Growth factor expression in normal and diabetic rats during peripheral nerve regeneration through silicone tubes

Evaluation of small intestine submucosa and poly(caprolactone-co-lactide) conduits for peripheral nerve regeneration

The present study employed nerve guidance conduits (NGCs) only, which were made of small intestine submucosa (SIS) and poly(caprolactone-co-lactide) (PCLA) to promote nerve regeneration in a peripheral nerve injury (PNI) model with nerve defects of 15 mm. The SIS- and PCLA-NGCs were easily prepared by rolling of a SIS sheet and a bioplotter using PCLA, respectively. The prepared SIS- and PCLA-NGCs fulfilled the general requirement for use as artificial peripheral NGCs such as easy fabrication, reproducibility for mass production, suturability, sterilizability, wettability, and proper mechanical properties to resist collapsing when applied to in vivo implantation. The SIS- and PCLA-NGCs appeared to be well integrated into the host sciatic nerve without causing dislocations and serious inflammation. All NGCs stably maintained their NGC shape for 8 weeks without collapsing, which matched well with the nerve regeneration rate. Staining of the NGCs in the longitudinal direction showed that the regenerated nerves grew successfully from the SIS- and PCLA-NGCs through the sciatic nerve-injured gap and connected from the proximal to distal direction along the NGC axis. SIS-NGCs exhibited a higher nerve regeneration rate than PCLA-NGCs. Collectively, our results indicate that SIS- and PCLA-NGCs induced nerve regeneration in a PNI model, a finding that has significant implications in the future with regard to the feasibility of clinical nerve regeneration with SIS- and PCLA-NGCs prepared through an easy fabrication method using promising biomaterials.

Peripheral nerve regeneration through silicone chambers in streptozocin-induced diabetic rats

The silicone chamber model was used to evaluate peripheral nerve regeneration (PNR) in streptozocin (STZ)-induced diabetic rats. Diabetic and control animals underwent sciatic nerve transection and silicone chamber implantation establishing gaps of various lengths between the transected nerve ends. In animals with 5 and 10 mm gaps, diabetes was induced in experimental rats 1 week before surgery, and the animals were sacrificed 3 weeks after surgery. In animals with 8 mm gaps, diabetes induction occurred 3 days after surgery, and they were sacrificed after 7 weeks. Diabetic rats with 10 mm gaps demonstrated an impaired ability to form bridging cables, the initial step of regeneration through chambers. Morphometric studies of bridging cables between transected nerve ends demonstrated a significant reduction in the mean endoneurial area in diabetic animals with 5 and 8 mm gaps compared to controls. The number of regenerated myelinated axons in the chamber was significantly decreased in diabetic rats with 8 and 10 mm gaps. The mean myelinated fiber area in the regenerated cables of the diabetic group was significantly decreased with 5 mm gaps and significantly increased with 8 mm gaps compared to controls. Size-frequency histograms of regenerated myelinated fiber areas suggest a delay in the maturation of small caliber axons. Schwann cell migration across 5 mm gaps was examined with S-100 immunohistochemistry. The total distance of Schwann cell migration into cables from both proximal and distal ends was significantly reduced in diabetic animals. Characterization of PNR across gaps through silicone chambers in diabetic rats showed impairment in multiple aspects of the regenerative process, including cable formation, Schwann cell migration, and axonal regeneration.