Analysis of human acellular nerve allograft reconstruction of 64 injured nerves in the hand and upper extremity: a 3 year follow‐up study

Human acellular nerve allografts have been increasingly applied in clinical practice. This study was undertaken to investigate the functional outcomes of nerve allograft reconstruction for nerve defects in the upper extremity. A total of 64 patients from 13 hospitals were available for this follow‐up study after nerve repair using human acellular nerve allografts. Sensory and motor recovery was examined according to the international standards for motor and sensory nerve recovery. Subgroup analysis and logistic regression analysis were conducted to identify the relationship between the known factors and the outcomes of nerve repair. Mean follow‐up time was 355 ± 158 (35–819) days; mean age was 35 ± 11 (14–68) years; average nerve gap length was 27 ± 13 (10–60) mm; no signs of infection, tissue rejection or extrusion were observed among the patients; 48/64 (75%) repaired nerves experienced meaningful recovery. Univariate analysis showed that site and gap length significantly influenced prognosis after nerve repair using nerve grafts. Delay had a marginally significant relationship with the outcome. A multivariate logistic regression model revealed that gap length was an independent predictor of nerve repair using human acellular nerve allografts. The results indicated that the human acellular nerve allograft facilitated safe and effective nerve reconstruction for nerve gaps 10–60 mm in length in the hand and upper extremity. Factors such as site and gap length had a statistically significant influence on the outcomes of nerve allograft reconstruction. Gap length was an independent predictor of nerve repair using human acellular nerve allografts. Copyright © 2016 John Wiley & Sons, Ltd.     

Accelerated outgrowth in cross‐facial nerve grafts wrapped with adipose‐derived stem cell sheets

In this study, we devised a novel cross‐facial nerve grafting (CFNG) procedure using an autologous nerve graft wrapped in an adipose‐derived stem cell (ADSC) sheet that was formed on a temperature‐responsive dish and examined its therapeutic effect in a rat model of facial palsy. The rat model of facial paralysis was prepared by ligating and transecting the main trunk of the left facial nerve. The sciatic nerve was used for CFNG, connecting the marginal mandibular branch of the left facial nerve and the marginal mandibular branch of the right facial nerve. CFNG alone, CFNG coated with an ADSC suspension, and CFNG wrapped in an ADSC sheet were transplanted in eight rats each, designated the CFNG, suspension, and sheet group, respectively. Nerve regeneration was compared histologically and physiologically. The time to reinnervation, assessed by a facial palsy scoring system, was significantly shorter in the sheet group than in the other two groups. Evoked compound electromyography showed a significantly higher amplitude in the sheet group (4.2 ± 1.3 mV) than in the suspension (1.7 ± 1.2 mV) or CFNG group (1.6 ± 0.8 mV; p < .01). Toluidine blue staining showed that the number of myelinated fibers was significantly higher in the sheet group (2,450 ± 687) than in the suspension (1,645 ± 659) or CFNG group (1,049 ± 307; p < .05). CFNG in combination with ADSC sheets, prepared using temperature‐responsive dishes, promoted axonal outgrowth in autologous nerve grafts and reduced the time to reinnervation.     

A laminin‐2‐derived peptide promotes early‐stage peripheral nerve regeneration in a dual‐component artificial nerve graft

The DLTIDDSYWYRI motif (Ln2‐P3) of human laminin‐2 has been reported to promote PC12 cell attachment through syndecan‐1; however, the in vivo effects of Ln2‐P3 have not been studied. In Schwann cells differentiated from skin‐derived precursors, the peptide was effective in promoting cell attachment and spreading in vitro. To examine the effects of Ln2‐P3 in peripheral nerve regeneration in vivo, we developed a dual‐component poly(p‐dioxanone) (PPD)/poly(lactic‐co‐glycolic acid) (PLGA) artificial nerve graft. The novel graft was coated with scrambled peptide or Ln2‐P3 and used to bridge a 10 mm defect in rat sciatic nerves. The dual‐component nerve grafts provided tensile strength comparable to that of a real rat nerve trunk. The Ln2‐P3‐treated grafts promoted early‐stage peripheral nerve regeneration by enhancing the nerve regeneration rate and significantly increased the myelinated fibre density compared with scrambled peptide‐treated controls. These findings indicate that Ln2‐P3, combined with tissue‐engineering scaffolds, has potential biomedical applications in peripheral nerve injury repair. Copyright © 2012 John Wiley & Sons, Ltd.     

