Autologous Schwann cells drive regeneration through a 6-cm autogenous venous nerve conduit

Peripheral nerve regeneration is a complex series of events, involving bi-directional interactions between regenerating axons and Schwann cells. These authors have demonstrated in their laboratory that nerves will regenerate through a 3-cm autogenous venous nerve conduit (AVNC) in an animal model and, with Dr. David Chiu, a similar distance in the human. They have shown that the upper limit of nerve regeneration in an empty AVNC was 3 cm, with no evidence of nerve growth at the 6-cm mark (no-growth model). Most recently, they have demonstrated rapid growth at 1 month in a 3-cm AVNC filled with Schwann cells, compared to poor-to-no-regrowth at 1 month in controls. While, in theory, Schwann-cell-derived growth factor should be sufficient to supplant the requirement for Schwann cells, in practice, therapies with growth factors have failed in clinical trials, with some resulting in severe morbidity and mortality for the subjects. The present study showed excellent nerve regeneration through a 6-cm AVNC with the addition of autologous Schwann cells, breaking the barrier in the previous no-growth model. In the first stage, autologous Schwann cells were harvested from the contralateral peroneal nerve of the rabbit and expanded in culture. The Schwann cells were purified to >99 percent homogeneity using differential adhesion and antibody-compliment-mediated cytolysis. In the second stage, 6 cm ofgluteal vein were harvested and used as a conduit that was filled with either Matrigel or a slurry of Matrigel and 10⁶/ml autologous Schwann cells (n=6 control and 6 experimental animals). The non-donor side peroneal was exposed and transected, leaving a gap of 6 cm. The filled gluteal vein graft (AVNC) was then anastomosed to the proximal and distal peroneal nerve stumps, and the rabbits were allowed to recover. Four months postoperatively, the animals were subjected to transcardiac perfusion with EM grade fixative. The grafts were analyzed at the light and electronmicroscopic levels, and showed excellent growth of nerve at 6 cm, the distal end of the AVNC.