Peripheral nerves have the capacity for regeneration, but the rate of regeneration is so slow that many nerve injuries lead to incomplete recovery and permanent disability for patients. Macrophages play a critical role in the peripheral nerve response to injury, both for Wallerian degeneration and for contributing to regeneration, and their function has recently been shown to be dependent on intracellular metabolism. To date, the impact of their intracellular metabolism on peripheral nerve regeneration has not been studied. Examining conditional transgenic mice with selective ablation of solute carrier family 16, member 1 (Slc16a1, which encodes the monocarboxylate transporter 1, MCT1) in macrophages, we found that MCT1 contributes to macrophage metabolism, phenotype, and function, specifically in regard to phagocytosis and supporting peripheral nerve regeneration. Adoptive cell transfer of wild-type macrophages ameliorated the impaired nerve regeneration in macrophage-selective MCT1 null mice. We also developed a mouse model that overexpresses MCT1 in macrophages and found that peripheral nerves in these mice regenerated more rapidly than control mice. Our study provides further evidence that MCT1 has an important biological role in macrophages and that manipulations of macrophage metabolism can enhance recovery from peripheral nerve injuries, for which there are currently no approved medical therapies.
Mithilesh Kumar Jha, Joseph V. Passero, Atul Rawat, Xanthe Heifetz Ament, Fang Yang, Svetlana Vidensky, Samuel L. Collins, Maureen R. Horton, Ahmet Hoke, Guy A. Rutter, Alban Latremoliere, Jeffrey D. Rothstein, Brett M. Morrison