Nerve guide material made from fibronectin: assessment of in vitro properties

We have previously used orientated mats of fibronectin as conduits to repair short gaps in peripheral nerves. Here we describe the in vitro properties of a new material in the form of large cables produced from a fibronectin-enriched solution with potential as a conduit for longer nerve defects. Large cables of fibronectin were made up to 14 cm long x 1.5 cm in diameter. When freeze dried, scanning electron microscopy revealed a predominant fiber orientation. Dried cables hydrated rapidly to 1.6 and 4.8 times their original length and diameter, respectively. Once hydrated these cables had pores that ranged from 10 to 100 microm through which Schwann cells and fibroblasts were able to grow in vitro and align with the axis of the fibrils by contact guidance. Furthermore, the porosity of the cable was enhanced by the natural dissolution of protein over a 3-week duration in culture with cells, such that 50- to 200-microm pores were observed. This study suggests that large fibronectin cables are a suitable alternative to the original fibronectin mats to guide components of the peripheral nerves and so to act as conduits with potential use in guiding regeneration across long nerve defects.