Nerve guides seeded with autologous schwann cells improve nerve regeneration

This study evaluates the ability of Schwann cells (SCs) transplanted into a nerve guide to improve regeneration and reinnervation after sciatic nerve resection and repair, leaving a 6-mm gap, in the mouse. SCs were isolated from predegenerated adult sciatic nerves and expanded in culture using a chemically defined medium. Syngeneic, isogeneic, and autologous SCs were suspended in Matrigel and seeded in resorbable, permeable poly(l-lactide-co-epsilon-caprolactone) guides at 150,000 cells/tube. Guides containing SCs were compared to guides filled with Matrigel alone and with peroneal nerve autografts. Functional reinnervation was assessed by noninvasive methods to determine recovery of sweating, nociceptive, sensory, and motor functions in the hindpaw during 4 months postoperation. Morphological analysis of the regenerated nerves was performed at the end of follow-up. The group with an autograft achieved faster and higher levels of reinnervation and higher number of regenerated myelinated fibers than groups repaired by tubulization. The immunogenicity of transplanted SCs influenced the outcome of nerve regeneration. Transplants of autologous SCs resulted in slightly lower levels of reinnervation than autografts, but higher recovery and number of regenerated fibers reaching the distal nerve than transplants of isologous and syngeneic SCs, although most of the differences were not statistically significant. Syngeneic SCs did not improve regeneration with respect to acellular guides. Prelabeled transplanted SCs were found to survive into the guide 1-3 months after implantation, to a larger number when they were autologous than syngeneic. Cellular prostheses composed of a resorbable guide seeded with autologous SCs appear as an alternative for repairing long gaps in injured nerves, approaching the success of autografts.     

Effects of FK506 on nerve regeneration and reinnervation after graft or tube repair of long nerve gaps.

We compared the effects of FK506 administration on regeneration and reinnervation after sciatic nerve resection and repair with an autologous graft or with a silicone tube leaving a 6-mm gap in the mouse. Functional reinnervation was assessed by noninvasive methods to determine recovery of motor, sensory, and sweating functions in the hindpaw over 4 months after operation. Morphometric analysis of the regenerated nerves was performed at the end of follow-up. The nerve graft allowed for faster and higher levels of reinnervation in the four functions tested than silicone tube repair. Treatment with FK506 (for the first 9 weeks only) resulted in a slight, although not significant, improvement of the onset of reinnervation and of the maximal degree of recovery achieved after autografting. The recovery of pain sensibility and of the compound nerve action potentials in the digital nerves, which directly depend on axonal regeneration, showed better progression with FK506 than reinnervation of muscles and sweat glands, which require reestablishment of synaptic contacts with target cells. The myelinated fibers in the regenerated nerve showed a more mature appearance in the FK506-treated rats. However, FK506 showed a marginal effect in situations in which regeneration was limited, as in a silicone tube bridging a 6-mm gap in the mouse sciatic nerve. In conclusion, treatment with FK506 improved the rate of functional recovery after nerve resection and autograft repair.     

Effects of motor and sensory nerve transplants on amount and specificity of sciatic nerve regeneration

Nerve regeneration after complete transection does not allow for adequate functional recovery mainly because of lack of selectivity of target reinnervation. We assessed if transplanting a nerve segment from either motor or sensory origin may improve specifically the accuracy of sensory and motor reinnervation. For this purpose, the rat sciatic nerve was transected and repaired with a silicone guide containing a predegenerated segment of ventral root (VR) or dorsal root (DR), compared to a silicone guide filled with saline. Nerve regeneration and reinnervation was assessed during 3 months by electrophysiologic and functional tests, and by nerve morphology and immunohistochemistry against choline acetyltransferase (ChAT) for labeling motor axons. Functional tests showed that reinnervation was successful in all the rats. However, the two groups with a root allotransplant reached higher degrees of reinnervation in comparison with the control group. Group VR showed the highest reinnervation of muscle targets, whereas Group DR had higher levels of sensory reinnervation than VR and saline groups. The total number of regenerated myelinated fibers was similar in the three groups, but the number of ChAT+ fibers was slightly lower in the VR group in comparison with DR and saline groups. These results indicate that a predegenerated root nerve allotransplant enhances axonal regeneration, leading to faster and higher levels of functional recovery. Although there is not clear preferential reinnervation, regeneration of motor axons is promoted at early times by a motor graft, whereas reinnervation of sensory pathways is increased by a sensory graft.     

