No abstract

Interactions between cultured nerve cells and surfaces are of importance for the implantation of biocompatible electrode materials such as glassy carbon (GC). Since implants serve as recording sensors in prosthetic neuroscience, we investigated whether coating electrodes with certain laminin derivatives containing the peptide sequences SIKVAV, CDPGYIGSR, PDSGR, YFQRYLI, and RNIAEIIKDA influences neuronal adhesion and neurite outgrowth in vitro. The coating of GC was performed by electrochemical polymerization and, for comparison, by adsorption or covalent coupling. Electrochemical polymerization is suitable for the coupling of peptides to GC, as shown by amino acid analysis and sequencing. Embryonic chicken retinal ganglion cells and brain cells (days E7 or E17) were used for both attachment and growth studies. Surfaces made by electrochemical polymerization of peptides were more efficient than those made by adsorption or covalent coupling of peptides. Synthetic cyclic peptide derivatives of CDPGYIGSR and 18-mer SIKVAV were found to be more efficient than the linear peptides. Competitive effects that resulted in a decreased cell attachment could be found upon application of soluble peptides. Nevertheless, irrespective of the method of coating, peptides were less efficient compared with the whole laminin molecule, as expected from its multiple adhesion sites. When small GC pins were implanted into the brain of E17 chicken after coating with the 18-mer SIKVAV peptide, nerve cell attachment was observed in vivo. The results suggest that chronically implantable materials may exert a higher neurocompatibility when coated with synthetic peptides.

The investigation of interactions between growing neurites and target cells during the development of the sensible corneal innervation is of crucial importance for understanding certain corneal diseases which are related to abnormal patterns of innervation. The purpose of the present work was to establish a culture system of cornea and trigeminal neurons and to examine interactions between these tissues. The responses of neurons derived from explanted embryonic chick trigeminal ganglia to co-explanted slices prepared from embryonic cornea were monitored over several days in culture. The growth of trigeminal fibers, but not of neurites derived from control tissues such as trigeminal mesencephalic nucleus or ciliary ganglion, was preferentially directed towards the co-cultured corneal slices. The ingrowth of trigeminal axons into the cornea was followed by formation of elaborate axonal terminal branches. Individual dissociated trigeminal neurons of pseudo-unipolar or bipolar classes developed their typical morphologies in culture. In co-cultures with corneal slices, they reacted to the corneal co-explant by frequently retracting some branches and forming or elongating other ones, which were predominantly directed towards the target tissue. In addition, the presence of a co-explanted trigeminal ganglion increased the rate of growth in the dissociated trigeminal neurons. The effect was not additive when cornea was present. Antibodies against nerve growth factor (NGF) and the low-affinity p75-NGF receptor (LANGFR) revealed that trigeminal ganglion cells support neuritic growth by secreting NGF, whereas corneal cells secrete additional factor(s) which act via the LANGFR.