Nerve Xenografts Research Articles

Gal - T Knockout Porcine Nerve Xenografts Support Axonal Regeneration in a Rodent Sciatic Nerve Model.

Nerve xenografts harvested from transgenic α1,3-galactosyltransferase knockout (GalT-KO) pigs lack the epitope responsible for hyperacute rejection in pig-to-primate transplants. It is unknown whether these cold preserved nerve grafts support axonal regeneration in another species during and after immunosuppression. In this study, we compare outcomes between autografts and cold preserved xenografts in a rat sciatic model of nerve gap repair. Fifty male Lewis rats had a 1 cm sciatic nerve defect repaired using either: autograft and suture (n=10); 1-week or 4-week cold preserved xenograft and suture (n=10 per group); 1-week or 4-week cold preserved xenograft and photochemical tissue bonding using a human amnion wrap (PTB/HAM) (n=10 per group). Rats with xenografts were given tacrolimus until 4 months post-operatively. At 4 and 7 months, rats were euthanized and nerve sections harvested. Monthly sciatic functional index (SFI) scores were calculated. All groups showed increases in SFI scores by 4 and 7 months. The autograft suture group had the highest axon density at 4 and 7 months. The largest decrease in axon density from 4 to 7 months was in the 1-week cold preserved PTB/HAM group. The only significant difference between group SFI scores occurred at 5 months, when both 1-week cold preserved groups had significantly lower scores than the 4-week cold preserved suture group. Our results in the rat sciatic model suggest that GalT-KO nerve xenografts may be viable alternatives to autografts and demonstrate the need for further studies of long-gap repair and comparison with acellular nerve allografts. This proof-of-concept study in the rat sciatic model demonstrates that cold preserved GalT-KO porcine xenografts support axonal regeneration, as well as axonal viability following immunosuppression withdrawal. These results further suggest a role for both cold preservation and photochemical tissue bonding in modulating the immunological response at the nerve repair site.

Physical processing for decellularized nerve xenograft in peripheral nerve regeneration.

In severe or complex cases of peripheral nerve injuries, autologous nerve grafts are the gold standard yielding promising results, but limited availability and donor site morbidity are some of its disadvantages. Although biological or synthetic substitutes are commonly used, clinical outcomes are inconsistent. Biomimetic alternatives derived from allogenic or xenogenic sources offer an attractive off-the-shelf supply, and the key to successful peripheral nerve regeneration focuses on an effective decellularization process. In addition to chemical and enzymatic decellularization protocols, physical processes might offer identical efficiency. In this comprehensive minireview, we summarize recent advances in the physical methods for decellularized nerve xenograft, focusing on the effects of cellular debris clearance and stability of the native architecture of a xenograft. Furthermore, we compare and summarize the advantages and disadvantages, indicating the future challenges and opportunities in developing multidisciplinary processes for decellularized nerve xenograft.

Acellular nerve xenografts based on supercritical extraction technology for repairing long-distance sciatic nerve defects in rats.

Compared to conventional artificial nerve guide conduits (NGCs) prepared using natural polymers or synthetic polymers, acellular nerve grafts (ACNGs) derived from natural nerves with eliminated immune components have natural bionic advantages in composition and structure that polymer materials do not have. To further optimize the repair effect of ACNGs, in this study, we used a composite technology based on supercritical carbon dioxide (scCO2) extraction to process the peripheral nerve of a large mammal, the Yorkshire pig, and obtained an innovative Acellular nerve xenografts (ANXs, namely, CD + scCO2 NG). After scCO2 extraction, the fat and DNA content in CD + scCO2 NG has been removed to the greatest extent, which can better supported cell adhesion and proliferation, inducing an extremely weak inflammatory response. Interestingly, the protein in the CD + scCO2 NG was primarily involved in signaling pathways related to axon guidance. Moreover, compared with the pure chemical decellularized nerve graft (CD NG), the DRG axons grew naturally on the CD + scCO2 NG membrane and extended long distances. In vivo studies further revealed that the regenerated nerve axons had basically crossed the CD + scCO2 NG 3 weeks after surgery. 12 weeks after surgery, CD + scCO2 NG was similar to autologous nerves in improving the quality of nerve regeneration, target muscle morphology and motor function recovery and was significantly better than hollow NGCs and CD NG. Therefore, we believe that the fully decellularized and fat-free porcine ACNGs may be the most promising “bridge” for repairing human nerve defects at this stage and for some time to come.