Histologic assessment of sciatic nerve regeneration following resection and graft or tube repair in the mouse

The present study determines the number and morphology of myelinated fibers that regenerate after resection of the mouse sciatic nerve. In different groups of mice, a resection of 4 or 6 mm of the sciatic nerve was left unrepaired, repaired with silicone or collagen guides or by an autologous nerve graft of the same or smaller calibre. Regeneration was examined, under light microscopy, 3 months after operation and quantified by morphometric analysis of light micrographs of cross-sectional nerve fibers. The results show that, without repair, few nerve fibers reach the distal nerve stump, while tubulization or autografts allowed better regeneration. Tube repair allowed a comparable degree of regeneration to that of an autograft with 4 mm gaps, but lower with 6 mm gaps. Regeneration was limited with a gap of 6 mm in silicone tubes, but was successful in half the mice with collagen tubes. The size and myelination of regenerated fibers were below normal values in all experimental groups, although they were closer to normal with sciatic autografts than after smaller grafts and tubulization. There were no signs of secondary degeneration in the nerve regenerates within silicone and collagen tubes. ? 1996 Elsevier Science Ireland Ltd. All rights reserved.     

Peripheral nerve regeneration through bioresorbable and durable nerve guides

We compared reinnervation of target organs after sciatic nerve resection and repair by tubulization with biodurable tubes of silicone and teflon, or bioresorbable nerve guides of collagen and poly(L-lactide-co-6-caprolactone) (PLC) leaving a 6 mm gap in different groups of mice. All tubes were of 1 mm inside diameter and thin-walled (50 to 250 microm). Functional reinnervation was assessed by noninvasive methods to determine recovery of sweating, sensory and motor functions in the hindpaw repeatedly during 5 months postoperation. PLC guides allowed faster and higher levels of reinnervation for the four functions tested than collagen and silicone tubes, while teflon tubes gave the lowest levels of recovery. Regenerative reinnervation by thin nociceptive and sudomotor fibers was higher than by large sensory and alphamotor fibers in all groups. Resorbable tubes promoted regeneration in a higher proportion of mice than durable tubes. In cases with effective regeneration the nerve cable was multifascicular, with mild to moderate mononuclear cell infiltrates and a thin newly formed perineurium. The number of myelinated fibers was higher in PLC and silicone tubes than in collagen and teflon tubes. There was only minimal inflammatory reaction within the remnants of collagen tubes, but not in the other materials. PLC tubes of slow reabsorption rate seem useful for repairing long gaps in injured nerves.     

The effects of an autologous transplant on patterns of regeneration in rat sciatic nerve

Autologous transplants are often used in repair of peripheral nerve injury. Quantitative evaluation of the results of such a transplant is obviously desirable. In previous study, we determined numerical and cytologic parameters of the regeneration that followed transection of rat sciatic nerve, but no transplant was used. This work now serves as a basis for evaluating the use of an autologous transplant in the same transection paradigm. Our procedure is to remove 8 mm of sciatic nerve in the thigh. The removed segment is then put into the center of a silicone tube and the proximal and distal stumps of the severed nerve are placed into the ends of the tube. The data show: (1) a high percentage of successful regenerations; (2) a relatively large nerve in the gap; (3) a typical outer perineurium underlying the epineurium; (4) a well-developed fascicular perineurium; and (5) approximately equal numbers of myelinated and unmyelinated axons in the gap and distal stump. If a transplant is not used there are: (1) a greater number of failures of regeneration; (2) a smaller nerve in the gap; (3) a less well-developed fascicular perineurium; (4) unequal numbers of axons in the gap as compared to the distal stump; and (5) no outer perineurium forms. The presence of a typical outer perineurium after a transplant and its absence if a transplant is not used is probably the most striking cytologic difference between the two paradigms. The equal numbers of axons in the gap and distal stump following regeneration after transplantation presumably indicate that all axons in the gap enter the distal stump without branching or ending blindly, a situation that is presumably beneficial and contrasts with the findings when a transplant is not used. Both paradigms show a remarkable increase in the density of blood vessels in the regenerated nerve in the gap between the two stumps. These findings will serve as a basis for further studies on the mechanisms of peripheral nerve regeneration.     

