Repair Strategies in the PNS

While damaged tissue in the PNS is able to spontaneously regenerate after injury, the regeneration rate is quite slow. Axonal growth rates have been estimated at about 0.5-1 mm/day (Archibald et al. 1995). Although those growth rates may translate into the bridging of a several millimeter nerve gap in a matter of days, reinnervation of target tissue can take months. Accelerating recovery is desirable due to the loss of function prior to appreciable tissue regeneration. The slow growth of axons delays the functional recovery of PNS tissue and allows for extended periods of muscle atrophy. A number of techniques used to accelerate tissue regeneration

Table 1 Commercially available, FDA-approved NGCs


Product name







Type I collagen

Type I collagen

Polyglycolic acid

Poly (85:15/L:D) lactide-



Maximum length

3 cm

2.5 cm

4 cm

3 cm

6.35 cm


1.5-7 mm

2-6 mm

2.3-8 mm

1.5-10 mm

2-10 mm

Degradation time

4-8 months

4-8 months

6 months

16 months

Does not degrade

FDA approval date





Late 2001

have been identified, such as electrical stimulation (Rajnicek et al. 1998; Borgens et al. 1999) and the release of a variety of growth factors such as brain-derived neurotrophic factor (BDNF) in the CNS (Bregman et al. 1997) and glial cell-line derived neurotrophic factor (GDNF) in the PNS (Henderson et al. 1994). Second, if the tissue damage is great enough, a critical defect incapable of spontaneously regenerating is produced. Both of these scenarios may benefit from the implantation of a NGC to permit or accelerate the regeneration process. It is important to note that mature neurons do not undergo mitosis. Thus, supporting the regrowth of axons from existing cells to distal targets is the goal of a NGC.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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