Interleukin 37's role in promoting nerve repair and attenuating immune rejection of peripheral nerve xenografts in mice

BackgroundThe aim of the study was to explore the potential role of IL-37 in nerve repair and immune regulation in peripheral nerve xenograft hosts.MethodsRat nerve xenografts were transplanted into mouse recipients. Transplanted mice received an intraperitoneal injection of IL-37 on the day before transplantation, whereas control mice remained untreated. At postoperative 2, 4, 8, and 12 weeks, the effects of IL-37 were examined on motor function, tissue morphology, and regenerative ability of xenograft nerves. Levels of IL-17 and IL-22 in serum and spleen were measured at 3, 7, 14, and 28 days after nerve transplantation.ResultsAt 12 postoperative weeks, grafted nerves grew well in IL-37 treatment group, as documented by the recovery in function of sciatic nerves compared to untreated controls. In particular, IL-37-treated mice showed more complete neuromorphology, thicker myelin sheath, compact structure, and the increased number of myelinated nerve fibers in histological examination. The number of T helper (Th)17 (CD3 + CD4 + IL-17+) and Th22 (CD3 + CD4 + IL-22+) cells in the spleen was reduced in the IL-37-treated group, as well as serum IL-17 and IL-22 were decreased after IL-37 treatment compared with the untreated group.ConclusionsIL-37 attenuates immunomodulatory responses induced by xenografts, contributing to the recovery of nerve function and the prevention of muscle atrophy caused by nerve grafts.

Decellularized peripheral nerve grafts by a modified protocol for repair of rat sciatic nerve injury.

Studies have shown that acellular nerve xenografts do not require immunosuppression and use of acellular nerve xenografts for repair of peripheral nerve injury is safe and effective. However, there is currently no widely accepted standard chemical decellularization method. The purpose of this study is to investigate the efficiency of bovine-derived nerves decellularized by the modified Hudson's protocol in the repair of rat sciatic nerve injury. In the modified Hudson's protocol, Triton X-200 was replaced by Triton X-100, and DNase and RNase were used to prepare accelular nerve xenografts. The efficiency of bovine-derived nerves decellularized by the modified Hudson's protocol was tested in vitro by hematoxylin & eosin, Alcian blue, Masson's trichrome, and Luxol fast blue staining, immunohistochemistry, and biochemical assays. The decellularization approach excluded cells, myelin, and axons of nerve xenografts, without affecting the organization of nerve xenografts. The decellularized nerve xenograft was used to bridge a 7 mm-long sciatic nerve defect to evaluate its efficiency in the repair of peripheral nerve injury. At 8 weeks after transplantation, sciatic function index in rats subjected to transplantation of acellular nerve xenograft was similar to that in rats undergoing transplantation of nerve allograft. Morphological analysis revealed that there were a large amount of regenerated myelinated axons in acellular nerve xenograft; the number of Schwann cells in the acellular nerve xenograft was similar to that in the nerve allograft. These findings suggest that acellular nerve xenografts prepared by the modified Hudson's protocol can be used for repair of peripheral nerve injury. This study was approved by the Research Ethics Committee, Research and Technology Chancellor of Guilan University of Medical Sciences, Iran (approval No. IR.GUMS.REC.1395.332) on February 11, 2017.

Combination of BMSCs-laden acellular nerve xenografts transplantation and G-CSF administration promotes sciatic nerve regeneration.

Peripheral nerve gaps often lead to interrupted innervation, manifesting as severe sensory and motor dysfunctions. The repairs of the nerve injuries have not achieved satisfactory curative effects in clinic. The transplantation of bone marrow stromal cells (BMSCs)-laden acellular nerve xenografts (ANX) has been proven more effective than the acellular nerve allografting. Besides, granulocyte colony-stimulating factor (G-CSF) can inhibit inflammation and apoptosis, and thus is conducive to the microenvironmental improvement of axonal regeneration. This study aims to investigate the joint effect of BMSCs-seeded ANX grafting and G-CSF administration, and explore the relevant mechanisms. Adult SD rats were divided into five groups randomly: ANX group, ANX combined with G-CSF group, BMSCs-laden ANX group, BMSCs-laden ANX combined with G-CSF group, and autograft group. Eightweeks after transplantation, the detection of praxiology and neuroelectrophysiology was conducted, and then the morphology of the regenerated nerves was analyzed. The inflammatory response and apoptosis in the nerve grafts as well as the expression of the growth-promoting factors in the regenerated tissues were further assayed. G-CSF intervention and BMSCs implanting synergistically promoted peripheral nerve regeneration and functional recovery following ANX bridging, and the restoration effect was matchable with that of the autologous nerve grafting. Moreover, local inflammation was alleviated, the apoptosis of the seeded BMSCs was decreased, and the levels of the neuromodulatory factors were elevated. In conclusion, the union application of BMSCs-implanted ANX and G-CSF ameliorated the niche of neurotization and advanced nerve regeneration substantially. The strategy achieved the favorable effectiveness as an alternative to the autotransplantation.