FK506 enhances regeneration of axons across long peripheral nerve gaps repaired with collagen guides seeded with allogeneic Schwann cells

We assessed the effects of FK506 administration on regeneration after a 6-mm gap repair with a collagen guide seeded with allogeneic Schwann cells (SCs) in the mouse sciatic nerve. SCs were isolated from predegenerated adult sciatic nerves and expanded in culture using a defined medium, before being seeded in the collagen guide embedded in Matrigel. Functional reinnervation was evaluated by noninvasive methods to determine recovery of motor, sensory, and autonomic functions in the hindpaw over 4 months postoperation. Histological analysis of the regenerated nerves was performed at the end of the study. Using simple collagen guides for tubulization repair, treatment with an immunosuppressant dose of FK506 (5 mg/kg/day) resulted in significant improvement of the onset and the degree of reinnervation. While the introduction of allogeneic SCs did not improve regeneration versus a collagen guide filled only with Matrigel, treatment with FK506 allowed for successful regeneration in all the mice and for significant improvement in the levels of functional recovery. Compared with the untreated group, there was greater survival of transplanted pre-labeled SCs in the FK506-treated animals. Morphologically, the best nerve regeneration (in terms of nerve caliber and numbers of myelinated axons) was obtained with SC-seeded guides from FK506-treated animals. Thus, FK506 should be considered as adjunct therapy for various types of tubulization repair.     

Chondrotinase ABC enhances axonal regeneration across nerve gaps.

We evaluated the effects of chondroitinase ABC on axonal regeneration across peripheral nerve gaps. We compared axonal regeneration after 15-mm tibial nerve resection and repair with a silicone tube filled with type I collagen gel (negative control group), with a silicone tube filled with type I collagen gel containing chondroitinase ABC at three different concentrations (2.5 units/mL, 5 units/mL, 10 units/mL) (chondroitinase ABC groups), and with an autologous nerve segment (nerve autograft group). Electrophysiological and histological assessments were carried out 12 weeks after surgery. In the electrophysiological study, compound muscle action potentials (CMAPs) and nerve conduction velocities (NCVs) were recorded in all groups except the negative control group. Although both CMAPs and NCVs were highest in the nerve autograft group, there were no significant differences among the three chondroitinase ABC groups in either parameter. Histological findings were consistent with electrophysiological results. Based on these findings, we conclude that topical injection of chondroitinase ABC can significantly increase the critical length of nerve gap repair by tubulization or artificial nerve placement.     

Sciatic nerve regeneration after autologous sural nerve transplantation in the rat