A polylactic acid non‐woven nerve conduit for facial nerve regeneration in rats

This study developed a biodegradable nerve conduit with PLA non‐woven fabric and evaluated its nerve regeneration‐promoting effect. The buccal branch of the facial nerve of 8 week‐old Lewis rats was exposed, and a 7 mm nerve defect was created. A nerve conduit made of either PLA non‐woven fabric (mean fibre diameter 460 nm), or silicone tube filled with type I collagen gel, or an autologous nerve, was implanted into the nerve defect, and their nerve regenerative abilities were evaluated 13 weeks after the surgery. The number of myelinated neural fibres in the middle portion of the regenerated nerve was the highest for PLA tubes (mean ± SD, 5051 ± 2335), followed by autologous nerves (4233 ± 590) and silicone tubes (1604 ± 148). Axon diameter was significantly greater in the PLA tube group (5.17 ± 1.69 µm) than in the silicone tube group (4.25 ± 1.60 µm) and no significant difference was found between the PLA tube and autograft (5.53 ± 1.93 µm) groups. Myelin thickness was greatest for the autograft group (0.65 ± 0.24 µm), followed by the PLA tube (0.54 ± 0.18 µm) and silicone tube (0.38 ± 0.12 µm) groups, showing significant differences among the three groups. The PLA non‐woven fabric tube, composed of randomly‐connected PLA fibres, is porous and has a number of advantages, such as sufficient strength to maintain luminal structure. The tube has demonstrated a comparable ability to induce peripheral nerve regeneration following autologous nerve transplantation. Copyright © 2012 John Wiley & Sons, Ltd.     

Electrospun silk fibroin‐based neural scaffold for bridging a long sciatic nerve gap in dogs

Silk fibroin (SF)‐derived silkworms represent a type of highly biocompatible biomaterial for tissue engineering. We have previously investigated biocompatibility of SF with neural cells isolated from the central nervous system or peripheral nerve system in vitro, and also developed a SF‐based nerve graft conduit or tissue‐engineered nerve grafts by introducing bone marrow mesenchymal stem cells, as support cells, into SF‐based scaffold and evaluated the outcomes of peripheral nerve repair in a rat model. As an extension of the previous study, the electrospun technique was performed here to fabricate SF‐based neural scaffold inserted with silk fibres for bridging a 30‐mm‐long sciatic nerve gap in dogs. Assessments including functional, histological and morphometrical analyses were applied 12 months after surgery. All the results indicated that the SF‐based neural scaffold group achieved satisfactory regenerative outcomes, which were close to those achieved by autologous nerve grafts as the golden‐standard for peripheral nerve repair. Overall, our results raise a potential possibility for the translation of SF‐based electrospun neural scaffolds as an alternative to nerve autografts into the clinic.     

Nanofibrous nerve conduit‐enhanced peripheral nerve regeneration

Fibre structures represent a potential class of materials for the formation of synthetic nerve conduits due to their biomimicking architecture. Although the advantages of fibres in enhancing nerve regeneration have been demonstrated, in vivo evaluation of fibre size effect on nerve regeneration remains limited. In this study, we analyzed the effects of fibre diameter of electrospun conduits on peripheral nerve regeneration across a 15‐mm critical defect gap in a rat sciatic nerve injury model. By using an electrospinning technique, fibrous conduits comprised of aligned electrospun poly (ε‐caprolactone) (PCL) microfibers (981 ± 83 nm, Microfiber) or nanofibers (251 ± 32 nm, Nanofiber) were obtained. At three months post implantation, axons regenerated across the defect gap in all animals that received fibrous conduits. In contrast, complete nerve regeneration was not observed in the control group that received empty, non‐porous PCL film conduits (Film). Nanofiber conduits resulted in significantly higher total number of myelinated axons and thicker myelin sheaths compared to Microfiber and Film conduits. Retrograde labeling revealed a significant increase in number of regenerated dorsal root ganglion sensory neurons in the presence of Nanofiber conduits (1.93 ± 0.71 × 10³ vs. 0.98 ± 0.30 × 10³ in Microfiber, p < 0.01). In addition, the compound muscle action potential (CMAP) amplitudes were higher and distal motor latency values were lower in the Nanofiber conduit group compared to the Microfiber group. This study demonstrated the impact of fibre size on peripheral nerve regeneration. These results could provide useful insights for future nerve guide designs. Copyright © 2012 John Wiley & Sons, Ltd.     

