Control of neuronal morphology in vitro: Interplay between adhesive substrate forces and molecular instruction

Abstract

Among the factors which influence neuronal morphology, the degree of substrate adhesivity has been suggested to play an important role in the growth and guidance of neurites. The present study was undertaken to investigate apparently contradictory results relating substrate adhesivity to the extent of neurite outgrowth. By using substrates coated with different concentrations of polyornithine to vary adhesivity, we could show that intermediate levels of neuron-to-substrate adhesive strength favored neurite outgrowth more than substrates of high or low adhesivity. However, when neurons were plated on substrates derived from the extracellular matrix, the strength of neuron-to-substrate adhesion was important for the growth of dendrite-like minor neurites, but not for the extension of axon-like major neurites, which grew independently of adhesive forces. On substrates of the cell adhesion molecule L1, growth of both major and minor neurites was adhesion-independent. Finally, in the presence of tenascin added to the culture medium, neurite growth was inhibited irrespective of the adhesivity of the substrate and the presence of substrate-bound extracellular matrix molecules or L1. These observations suggest that intermediate forces of adhesivity favor neurite growth in general, but that purely adhesive forces can be dominated by specific molecular instructions which differentially affect growth of major and minor neurites in positive and negative ways.

Effect of collagen gel stiffness on neurite extension

“…For example, a biphasic response in chick DRG extension length was noted in response to increasing numbers of conjugated RGD peptides to fibrin gels, with highest growth rates at intermediate adhesivity [17]. A biphasic response with adhesion strength has also been noted in other systems, including cell migration [34,35] and neural morphology [36]. In addition to potential nonlinearities of binding interactions, the fit of F interaction was an order of magnitude higher than F structure , indicating that the interaction between the collagen gel and the extending neurite has more influence on outgrowth than the stiffness of the gel at the concentrations studied here.…”

?1?1-Integrin is an essential signal for neurite outgrowth induced by thrombospondin type 1 repeats of SCO-spondin

“…Also, directional axonal growth in the course of development depends on the strength of the cell-tosubstratum adhesivity (Lochter et al 1995), in addition to other environmental cues including cell-to-cell interaction and gradients of chemoattractant and chemorepellent molecules (see Cook et al 1998 for a review). Thus, several ECM molecules implicated in cell migration such as laminin, tenascin, vitronectin, and fibronectin were shown to act on directional axonal pathfinding, involving proteins of the thrombospondin superfamily.…”

The design of electrospun PLLA nanofiber scaffolds compatible with serum-free growth of primary motor and sensory neurons

“…Third, serum in the DRG explant media may have an effect on neurite orientation along the fibers. Serum contains both proteins that potentiate neurite outgrowth, including IGF-I [19], laminin [45] and fibronectin [21], as well as non-adhesive proteins, such as serum albumin, that likely reduce neurite-to-fiber adhesion [46]. Therefore, serum could decrease neurite alignment by simultaneously potentiating rapid neurite growth on less adhesive nanofibers, encouraging neurites to jump from one nanofiber to another.…”