axon-Schwann Cell Research Articles

Loss of prohibitin 2 in Schwann cells dysregulates key transcription factors controlling developmental myelination.

Schwann cells are critical for the proper development and function of the peripheral nervous system (PNS), where they form a collaborative relationship with axons. Past studies highlighted that a pair of proteins called the prohibitins play major roles in Schwann cell biology. Prohibitins are ubiquitously expressed and versatile proteins. We have previously shown that while prohibitins play a crucial role in Schwann cell mitochondria for long-term myelin maintenance and axon health, they may also be present at the Schwann cell-axon interface during development. Here, we expand on this, showing that drug-mediated modulation of prohibitins in vitro disrupts myelination and confirming that Schwann cell-specific ablation of prohibitin 2 (Phb2) in vivo results in severe defects in radial sorting and myelination. We show in vivo that Phb2-null Schwann cells cannot effectively proliferate and the transcription factors EGR2 (KROX20), POU3F1 (OCT6), and POU3F2 (BRN2), necessary for proper Schwann cell maturation, are dysregulated. Schwann cell-specific deletion of Jun, a transcription factor associated with negative regulation of myelination, confers partial rescue of the developmental defect seen in mice lacking Schwann cell Phb2. Finally, we identify a pool of candidate PHB2 interactors that change their interaction with PHB2 depending on neuronal signals, and thus are potential mediators of PHB2-associated developmental defects. This work develops our understanding of Schwann cell biology, revealing that Phb2 may modulate the timely expression of transcription factors necessary for proper PNS development, and proposing candidates that may play a role in PHB2-mediated integration of axon signals in the Schwann cell.

Glia trigger endocytic clearance of axonal proteins to promote rodent myelination

Axons undergo striking changes in their content and distribution of cell adhesion molecules (CAMs) and ion channels during myelination that underlies the switch from continuous to saltatory conduction. These changes include the removal of a large cohort of uniformly distributed CAMs that mediate initial axon-Schwann cell interactions and their replacement by a subset of CAMs that mediate domain-specific interactions of myelinated fibers. Here, using rodent models, we examine the mechanisms and significance of this removal of axonal CAMs. We show that Schwann cells just prior to myelination locally activate clathrin-mediated endocytosis (CME) in axons, thereby driving clearance of a broad array of axonal CAMs. CAMs engineeredto resist endocytosis are persistently expressed along the axon and delay both PNS and CNS myelination. Thus, glia non-autonomously activate CME in axons to downregulate axonal CAMs and presumptively axo-glial adhesion. This promotes the transition from ensheathment to myelination while simultaneously sculpting the formation of axonal domains.

Peripheral Nervous System (PNS) Myelin Diseases.

This is a review of inherited and acquired causes of human demyelinating neuropathies and a subset of disorders that affect axon-Schwann cell interactions. Nearly all inherited demyelinating neuropathies are caused by mutations in genes that are expressed by myelinating Schwann cells, affecting diverse functions in a cell-autonomous manner. The most common acquired demyelinating neuropathies are Guillain-Barré syndrome and chronic, inflammatory demyelinating polyneuropathy, both of which are immune-mediated. An additional group of inherited and acquired disorders affect axon-Schwann cell interactions in the nodal region. Overall, these disorders affect the formation of myelin and its maintenance, with superimposed axonal loss that is clinically important.

Chemokine platelet factor 4 accelerates peripheral nerve regeneration by regulating Schwann cell activation and axon elongation.

Schwann cells in peripheral nerves react to traumatic nerve injury by attempting to grow and regenerate. However, it is unclear what factors play a role in this process. In this study, we searched a GEO database and found that expression of platelet factor 4 was markedly up-regulated after sciatic nerve injury. Platelet factor is an important molecule in cell apoptosis, differentiation, survival, and proliferation. Further, polymerase chain reaction and immunohistochemical staining confirmed the change in platelet factor 4 in the sciatic nerve at different time points after injury. Enzyme-linked immunosorbent assay confirmed that platelet factor 4 was secreted by Schwann cells. We also found that silencing platelet factor 4 decreased the proliferation and migration of primary cultured Schwann cells, while exogenously applied platelet factor 4 stimulated Schwann cell proliferation and migration and neuronal axon growth. Furthermore, knocking out platelet factor 4 inhibited the proliferation of Schwann cells in injured rat sciatic nerve. These findings suggest that Schwann cell-secreted platelet factor 4 may facilitate peripheral nerve repair and regeneration by regulating Schwann cell activation and axon growth. Thus, platelet factor 4 may be a potential therapeutic target for traumatic peripheral nerve injury.