Synergistic effects of G-CSF and bone marrow stromal cells on nerve regeneration with acellular nerve xenografts.

Peripheral nerve defects result in severe denervation presenting sensory and motor functional incapacitation. Currently, a satisfactory therapeutic treatment promoting the repair of injured nerves is not available. As shown in our previous study, acellular nerve xenografts (ANX) implanted with bone marrow stromal cells (BMSCs) replaced allografts and promoted nerve regeneration. Additionally, granulocyte-colony stimulating factor (G-CSF) has been proven to mobilize supplemental cells and enhance vascularization in the niche. Thus, the study aimed to explore whether the combination of G-CSF and BMSC-laden ANX exhibited a synergistic effect. Adult Sprague-Dawley (SD) rats were randomly divided into five groups: ANX group, ANX combined with G-CSF group, BMSCs-laden ANX group, BMSCs-laden ANX combined with G-CSF group and autograft group. Electrophysiological parameters and weight ratios of tibialis anterior muscles were detected at 8 weeks post-transplantation. The morphology of the regenerated nerves was assayed, and growth-promoting factors present in the nerve grafts following G-CSF administration or BMSCs seeding were also investigated. Nerve regeneration and functional rehabilitation induced by the combination therapy were significantly advanced, and the rehabilitation efficacy was comparable with autografting. Moreover, the expression of Schwann cell markers, neurotrophic factors and neovessel markers in the nerve grafts was substantially increased. In conclusion, G-CSF administration and BMSCs transplantation synergistically promoted the regeneration of ANX-bridged nerves, which offers a superior strategy to replace autografts in repairing peripheral nerve injuries.

Decellularized nerve xenograft combined with lycium barbarum polysaccharide for repair of sciatic nerve defect in rats

Objective To explore the effect of lycium barbarum polysaccharide (LBP) and decellularized nerve xenograft combination on nerve regeneration and recovery in repairing rat sciatic nerve defects. Methods Xenogeneic acellular nerve scaffolds were prepared by chemical extraction of tibial nerves from rabbits. A 10 mm left sciatic nerve defect model was created in 90 healthy adult Sprague-Dawley rats who were randomly divided into 5 groups: blank group (n=18), model group (n=18), LBP group (n=18), scaffold group (n=18), LBP and scaffold combination group (n=18). Two weeks after model creation. The sciatic nerve defect in LBP, scaffold and combination groups was repaired either by LBP, by scaffold, or by the LBP xenograft combination. After the second surgery, the rats survived for 4, 8 and 12 weeks, respectively. Gross observation of the scaffold, nerve conduction study to measure sciatic nerve motor nerve conduction velocity (MNCV), and neuromorphometry analysis of the graft were carried out at these three time points. Results Neuroma formation at the proximal nerve end was observed in the model group and LBP group. Adhesion of nerve ends to the surrounding tissue was more severe in the model group than in the LBP group. The sizes of the nerve grafts in the scaffold group and combination group were comparable. Proficient vascularization on the surface of these grafts was seen. There was only slight adhesion to the surrounding tissue. The regenerated nerve fibers in the combination group were denser and better oriented. Motor nerve conduction velocity recovery and the number of myelinated nerve fibers in the grafts were measured at 12 weeks postoperatively for blank, model, LBP, scaffold and combination groups, respectively. The differences among the groups were significant (P<0.05). Conclusion The combination of LBP and xenogeneic acellular nerve scaffold enhances peripheral nerve regeneration and recovery when used to repair nerve defects. Key words: Sciatic nerve; Nerve regeneration; Xenogeneic acellular nerve scaffold; Lycium barbarum polysaccharide

