Confocal imaging of Schwann-cell migration along muscle-vein combined grafts used to bridge nerve defects in the rat

Università degli Studi di Torino, Torino, Piedmont, Italy
Microsurgery (Impact Factor: 2.42). 01/2001; 21(4):153-5. DOI: 10.1002/micr.1029
Source: PubMed


Schwann cells guide axonal regrowth during peripheral nerve repair. In a case of a nerve lesion with substance loss, a graft conduit is necessary to enable axons to reach the distal nerve stump. If a non-nervous autograft is used, the question arises as to the presence and origin of Schwann cells along the grafted tube. We addressed this issue using a tubulization technique based on the use of an autologous vein filled with fresh skeletal muscle for the repair of sciatic nerve defects in the rat. We showed that both ends of the graft were early and progressively colonized by a number of glial fibrillar acid protein-immunopositive and S-100 immunonegative cells, an immunocytochemical pattern typical of immature Schwann cells. These cells, which were located in the interstice between grafted skeletal muscle fibers, are mainly organized into long chains oriented along the main axis of the graft and progressively colonize all the graft. Schwann cells coming from the distal nerve end are suitable for being responsible for guiding regeneration of nerve fibers along the graft toward the correct periphery (tissue specificity).

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Available from: Pierluigi Tos, Feb 21, 2015
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    • "While the latter approach has only been addressed by few studies [61,62] because of the demonstration that pre-degeneration is not a pre-requisite for promoting nerve regeneration [63], the use of fresh skeletal muscle fibers has attracted much attention since the successful experimental validation of this paradigm by Brunelli et al. [64]. Experimental studies in laboratory animal models have shown that the fresh muscle-vein-combined guides are rapidly colonized by migratory Schwann cells (especially coming back from the distal nerve end) and that these cells maintain the capability to actively proliferate inside the conduit [65-67]. Transmission electron microscopy investigation showed that most of the grafted skeletal muscle fibers degenerate completely over the first postoperative days [64] and that new endoneurial tubes are formed very soon by perineurial cells [67]. "
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    ABSTRACT: Many surgical techniques are available for bridging peripheral nerve defects. Autologous nerve grafts are the current gold standard for most clinical conditions. In selected cases, alternative types of conduits can be used. Although most efforts are today directed towards the development of artificial synthetic nerve guides, the use of non-nervous autologous tissue-based conduits (biological tubulization) can still be considered a valuable alternative to nerve autografts. In this paper we will overview the advancements in biological tubulization of nerve defects, with either mono-component or multiple-component autotransplants, with a special focus on the use of a vein segment filled with skeletal muscle fibers, a technique that has been widely investigated in our laboratory and that has already been successfully introduced in the clinical practice.
    Journal of Brachial Plexus and Peripheral Nerve Injury 03/2014; 9(1):3. DOI:10.1186/1749-7221-9-3
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    • "Axonal regeneration in ANAs has been demonstrated to be similar to that in autografts across short gaps (Moore et al., 2011a, 2011b; Whitlock et al., 2009), but is reduced across longer defects (Whitlock et al., 2009), due to a poorly-understood mechanism. Following nerve repair with ANAs, there is early and progressive migration of SCs from both the proximal and especially the distal nerve stumps (Fornaro et al., 2001; Hayashi et al., 2007; Tseng et al., 2003; Whitlock et al., 2010a, 2010b). Host SCs provide the environment necessary for axonal regeneration in ANAs (Hall, 1986a, 1986b) through synthesis of neurotrophic factors (Bunge, 1993), adhesion molecules (Bixby et al., 1988), and axonal myelination (Bunge, 1993; Levi et al., 1994, 1997) and organization(Fansa et al., 2001). "
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    ABSTRACT: Repair of large nerve defects with acellular nerve allografts (ANAs) is an appealing alternative to autografting and allotransplantation. ANAs have been shown to be similar to autografts in supporting axonal regeneration across short gaps, but fail in larger defects due to a poorly-understood mechanism. ANAs depend on proliferating Schwann cells (SCs) from host tissue to support axonal regeneration. Populating longer ANAs places a greater proliferative demand on host SCs that may stress host SCs, resulting in senescence. In this study, we investigated axonal regeneration across increasing isograft and ANA lengths. We also evaluated the presence of senescent SCs within both graft type. A sciatic nerve graft model in rats was used to evaluate regeneration across increasing isograft (~autograft) and ANA lengths (20, 40, and 60mm). Axonal regeneration and functional recovery decreased with increased graft length and the performance of the isograft was superior to ANAs at all lengths. Transgenic Thy1-GFP rats and qRT-PCR demonstrated that failure of the regenerating axonal front in ANAs was associated with increased levels of senescence related markers in the graft (senescence associated β-galactosidase, p16(INK4A), and IL6). Lastly, electron microscopy (EM) was used to qualitatively assess senescence-associated changes in chromatin of SCs in each graft type. EM demonstrated an increase in the presence of SCs with abnormal chromatin in isografts and ANAs of increasing graft length. These results are the first to suggest that SC senescence plays a role in limited axonal regeneration across nerve grafts of increasing gap lengths.
    Experimental Neurology 05/2013; 247. DOI:10.1016/j.expneurol.2013.04.011 · 4.70 Impact Factor
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    • "These experiments provide evidence that without functional blood vessel-derived cell involvement, nerve regeneration mediated by vein wrapping is limited. The proper nerve regeneration and reduced endoneurial scarring seen when untreated venous grafts were utilized as the nerve guide conduit is believed to be due in part to i) the facilitation of graft invasion by increased Schwann cell motility [29], ii) the decrease in fibroblast infiltration [30], iii) the prevention of uncontrolled fiber outgrowth [31] and neuroma formation [15], [16], iv) the improvement of gliding on the smooth inner surface of the vein [9], and v) the prevention of scar tissue formation [7]. Furthermore, the venous conduits facilitate nerve regeneration through neovascularization [14] and growth factor secretion [31]. "
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    ABSTRACT: Based on growing evidence that some adult multipotent cells necessary for tissue regeneration reside in the walls of blood vessels and the clinical success of vein wrapping for functional repair of nerve damage, we hypothesized that the repair of nerves via vein wrapping is mediated by cells migrating from the implanted venous grafts into the nerve bundle. To test the hypothesis, severed femoral nerves of rats were grafted with venous grafts from animals of the opposite sex. Nerve regeneration was impaired when decellularized or irradiated venous grafts were used in comparison to untreated grafts, supporting the involvement of venous graft-derived cells in peripheral nerve repair. Donor cells bearing Y chromosomes integrated into the area of the host injured nerve and participated in remyelination and nerve regeneration. The regenerated nerve exhibited proper axonal myelination, and expressed neuronal and glial cell markers. These novel findings identify the mechanism by which vein wrapping promotes nerve regeneration.
    PLoS ONE 09/2011; 6(9):e24801. DOI:10.1371/journal.pone.0024801 · 3.23 Impact Factor
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