EBP50 is a key molecule for the Schwann cell-axon interaction in peripheral nerves

Peripheral nerve injury disrupts the Schwann cell-axon interaction and the cellular communication between them. The peripheral nervous system has immense potential for regeneration extensively due to the innate plastic potential of Schwann cells (SCs) that allows SCs to interact with the injured axons and exert specific repair functions essential for peripheral nerve regeneration. In this study, we show that EBP50 is essential for the repair function of SCs and regeneration following nerve injury. The increased expression of EBP50 in the injured sciatic nerve of control mice suggested a significant role in regeneration. The ablation of EBP50 in mice resulted in delayed nerve repair, recovery of behavioral function, and remyelination following nerve injury. EBP50 deficiency led to deficits in SC functions, including proliferation, migration, cytoskeleton dynamics, and axon interactions. The adeno-associated virus (AAV)-mediated local expression of EBP50 improved SCs migration, functional recovery, and remyelination. ErbB2-related proteins were not differentially expressed in EBP50-deficient sciatic nerves following injury. EBP50 binds and stabilizes ErbB2 and activates the repair functions to promote regeneration. Thus, we identified EBP50 as a potent SC protein that can enhance the regeneration and functional recovery driven by NRG1-ErbB2 signaling, as well as a novel regeneration modulator capable of potential therapeutic effects.

YAP and TAZ regulate remyelination in the central nervous system.

Myelinating cells are sensitive to mechanical stimuli from their extracellular matrix. Ablation of YAP and TAZ mechanotransducers in Schwann cells abolishes the axon-Schwann cell recognition, myelination, and remyelination in the peripheral nervous system. It was unknown if YAP and TAZ are also required for myelination and remyelination in the central nervous system. Here we define the importance of oligodendrocyte (OL) YAP and TAZ in vivo, by specific deletion in oligodendroglial cells in adult OLs during myelin repair. Blocking YAP and TAZ expression in OL lineage cells did not affect animal viability or any major defects on OL maturation and myelination. However, using a mouse model of demyelination/remyelination, we demonstrate that YAP and TAZ modulate the capacity of OLs to remyelinate axons, particularly during the early stage of the repair process, when OL proliferation is most important. These results indicate that YAP and TAZ signaling is necessary for effective remyelination of the mouse brain.

First person – Clara Mutschler

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Clara Mutschler is first author on ‘Schwann cells are axo-protective after injury irrespective of myelination status in mouse Schwann cell–neuron cocultures’, published in JCS. Clara is a PhD student in the lab of Peter Arthur-Farraj at the John Van Geest Centre for Brain Repair, University of Cambridge, UK, investigating axon–Schwann cell interactions after peripheral nervous system injury.

Influence of cold-stimulated adipocyte supernatant on the expression of adhesion-related molecules in Schwann cell line

Bell's palsy is the most common form of facial nerve palsy. This study aimed to explore the pathogenesis of Bell's palsy by investigating the effect of cold-stimulated adipocyte supernatant on adhesion molecule expression in Schwann cell line. Schwann cells were cultured in regular or adipocyte-conditioned medium and analyzed using RNA sequencing. The mRNA expression of Schwann cell adhesion molecules melanoma cell adhesion molecule (MCAM), protocadherin 9 (PCDH9), and intercellular cell adhesion molecule 1 (ICAM1) was determined using real-time reverse-transcription polymerase chain reaction. Differentially expressed genes were identified, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were conducted. Compared with Schwann cells in 37 °C, the expression of MCAM, PCDH9, and ICAM1 was downregulated in Schwann cells treated with cold-stimulated adipocyte supernatant compared with Schwann cells in 37 °C. Adipocytes subjected to cold exposure may weaken the adhesion capacity of Schwann cells and disrupt the local homeostasis of Schwann cell–axon interactions by affecting the expression of MCAM, PCDH9, and ICAM1, ultimately leading to the development of demyelinating lesions.

