No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Nerve regeneration over a 20-mm gap through a nerve conduit containing blood vessels in rats: the influence of interstump distance on nerve regeneration
Abstract
The present study was conducted in rats to investigate whether a tube with additional intrachamber vascularization could permit axons to extend over a distance greater than 10 mm, which appears to be the maximum axon regeneration distance for rat sciatic nerve axons through a normal empty tube.
A sural vessel-containing tube (VCT) was designed and interposed between transected sciatic nerve stumps in the thigh, leaving a 20-mm interneural gap.
Twelve weeks after tubulation, six out of nine rats showed successful nerve regeneration and re-innervation of the soleus muscle using the VCT. At 24 weeks, intrachamber nerve regeneration and re-innervation of the soleus and pedal adductor muscles were electrophysiologically and histologically confirmed in all rats. However, no neural tissue was observed within any ligated sural vessel-containing tube (LVCT) or empty unmodified tube (ET) with a 20-mm interneural gap. When nerves regenerated in the VCT with a 20-mm gap were compared with those regenerated in a VCT with a 10-mm gap 12 and 24 weeks after surgery, the results produced by the VCT with a 20-mm gap were inferior to those after use of the VCT with a 10-mm gap, except for motor nerve conduction velocity at 24 weeks.
The value recovered to almost identical levels (about 50-60% normal) in both groups.
... a, Sural nerve; b, sural vascular pedicle; c, myocutaneous flap supplied by the sural vessels; d, sciatic nerve stump; e, tibial nerve; f, peroneal nerve; g, silicone tube; h, longitudinal slit (this was sealed with liquid silicone after vascular insertion) myelinated axons and the myelinated axon diameters measured on the sections harvested from the most distal part of each regenerated nerve [5]. We were able to successfully increase the nerve regeneration distance up to 25 mm through a vessel-containing tube in the rat sciatic nerve [6,7]. ...
... It can be easily anticipated that the acceleration of vascularization within a tube is followed by axon extension. In Study 1, we demonstrated that the nerve regeneration distance and speed were ameliorated by vascular insertion into the tubes; however, the number and the diameter of axons regenerated within the tube cannot be increased solely by promoting vascularity during tubulation [5,6]. Because several chemical factors are secreted by BMSCs [19][20][21][22][23][24][25][26], intervention using various cells and chemical factors is needed to increase the number and diameter of axons to be regenerated intratubularly. ...
To promote nerve regeneration within a conduit (tubulation), we have performed studies using a tube model based on four important concepts for tissue engineering: vascularity, growth factors, cells, and scaffolds. A nerve conduit containing a blood vascular pedicle (vessel-containing tube) accelerated axon regeneration and increased the axon regeneration distance; however, it did not increase the number or diameter of the axons that regenerated within the tube. A vessel-containing tube with bone-marrow-derived mesenchymal stem cell (BMSC) transplantation led to the increase in the number and diameter of regenerated axons. Intratubularly transplanted decellularized allogenic nerve basal lamellae (DABLs) worked as a frame to maintain the fibrin matrix structure containing neurochemical factors and to anchor the transplanted stem cells within the tube. For the clinical application of nerve conduits, they should exhibit capillary permeability, biodegradability, and flexibility. Nerbridge® (Toyobo Co. Ltd., Osaka, Japan) is a commercially available artificial nerve conduit. The outer cylinder is a polyglycolic acid (PGA) fiber mesh and possesses capillary permeability. We used the outer cylinder of Nerbridge as a nerve conduit. A 20-mm sciatic nerve deficit was bridged by the PGA mesh tube containing DABLs and BMSCs, and the resulting nerve regeneration was compared with that obtained through a 20-mm autologous nerve graft. A neve-regeneration rate of about 70%–80% was obtained in 20-mm-long autologous nerve autografts using the new conduits.