Athymic rat model for studying acellular human allograft

BackgroundAlthough human acellular nerve allograft is a promising nerve repair tool, optimizing graft application and understanding effective graft dimensions has been hampered by lack of an appropriate animal model. Rodent nerve acellular allograft can be tested in the utilitarian rodent nerve repair model, but testing different size options is limited by the size of the rodent donor animal. Human acellular nerve allograft offers the variety of sizes desired for more complete study but poses a high risk of rejection as xenograft tissue in the rodent model. Athymic nude rats are less prone to reject xenograft tissue due to their immunocompromised state and may offer an animal model for testing human acellular allograft. MethodsFifteen athymic nude and 15 Sprague-Dawley rats underwent unilateral excision and repair of a 10mm tibial nerve segment using 10mm of human acellular nerve graft. Testing at 3 months consisted of muscle force measurements, wet muscle weight, and histological assessment from the middle of the nerve grafts. ResultsAthymic rats repaired with human acellular xenograft demonstrated higher reinnervated muscle weight Gross inspection of the xenograft in euthymic rats revealed a brown and scarred center and histological inspection demonstrated larger axon diameters, and higher midgraft axon counts in the grafts of athymic rats.Comparison with existing methods: The athymic rat has been used in many studies that require an immunocompromised host, including implantation of foreign nervous tissue. Previous attempts at implanting acellular nerve xenograft into immunocompetent rats have yielded suboptimal results when compared to allograft. This study is the first to test acellular human nerve allograft in an athymic rat. ConclusionThe nerve regeneration was better in human acellular nerve allograft implanted into immunocompromised athymic rats when compared to euthymic rats supporting a potential role of this model in studying acellular human nerve tissue.

Regulatory and Effector Helper T-Cell Profile after Nerve Xenografting in the Toll-Like Receptor-Deficient Mice.

Introduction: The balance between regulatory T cells (Tregs) and effector T help cells (Th cells) is critical for the control of adaptive immune response during nerve transplantation. However, whether the homeostasis of immune regulation between Tregs and Th cells requires toll-like receptor (TLR) signaling is unclear. The aim of this study is to profile the distribution of spleen Tregs and Th cells in a mouse model of nerve xenografting in the TLR2 and NF-κB gene knockout mice.Methods: The sciatic nerve was taken from a SD rat or an allogeneic mouse and transplanted to a right back leg of recipient C57BL/6, TLR2-/-, or NF-κB-/- mice by subcutaneous transplantation. After 7 days, the T lymphocytes were then isolated from spleen, stained with phenotyping kits, and analyzed by flow cytometry.Results: The results showed that Tregs were decreased after nerve xenografting in the recipient C57BL/6 mouse. In addition, nerve xenografting also increased the Th1 and Th17 but not the Th2 cell populations. In contrast, amelioration of the Tregs elimination was found in TLR2-/- and NF-κB-/- mice after transplantation of the nerve xenograft. Moreover, the mice lacking TLR2 or NF-κB showed attenuation of the increase in Th1 and Th17 cells after nerve xenografting.Conclusions: TLR signaling is involved in T cell population regulation during tissue transplantation. Knock-out of TLR2 and NF-κB prevented Tregs elimination and inhibited Th1- and Th17-driven immune response after nerve xenografting. This study highlighted the potential of inhibiting TLR signaling to modulate T cell-mediated immune regulation to facilitate tolerance to nerve transplantation.

Repair of nerve defect with acellular nerve xenograft laden with allogenic adipose-derived stem cells in rhesus monkey

Objective To study the effects after repair of nerve defect with acellular nerve xenograft laden with allogenic adipose-derived stem cells (ADSCs)in rhesus monkey.Methods Experiment time:March 2011 to May 2013.Isolated from the popliteal fossa fat of male Rhesus monkey,ADSCs were microinjected and planted on porcine acellular nerve xenograft by chemical extraction.The radial nerve defect models with 25 mm in length were established in 10 healthy adult female rhesus monkeys,and they were divided into group A,B and C (n =5) randomly,which were repaired with acellular nerve xenograft laden with allogenic ADSCs,acellular nerve xenograft only and nerve autograft.At 5 months after operation,the evaluation of wrist extension,electrophysiology and histological examination of the grafts and wrist extensor muscles were perform for nerve regeneration.Results At 5 months after operation,the recovery rate of wrist extension angle of group A,B and C were (80.53 ± 15.30) ％,(69.06 ± 7.02)％ and (99.91 ± 22.16)％ respectively.The conduction of radial nerve was recovered by electrophysiologcal detection and nerve fibers have regenerated by histological examination.In all indexes,group A was better than group B,while group C was better than group A and group B,which there was no statistical significance.Conclusion Porcine acellular nerve xenograft could repair 25 mm long radial nerve defect effectively in monkeys,whcih laden with allogenic ADSCs may be better than no laden with allogenic ADSCs. Key words: Acellular nerve graft; Adipose-derived stem cells; Xenograft; Rhesus monkey

The cellular immune mechanism after transfer of chemically extracted acellular nerve xenografts.

