Insulin-like growth factor-I given subcutaneously reduces clinical deficits, decreases lesion severity and upregulates synthesis of myelin proteins in experimental autoimmune encephalomyelitis.

To extend our evaluation of insulin-like growth factor-1 (IGF-1) treatment for human demyelinating diseases, we compared effects of s.c. and i.v. IGF-1 in an in vivo model with lesions resembling those seen in multiple sclerosis. Experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats with an emulsion containing guinea pig spinal cord and treatment with placebo or with s.c. or i.v. IGF-1 was started when definite clinical weakness was present. IGF-I given subcutaneously significantly reduced clinical deficits and lesion severity. The clinical improvement, as measured by clinical deficit scores, stride lengths and exercise wheel rotations, was evident in 48 hrs and was comparable to that produced by the same IGF-I dose administered intravenously. Subcutaneously administered IGF-I also increased relative mRNA levels of myelin basic protein (MBP), proteolipid (PLP) and 2',3' cyclic nucleotide 3'-phosphodiesterase (CNP), thereby promoting myelin regeneration. We conclude that s.c. IGF-I produces dramatic improvement in acute, demyelinating EAE. Our results also suggest that this growth factor may be useful in treating multiple sclerosis patients with active demyelination.