Induced Neural Stem Cell Grafts Exert Neuroprotection Through an Interaction Between Crry and Akt in A Mouse Model of Closed Head Injury

Background: Recently, growing evidence has indicated an important role of the complement system, a crucial component of immunity, in mediating neuroinflammation and promoting neuronal apoptosis following closed head injury (CHI). We previously reported that transplanted induced neural stem cells (iNSCs) pre-treated with CHI mouse serum could enhance complement receptor type 1-related protein y (Crry) expression and ameliorate complement-mediated damage in mouse CHI models. However, the mechanism underlying the elevated levels of Crry expression remains elusive. Methods: : CHI models were established using a standardized weight-drop device and CHI mouse serum was collected at 12 h post-trauma. Complement deposition assay, Akt inhibition assay, cell viability assay, functional assay, cell transplantation, morphological and molecular biological analyses were performed. Results: : In the present study, we observed dramatic increases in the levels of Crry expression and Akt activation in iNSCs receiving CHI mouse serum treatment. Remarkably, Akt inhibition led to the reduction of Crry expression in iNSCs. Intriguingly, the treatment of iNSC-derived neurons with recombinant complement receptor 2-conjugated Crry (CR2-Crry), which inhibits all complement pathways, substantially enhanced Crry expression and Akt activation in neurons after CHI mouse serum treatment. In subsequent in vitro experiments of pre-treatment of iNSCs with CR2-Crry, we observed significant increases in the levels of Crry expression and Akt activation in iNSCs, iNSC-derived astrocytes and neurons post-treatment with CHI mouse serum. Additionally, an in vivo study showed that intracerebral-transplanted iNSCs pre-treated with CR2-Crry markedly enhanced Crry expression in neurons and protected neurons from complement-dependent damage in the brains of CHI mice. Conclusions: : In summary, iNSCs receiving CR2-Crry pre-treatment increased the levels of Crry expression in iNSCs, iNSC-derived astrocytes and neurons and attenuated complement-mediated injury following CHI.