Severe peripheral nerve defect by injuries causing functional loss require nerve grafting. Autograft has limitations for clinical use because it results in the creation of a new nerve injury and the generation of donor site morbidity. Based on these limitations, nerve allografts and xenografts provide a readily accessible alternative strategy. The aim of the present study was to observe the immune mechanism underlying the rejection of chemically extracted acellular nerve xenografts, and further evaluate immunogenicity of chemically treated acellular nerve grafts for clinical applications. A total of 160 BALB/c mice were randomly divided into a negative contrast group (NC, 40 mice), a fresh autograft group (AG, 40 mice), a fresh xenogeneic nerve group (FXN, 40 mice) and a chemically extracted acellular xenogeneic nerve group (CEXN, 40 mice). Various types of nerve grafts were implanted into the thigh muscle of BALB/C mice in the corresponding groups. At 3, 7, 14 and 28 days post-operation, the mice (10 mice from each group) were sacrificed and their spleens were extracted. The spleens were ground into paste. The erythrocytes and other cells were lysed using distilled water and the T lymphocytes were collected. Fluorescein isothiocyanate (FITC) -labeled monoclonal antibodies (CD3, CD4, CD8, CD25, IL-2, IFN-γ and TNF-α) were then added to the solution. The Fluorescence Activated Cell Sorting (FACS) was used to determine the positivity rate of the cells combined with the monoclonal antibodies above. No significant statistical differences were observed between the CEXN, NC and AG groups, so that no obvious immune rejections were observed among the chemically extracted acellular nerve xenografts.

Rat‐derived processed nerve allografts support more axon regeneration in rat than human‐derived processed nerve xenografts

Processed nerve allografts are increasingly used as "off the shelf" nerve replacements for surgically bridging nerve gaps. Benchmarking the regenerative capacity of a commercially available human-derived nerve or xenograft in a rat nerve injury model would provide a convenient platform for future studies seeking to modify the processed nerve graft. Human and rat processed nerve grafts were used to bridge a 14 mm defect in a Sprague-Dawley rat sciatic nerve. Reversed autografts served as a positive control group. Twelve weeks following surgery, the distal nerve stumps were retrograde labeled and harvested for histology and histomorphometry. The cross-sectional areas of the human- and rat-derived processed nerve grafts were similar. Neuron counts and myelinated axon counts following use of the human-derived processed xenografts were decreased compared with those obtained from both the rat-derived processed nerve allografts and the autografts; the rat-derived processed nerve allografts were statistically equivalent to autografts. Measures of nerve fiber diameter and myelination revealed inferior axon regeneration maturity in both processed nerve grafts compared with autografts. Processed xenografts showed significantly reduced regeneration compared with autografts or processed allografts indicating that cross-species immunological reactions are important considerations in this rat model.

A crucial role of IL-17 and IFN-γ during acute rejection of peripheral nerve xenotransplantation in mice.

Nerve injuries causing segmental loss require nerve grafting. However, autografts and allografts have limitations for clinical use. Peripheral nerve xenotransplantation has become an area of great interest in clinical surgery research as an alternative graft strategy. However, xenotransplant rejection is severe with cellular immunity, and Th1 cells play an important role in the process. To better understand the process of rejection, we used peripheral nerve xenografts from rats to mice and found that mononuclear cells expressing IFN-γ and IL-17 infiltrated around the grafts, and IFN-γ and IL-17 producing CD4+ and CD8+ T cells increased during the process of acute rejection. The changes of IL-4 level had no significant difference between xenotransplanted group and sham control group. The rejection of xenograft was significantly prevented after the treatment of IL-17 and IFN-γ neutralizing antibodies. These data suggest that Th17 cells contribute to the acute rejection process of peripheral nerve xenotransplant in addition to Th1 cells.