Graphical Abstract
... In a tubulation model using a silicone tube, capillaries extended into the fibrin matrix only from the nerve stumps joined to either end of the tube [4]. Previous researchers have attempted to promote capillary extension in tubulation in several ways: by transplantation of a thin vascular pedicle into the conduit lumen [6,7,[15][16][17][18][19]; by the use of capillary permeable tubes [8,20,21]; by the creation of prefabricated vascularized tubes [22,23]; and by intrachamber administration of chemical factors promoting capillary proliferation [24,25]. ...
There are many commercially available artificial nerve conduits, used mostly to repair short gaps in sensory nerves. The stages of nerve regeneration in a nerve conduit are fibrin matrix formation between the nerve stumps joined to the conduit, capillary extension and Schwann cell migration from both nerve stumps, and, finally, axon extension from the proximal nerve stump. Artificial nerves connecting transected nerve stumps with a long interstump gap should be biodegradable, soft and pliable; have the ability to maintain an intrachamber fibrin matrix structure that allows capillary invasion of the tubular lumen, inhibition of scar tissue invasion and leakage of intratubular neurochemical factors from the chamber; and be able to accommodate cells that produce neurochemical factors that promote nerve regeneration. Here, we describe current progress in the development of artificial nerve conduits and the future studies needed to create nerve conduits, the nerve regeneration of which is compatible with that of an autologous nerve graft transplanted over a long nerve gap.
... Vascularization is an attractive graft feature for chronic injuries or delayed surgical repairs characterized by low vascularity because these grafts could accelerate the rate of axonal elongation [133,134]. Synthetic nerve graft performance has also been found to improve when paired with local vasculature [135][136][137]. However, studies suggest that while these vascularized grafts can improve reinnervation over non-vascularized grafts, they have yet to equal nonvascularized graft performance [135]. ...
Nerve guidance conduits (NGCs) have emerged from recent advances within tissue engineering as a promising alternative to autografts for peripheral nerve repair. NGCs are tubular structures with engineered biomaterials, which guide axonal regeneration from the injured proximal nerve to the distal stump. NGC design can synergistically combine multiple properties to enhance proliferation of stem and neuronal cells, improve nerve migration, attenuate inflammation and reduce scar tissue formation. The aim of most laboratories fabricating NGCs is the development of an automated process that incorporates patient-specific features and complex tissue blueprints (e.g. neurovascular conduit) that serve as the basis for more complicated muscular and skin grafts. One of the major limitations for tissue engineering is lack of guidance for generating tissue blueprints and the absence of streamlined manufacturing processes. With the rapid expansion of machine intelligence, high dimensional image analysis, and computational scaffold design, optimized tissue templates for 3D bioprinting (3DBP) are feasible. In this review, we examine the translational challenges to peripheral nerve regeneration and where machine intelligence can innovate bottlenecks in neural tissue engineering.
... The use of biological or synthetic conduits to bridge a nerve gap and enable nerve fibers to reconnect the distal stump, where the axons can grow and subsequently reconnect to the respective end organs continue to their end organs, stands as a promising option. The ability of peripheral nerves to regenerate through various guidance tubes has bee reported ( Chiu, Janecka et al. 1982;Kakinoki, Nishijima et al. 1998;Chiu 1999;Hazari, Wiberg et al. 1999;Strauch 2000;Kim and Dellon 2001;Watanabe, Tsukagoshi et al. 2001;Meek and Coert 2002). These conduits protect nerve axons and prevent the invasion of connective tissue into growth areas that can lead to scarring and they also concentrate conduction latency studies were performed and then the whole grafted segment was taken for histological examination before the rat was sacrificed. ...
... Kosaka 10 reported that nerve regeneration was promoted within a silicone tube in conjunction with arterial implantation for bridging a 5-mm sciatic nerve gap in rats. Kakinoki et al 11 also showed that the distance across which axons extend can be increased to 20 mm in a rat sciatic nerve by using a silicone rubber tube containing autogenous sural blood vessels. ...
