Schwann cells as a source of insulin‐like growth factor‐1 for extraocular muscles

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Abstract
Precise force regulation is fundamentally important for extraocular muscle (EOM) function. Insulin‐like growth factor‐1 (IGF‐1) plays a major role in EOM force regulation, but the source of endogenous IGF‐1 is unclear. Multiple IGF‐1 sources may supply EOMs, including: the EOM itself; the systemic circulation; innervating motoneurons; and Schwann cells within nerves. IGF‐1 expression was measured in chicken during oculomotor system maturation by using real‐time polymerase chain reaction (PCR). Accumulation of radiolabeled IGF‐1 in EOMs was compared after either injection into the vascular circulation or into the trochlear nerve. Schwann cells were the most prominent IGF‐1 source. A microtubule‐dependent mechanism exists to anterogradely transport IGF‐1 to EOMs. EOMs were significantly more efficient in extracting IGF‐1 from the nerve than from the systemic circulation. Therefore, Schwann cells are the most prominent and potentially the most important source of IGF‐1 for EOMs. These findings may contribute to a better understanding of EOM force regulation and its failure in strabismus. Muscle Nerve, 2010
Funding Information
  • National Institutes of Health (EY12841)
  • IDeA Network of Biomedical Research Excellence
  • NCRR (P20RR016464)
  • Graduate Student Association at the University of Nevada, Reno

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