A RhoA-mediated biomechanical response in Schwann cells modulates peripheral nerve myelination

Myelin improves axonal conduction velocity and is essential for nerve development and regeneration. In peripheral nerves, Schwann cells depend on bidirectional mechanical and biochemical signaling to form the myelin sheath but the mechanism underlying this process is not understood. Rho GTPases are integrators of “outside-in” signaling that link cytoskeletal dynamics with cellular architecture to regulate morphology and adhesion. Using Schwann cell-specific gene inactivation in the mouse, we discovered that RhoA promotes the initiation of myelination, and is required to both drive and terminate myelin growth at different stages of peripheral myelination, suggesting developmentally-specific modes of action. In Schwann cells, RhoA targets actin filament turnover, via Cofilin 1, actomyosin contractility and cortical actin-membrane attachments. This mechanism couples actin cortex mechanics with the molecular organization of the cell boundary to target specific signaling networks that regulate axon-Schwann cell interaction/adhesion and myelin growth. This work shows that RhoA is a key component of a biomechanical response required to control Schwann cell state transitions for proper myelination of peripheral nerves.

Deferoxamine Promotes Peripheral Nerve Regeneration by Enhancing Schwann Cell Function and Promoting Axon Regeneration of Dorsal Root Ganglion

Deferoxamine (DFO) is a potent iron chelator for clinical treatment of various diseases. Recent studies have also shown its potential to promote vascular regeneration during peripheral nerve regeneration. However, the effect of DFO on the Schwann cell function and axon regeneration remains unclear. In this study, we investigated the effects of different concentrations of DFO on Schwann cell viability, proliferation, migration, expression of key functional genes, and axon regeneration of dorsal root ganglia (DRG) through a series of in vitro experiments. We found that DFO improves Schwann cell viability, proliferation, and migration in the early stages, with an optimal concentration of 25 μM. DFO also upregulates the expression of myelin-related genes and nerve growth-promoting factors in Schwann cells, while inhibiting the expression of Schwann cell dedifferentiation genes. Moreover, the appropriate concentration of DFO promotes axon regeneration in DRG. Our findings demonstrate that DFO, with suitable concentration and duration of action, can positively affect multiple stages of peripheral nerve regeneration, thereby improving the effectiveness of nerve injury repair. This study also enriches the theory of DFO promoting peripheral nerve regeneration and provides a basis for the design of sustained-release DFO nerve grafts.

Evaluation and Comparison of the Effects of Mature Silkworm (Bombyx mori) and Silkworm Pupae Extracts on Schwann Cell Proliferation and Axon Growth: An In Vitro Study.

Silkworm products were first used by physicians more than 8500 years ago, in the early Neolithic period. In Persian medicine, silkworm extract has several uses for treating and preventing neurological, cardiac, and liver diseases. Mature silkworms (Bombyx mori) and their pupae contain a variety of growth factors and proteins that can be used in many repair processes, including nerve regeneration. The study aimed to evaluate the effects of mature silkworm (Bombyx mori), and silkworm pupae extract on Schwann cell proliferation and axon growth. Silkworm (Bombyx mori) and silkworm pupae extracts were prepared. Then, the concentration and type of amino acids and proteins in the extracts were evaluated by Bradford assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and liquid chromatograph-mass spectrometer (LC-MS/MS). Also, the regenerative potential of extracts for improving Schwann cell proliferation and axon growth was examined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay, electron microscopy, and NeuroFilament-200 (NF-200) immunostaining. According to the results of the Bradford test, the total protein content of pupae extract was almost twice that of mature worm extract. Also, SDS-PAGE analysis revealed numerous proteins and growth factors, such as bombyrin and laminin, in extracts that are involved in the repair of the nervous system. In accordance with Bradford's results, the evaluation of extracts using LC-MS/MS revealed that the number of amino acids in pupae extract was higher than in mature silkworm extract. It was found that the proliferation of Schwann cells at a concentration of 0.25 mg/mL in both extracts was higher than the concentrations of 0.01 and 0.05 mg/mL. When using both extracts on dorsal root ganglion (DRGs), an increase in length and number was observed in axons. The findings of this study demonstrated that extracts obtained from silkworms, especially pupae, can play an effective role in Schwann cell proliferation and axonal growth, which can be strong evidence for nerve regeneration, and, consequently, repairing peripheral nerve damage.

