Reduction of post‐traumatic neuroma and epineural scar formation in rat sciatic nerve by application of microcrystallic chitosan

Abstract

Injury of peripheral nerve is associated with the development of post-traumatic neuroma at the end of the proximal stump, often being the origin of neuropathic pain. This type of pain is therapy-resistant and therefore extremely nagging for patients. We examined the influence of the microcrystallic chitosan gel applied to the proximal stump of totally transected sciatic nerve on the neuroma formation and neuropathic pain development in rats. In 14 rats, right sciatic nerve was transected and the distal stump was removed to avoid spontaneous rejoining. In the chitosan (experimental) group (n = 7), the proximal stump was covered with a thin layer of the microcrystallic chitosan gel. In control animals (n = 7), the cut nerve was left unsecured. Autotomy, an animal model of neuropathic pain, was monitored daily for 20 weeks following surgery. Then, the animals were perfused transcardially and the proximal stumps of sciatic nerves were dissected and subjected to histologic evaluation. The presence, size, and characteristics of neuromas as well as extraneural fibrosis were examined. In chitosan group, the incidence and the size of the neuroma were markedly reduced, as compared with the control group; however, there was no difference in autotomy behavior between groups. In addition, extraneural fibrosis was significantly reduced in chitosan group when compared to the control group. The results demonstrate beneficial influence of microcrystallic chitosan applied to the site of nerve transection on the development of post-traumatic neuroma and reduction of extraneural fibrosis, however without reduction of neuropathic pain.

A systematic review of animal models for experimental neuroma

“…20,43,44 Data on the level where biopsies of the nerve and the neuroma are taken and analysed are heterogeneous and often missing, preventing appropriate comparison of results: Chim et al 16 Haematoxylin and eosin 16,18e20,36,50,37,40,49 and toluidine blue 10,18,22,32,45,46,24,19,25,27,30,38,43,44 are the most commonly used stains; some studies also use Masson's thricome, 10,20,37 which also allows the labelling of the connective tissue. 70 This is sometimes combined with immunolabelling, the most common targets being S100 protein, 16,25e27,43 neurofilament 200 (NF200), 10,25,30,37,38 neuronal growthassociated protein (GAP)-43, 20,24,43,44 macrophages (ED-1), 20,27,28,43 nerve growth factor (NGF) 27 and calcitonin gene-related peptide (CGRP). 24,28,30 Double staining has also been reported to identify axons of different origin.…”

“…24,28,30 Double staining has also been reported to identify axons of different origin. 36,39 The most studied morphologic parameters are nerve cross-sectional area, 16,24,26,43e47 the ratio of neural to connective tissue, 16,26,51 myelinated axon count, 24,45e47 neuroma cross-sectional area, 45e47 neuroma size, 20,32,36 scar and regenerative nerve thickness, 19,20 axon and myelin fibre diameter and area. 38 In a recent paper, Yan et al 10 proposed the weight ratio of neuroma/normal nerve segment, which allows to normalise the results, making their comparison easier.…”

“…Morphological analysis is the most commonly used method, usually performed in light, 18,22,24,26,27,29,45,46,32,34,50,36,38,43,44,49,19,20,47,39,49 electron, 10,30,32,50,36,40 fluorescence 19,37,38,40 or confocal laser microscopy. 20,43,44 Data on the level where biopsies of the nerve and the neuroma are taken and analysed are heterogeneous and often missing, preventing appropriate comparison of results: Chim et al 16 Haematoxylin and eosin 16,18e20,36,50,37,40,49 and toluidine blue 10,18,22,32,45,46,24,19,25,27,30,38,43,…”

“…To date, the most popular model for terminal neuroma continues to be sciatic nerve neurotmesis in the rat, 10,19,20,24,25,27,29,30,32,34,35,38 but recently, a number of alternative models have been developed, which focus on the investigation of specific aspects of peripheral neuromas.…”

Chitooligosaccharide Inhibits Scar Formation and Enhances Functional Recovery in a Mouse Model of Sciatic Nerve Injury

“…Previous studies have indicated that nerve ducts composed of chitosan could effectively promote nerve regeneration and inhibit scar tissue proliferation, but the use of these chitosan ducts was challenging [7]. It was proposed that the degradation product of chitosan (chitooligosaccharide [COS]) was the key molecule involved in inhibiting scar formation, and a study in which COS was grafted onto poly[3-hydroxybutyrate-co-3-Hongping Hou and Lihai Zhang contributed equally to this work.…”