Search

In order to assess the usefulness of collagen and laminin gels prefilling nerve chambers to enhance nerve regeneration, we compared reinnervation of target organs after sciatic nerve resection leaving gaps of 4 or 6 mm followed by repair with silicone tubes in different groups of mice. Tubes were prefilled with saline solution, collagen gels, or laminin-containing gels at different concentrations. Functional reinnervation was assessed by noninvasive methods to quantitate recovery of sweating, nociceptive, sensory, and motor functions in the hindpaw repeatedly during 4-5 months postoperation. The increase in gap length between nerve stumps delayed the beginning and reduced the degree of functional recovery achieved. Reinnervation started earlier and achieved slightly higher levels with collagen gel diluted at 1.28 mg/ml than with more concentrated (1.92 and 2.56 mg/ml) collagen gels and with saline-prefilled tubes bridging a 4-mm gap. Recovery was also better with diluted (4 mg/ml) than with concentrated (12 mg/ml) laminin-containing gel, although lower than with collagen gels and saline. By prefilling silicone tubes bridging a 6-mm gap, a length considered limiting for regeneration in the mouse sciatic nerve, with diluted collagen or laminin gels, both matrices allowed for higher levels of recovery and for successful regeneration in a higher proportion of mice than saline solution. The laminin gel performed slightly better than the collagen gel.

We compared reinnervation of target organs after sciatic nerve section leaving gaps of 2, 4, 6, or 8 mm or gaps repaired with silicone tubes in different groups of mice. Functional reinnervation was assessed by noninvasive methods to determine recovery of sweating, nociceptive, and muscular functions in the hindpaw repeatedly during 3 months postoperation. The increase of gap length between nerve stumps delayed the beginning and reduced the degree of functional recovery achieved either with or without repair. When lesions were left unrepaired, functional reinnervation was only noticeable with a 2-mm gap and practically absent with longer gaps. With tube repair, reinnervation started earlier and achieved higher values than in the corresponding unrepaired groups. Tubulization was most effective with 4-mm gaps and comparatively less with shorter and longer gaps. With 4-mm gaps, recovery was higher when the silicone tube had a cross-sectional area 2.5 times that of the sciatic nerve than with narrower or wider tubes and when the wall was the thinnest available. In all cases muscle reinnervation showed a lower progression than sweating and nociceptive recovery.

Functional reinnervation of sweat glands (SGs), skin, and muscle in the mouse paw after sciatic nerve lesions was evaluated to allow comparisons of the regeneration efficiency of different functional types of nerve fibers. In four groups of mice the sciatic nerve was crushed, sectioned, and left unrepaired or repaired by suture or tubulization. Reappearance of SG secretion and pinprick responses occurred slightly earlier than recordings of compound muscle and nerve action potentials in all groups. The degree of reinnervation, with respect to preoperative control values, of SGs and skin nociceptors was higher than the amplitude of the action potentials, mainly when the nerve injury was severe. The chances for recovery progressively decreased with the severity of the lesion, affecting the larger nerve fibers most. These results indicate that, after injuries of peripheral nerves, all types of nerve fibers are able to regenerate in the mouse, although small size fibers (sudomotor and nociceptive) allow for a higher degree of functional recovery than large myelinated fibers (skeletomotor and sensory).