Neurite Growth and Polarization on Vitronectin Substrate after in Vitro Trauma is not Enhanced after IGF Treatment

Artificial spider silk supports and guides neurite extension in vitro

Surgical intervention with the use of autografts is considered the gold standard to treat peripheral nerve injuries. However, a biomaterial that supports and guides nerve growth would be an attractive alternative to overcome problems with limited availability, morbidity at the site of harvest, and nerve mismatches related to autografts. Native spider silk is a promising material for construction of nerve guidance conduit (NGC), as it enables regeneration of cm-long nerve injuries in sheep, but regulatory requirements for medical devices demand synthetic materials. Here, we use a recombinant spider silk protein (NT2RepCT) and a functionalized variant carrying a peptide derived from vitronectin (VN-NT2RepCT) as substrates for nerve growth support and neurite extension, using a dorsal root ganglion cell line, ND7/23. Two-dimensional coatings were benchmarked against poly-d-lysine and recombinant laminins. Both spider silk coatings performed as the control substrates with regards to proliferation, survival, and neurite growth. Furthermore, NT2RepCT and VN-NT2RepCT spun into continuous fibers in a biomimetic spinning set-up support cell survival, neurite growth, and guidance to an even larger extent than native spider silk. Thus, artificial spider silk is a promising biomaterial for development of NGCs.

Efficient differentiation and polarization of primary cultured neurons on poly(lactic acid) scaffolds with microgrooved structures

Synthetic biodegradable polymers including poly(lactic acid) (PLA) are attractive cell culture substrates because their surfaces can be micropatterned to support cell adhesion. The cell adhesion properties of a scaffold mainly depend on its surface chemical and structural features; however, it remains unclear how these characteristics affect the growth and differentiation of cultured cells or their gene expression. In this study, we fabricated two differently structured PLA nanosheets: flat and microgrooved. We assessed the growth and differentiation of mouse primary cultured cortical neurons on these two types of nanosheets after pre-coating with poly-D-lysine and vitronectin. Interestingly, prominent neurite bundles were formed along the grooves on the microgrooved nanosheets, whereas thin and randomly extended neurites were only observed on the flat nanosheets. Comparative RNA sequencing analyses revealed that the expression of genes related to postsynaptic density, dendritic shafts, and asymmetric synapses was significantly and consistently up-regulated in cells cultured on the microgrooved nanosheets when compared with those cultured on the flat nanosheets. These results indicate that microgrooved PLA nanosheets can provide a powerful means of establishing a culture system for the efficient and reproducible differentiation of neurons, which will facilitate future investigations of the molecular mechanisms underlying the pathogenesis of neurological disorders.