Biosynthetic nerve grafts are developed in order to complement or replace autologous nerve grafts for peripheral nerve reconstruction. Artificial nerve guides currently approved for clinical use are not widely applied in reconstructive surgery as they still have limitations especially when it comes to critical distance repair. Here we report a comprehensive analysis of fine-tuned chitosan nerve guides (CNGs) enhanced by introduction of a longitudinal chitosan film to reconstruct critical length 15 mm sciatic nerve defects in adult healthy Wistar or diabetic Goto-Kakizaki rats. Short and long term investigations demonstrated that the CNGs enhanced by the guiding structure of the introduced chitosan film significantly improved functional and morphological results of nerve regeneration in comparison to simple hollow CNGs. Importantly, this was detectable both in healthy and in diabetic rats (short term) and the regeneration outcome almost reached the outcome after autologous nerve grafting (long term). Hollow CNGs provide properties likely leading to a wider clinical acceptance than other artificial nerve guides and their performance can be increased by simple introduction of a chitosan film with the same advantageous properties. Therefore, the chitosan film enhanced CNGs represent a new generation medical device for peripheral nerve reconstruction.

Biosynthetic nerve grafts are desired as alternative to autologous nerve grafts in peripheral nerve reconstruction. Artificial nerve conduits still have their limitations and are not widely accepted in the clinical setting. Here we report an analysis of fine-tuned chitosan tubes used to reconstruct 10 mm nerve defects in the adult rat. The chitosan tubes displayed low, medium and high degrees of acetylation (DAI: ≈ 2%, DA: ≈ 5%, DAIII: ≈ 20%) and therefore different degradability and microenvironments for the regenerating nerve tissue. Short and long term investigations were performed demonstrating that the chitosan tubes allowed functional and morphological nerve regeneration similar to autologous nerve grafts. Irrespective of the DA growth factor regulation demonstrated to be the same as in controls. Analyses of stereological parameters as well as the immunological tissue response at the implantation site and in the regenerated nerves, revealed that DAI and DAIII chitosan tubes displayed some limitations in the support of axonal regeneration and a high speed of degradation accompanied with low mechanical stability, respectively. The chitosan tubes combine several pre-requisites for a clinical acceptance and DAII chitosan tubes have to be judged as the most supportive for peripheral nerve regeneration.

To understand the mechanisms of remyelination and the reasons for regeneration failure is one of the major challenges in multiple sclerosis research. This requires a good knowledge and reliable analysis of experimental models. This work was undertaken to characterize the pattern of myelin protein expression during experimental remyelination. Acute demyelination of the corpus callosum was induced by feeding of 0.3% cuprizone for 6 weeks, followed by a 10‐week remyelination period. We used a combination of Luxol fast blue (LFB) myelin staining, electron microscopy (EM) and immunohistochemistry for the myelin proteins 2′,3′‐cyclic nucleotide 3′ phosphodiesterase (CNPase), myelin basic protein (MBP), proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein (MOG). Early remyelination was detected by the re‐expression of CNPase, MBP and PLP as early as 4 days. MOG, as a marker for late differentiation of oligodendrocytes, was not detectable until 2 weeks of remyelination. EM data correlated well with the LFB myelin staining and myelin protein expression, with 50% of the axons being rapidly remyelinated within 2 weeks. While particularly MBP but also PLP and CNPase are re‐expressed very early before significant remyelination is observed by EM, the late marker MOG shows a lag behind the remyelination detected by EM. The presented data indicate that immunohistochemistry for various myelin proteins expressed early and late during myelin formation is a suitable and reliable method to follow remyelination in the cuprizone model. Furthermore, investigation of early remyelination confirms that the intrinsic repair programme is very fast and switched on within days.