Sciatic nerve repair by acellular nerve xenografts implanted with BMSCs in rats xenograft combined with BMSCs

Acellular nerves possess the structural and biochemical features similar to those of naive endoneurial tubes, and have been proved bioactive for allogeneil graft in nerve tissue engineering. However, the source of allogenic donators is restricted in clinical treatment. To explore sufficient substitutes for acellular nerve allografts (ANA), we investigated the effectiveness of acellular nerve xenografts (ANX) combined with bone marrow stromal cells (BMSCs) on repairing peripheral nerve injuries. The acellular nerves derived from Sprague-Dawley rats and New Zealand rabbits were prepared, respectively, and BMSCs were implanted into the nerve scaffolds and cultured in vitro. All the grafts were employed to bridge 1 cm rat sciatic nerve gaps. Fifty Wistar rats were randomly divided into five groups (n = 10 per group): ANA group, ANX group, BMSCs-laden ANA group, BMSCs-laden ANX group, and autologous nerve graft group. At 8 weeks post-transplantation, electrophysiological study was performed and the regenerated nerves were assayed morphologically. Besides, growth-promoting factors in the regenerated tissues following the BMSCs integration were detected. The results indicated that compared with the acellular nerve control groups, nerve regeneration and functional rehabilitation for the xenogenic nerve transplantation integrated with BMSCs were advanced significantly, and the rehabilitation efficacy was comparable with that of the autografting. The expression of neurotrophic factors in the regenerated nerves, together with that of brain-derived neurotrophic factor (BDNF) in the spinal cord and muscles were elevated largely. In conclusion, ANX implanted with BMSCs could replace allografts to promote nerve regeneration effectively, which offers a reliable approach for repairing peripheral nerve defects.

Regeneration in, and properties of, extracted peripheral nerve allografts and xenografts

When not enough conventional autologous nerve grafts are available, alternatives are needed to bridge nerve defects. Our aim was to study regeneration of nerves in chemically-extracted acellular nerve grafts from frogs, mice, humans (fresh and stored sural nerve), pigs and rats when defects in rat sciatic nerves were bridged. Secondly, we compared two different extraction procedures (techniques described by Sondell et al. and Hudson et al.) with respect to how efficiently they supported axonal outgrowth, and remaining laminin and myelin basic protein (MBP), after extraction. Isografts (rat) and xenografts (mouse) were transplanted into defects in rat sciatic nerves. Acellular nerve allografts from rats, extracted by the Sondell et al's technique, had an appreciably longer axonal outgrowth based on immunohistochemical staining of neurofilaments, than acellular nerve xenografts except those from the pig. Among acellular xenografts there was considerably longer axonal outgrowth in the grafts from pigs compared with those from humans (fresh), but there were no other differences among the xenografts with respect to axonal outgrowth. Axonal outgrowth in acellular nerve xenografts from mice, extracted by the method described by Sondell et al. was longer than in those extracted by Hudson et al's method, while there was no difference in outgrowth between extracted nerve isografts from rats. Electrophoretic analysis of extracted acellular nerve grafts showed remaining laminin, but not MBP, after both extraction procedures. These preserved laminin and removed MBP in acellular nerve grafts. Such grafts can be used to reconstruct short defects in nerves irrespective of their origin. However, selecting and matching a suitable combination of graft and host species may improve axonal outgrowth.

Harvey Cushing's Innovative Attempt at Xenotransplanting a Rabbit Spinal Cord in a Patient After Resection of a Peripheral Nerve Tumor in 1902

A review of Harvey Cushing's surgical cases at Johns Hopkins Hospital revealed new information about his early work using nerve xenografts to repair peripheral nerve injuries. The Johns Hopkins Hospital surgical records from 1896 to 1912 were reviewed. A single case in which Cushing used a xenograft to repair a peripheral nerve defect was selected for further study. In August 1902, a 23-year-old woman presented with tingling and numbness in her left foot and focal tenderness in the popliteal region. Cushing performed an exploratory operation, revealing an encapsulated tumor originating from the internal popliteal nerve. After resecting the segment of involved nerve, Cushing harvested the spinal cord from a rabbit and used it to span the 18-cm defect. At a 5-month postoperative follow-up, according to Cushing's clinical notes, the patient had partially regained some sensation in her leg and foot. Seven months later, the patient presented with a local tumor recurrence, and her leg was amputated. An examination of the amputated specimen demonstrated that the xenograft was still intact without gross evidence of xenograft rejection. Despite its questionable functional success, we report a previously unpublished operative case by Harvey Cushing in which a rabbit spinal cord was transplanted into a human to bridge a sciatic nerve gap. This sheds light on the potential for animal tissue as a source for the treatment of neurological disease in humans.

