Molecular Mechanisms of Axonal Growth and Neuronal Differentiation on Surface with Adhesion Energy Nanogradients

Neuronal repair is promoted after a nerve injury by chemical and physical stimuli from their environment. Among them, local adhesion energy gradients generated on surfaces trigger cone formation and neurite outgrowth without any nerve growth factor (NGF) addition. In this study, the molecu- lar mechanisms leading to neuronal differentiation after stimulation via energy gradients are inves- tigated. For this purpose, PC12 cells are cultured on n-[3-(trimethoxysilyl)propyl] ethylendiamine (EDA) and n-hexyl trimethoxysilane (HTMS), two functionalized surfaces possessing local energy gradients but chemically different. These surfaces similarly trigger neurite and growth cone forma- tion after 3 days in culture. The gene expression analysis of a microarray reveals the activation of the PI3/Akt signaling pathway from these surfaces in the same way than NGF does after binding on its TrkA receptor. The biological downstream effectors of this signaling pathway are also upreg- ulated, thereby promoting cell survival, growth cone formation and neurite outgrowth. EDA and HTMS surfaces act as an ongoing stimulus of the TrkA receptor as the addition of 100 nM K252a, its specific inhibitor, leads to the inhibition of neurite growth. Taken together, these results show that functionalized surface with energy surface gradients could be useful to promote nerve repair after an injury. For each surface, i.e EDA, HTMS, PLL and PLL + activation via NGF, three samples were analyzed.