Regenerative effect of adipose tissue‐derived stem cells transplantation using nerve conduit therapy on sciatic nerve injury in rats

This study proposed a biodegradable GGT nerve conduit containing genipin crosslinked gelatin annexed with tricalcium phosphate (TCP) ceramic particles for the regeneration of peripheral nerves. Cytotoxicity tests revealed that GGT‐extracts were non‐toxic and promoted proliferation and neuronal differentiation in the induction of stem cells (i‐ASCs) derived from adipose tissue. Furthermore, the study confirmed the effectiveness of a GGT/i‐ASCs nerve conduit as a guidance channel in the repair of a 10‐mm gap in the sciatic nerve of rats. At eight weeks post‐implantation, walking track analysis showed a significantly higher sciatic function index (SFI) (P < 0.05) in the GGT/i‐ASC group than in the autograft group. Furthermore, the mean recovery index of compound muscle action potential (CMAP) differed significantly between GGT/i‐ASCs and autograft groups (P < 0.05), both of which were significantly superior to the GGT group (P < 0.05). No severe inflammatory reaction in the peripheral nerve tissue at the site of implantation was observed in either group. Histological observation and immunohistochemistry revealed that the morphology and distribution patterns of nerve fibers in the GGT/i‐ASCs nerve conduits were similar to those of the autografts. These promising results achieved through a combination of regenerative cells and GGT nerve conduits suggest the potential value in the future development of clinical applications for the treatment of peripheral nerve injury. Copyright © 2012 John Wiley & Sons, Ltd.     

Nerve lengthening and subsequent end‐to‐end repair yield more favourable outcomes compared with autograft repair of rat sciatic nerve defects

Outcomes of end‐to‐end nerve repairs are more successful compared with outcomes of repairs bridged by nerve grafts. However, end‐to‐end repairs are not always possible for large nerve gaps, as excessive tension may cause catastrophic failure. In this study, we built on previous nerve‐lengthening studies to test the hypotheses that gradual lengthening of the proximal stump across a large nerve gap enables an end‐to‐end repair and such a repair results in more favourable regenerative outcomes than autografts, which represent the gold standard in bridging nerve gaps. To test these, we compared structural and functional outcomes in Lewis rats after repair of sciatic nerve gaps using either autografts or a novel compact internal fixator device, which was used to lengthen proximal nerve stumps towards the distal stump over 2 weeks, prior to end‐to‐end repair. Twelve weeks after the initial injury, outcomes following nerve lengthening/end‐to‐end repair were either comparable or superior in every measure compared with repair by autografting. The sciatic functional index was not significantly different between groups at 12 weeks. However, we observed a reduced rate of contracture and corresponding significant increase in paw length in the lengthening group. This functional improvement was consistent with structural regeneration; axonal growth distal to the injury was denser and more evenly distributed compared with the autograft group, suggesting substantial regeneration into both tibial and peroneal branches of the sciatic nerve. Our findings show that end‐to‐end repairs following nerve lengthening are possible for large gaps and that this strategy may be superior to graft‐based repairs.     

端侧吻合与自体神经移植神经再生的比较研究

目的比较周围神经端侧吻合与自体神经移植后神经再生的效果,为临床提供实验依据。方法选用Wister大白鼠60只,随机分成3组。A组:切断左侧腓神经1cm,造成神经缺损,取对侧相应的腓神经桥接缺损。B组:切断左侧腓神经,在邻近的胫神经干外膜上开一1mm小窗,将腓神经远端吻合到胫神经干侧方开窗处。C组:方法同B组,但束膜开窗。各组分别于术后8、12周取材并进行大体、组织学、形态定量学和电生理检测。结果自体神经移植体修复神经缺损后,再生神经的数目、有髓神经纤维截面积、运动神经传导速度均优于端侧吻合的外膜、束膜开窗组(P<0.05);外膜开窗组与束膜开窗组之间无显著性差异(P>0.05)。结论自体神经移植修复大鼠周围神经缺损,其再生神经纤维质量优于端侧吻合法。     

