Journal of Neuroscience, Vol 9, 3590-3595, Copyright © 1989 by Society for Neuroscience
Peripheral nerve regeneration through blind-ended semipermeable guidance channels: effect of the molecular weight cutoff
P Aebischer, V Guenard and S Brace
Artificial Organ Laboratory, Brown University, Providence, Rhode Island 02912.
Synthetic nerve guidance channels are used to better understand the
cellular and molecular events controlling peripheral nerve regeneration. In
the present study, the contribution of wound-healing molecules to
peripheral nerve regeneration was assessed by varying the molecular weight
cutoff of the tubular membrane. Nerve regeneration through polysulfone
tubular membranes with molecular weight (Mw) cutoffs of 10(5) and 10(6) Da
was analyzed in a transected hamster sciatic nerve model. Cohorts of 6
animals received tubes of either type for 4 or 8 weeks with the distal end
of the polymer tube capped. Other cohorts of 6 animals received tubes of
either type for 4 weeks with the distal nerve stump secured within the
guidance channel so as to create a 4 or 8 mm gap between both nerve stumps.
Both types of channels contained regenerated tissue cables extending to the
distal end of the guidance channel at both 4 and 8 weeks in the absence of
a distal nerve stump. The cables regenerated in the 10(5) Da channels were
composed of nerve fascicles surrounded by a loose epineurial sheath,
whereas those regenerated in the 10(6) Da channels were composed mainly of
granulation tissue. The numbers of myelinated and unmyelinated axons were
significantly greater in the 10(5) Da than in the 10(6) Da channels at both
4 and 8 weeks. Both types of channel contained regenerated tissue cables
with numerous nerve fascicles when the distal nerve stump was present with
either gap length. However, when the gap distance was 8 mm, the 10(6) Da
channels contained significantly fewer myelinated axons than the 10(5) Da
channels. The present study reveals that the Mw cutoff of a semipermeable
guidance channel strongly influences the outcome of peripheral nerve
regeneration, possibly by controlling the exchange of molecules between the
channel's lumen and the external wound-healing environment. These results
suggest that the wound-healing environment secretes humoral factors that
can either promote or inhibit the nerve-regeneration process.