Effects of target tissue on growth of snail neurones in collagen gel culture

Three-dimensional culture of leech and snail ganglia for studies of neural repair

Three-dimensional (3D) collagen gels provide a stable matrix in which isolated regenerating ganglia from leech and snail can be maintained for studies of the molecular and cellular mechanisms underlying the regenerative process. Segmental ganglia from leech, or supraoesophageal, suboesophageal or buccal ganglia from snail were maintained for up to 3 weeks in 3D matrices of mammalian Type I collagen. The collagen matrix supports the regenerative outgrowth of axon tracts as well as the migration of microglial cells, important elements in the repair process. Proteins or soluble factors or target tissue may be added to the basic collagen matrix to manipulate the environment of the regenerating tissue. We describe techniques for immunostaining of regenerating axons and microglial cells within the gel matrix in combination with staining of cell nuclei, and the use of intracellular labelling to distinguish axons of identified neurons within the regenerative outgrowth.

Effect of collagen gel stiffness on neurite extension

Although collagen is commonly used as components of tissue-engineered nerve-guidance channels, little is known about the effect of the mechanical properties of commonly used gel concentrations on the extension of neurites. This study focused on neurite extension of dissociated chick dorsal root ganglia in vitro over a range of collagen concentrations (0.4-2.0 mg/ml). Neurite length increased in all gels between day 1 and day 4, except at the highest collagen concentration, where a 9% decrease was noted at day 4. Although maximum neurite extension was seen in lower concentration gels (0.6-0.8 mg/ml), mechanical stiffness of each gel significantly increased with increasing concentration, from 2.2 Pa at 0.4 mg/ml to 17.0 Pa at 2.0 mg/ml. A previous model of mechanical stiffness versus neurite outgrowth did not fit this data well, likely because of interactions between the growth cone and the collagen fibers. Overall, these results provided insight regarding factors that influence neurite elongation and may be utilized to further optimize tissue-engineered scaffolds.

The effect of extracellular matrix on the growth of mouse olfactory tissue in vitro

The aim of this study was to compare the capacity of extracellular matrix (ECM) components to support the growth and differentiation of olfactory tissue in vitro. Reconstituted basement membrane matrix (RBM) supported profuse neurite outgrowth from explants of olfactory bulb (OB), with no non-neuronal cell migration. In contrast, nasal tissue (NT) explants cultured on RBM produced profuse fibroblastic outgrowth, but no neurite outgrowth from olfactory sensory neurones (OSN). Three-dimensional collagen gels, on the other hand, supported extensive outgrowth of both non-neuronal and neurite outgrowth from OB and NT explants, mature OSNs in the latter being identified using antibodies against olfactory marker protein (OMP). These culture systems represent useful tools for investigating potential tropic influences of target tissue.