Long acellular nerve transplants for allogeneic grafting and the effects of basic fibroblast growth factor on the growth of regenerating axons in dogs: A preliminary report

Sciatic nerves were excised from 3 beagle dogs about 5 h after their sacrif ice, treated three times by freezing and thawing, and stored in physiologic al saline for 3 months at -20 degrees C until used. Nerve segments 5 cm in length prepared from these stored nerves were transplanted to the common pe roneal nerve in the right hindlimb of beagle dogs. Sixteen beagle dogs in t otal were used, in four treatment groups of two pairs each studied at 1 and 3 months. Five-hundred microliters basic fibroblast growth factor (bFGF) o f two different concentrations (10 mu g/300 mu l and 100 mu g/300 mu l) whi ch were impregnated in 0.5 ml gelatin hydrogels was applied around the sutu red allografts. Autografting was also done in 4 beagle dogs, with no bFGF a pplication. One month after the grafting, no regenerating nerves extended b eyond the middle of the transplant in any of the allografts, except in the autografts in which a number of regenerated (myelinated) axons were present . Three months after the grafting, an abundance of myelinated axons was fou nd at the middle of the graft: the numbers of axons per 10(4) mu m(2) were 22.6 in the autografts and 10.6, 10.4 and 19.2 in the allografts treated wi th no bFGF, low-dose bFGF, and high-dose bFGF, respectively. Regenerating a xons extended into the host nerve: the numbers of myelinated axons at the l evel 1.5 cm distal to the distal suture were 35.7, 0.9, 3.8, and 12.1 per 1 0(4) mu m(2) in the above respective order. Although it was inferior in qua lity to the autograft, peripheral nerve regeneration was extensive in the d istal nerve using freeze-thawed and bFGF-treated allografts at 3 months. El ectromyography showed that the peroneus longus muscle responded to the elec trical stimuli given at the site proximal to the transplant in all four gro ups. These data indicate that a 5-cm acellular nerve segment containing Sch wann cell basal laminae can be used successfully as an allograft without an y immunosuppressants and that exogenously applied bFGF can improve nerve re generation by enhancing the growth of regenerating axons. (C) 1998 Academic Press.