Repairing peripheral nerve defects with revascularized tissue‐engineered nerve based on a vascular endothelial growth factor‐heparin sustained release system

To enhance the angiogenic capacity of tissue‐engineered peripheral nerves, we have constructed revascularized tissue‐engineered nerves based on a vascular endothelial growth factor (VEGF)‐heparin sustained release system. However, the effects of the repair of large peripheral nerve defects are not known. In this study, we used the above revascularized tissue‐engineered nerve to repair large nerve defects in rats. The repair effects were observed through general observation, functional evaluation of nerve regeneration, ultrasound examination, neural electrophysiology, wet weight ratio of bilateral gastrocnemius muscle, histological evaluation, and quantitative real‐time polymerase chain reaction (PCR) analysis. The results showed that the tissue‐engineered peripheral nerve based on a VEGF‐heparin sustained release system can achieve early vascularization and restore blood supply in the nerve graft area. The realization of early vascularization in the area of the nerve defect greatly promotes the speed of nerve regeneration and reconstruction in the area of the nerve defect, which greatly advances the process of nerve repair and reconstruction and accelerates the restoration of the normal morphological structure and function of peripheral nerves.     

Testosterone propionate can promote effects of acellular nerve allograft‐seeded bone marrow mesenchymal stem cells on repairing canine sciatic nerve

Peripheral human nerves fail to regenerate across long tube implants (>2 cm), and tissue‐engineered nerve grafts represent a promising treatment alternative. The present study aims to investigate the testosterone propionate (TP) repair effect of acellular nerve allograft (ANA) seeded with allogeneic bone marrow mesenchymal stem cells (BMSCs) on 3‐cm canine sciatic nerve defect. ANA cellularized with allogeneic BMSCs was implanted to the defect, and TP was injected into the lateral crus of the defected leg. The normal group, the autograft group, the ANA + BMSCs group, the ANA group, and the nongrafted group were used as control. Five months postoperatively, dogs in the TP + ANA + BMSCs group were capable of load bearing, normal walking, and skipping, the autograft group and the ANA + BMSCs group demonstrated nearly the same despite a slight limp. The compound muscle action potentials (CMAPs) on the injured side to the uninjured site in the TP + ANA + BMSCs group were significantly higher than that in the ANA + BMSCs group [CMAPs ratio at A: F(3, 20) = 191.40; 0.02, CMAPs ratio at B: F(3, 20) = 43.27; 0.01]. Masson trichrome staining revealed that in the TP + ANA + BMSCs group, both the diameter ratio of the myelinated nerve and the thickness ratio of regenerated myelin sheath were significantly larger than that in the other groups [the diameter of myelinated nerve fibers: F(3, 56) = 13.45; P < .01, the thickness ratio of regenerated myelin sheath: F(3, 56) = 51.25; P < .01]. In conclusion, TP could significantly increase the repairing effects of the ANA + BMSCs group, and their combination was able to repair 3‐cm canine sciatic nerve defect. It therefore represents a promising therapeutic approach.     

Decellularized nerve matrix hydrogel and glial‐derived neurotrophic factor modifications assisted nerve repair with decellularized nerve matrix scaffolds

Nerve defects are challenging to address clinically without satisfactory treatments. As a reliable alternative to autografts, decellularized nerve matrix scaffolds (DNM‐S) have been widely used in clinics for surgical nerve repair. However, DNM‐S remain inferior to autografts in their ability to support nerve regeneration for long nerve defects. In this study, we systematically and clearly presented the nano‐architecture of nerve‐specific structures, including the endoneurium, basement membrane and perineurium/epineurium in DNM‐S. Furthermore, we modified the DNM‐S by supplementing decellularized nerve matrix hydrogel (DNMG) and glial‐derived neurotrophic factor (GDNF) and then bridged a 50‐mm sciatic nerve defect in a beagle model. Fifteen beagles were randomly divided into three groups (five per group): an autograft group, DNM‐S group and GDNF‐DNMG‐modified DNM‐S (DNM‐S/GDNF@DNMG) group. DNM‐S/GDNF@DNMG, as optimized nerve grafts, were used to bridge nerve defects in the same manner as in the DNM‐S group. The repair outcome was evaluated by behavioural observations, electrophysiological assessments, regenerated nerve tissue histology and reinnervated target muscle examinations. Compared with the DNM‐S group, limb function, electrophysiological responses and histological findings were improved in the DNM‐S/GDNF@DNMG group 6 months after grafting, reflecting a narrower gap between the effects of DNM‐S and autografts. In conclusion, modification of DNM‐S with DNMG and GDNF enhanced nerve regeneration and functional recovery, indicating that noncellular modification of DNM‐S is a promising method for treating long nerve defects.     

