Biomedical Engineering Reference
In-Depth Information
Increasing degradation half-life of collagen scaffold
Bars: 50μm (top), 25 μm (bottom). t= 9 weeks, middle of gap
Fig. 8.13
Relation between capsule thickness and quality of peripheral nerve regeneration at 9
weeks. Representative cross sections of transected nerves tubulated with collagen scaffolds of
increasing degradation half-life, stained with osmium tetroxide.
Top row
: contractile capsule
around the regenerate. Data obtained at nerve gap midpoint at 9 weeks following transection of the
rat sciatic nerve.
Bottom row
: newly formed myelinated nerve tissue corresponding to the capsule
shown directly above.
Broken line
(
top
): Capsule border.
Scale bars
: 50 μm (
top
); 25 μm (
bottom
).
(Soller et al. 2012)
A detailed study of the relation between capsule thickness and quality of regen-
erated peripheral nerve was conducted using a collagen scaffold library with five
members that differed in degradation half-life over the range < 1.5 to > 100 weeks
(Soller et al. 2012). The animal model used, the transected rat sciatic nerve, was
identical to that used earlier in a study with a similar collagen library that showed
optimal quality of regeneration at a half-life of 1.5-2 week (Harley et al. 2004). In
the later study (Soller et al. 2012), the thickness of contractile cell capsule around
regenerating nerves was measured and related to various markers of nerve regenera-
tion. The earlier finding that quality of nerve regeneration (number myelinated ax-
ons, number A-fibers) was optimized at about 1.5 week half-life (Harley et al. 2004)
was confirmed. Significant associations were obtained between the thickness of
the capsule and various measures of nerve regeneration. Regenerated nerves were
analyzed at 9 weeks. The morphological evidence showed a thick capsule at the
ends of the half-life range and a thinner one somewhere in the middle of the range
(Fig.
8.13
). Quantitative relations that were obtained in this study included the find-
ing that the number of myelinated fibers decreased with increasing capsule thick-
ness (Fig.
8.14
, left). Another finding was an inverse relationship between capsule
thickness and number of myelinated fibers as well as the diameter of regenerated
nerve (Fig.
8.15
, Soller et al. 2012).
Mature regenerated peripheral nerves, observed at 60 week following transec-
tion, showed similar morphologies for contractile cells. Use of a silicone tube,
which yields poorly regenerated nerves, resulted in regeneration of nerves that were
