Differences between the effect of anisotropic and isotropic laminin and nerve growth factor presenting scaffolds on nerve regeneration across long peripheral nerve gaps

Abstract

Anisotropic scaffolds of agarose hydrogels containing gradients of laminin-1 (LN-1) and nerve growth factor (NGF) molecules were used to promote sciatic nerve regeneration across a challenging 20 mm nerve gap in rats.Step and continuous gradient anisotropic scaffolds were fabricated and characterized and regeneration was compared to that in isotropic scaffolds with uniform concentrations of LN-1 and NGF and sciatic nerve grafts harvested from syngenic rats. Polysulfone tubular guidance channels were used to present the agarose based scaffolds to the nerve stumps. Fourmonths after implantation, regenerating axons were observed in animals implanted with anisotropic scaffolds with gradients of both LN-1 and NGF molecules and nerve grafts, but not in animals with isotropic scaffold implants. Also, the scaffolds with gradient of either LN-1 or NGF, with the other component being uniformly distributed in the scaffold, did not elicit axonal regeneration. The total number of myelinated axons was similar for the anisotropic scaffold and the nerve graft conditions, with the anisotropic scaffolds having a higher density of axons than the nerve grafts. Axonal diameter distribution was similar for the anisotropic scaffolds and the nerve grafts. The nerve grafts and anisotropic scaffolds resulted in better functional outcome compared to isotropic scaffolds as measured by the relative gastrocnemius muscle weight (RGMW). Additionally the state of neuromuscular junctions as assessed by pre-and post-synaptic staining revealed that both the anistropic scaffolds performed as well as nerve grafts.

The sciatic nerve injury model in pre-clinical research

“…A number of innovative artificial nerve guides have been developed and this body of experimental research has been mainly based on experiments made using the SNI model aimed at comparing, in a pre-clinical view, the effectiveness of different types of scaffolds (Rodriguez et al, 2000;Varejao et -9 -al., 2003;Dodla and Bellamkonda, 2008;Carriel et al, 2013;Haastert-Talini et al, 2013;Reid et al, 2013;Johansson and Dahlin, 2014). …”

“…Although the bridging of gaps longer than 1.5 cm have been described in the rat (e.g. Geuna et al, 2000;Dodla and Bellamkonda, 2008), it is preferable to move to large animal models (e.g. rabbit or sheep) when long nerve prostheses have to be tested in vivo.…”

Immunoengineering nerve repair

“…9D). alternative to autografts, synthetic biomaterial-based nerve conduits have been developed that are capable of bridging short gaps (11,13,21,59,60). However, these nerve conduits have not been very successful in bridging critically sized nerve gaps.…”

“…In both clinical and research settings, use of synthetic and natural guidance channels to bridge nerve gaps has been shown to improve nerve regeneration in small gaps (less than 10 mm in rat and 30 mm in human), but these constructs fail when the gaps are longer (11). Some tissue engineering strategies have shown promise, including the design of novel nerve conduits (3,13), the addition of fillers within nerve conduits (14,15), transplantation of cells (16,17), local delivery of neurotrophic factors (18,19), and application of topographical cues (20)(21)(22); however, none of these techniques has been able to match the autograft's performance for long nerve gap repair (11,12). Therefore, despite concerted effort over the last several decades, no suitable replacement for autografts has been found (3).…”

Polyester Fleeces used as an Artificial Interstitium Influence the Spatial Growth of Regenerating Tubules

“…Further an optimal ratio between surface area and volume can be achieved in order to provide the diseased organ with a high density of s/pC [23]. Another advantage is the possibility to incorporate later growth factors in the fleece fibers playing a key role in tissue restoration and regeneration [24][25][26].…”