Different strategies are being investigated for treatment of
spinal cord injuries, one of the most promising being application of
neurotrophic factors, which have been shown to prevent neuronal death and stimulate regeneration of injured axons. Ex vivo gene therapy has emerged as the leading delivery method at the site of the injury, and we have shown previously that encapsulating genetically engineered fibroblasts in an immunoprotective
alginate capsule can permit implantation of the factor-secreting cells without need for immunosuppression. This strategy could be greatly enhanced by providing the sprouting neurons with a permissive substrate upon which to attach and grow. We report here studies on the modification of an
alginate gel surface by either coating it with
laminin or by covalent attachment of
YIGSR peptide. Using NB2a
neuroblastoma cells, we found that native
alginate elicited minimal cell attachment ( approximately 1.5%); however,
YIGSR-
alginate conjugate elicited a fivefold increase in numbers of cells attached using
peptide ratios of 0.5 and 1 mg/g
alginate, ranging from 9.5% of the cells at the lower ratio, to about 44% at the higher. Only a further 19% increase was obtained at an increased
peptide density of 2 mg/g
alginate ( approximately 63% over control).
Laminin-coated
gels showed approximately 60% cell attachment. However,
laminin coating did not stimulate differentiation and neurite growth, whereas both numbers and lengths of outgrowths increased with increasing
peptide density on
peptide-modified
alginate. We demonstrate here the ability of the
peptide-modified
alginate gels to allow adhesion of NB2a
neuroblastoma cells and to promote neurite outgrowth from these cells when attached to the
peptide-modified
alginate surface. Also, we show that the adhesion of NB2a
neuroblastoma cells and neurite outgrowth from the attached cells is a function of the
peptide density on the gel surface.