The Tenascin-C-Derived Peptide VSWRAPTA Promotes Neuronal Branching Via Transcellular Activation of the Focal Adhesion Kinase (FAK) and the ERK1/2 Signaling Pathway In Vitro.

The central nervous system (CNS) of mammals has a limited regeneration capacity after traumatic events, which causes chronic functional disability. The development of biomaterials aims at providing support for the regeneration process. One strategy integrates peptides that mimic functional domains of extracellular matrix (ECM) or cell adhesion molecules with synthetic polymers designed to present growth-supporting cues to the neuronal microenvironment. Thus, small peptide sequences originating from molecules of the ECM may serve as promising bio-additives, acting as artificial matricryptins to gear cellular processes. The glycoprotein tenascin-C (Tnc) is a major constituent of the ECM of the developing brain and persists in the neurogenic regions of the adult CNS. It is a multimodular glycoprotein that comprises distinct domains with neurite growth promoting and axon growth repulsing properties. In the present study, the novel peptide motif VSWRAPTA that is encoded in the neurite growth promoting 6th fibronectin type III repeat close to the alternative splice site of Tnc was tested for its effects on neuron differentiation. When this newly synthesized biomimetic peptide was added to cultures of embryonic cortical neurons it significantly promoted the outgrowth of neurites. The neuron differentiation supporting effect was thereby associated with the trans-cellular activation of the focal adhesion kinase (FAK) and the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway. Cortical neurons supplemented with the Tnc peptide displayed a dose-dependent increase in neurite outgrowth that saturated at a peptide concentration of 50 µg/ml (56.4 mMol/l). The analysis of neuron morphology revealed that neurite branching rather than fiber length was stimulated by the Tnc peptide. Therefore, we predict that the analyzed peptide motif of the 6th constitutively expressed FNIII domain of the Tnc molecule might be a major contributor for neurite outgrowth and guiding events in the native CNS microenvironment. In conclusion, the Tnc-derived VSWRAPTA peptide may represent a promising tool to spike regeneration supportive microenvironments.

The Synergistic Effect of Cationic Moieties and GRGDSF-Peptides in Hydrogels on Neural Stem Cell Behavior.

This article reports the behavior of embryonic neural stem cells on a hydrogel that combines cationic, non-specific cell adhesion motifs with glycine-arginine-glycine-aspartic acid-serine-phenylalanine (GRGDSF)-peptides as specific cell adhesion moieties. Therefore, three hydrogels are prepared by free radical polymerization that contains either a GRGDSF-peptide residue (P1), amino ethylmethacrylate as a cationic residue (P2), or a combination of both motifs (P3). For each gel, cross linker concentrations of 8 mol% is used to have a comparable gel stiffness of 8-9 kPa. The cell experiments indicate a synergistic effect of the non-specific, cationic residues, and the specific GRGDSF-peptides on embryonic neural stem cell behavior that is especially pronounced in the cell adhesion experiments by more than doubling the number of cells after 72 h when comparing P3 with P2 and is less pronounced in the proliferation and differentiation experiments.