Cell‐free artificial implants of electrospun fibres in a three‐dimensional gelatin matrix support sciatic nerve regeneration in vivo

Surgical repair of larger peripheral nerve lesions requires the use of autologous nerve grafts. At present, clinical alternatives to avoid nerve transplantation consist of empty tubes, which are only suitable for the repair over short distances and have limited success. We developed a cell‐free, three‐dimensional scaffold for axonal guidance in long‐distance nerve repair. Sub‐micron scale fibres of biodegradable poly‐ε‐caprolactone (PCL) and collagen/PCL (c/PCL) blends were incorporated in a gelatin matrix and inserted in collagen tubes. The conduits were tested by replacing 15‐mm‐long segments of rat sciatic nerves in vivo. Biocompatibility of the implants and nerve regeneration were assessed histologically, with electromyography and with behavioural tests for motor functions. Functional repair was achieved in all animals with autologous transplants, in 12 of 13 rats that received artificial implants with an internal structure and in half of the animals with empty nerve conduits. In rats with implants containing c/PCL fibres, the extent of recovery (compound muscle action potentials, motor functions of the hind limbs) was superior to animals that had received empty implants, but not as good as with autologous nerve transplantation. Schwann cell migration and axonal regeneration were observed in all artificial implants, and muscular atrophy was reduced in comparison with animals that had received no implants. The present design represents a significant step towards cell‐free, artificial nerve bridges that can replace autologous nerve transplants in the clinic. Copyright © 2017 John Wiley & Sons, Ltd.     

Sonographic Evaluation of the Peripheral Nerve in Diabetic Patients

Objective. Early detection of nerve dysfunction is important to provide appropriate care for patients with diabetic polyneuropathy. The aim of this study was to assess the echo intensity of the peripheral nerve and to evaluate the relationship between nerve conduction study results and sonographic findings in patients with type 2 diabetes mellitus. Methods. Thirty patients with type 2 diabetes (mean ± SD, 59.8 ± 10.2 years) and 32 healthy volunteers (mean, 53.7 ± 13.9 years) were enrolled in this study. The cross‐sectional area (CSA) and echo intensity of the peripheral nerve were evaluated at the carpal tunnel and proximal to the wrist (wrist) of the median nerve and in the tibial nerve at the ankle. Results. There was a significant increase in the CSA and hypoechoic area of the nerve in diabetic patients compared with controls (wrist, 7.1 ± 2.0 mm², 62.3% ± 3.0%; ankle, 8.9 ± 2.8 mm², 57.6% ± 3.9%; and wrist, 9.8 ± 3.7 mm², 72.3% ± 6.6%; ankle, 15.0 ± 6.1 mm², 61.4% ± 5.3% in controls and diabetic patients, respectively; P < .05). Cross‐sectional areas were negatively correlated with reduced motor nerve conduction velocity and delayed latency. Conclusions. These results suggest that sonographic examinations are useful for the diagnosis of diabetic neuropathy.     

Transplantation of embryonic motor neurons into peripheral nerve combined with functional electrical stimulation restores functional muscle activity in the rat sciatic nerve transection model

Reinnervation of denervated muscle by motor neurons transplanted into the peripheral nerve may provide the potential to excite muscles artificially with functional electrical stimulation (FES). Here we investigated whether transplantation of embryonic motor neurons into peripheral nerve combined with FES restored functional muscle activity in adult Fischer 344 rats after transection of the sciatic nerve. One week after sciatic nerve transection, cell culture medium containing (cell transplantation group, n = 6) or lacking (surgical control group, n = 6) dissociated embryonic spinal neurons was injected into the distal stump of the tibial and peroneal nerves. Electrophysiological and tissue analyses were performed in the cell transplantation and surgical control groups 12 weeks after transplantation, as well as a in naïve control group (n = 6) that received no surgery. In the cell transplantation group, ankle angle was measured during gait, with and without FES of the peroneal nerve. Ankle angle at mid‐swing was more flexed during gait with FES (26.6 ± 8.7°) than gait without FES (51.4 ± 12.8°, p = 0.011), indicating that transplantated motor neurons in conjunction with FES restored ankle flexion in gait, even though no neural connection between central nervous system and muscle was present. These results indicate that transplantation of embryonic motor neurons into peripheral nerve combined with FES can provide a novel treatment strategy for paralysed muscles. Copyright © 2013 John Wiley & Sons, Ltd.     