The present study is concerned with the question as to whether the size of a nerve used as a transplant to bridge a gap between the stumps of transected nerves has a bearing on the number of axons and the cytological structure of the regenerate. The paradigm is rat sciatic nerve transection with 8 mm of nerve removed with the stumps placed in a silicone tube and two strands of the smaller sural nerve used as bridging transplants. The comparisons are with previously published results where the transplant, which is the removed piece of sciatic nerve, is exactly matched in size and with no transplant in the same regeneration paradigm. One surprising finding is that the size of the transplant does not seem to determine the size of the regenerated nerve. The cytological structure of the regenerated nerve is related to the size of the transplant, however, in that the proportion of axons that regenerate inside and outside the transplanted perineurial tubes differs in relation to the size of the transplant. In addition, although there is an increase in the number of blood vessels in all of these paradigms, the greatest increase is with the sural nerve transplants. The key finding in the study, however, is the similarity in numbers of regenerated axons in the gap, distal stump and tributary nerves when regeneration after sciatic nerve transplantation is compared with regeneration after sural nerve transplantation. Thus, notwithstanding the cytologic differences of the two types of regenerate, regenerated axon numbers are approximately the same. The conclusion is that the size of the transplant determines neither the size of the regenerate nor the numbers of regenerated axons in this paradigm. On the assumption that regeneration is better when axonal numbers are closer to normal, the non-matched sural nerve transplant is approximately equal to the matched sciatic nerve transplant and both are superior to the regeneration that takes place in the absence of a transplant in this paradigm.     

Motoneurotrophins derived from limb buds protect the motoneurons in anterior spinal cord after nerve injury and promote nerve regeneration

The effects of limb bud-derived motoneurotrophins (LBMNTs) as seen in the motoneurons in the anterior spinal cord and sciatic nerve regeneration of adult rats, were evaluated in the present study. A nerve regeneration chamber with a nerve gap of 9 mm was created by suturing the proximal and distal ends of a random sciatic nerve into a silicone tube after removal of a 5 mm piece of nerve in the distal end, The chamber of the experimental group was filled with 34.34 μg LBMNTs and PBS (0.01 mol/ml, pH 7.0),and the control group with PBS only. At 1 day, 4 days, 1 week, 2 weeks, 4 weeks and 6 weeks post surgery, the content of acetylcholine esterase (AchE) and acid phosphatase (ACP) of the anterior spinal cord (injured side) was quantified, and the corresponding motoneuron's ultrastructure and the existant ratio were also examined. Meanwhile, the regenerated nerve from within the silicone tube was examined at 2, 4 and 6 weeks post surgery for histological studies at both the light microscopic and ultrastructural levels. The experimental group showed a smaller decrease of AchE and an increase of ACP, a larger existant ratio of motoneurons, better ultrastructure and a more mature regenerated nerve based on a larger diameter of the regenerated nerve trunk, a greater number of axons and thicker myelin sheaths than the control group. So it was concluded that LBMNTs had a high activity of protecting motoneurons in the anterior spinal cord after nerve injury and promoting nerve regeneration, and it may be a new source of neurotrophic factors (NTFs).     

Evaluation of the long-term regenerative potential in an experimental nerve amputee model

In this study, we evaluated the long-term maintenance of regenerated axons in an experimental nerve amputee model. The sciatic nerve of adult rats was transected and repaired with a silicone tube leaving a short gap; the distal nerve segment was again transected 10 mm distally and the distal stump either introduced in a capped silicone chamber (amputee group) or connected to denervated targets (tibial branch into the gastrocnemius muscle and peroneal nerve apposed to skin) (reinnervation group). Morphological studies were performed at 2.5, 6, and 9 months after surgery. In all cases, axons regenerated across the silicone tube and grew in the distal nerve segment. In the amputee group, the morphological results show the expected features of a neuroma that is formed when regenerating axons are prevented from reaching the end organs, with a large number of axonal profiles indicative of regenerative sprouting. The number of myelinated axons counted at the distal nerve was sustained over 9 months follow-up, indicating that regenerated axons are maintained chronically. Immunohistochemical labeling showed maintained expression of choline acetyltransferase, calcitonin gene-related peptide, and growth-related peptides 43 in the distal neuroma at 6 and 9 months. Reconnection of the distal nerve to foreign targets mildly improved the pattern of nerve regeneration, decreasing the number of excessive sprouts. These results indicate that axons regenerated may be eventually interfaced with external input-output systems over long time, even if ending in the absence of distal targets as will occur in amputee limbs.     

