sclerosis (MS). In normal appearing white matter, we found that IGF-I receptor densities and binding characteristics were not different between MS patients and controls. In chronic plaques, histologically characterized by astrogliosis, we found densities of IGF-I receptors which were in the same range as those measured in the normal appearing white matter. In vitro studies have shown that IGF-I also acts as a mitogenic factor for astrocytes. Since MS lesions are rapidly invaded by reactive astrocytes, IGF-I may not only protect oligodendrocytes and stimulate remyelination but also enhance the astrogliosis that limits repair.