Background:
Several types of artificial nerve conduit have been used for bridging peripheral nerve gaps as an alternative to autologous nerves. However, their efficacy in repairing nerve injuries accompanied by surrounding tissue damage remains unclear. We fabricated a novel nerve conduit vascularized by superficial inferior epigastric (SIE) vessels and evaluated whether it could promote axonal regeneration in a necrotic bed.
Methods:
A 15-mm nerve conduit was implanted beneath the SIE vessels in the groin of a rat to supply it with blood vessels 2 weeks before nerve reconstruction. We removed a 13-mm segment of the sciatic nerve and then pressed a heated iron against the dorsal thigh muscle to produce a burn. The defects were immediately repaired with an autograft (n = 10), nerve conduit graft (n = 8), or vascularized nerve conduit graft (n = 8). Recovery of motor function was examined for 18 weeks after surgery. The regenerated nerves were electrophysiologically and histologically evaluated.
Results:
The vascularity of the nerve conduit implanted beneath the SIE vessels was confirmed histologically 2 weeks after implantation. Between 14 and 18 weeks after surgery, motor function of the vascularized conduit group was significantly better than that of the nonvascularized conduit group. Electrophysiological and histological evaluations revealed that although the improvement did not reach the level of reinnervation achieved by an autograft, the vascularized nerve conduit improved axonal regeneration more than did the conduit alone.
Conclusion:
Vascularization of artificial nerve conduits accelerated peripheral nerve regeneration, but further research is required to improve the quality of nerve regeneration.
... The distal nerve stump of the sciatic nerve is branched into the peroneal and tibial nerve, resulting in a lower resistance between the recording pools, hence in a worse signal to noise ratio in orthodromic stimulation. We therefore choose to base our observations on the measurements of Q after antidromic stimulation, as did other authors using a similar experimental paradigm (Fugleholm et al., 1994; Kakinoki et al., 1998; Rosen et al., 1992). Stimulus– recruitment To gain insight in the fiber type composition of the nerves, the constituent fibers were gradually recruited by increasing the stimulus voltage from subthreshold to supramaximal levels. ...
In the present study the authors consider the influence of the porosity of synthetic nerve grafts on peripheral nerve regeneration.
Microporous (1-13 microm) and nonporous nerve grafts made of a copolymer of trimethylene carbonate and epsilon-caprolactone were tested in an animal model. Twelve weeks after surgery, nerve and muscle morphological and electrophysiological results of regenerated nerves that had grown through the synthetic nerve grafts were compared with autografted and untreated (control) sciatic nerves. Based on the observed changes in the number and diameter of the nerve fibers, the predicted values of the electrophysiological parameters were calculated.
The values of the morphometric parameters of the peroneal nerves and the gastrocnemius and anterior tibial muscles were similar if not equal in the rats receiving synthetic nerve grafts. The refractory periods, however, were shorter in porous compared with nonporous grafted nerves, and thus were closer to control values.
A shorter refractory period enables the axon to follow the firing frequency of the neuron more effectively and allows a more adequate target organ stimulation. Therefore, porous are preferred over nonporous nerve grafts.
... Presently, we are examining methods to maintain even dispersion of filaments within the guidance chamber. Numerous investigators have studied regeneration across extended gap lesions (longer than 1.4 cm) in the rat model (Williams et al., 1987; Yannas et al., 1987; Madison et al., 1988; Kakinoki et al., 1997 Kakinoki et al., , 1998 Hadlock et al., 1998; Arai et al., 2000). To our knowledge, none had reported regeneration across these gap distances with empty tube controls. ...