In Vitro Myelination of Peripheral Axons in a Coculture of Rat Dorsal Root Ganglion Explants and Schwann Cells.

The process of myelination is essential to enable rapid and sufficient signal transduction in the nervous system. In the peripheral nervous system, neurons and Schwann cells engage in a complex interaction to control the myelination of axons. Disturbances of this interaction and breakdown of the myelin sheath are hallmarks of inflammatory neuropathies and occur secondarily in neurodegenerative disorders. Here, we present a coculture model of dorsal root ganglion explants and Schwann cells, which develops a robust myelination of peripheral axons to investigate the process of myelination in the peripheral nervous system, study axon-Schwann cell interactions, and evaluate the potential effects of therapeutic agents on each cell type separately. Methodologically, dorsal root ganglions of embryonic rats (E13.5) were harvested, dissociated from their surrounding tissue, and cultured as whole explants for 3 days. Schwann cells were isolated from 3-week-old adult rats, and sciatic nerves were enzymatically digested. The resulting Schwann cells were purified by magnetic-activated cell sorting and cultured under neuregulin and forskolin-enriched conditions. After 3 days of dorsal root ganglion explant culture, 30,000 Schwann cells were added to one dorsal root ganglion explant in a medium containing ascorbic acid. The first signs of myelination were detected on day 10 of coculture, through scattered signals for myelin basic protein in immunocytochemical staining. From day 14 onward, myelin sheaths were formed and propagated along the axons. Myelination can be quantified by myelin basic protein staining as a ratio of the myelination area and axon area, to account for the differences in axonal density. This model provides experimental opportunities to study various aspects of peripheral myelination in vitro, which is crucial for understanding the pathology of and possible treatment opportunities for demyelination and neurodegeneration in inflammatory and neurodegenerative diseases of the peripheral nervous system.

Thermosensitive hydrogel carrying extracellular vesicles from adipose-derived stem cells promotes peripheral nerve regeneration after microsurgical repair.

Peripheral nerve injuries are commonly occurring traumas of the extremities; functional recovery is hindered by slow nerve regeneration (<1 mm/day) following microsurgical repair and subsequent muscle atrophy. Functional recovery after peripheral nerve repair is highly dependent on local Schwann cell activity and axon regeneration speed. Herein, to promote nerve regeneration, paracrine signals of adipose-derived stem cells were applied in the form of extracellular vesicles (EVs) loaded in a thermosensitive hydrogel (PALDE) that could solidify rapidly and sustain high EV concentration around a repaired nerve during surgery. Cell experiments revealed that PALDE hydrogel markedly promotes Schwann-cell migration and proliferation and axon outgrowth. In a rat sciatic nerve repair model, the PALDE hydrogel increased repaired-nerve conduction efficacy; contraction force of leg muscles innervated by the repaired nerve also recovered. Electromicroscopic examination of downstream nerves indicated that fascicle diameter and myeline thickness in the PALDE group (1.91 ± 0.61 and 1.06 ± 0.40 μm, respectively) were significantly higher than those in PALD and control groups. Thus, this EV-loaded thermosensitive hydrogel is a potential cell-free therapeutic modality to improve peripheral-nerve regeneration, offering sustained and focused EV release around the nerve-injury site to overcome rapid clearance and maintain EV bioactivity in vivo.

Structure and barrier functions of the perineurium and its relationship with associated sensory corpuscles: A review.

Peripheral nerves are provided with a blood-nerve barrier which prevents the invasion of harmful substances and pathogens, and also regulates metabolic and ionic homeostasis within nerve fascicles. The barrier functions are attributed to both the concentric layer of flattened cells in the perineurium and blood vessels running in the endoneurium. The perineurial cells develop continuous tight junctions as a diffusion barrier. In order to take up a predominant nutrient, glucose, the perineurium as well as endoneurial capillaries expresses GLUT1, a glucose transporter. An axon-Schwann cell complex within peripheral nerves utilizes glucose as a major energy source via the GLUT1, as does the brain. Under conditions of a reduced utilization of glucose, only the perineurial cells can transfer other nutrients, namely monocarboxylates such as ketone bodies and lactate via MCT1. Thus, MCT1 colocalizes with GLUT1 in the perineurium but not in endoneurial capillaries. To identify the cellular origins of the nerve sheath, marker proteins such as glial specific S100 protein, GLUT1, endoneurial CD34, and EMA (epithelial membrane antigen) are useful. Immunohistochemical findings for these markers are reviewed in this paper, focusing on the perineurium and endoneurium and their derivatives, Pacinian and Meissner corpuscles. Growing evidence throws light on the critical involvement of the nerve sheaths in the development, maintenance, and diseases of peripheral nerves.

