A promising alternative for the repair of peripheral nerve injuries is the bioartificial nerve graft,or BNG,comprised of a tubular conduit presseeded with Schwann cells,which are an effective substrate for enhancing nerve regeneration.The physical properties of the conduit,porosity and wall thichness,as well as the Schwann cell seeding density,were tested for their effect on anon growth using rat dorsal root ganglia.These parameters can influence the mount of nutrients and growth factors made available to the neural tissue.Results show that a greater wall thickness and lower porosities have a detrimental effect on the growth of the axons.Over a four week period,axons extended 3.2nm for the optimum case (trangle open R=0.82mm,#epsilon#=0.75)compared to 1.8 and 1.6mm for a lower porosity(0.55)and a greater wall thickness (1.4mm),respectively.A maximum in the growth rate occurs at a porosity of 75% for Schwann cell seeded conduits but not for nuseeded ones.When compared to mass transfer predictions,the results suggest that,at higher porosites,more growth factors diffuse out of the conduit,while at low porosities there is competition for nutrients.Increasing the Schwann cell seeding density enhances grwoth but also leads to an increase in the number of axons along the length of the conduit.This in indicative of branching of the axons,which requires additional resources to amintain and can lead to painful neuroma formation.Wall thickness and porosity were found not to have any significant effect on the axon number sprouting from the dorsal root ganglia and the mean diameter(P>0.05).Considerations need to be made,not just onthe polymer used,but also on its porosity,wall thickness,and Schwann cell seeding density.These parameters can be adjusted to create a bioartificial nerve graft that provides the optimal envionment for nerve growth.
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