Processed allografts and type I collagen conduits for repair of peripheral nerve gaps

Autografting is the gold standard in the repair of peripheral nerve injuries that are not amenable to end‐to‐end coaptation. However, because autografts result in donor‐site defects and are a limited resource, an effective substitute would be valuable. In a rat model, we compared isografts with Integra NeuraGen® (NG) nerve guides, which are a commercially available type I collagen conduit, with processed rat allografts comparable to AxoGen's Avance® human decellularized allograft product. In a 14‐mm sciatic nerve gap model, isograft was superior to processed allograft, which was in turn superior to NG conduit at 6 weeks postoperatively (P < 0.05 for number of myelinated fibers both at midgraft and distal to the graft). At 12 weeks, these differences were no longer apparent. In a 28‐mm graft model, isografts again performed better than processed allografts at both 6 and 22 weeks; regeneration through the NG conduit was often insufficient for analysis in this long graft model. Functional tests confirmed the superiority of isografts, although processed allografts permitted successful reinnervation of distal targets not seen in the NG conduit groups. Processed allografts were inherently non‐immunogenic and maintained some internal laminin structure. We conclude that, particularly in a long gap model, nerve graft alternatives fail to confer the regenerative advantages of an isograft. However, AxoGen processed allografts are superior to a currently available conduit‐style nerve guide, the Integra NeuraGen®. They provide an alternative for reconstruction of short nerve gaps where a conduit might otherwise be used. Muscle Nerve, 2008     

Inaccurate projection of rat soleus motoneurons: A comparison of nerve repair techniques

The objectives of this study were 1) to determine the degree to which soleus motoneurons find their appropriate target following crush and transection injuries to the sciatic nerve, and 2) to determine whether repair of a transected nerve with a silicone tube leads to greater specificity of reinnervation and recovery of muscle function than the standard epineurial suture repair method. Sixty adult female Sprague-Dawley rats were randomly assigned to one of three sciatic nerve injury groups: crush injury, transection with epineurial suture repair, or transection with a silicone tube repair. The degree to which soleus motoneurons were able to find their appropriate target following a sciatic nerve injury was examined using a double labeling dye technique in which the original soleus motor pool was labeled with fast blue and reinnervating motoneurons were labeled with Dil. Soleus motoneurons were able to find their appropriate target following a crush injury. The accuracy of reinnervation following a transection injury and repair, however, was relatively poor. Only 14% of the original soleus motoneurons found the correct target following a transection injury. Repair of a lesioned nerve with a silicone tube and a 5-mm gap as opposed to epineurial sutures did not increase the specificity of reinnervation or the degree of muscle recovery. © 1997 John Wiley & Sons, Inc.     

Permeable tubes increase the length of the gap that regenerating axons can span

After placement of stumps of transected rat sciatic nerve in an impermeable tube, the maximum gap the axons can span is 10 mm. The present study shows that the regenerating axons cross much longer gaps if the tube is made permeable. This improvement does not require another nerve as a transplant nor the preplacement of extracellular materials in the tube. Possible mechanisms for this improvement are discussed.     

Regeneration of lesioned cholinergic septal neurons of the adult rat can be promoted by peripheral nerve grafts and a fibrin-fibronectin-containing matrix of peripheral regeneration chambers

Axonal regeneration of septal cholinergic neurons was examined after lesion of the septohippocampal pathway of the adult rat and implantation of tubes containing peripheral cellular or acellular substrates. After empty tube implantation, no regenerated structures were observed in the conduit. However, after implanting tubes filled with sections of predegenerated sciatic nerves or a fibrin-fibronectin-containing matrix provided by peripheral regeneration chambers, numerous regenerated axons were detected 6 weeks after the operation. At the electron microscopic level, regenerated axons were observed in the grafted sciatic nerves in contact with Schwann cells but also in contact with astrocytes which were able to migrate and send processes into the graft. After fibrin-fibronectin-containing-matrix implantation, the regenerated structure between septum and hippocampus was composed mainly of fibroblasts, astrocytes and regenerated axons associated to these central glial cells.     