Pluripotent Hair Follicle Neural Crest Stem-Cell-Derived Neurons and Schwann Cells Functionally Repair Sciatic Nerves in Rats

In this paper, we constructed a novel acellular nerve xenograft (ANX) seeded with neurons and Schwann cells to bridge long-distance gaps in rat sciatic nerves. The neurons and Schwann cells were induced from Sprague Dawley (SD) rat hair follicle neural crest stem cells with sonic hedgehog/retinoic acid and neuregulin 1, respectively. Fifty male SD rats were randomly divided into two groups (n = 25): ANX + cells group and ANX group. A 4-cm-long sciatic nerve defect was created on the right hind limb and bridged with cell-seeded ANX in ANX + cells group or ANX alone in ANX group. We found that the implanted neurons and Schwann cells could survive by 4 weeks and as far as 52 weeks posttransplantation. In implanted grafts, chemical synaptic structures were also found under transmission electron microscope and confirmed with immunostaining of synapsin 1, a synaptic marker. The number of regenerated axons in ANX + cells group was higher than that in ANX group (P < 0.01). This novel implantation of neurons and Schwann cells via acellular nerve graft may provide an alternative way for repairing peripheral nerve defect.

Immune Responses Following Mouse Peripheral Nerve Xenotransplantation in Rats

Xenotransplantation offers a potentially unlimited source for tissues and organs for transplantation, but the strong xenoimmune responses pose a major obstacle to its application in the clinic. In this study, we investigate the rejection of mouse peripheral nerve xenografts in rats. Severe intragraft mononuclear cell infiltration, graft distension, and necrosis were detected in the recipients as early as 2 weeks after mouse nerve xenotransplantation. The number of axons in xenografts reduced progressively and became almost undetectable at week 8. However, mouse nerve xenotransplantation only led to a transient and moderate increase in the production of Th1 cytokines, including IL-2, IFN-γ, and TNF-α. The data implicate that cellular immune responses play a critical role in nerve xenograft rejection but that further identification of the major effector cells mediating the rejection is required for developing effective means to prevent peripheral nerve xenograft rejection.

Expression of carbohydrate xenoantigens on porcine peripheral nerve

The use of thin easily revascularized cutaneous nerve autografts, which has been the gold standard, or the alternative use of nerve allografts or artificial grafts for nerve reconstructing have all their pros and cons. Nerve xenotransplantation may offer a potential alternative. In a potential pig to human nerve xenograft transplantation set-up several porcine antigen barriers have to be considered such as carbohydrate antigens system like the blood group A/O, the Galalpha1-3Gal (alphaGal) and the Hanganutziu-Deicher (HD) antigens. The swine leukocyte protein antigens system may also have to bee considered. The knowledge of the antigen expression on pig peripheral nerves is today limited. The present study describes the distribution of glycolipid based carbohydrate xenoantigens in ischiadicus nerve from blood group A and O pigs. Glycolipid fractions were separated on thin layer chromatography plates and immunostained with human AB sera, biotinylated Griffonia simplicifolia isolectin B4, monoclonal antibodies reacting with the HD antigen and with blood group A antigens based on different core saccharide structures. In addition, the subcellular distribution of alphaGal and HD antigens were studied by light- and electron-microscopical immunohistochemistry. The total amount of neutral glycolipids was 15 mg/g tissue for both blood group A and O nerves with mono-glycosylceramides as the dominating component. The total amount of acidic glycolipids (gangliosides and sulpholipids) was 9 mg/g tissue for both the blood group O and A nerves with sulphatides as the dominating components. Analyses of the glycolipid fractions showed strong expression of both the alphaGal and the HD antigens in nerves from both blood group A and O pigs. In addition, small amounts of blood group A antigens were expressed in nerves from blood group A pigs. Staining of neutral glycolipids from blood group A pigs using monoclonal antibodies reacting with A antigen having different core structures suggested that the A epitope expressed on pig ischiadicus nerves is based on the type 1 core chain structure. Light and electron microscopical studies on the alphaGal and HD-antigen distribution revealed that the neural cells were alphaGal antigen negative. Endothelial cells of blood vessels, and lymphatic and perineural cells expressed alphaGal antigen. Both endothelial cells and myelinized axons revealed positively labelled for the HD antigen.