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Single-Lumen and Multi-Lumen Poly(Ethylene Glycol) Nerve Conduits Fabricated by Sterolithography for Peripheral Nerve Regeneration In Vivo
Maristella Evangelista, MD, MBA1, Mireya Perez, BS2, Ara A. Salibian, BS1, Jeffrey Hassan, BS1, Keyianoosh Z. Paydar, MD, FACS1, Ryan Wicker, PhD2, Karina Arcaute, PhD2, Brenda K. Mann, PhD3 and Gregory R. D. Evans, MD, FACS1
1Aesthetic and Plastic Surgey Institute, University of California at Irvine, Orange, CA, 2W. M. Keck Center for 3D Innovation, University of Texas at El Paso, El Paso, TX, 3SentrX Animal Care, Salt Lake City, UT
Background: Several techniques are currently utilized to repair and reconstruct peripheral nerve defects including direct neurorraphy, autologous nerve grafts and nerve conduits. The use of nerve conduits to facilitate nerve regrowth is limited to defects <3cm, but can potentially avoid the possible comorbidities associated with autologous nerve transfer. The purpose of this study is to determine the capability of novel single and multi-lumen poly(ethylene glycol) (PEG) conduits manufactured by stereolithography to promote nerve regeneration after transection injuries in the rat sciatic nerve. Methods: 8 Sprague Dawley rats received sharp transection injuries of the sciatic nerve and were randomly assigned to receive either single-lumen or multi-lumen PEG conduits fabricated using stereolithography to bridge a 10mm gap. After 5 weeks, sciatic nerve and conduit samples were harvested, and histomorphological parameters such as axon number, myelin thickness, fiber diameter, and g-ratio were analyzed to determine peripheral nerve regeneration. Contralateral intact nerve was also harvested from each specimen for comparison. Results: Partial nerve regeneration was observed in 3 out of the 4 single-lumen conduits and 1 out of the 4 multi-lumen conduits. The number of axons in the single-lumen regenerated nerve approached that of the contralateral intact nerve at 4492 ± 2810.0 and 6080 ± 627.9 fibers/mm2, respectively. The percentage of small fibers was greater in the single-lumen conduit compared to the intact nerve, whereas myelin thickness and g-ratio were both consistently greater in the autologous nerve. Axon regrowth through the multi-lumen conduits, on the other hand, was severely limited and could not be quantified. Conclusions: Poly(ethylene glycol) conduits using stereolithography have promise as a new substrate for nerve conduits boasting ease of mass production and distribution. Single-lumen PEG nerve conduits seem to promote nerve regeneration with regenerating axon numbers approaching that of normal nerve. Multi-lumen PEG conduits demonstrated significantly less nerve regeneration, possibly due to physical properties of the conduit inhibiting growth. Further studies are necessary to precisely compare the efficacy of the two conduits for functional recovery and to better understand the reasons underlying their differences in nerve regeneration potential. Figure 1: Single-lumen conduit specimens show healthy axons at different stages of regeneration. 
Figure 2: Multi-lumen conduit specimens show some axonal and myelin formation but no quantifiable axons. 
Reference Citation: Jiang X, Lim SH, Mao HQ, et al. Current applications and future perspectives of artificial nerve conduits. Exp Neurol 2010;223:86-101
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