Superior muscle reinnervation after autologous nerve graft or poly-L-lactide-epsilon-caprolactone (PLC) tube implantation in comparison to silicone tube repair

Recovery after peripheral nerve injury depends not only on the amount of reinnervation, but also on its accuracy. The rat sciatic nerve was subjected to an 8 mm long gap lesion repaired either by autograft (AG, n = 6) or tubulization with impermeable silicone tube (SIL, n = 6) or permeable tube of poly-L-lactide-epsilon-caprolactone (PLC, n = 8). Recordings of the compound muscle action potential (CMAP) from gastrocnemius (mGC), tibialis anterior (mTA) and plantar (mPL) muscles were performed 90 days after injury to assess the amount of muscle reinnervation. The CMAP amplitude achieved in mGC, mTA and mPL was similar in after nerve autograft (39%, 42%, 22% of control values) and PLC tube implantation (37%, 36%, 24%) but lower with SIL tube (29%, 30%, 14%). The nerve fascicles projecting into each of these muscles were then transected and retrograde tracers (Fluoro Gold, Fast Blue, DiI) were applied to quantify the percentage of motoneurons with single or multiple branches to different targets. The total number of labeled motoneurons for the three muscles did not differ in autografted rats (1186 +/- 56; mean +/- SEM) with respect to controls (1238 +/- 82), but was reduced with PLC tube (802 +/- 101) and SIL tube (935 +/- 213). The percentage of neurons with multiple projections was lower after autograft and PLC tube (6%) than with SIL tube (10%). Considering the higher CMAP amplitude and lower number of neurons with multiple projections, PLC nerve conduits seem superior to SIL tubes and a suitable alternative to autografts for the repair of long gaps.     

Reorganization and orientation of regenerating nerve fibres,perineurium, and epineurium in preformed mesothelial tubes – an experimental study on the sciatic nerve of rats

Regeneration of severed peripheral nerves is unfortunately often incomplete, due to loss of nerve fibers and neuroma formation. A new approach is presented with the intention of improving the conditions for nerve repair. In the first of the two stages, a pseudosynovial tube is formed around a silicone rubber rod, surrounded by a stainless steel spiral, which was placed in the backs of rats. This tube, in the second stage, is used as a free “tube graft” to bridge gaps of about 10–12-mm lengths in the severed sciatic nerve. The tube was kept open by the metal spiral. Regenerating nerve fibers with their sprouts grew into the initially open space in the tube. A new nerve trunk was formed, comprised of closely packed myelinated and unmyelinated axons, organized into fascicles. Demonstration by electron microscopy and by EMG recording of reinnervation of foot muscles supported successful long-term results. The fascicles were delimited by perineurial and epineurial sheaths and, furthermore, showed signs of maturation. It was also demonstrated that the nerve-fiber regeneration ceased after a few weeks if there was no distal nerve inserted into the tube. The importance of optimizing the interaction between local factors and regenerating nerve fibers for reestablishment of functionally valuable motor units is discussed.     

