Nerve growth factor (NGF)-conjugated electrospun nanostructures with topographical cues for neuronal differentiation of mesenchymal stem cells

Abstract

Mesenchymal stem cells (MSCs) were cultivated on the surface of nerve growth factor (NGF)-conjugated aligned nanofibrous meshes for neuronal differentiation. Amine-terminated poly(ethylene glycol) was conjugated to poly(ε-caprolactone) to prepare amine-functionalized block copolymers. The synthesized polymer was electrospun in a rotating drum to prepare aligned nanofibrous meshes. A nerve growth factor was chemically immobilized on the surface-exposed amine groups of the electrospun nanofibrous meshes in the aqueous phase. In vitro release profiles of the nerve growth factor were investigated for NGF-immobilized nanofibrous meshes. The conjugated nerve growth factor was not released for 7 days, while the growth factor physically adsorbed on the nanofibrous meshes showed an initial burst release. MSCs were cultivated on the NGF-conjugated nanofibrous meshes for 5 days, and total RNA was extracted from the cultivated cells. mRNA was extracted from cells for measuring expression levels of neuronal differentiation markers, including nestin, tubulin βIII and map2, in the cultivated stem cells. The conjugation of NGF significantly increased the expression levels of the marker proteins for neuron cells while physically adsorbed NGFs on nanofibrous meshes showed low expression of these marker genes. Furthermore, alignments of nanofibrous meshes clearly increased the expression levels of neuronal makers while the nanofibrous mesh without the topographical cue did not affect neuronal differentiation of the cultivated stem cells. Confocal microscopy revealed that the stem cells on the NGF-conjugated aligned nanofibrous meshes showed intense staining with antibodies against neuronal makers as well as elongated morphology compared to other groups. Thus, the NGF-conjugated nanofibrous meshes with topographical cues significantly increased the neuronal differentiation of mesenchymal stem cells in comparison to NGF-adsorbed nanofibrous meshes.