Sonographic Evaluation of the Median Nerve in Diabetic Patients

Objective. Diabetes mellitus is becoming a major cause of premature disability in Japan, and peripheral neuropathy is a common complication of diabetes. The aim of this study was to evaluate the relationship between the results of nerve conduction studies (NCS) and the size of the nerve determined by sonography in diabetic patients. Methods. Twenty diabetic patients (mean age ± SD, 57.1 ± 13.6 years) and 20 healthy volunteers (mean, 61.1 ± 8.9 years) were enrolled in this study. Patients' wrists that had symptoms of carpal tunnel syndrome were not included in the study; those that were included had negative Phalen test results. We then divided the patients into 2 groups (patients with and without diabetic symmetric polyneuropathy [DPN]). The cross‐sectional area (CSA) was measured in the carpal tunnel 5 cm proximal to the wrist and elbow joint of the median nerve. Results. There was a significant increase in the CSA in patients with DPN in the carpal tunnel compared with the control participants (P < .01) and patients without DPN (P < .01). The CSA in the carpal tunnel showed a significant correlation with the motor nerve conduction velocity (r = ?0.473). Conclusions. The CSA of the median nerve in the carpal tunnel of patients with DPN is greater than that in patients without DPN and healthy individuals and correlates with NCS.     

Ultrasound‐guided plasma rich in growth factors injections and scaffolds hasten motor nerve functional recovery in an ovine model of nerve crush injury

In the present study we evaluated the motor recovery process of peripheral nerve injury (PNI), based on electrophysiological and histomorphometric criteria, after treatment with plasma rich in growth factors (PRGF) injections and scaffolds in an ovine model. Three groups of sheep underwent a nerve crush lesion: the first group (n = 3) was left to recover spontaneously (SR); the second group was administered saline injections (SI; n = 5) and a third group (n = 6) received PRGF injections and scaffolds immediately after the crush injury. At post‐intervention week 8, 70% of sheep in the PRGF group were CMAP‐positive, with no electrophysiological response in the rest of the groups. Histomorphometric analysis 12 weeks after the surgical intervention revealed that the average axonal density of the SR (1184 ± 864 axons/µm²) and SI (3109 ± 2450 axons/µm²) groups was significantly inferior to the control (8427 ± 2433 axons/µm²) and also inferior to the PRGF group (5276 ± 4148 axons/µm²), showing no significant differences between the control and PRGF groups. The axonal size of the SR and SI groups was significantly smaller compared with the control group (18 ± 4 µm²), whereas the axonal size of the PRGF group (6 ± 5 µm²) did not show statistical differences from the control. Morphometry of the target muscles indicated that the PRGF group had the lowest percentage volume reduction 12 weeks after the crush injury. The PRGF group had larger muscle fibre areas than the SI and SR groups, although the differences did not reach statistical significance. Overall, these data suggest that the PRGF injections and scaffolds hastened functional axon recovery and dampened atrophy of the target muscles in an ovine model. Copyright © 2015 John Wiley & Sons, Ltd.     

Post‐ischaemic angiogenic therapy using in vivo prevascularized ascorbic acid‐enriched myocardial artificial grafts improves heart function in a rat model