After injury, axonal regeneration occurs across short gaps in the peripheral nervous system, but regeneration across larger gaps remains a challenge. To improve regeneration across extended nerve defects, we have fabricated novel microfilaments with the capability for drug release to support cellular migration and guide axonal growth across a lesion. In this study, we examine the nerve repair parameters of non-loaded filaments. To examine the influence of packing density on nerve repair, wet-spun poly(L-Lactide) (PLLA) microfilaments were bundled at densities of 3.75, 7.5, 15, and 30% to bridge a 1.0-cm gap lesion in the rat sciatic nerve. After 10 weeks, nerve cable formation increased significantly in the filament bundled groups when compared to empty-tube controls. At lower packing densities, the number of myelinated axons was more than twice that of controls or the highest packing density. In a consecutive experiment, PLLA bundles with lower filament-packing density were examined for nerve repair across 1.4- and 1.8-cm gaps. After 10 weeks, the number of successful regenerated nerves receiving filaments was more than twice that of controls. In addition, nerve cable areas for control groups were significantly less than those observed for filament groups. Axonal growth across 1.4- and 1.8-cm gaps was more consistent for the filament groups than for controls. These initial results demonstrate that PLLA microfilaments enhance nerve repair and regeneration across large nerve defects, even in the absence of drug release. Ongoing studies are examining nerve regeneration using microfilaments designed to release neurotrophins or cyclic AMP.
... The distal nerve stump of the sciatic nerve is branched into the peroneal and tibial nerve, resulting in a lower resistance between the recording pools, hence in a worse signal to noise ratio in orthodromic stimulation. We therefore choose to base our observations on the measurements of Q after antidromic stimulation, as did other authors using a similar experimental paradigm (Fugleholm et al., 1994;Kakinoki et al., 1998;Rosen et al., 1992). ...
We studied electrophysiological and morphological properties of the Aalpha- and Abeta-fibers in the regenerating sciatic nerve to establish whether these fiber types regenerate in numerical proportion and whether and how the electrophysiological properties of these fiber types are adjusted during regeneration. Compound action potentials were evoked from isolated sciatic nerves 12 weeks after autografting. Nerve fibers were gradually recruited either by increasing the stimulus voltage from subthreshold to supramaximal levels or by increasing the interval between two supramaximal stimuli to obtain the cumulative distribution of the extracellular firing thresholds and refractory periods, respectively. Thus, the mean conduction velocity (MCV), the maximal charge displaced during the compound action potential (Q(max)), the mean firing threshold (V(50)), and the mean refractory period (t(50)) were determined. The number of myelinated nerve fibers and their fiber diameter frequency distributions were determined in the peroneal nerve. Mathematical modeling applied to fiber recruitment and diameter distributions allowed discrimination of the Aalpha- and Abeta-fiber populations. In regenerating nerves, the number of Aalpha-fibers increased fourfold while the number of Abeta-fibers did not change. In regenerating Aalpha- and Abeta-fibers, the fiber diameter decreased and V(50) and t(50) increased. The regenerating Aalpha-fibers' contribution to Q(max) decreased considerably while that of the Abeta-fibers remained the same. Correlation of the electrophysiological data to the morphological data provided indications that the ion channel composition of both the Aalpha- and Abeta-fibers are altered during regeneration. This demonstrates that combining morphometric and electrophysiological analysis provides better insight in the changes that occur during regeneration.
The treatment of peripheral nerve defects has always been one of the most challenging clinical practices in neurosurgery. Currently, nerve autograft is the preferred treatment modality for peripheral nerve defects, while the therapy is constantly plagued by the limited donor, loss of donor function, formation of neuroma, nerve distortion or dislocation, and nerve diameter mismatch. To address these clinical issues, the emerged nerve guide conduits (NGCs) are expected to offer effective platforms to repair peripheral nerve defects, especially those with large or complex topological structures. Up to now, numerous technologies are developed for preparing diverse NGCs, such as solvent casting, gas foaming, phase separation, freeze‐drying, melt molding, electrospinning, and three‐dimensional (3D) printing. 3D printing shows great potential and advantages because it can quickly and accurately manufacture the required NGCs from various natural and synthetic materials. This review introduces the application of personalized 3D printed NGCs for the precision repair of peripheral nerve defects and predicts their future directions. The personalized nerve guide conduits are quickly and accurately manufactured from various natural and synthetic materials by a three‐dimensional printing technique, which meets personalized imaging data to repair nerve defects of complex anatomical structures with the assistance of different growth factors and cells.