应用肌膜瓣包裹、羊膜管预置聚乳酸-羟基乙酸微丝模拟周围神经再生

背景：周围神经损伤部位的微环境状况是影响神经再生的重要因素之一。周围神经损伤后，良好的神经再生微环境有利于保护受损神经元、促进轴突的有效再生。 目的：应用肌膜瓣包裹、羊膜管预置聚乳酸-羟基乙酸微丝，充填大鼠自体周围神经组织浆模拟周围神经再生微环境，探讨其修复坐骨神经缺损的可行性。 设计、时间及地点：随机对照动物实验，于2006-06/2007-10在广东医学院实验动物中心完成。 材料：清洁级2月龄SD大鼠30只，随机分为实验组、对照组、标准组3组，每组10只，右侧为实验侧，左侧为正常对照侧。取健康、足月、顺产的新鲜胎儿羊膜(产妇知情同意) 制备羊膜基质膜。用医用Vicryl缝线和羊膜基质膜制备聚乳酸-羟基乙酸微丝桥接物。 方法：大鼠切除坐骨神经6.0 mm，自然回缩建立坐骨神经缺损模型。实验组采用带蒂肌膜瓣、人羊膜管预置Vicryl微丝并充填大鼠自体坐骨神经组织浆；对照组采用单纯人羊膜管充填大鼠自体坐骨神经组织浆；标准组采用自体神经移植，桥接大鼠坐骨神经缺损。 主要观察指标：术后8，12周行大体观察、组织学检查、胫前肌湿质量、有髓神经纤维通过率及神经电生理学检测。 结果：术后12周，实验组、标准组肌萎缩有所恢复，对照组则恢复不明显。实验、标准组患侧胫前肌色泽红润，饱满富有弹性；对照组色泽相对较暗，弹性度较差。术后8，12周3组胫前肌恢复率组间比较，术后12周3组有髓神经纤维总数、截面积，神经移植体血管数和血管截面积组间比较，以及小腿三头肌复合肌动作电位幅值组间比较，差异均有显著性意义(P < 0.05），其中标准组神经纤维再生质量最佳，实验组优于对照组。 结论：肌膜转位、羊膜管预置聚乳酸-羟基乙酸微丝，并填充大鼠自体周围神经组织浆导管能较好的模拟周围神经再生之微环境，促进神经纤维再生，但与自体神经移植尚有差距。     

Delayed nerve regeneration in streptozotocin diabetic rats

Nerve regeneration across a 10-mm gap was delayed in streptozotocin diabetic rats 3 and 4 weeks after transecting the sciatic nerve. Opposite ends of each cut nerve were introduced into a silicone tube, leaving a 10-mm gap. Electron microscopy was used to evaluate the progress of regeneration in sections at 2-mm intervals across the 10-mm gap. After 3 weeks, control axons had bridged the 10-mm gap, and myelin sheaths extended for 6-8 mm. By contrast, axons and their myelin sheaths were seen no further than 2 mm from the proximal stump in diabetic animals. By 4 weeks, axons had bridged the gap in diabetics; however, they appeared immature and showed dystrophic changes. The findings suggest that although regeneration does occur in diabetic nerves, it is significantly delayed and qualitatively impaired.     

Skin-derived stem cells transplanted into resorbable guides provide functional nerve regeneration after sciatic nerve resection

The regeneration in the peripheral nervous system is often incomplete and the treatment of severe lesions with nerve tissue loss is primarily aimed at recreating nerve continuity. Guide tubes of various types, filled with Schwann cells, stem cells, or nerve growth factors are attractive as an alternative therapy to nerve grafts. In this study, we evaluated whether skin-derived stem cells (SDSCs) can improve peripheral nerve regeneration after transplantation into nerve guides. We compared peripheral nerve regeneration in adult rats with sciatic nerve gaps of 16 mm after autologous transplantation of GFP-labeled SDSCs into two different types of guides: a synthetic guide, obtained by dip coating with a L-lactide and trimethylene carbonate (PLA-TMC) copolymer and a collagen-based guide. The sciatic function index and the recovery rates of the compound muscle action potential were significantly higher in the animals that received SDSCs transplantation, in particular, into the collagen guide, compared to the control guides filled only with PBS. For these guides the morphological and immunohistochemical analysis demonstrated an increased number of myelinated axons expressing S100 and Neurofilament 70, suggesting the presence of regenerating nerve fibers along the gap. GFP positive cells were found around regenerating nerve fibers and few of them were positive for the expression of glial markers as S-100 and glial fibrillary acidic protein. RT-PCR analysis confirmed the expression of S100 and myelin basic protein in the animals treated with the collagen guide filled with SDSCs. These data support the hypothesis that SDSCs could represent a tool for future cell therapy applications in peripheral nerve regeneration.