Angiogenesis plays a key role in post‐ischaemic myocardial repair. We hypothesized that epicardial implantation of an ascorbic acid (AA)‐enriched myocardial artificial graft (MAG), which has been prevascularized in the recipients' own body, promotes restoration of the ischaemic heart. Gelatin patches were seeded with GFP–luciferase‐expressing rat cardiomyoblasts and enriched with 5 μm AA. Grafts were prevascularized in vivo for 3 days, using a renal pouch model in rats. The MAG patch was then implanted into the same rat's ischaemic heart following myocardial infarction (MI). MAG‐treated animals (MAG group, n = 6) were compared to untreated infarcted animals as injury controls (MI group, n = 6) and sham‐operated rats as healthy controls (healthy group, n = 7). In vivo bioluminescence imaging indicated a decrease in donor cell survival by 83% during the first week post‐implantation. Echocardiographic and haemodynamic assessment 4 weeks after MI revealed that MAG treatment attenuated left ventricular (LV) remodelling (LV end‐systolic volume, 0.31 ± 0.13 vs 0.81 ± 0.01 ml, p < 0.05; LV end‐diastolic volume 0.79 ± 0.33 vs 1.83 ± 0.26 ml, p < 0.076) and preserved LV wall thickness (0.21 ± 0.03 vs 0.09 ± 0.005 cm, p < 0.05) compared to the MI group. Cardiac output was higher in MAG than MI (51.59 ± 6.5 vs 25.06 ± 4.24 ml/min, p < 0.01) and comparable to healthy rats (47.08 ± 1.9 ml/min). Histology showed decreased fibrosis, and a seven‐fold increase in blood vessel density in the scar area of MAG compared to MI group (15.3 ± 1.1 vs 2.1 ± 0.3 blood vessels/hpf, p < 0.0001). Implantation of AA‐enriched prevascularized grafts enhanced vascularity in ischaemic rat hearts, attenuated LV remodelling and preserved LV function. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrophysiological assessment of a peptide amphiphile nanofiber nerve graft for facial nerve repair

Facial nerve injury can cause severe long‐term physical and psychological morbidity. There are limited repair options for an acutely transected facial nerve not amenable to primary neurorrhaphy. We hypothesize that a peptide amphiphile nanofiber neurograft may provide the nanostructure necessary to guide organized neural regeneration. Five experimental groups were compared, animals with (1) an intact nerve, (2) following resection of a nerve segment, and following resection and immediate repair with either a (3) autograft (using the resected nerve segment), (4) neurograft, or (5) empty conduit. The buccal branch of the rat facial nerve was directly stimulated with charge balanced biphasic electrical current pulses at different current amplitudes whereas nerve compound action potentials (nCAPs) and electromygraphic responses were recorded. After 8 weeks, the proximal buccal branch was surgically reexposed and electrically evoked nCAPs were recorded for groups 1–5. As expected, the intact nerves required significantly lower current amplitudes to evoke an nCAP than those repaired with the neurograft and autograft nerves. For other electrophysiologic parameters such as latency and maximum nCAP, there was no significant difference between the intact, autograft, and neurograft groups. The resected group had variable responses to electrical stimulation, and the empty tube group was electrically silent. Immunohistochemical analysis and transmission electron microscopy confirmed myelinated neural regeneration. This study demonstrates that the neuroregenerative capability of peptide amphiphile nanofiber neurografts is similar to the current clinical gold standard method of repair and holds potential as an off‐the‐shelf solution for facial reanimation and potentially peripheral nerve repair.     

In vitro characterization of a nanostructured fibrin agarose bio‐artificial nerve substitute

Neural tissue engineering is focused on the design of novel biocompatible substitutes to repair peripheral nerve injuries. In this paper we describe a nanostructured fibrin–agarose bioartificial nerve substitute (NFABNS), based on nanostructured fibrin–agarose hydrogels (FAHs) with human adipose‐derived mesenchymal stem cells (HADMSCs). These NFABNSs were mechanically characterized and HADMSCs behaviour was evaluated using histological and ultrastructural techniques. Mechanical characterization showed that the NFABNSs were resistant, flexible and elastic, with a high deformation capability. Histological analyses carried out in vitro during 16 days revealed that the number of HADMSCs decreased over time, with a significant increase after 16 days. HADMSCs formed cell clusters and degraded the surrounding scaffold during this time; additionally, HADMSCs showed active cell proliferation and cytoskeletal remodelling, with a progressive synthesis of extracellular matrix molecules. Finally, this study demonstrated that it is possible to generate biologically active and mechanically stable tissue‐like substitutes with specific dimensions, based on the use of HADMSCs, FAHs and a nanostructure technique. However, in vivo analyses are needed to demonstrate their potential usefulness in peripheral nerve repair. Copyright © 2015 John Wiley & Sons, Ltd.