Over the past two decades, a number of fabrication methods, including 3D printing and bioprinting, have emerged as promising technologies to bioengineer nerve conduits that closely replicate features of the native peripheral nerve, with the aim of augmenting or supplanting autologous nerve grafts. 3D printing and bioprinting offer the added advantage of rapidly creating composite peripheral nerve matrices from micron-scaled units, using an assortment of synthetic, natural and biologic materials. In this review, we explore the evolution of automated 3D manufacturing technologies for the development of peripheral nerve conduits and discuss aspects of conduit design, based on microarchitecture, material selection, cell and protein inclusion, and mechanical properties, as they are adaptable to 3D printing. Additionally, we highlight advancements in the application of bio-imaging modalities toward the fabrication of patient-specific nerve conduits. Lastly, we outline regulatory as well as clinical challenges that must be surmounted for the translation of 3D printing and bioprinting technology to the clinic. As a whole, this review addresses topics that may situate 3D manufacturing at the forefront of fabrication technologies that are exploited for the generation of future revolutionary therapies like in situ printing of peripheral nerves.
Although autogenous nerve grafting remains the gold standard for repair of peripheral nerve defects, the use of various conduits can be a substitute provided these conduits meet the above-mentioned prerequisites. For the moment, autogenous vein grafts or denatured muscle grafts can be used to bridge short defects, especially in distal sensory nerves. Incorporation of muscle into a vein graft expands its application to longer defects in bigger nerves. PGA conduits have also been clinically proven to be reliable in reconstruction of digital nerve defects. Although nonabsorbable conduits cause irritation and nerve compression that necessitates secondary surgery removal, silicone tubes or Goretex tubes can be used in selected cases until absorbable conduits large enough for major peripheral nerves are available. To date, 3 cm seems to be the barrier for conduits. Incorporation of trophic factors and Schwann cells into the conduits will make their way into the clinic if problems like controlled release of trophic factors, obtaining and sustenance of an appropriate number of viable Schwann cells, are solved.
After a survival time of 180 days following the excision of a 2 mm segment of the vibrissal nerve to the gamma straddler vibrissa in the adult rat, a retrograde fluorescent single-labelling experiment revealed that 46% of the injured vibrissal sensory neurones had regenerated their peripheral processes. Peripheral collateral sprouting was not involved in the reinnervation of the denervated gamma vibrissa, as proved by a retrograde fluorescent double-labelling experiment. The regenerating nerve fibres did not invade the intact neighbouring vibrissae of the gamma vibrissa, and the sensory nerve fibres of the intact vibrissae were not translocated to the denervated gamma vibrissa. Thus, the sensory function of the denervated gamma vibrissa was restored exclusively by the regeneration of the damaged vibrissal nerve.
We investigated whether a tube with its inner surface implanted with negatively-charged carbon ions (C(-) ions) would enable axons to extend over a distance greater than 10 mm. The tube was found to support nerves regenerating across a 15-mm-long inter-stump gap. Silicone treated with C(-) ions showed increased hydrophilic properties and cellular affinity, and axon regeneration was promoted with this increased biocompatibility.
We reported previously that a silicone tube whose inner surface has been implanted with negatively charged carbon ions (C-) enables a nerve to regenerate across a 15-mm inter-stump gap. In this study, we investigated whether a C- -ion-implanted tube pretreated with basic fibroblast growth factor promotes peripheral nerve regeneration. The C- -ion-implanted tube significantly accelerated nerve regeneration, and this effect was enhanced by basic fibroblast growth factor.
ResearchGate has not been able to resolve any references for this publication.