Functional, morphological and molecular characteristics in a novel rat model of spinal sacral nerve injury-surgical approach, pathological process and clinical relevance

Spinal sacral nerve injury represents one of the most serious conditions associated with many diseases such as sacral fracture, tethered cord syndrome and sacral canal tumor. Spinal sacral nerve injury could cause bladder denervation and detrusor underactivity. There is limited clinical experience resolving spinal sacral nerve injury associated detrusor underactivity patients, and thus the treatment options are also scarce. In this study, we established a spinal sacral nerve injury animal model for deeper understanding and further researching of this disease. Forty 8 w (week) old Sprague Dawley rats were included and equally divided into sham (n = 20) and crush group (n = 20). Bilateral spinal sacral nerves of rats were crushed in crush group, and sham group received same procedure without nerve crush. Comprehensive evaluations at three time points (1 w, 4 w and 6 w) were performed to comprehend the nature process of this disease. According to urodynamic test, ultrasonography and retrograde urography, we could demonstrate severe bladder dysfunction after spinal sacral nerve injury along the observation period compared with sham group. These functional changes were further reflected by histological examination (hematoxylin-eosin and Masson’s trichrome staining) of microstructure of nerves and bladders. Immunostaining of nerve/bladder revealed schwann cell death, axon degeneration and collagen remodeling of bladder. Polymerase Chain Reaction results revealed vigorous nerve inflammation and bladder fibrosis 1 week after injury and inflammation/fibrosis returned to normal at 4 w. The CatWalk gait analysis was performed and there was no obvious difference between two groups. In conclusion, we established a reliable and reproducible model for spinal sacral nerve injury, this model provided an approach to evaluate the treatment strategies and to understand the pathological process of spinal sacral nerve injuries. It allowed us to understand how nerve degeneration and bladder fibrosis changed following spinal sacral nerve injury and how recovery could be facilitated by therapeutic options for further research.

Electrical Stimulation Increases Axonal Growth from Dorsal Root Ganglia Co-Cultured with Schwann Cells in Highly Aligned PLA-PPy-Au Microfiber Substrates.

Nerve regeneration is a slow process that needs to be guided for distances greater than 5 mm. For this reason, different strategies are being studied to guide axonal growth and accelerate the axonal growth rate. In this study, we employ an electroconductive fibrillar substrate that is able to topographically guide axonal growth while accelerating the axonal growth rate when subjected to an exogenous electric field. Dorsal root ganglia were seeded in co-culture with Schwann cells on a substrate of polylactic acid microfibers coated with the electroconductive polymer polypyrrole, adding gold microfibers to increase its electrical conductivity. The substrate is capable of guiding axonal growth in a highly aligned manner and, when subjected to an electrical stimulation, an improvement in axonal growth is observed. As a result, an increase in the maximum length of the axons of 19.2% and an increase in the area occupied by the axons of 40% were obtained. In addition, an upregulation of the genes related to axon guidance, axogenesis, Schwann cells, proliferation and neurotrophins was observed for the electrically stimulated group. Therefore, our device is a good candidate for nerve regeneration therapies.

Localisation of S100 Protein and Acetylated Tubulin in Sheep Pancreas

Abstract The pancreas plays a critical role in the control of nutritional homeostasis. It consists of two major parts, the exocrine pancreas, and the endocrine pancreas. In the present study S100 protein and acetylated α-tubulin were used to identify positive structures in both the exocrine and endocrine part of the ovine pancreas. In the exocrine part of the pancreas, a positive reaction to S100 protein was confined to centroacinar cells, intercalated, and intralobular ducts cells. In addition, the S100 protein was localized in the Schwann cells of nerve fibres. On the pancreatic islets, the S100 protein has been observed in Schwann cells of nerve axons, where they form a fine envelope that invests the islet surface. Inside the pancreatic islets, the Schwann cells positive for S100 protein envelope the endocrine cells of the islets. The difference in positivity of the S100 protein was found in relation to the endocrine cells. The relationship between endocrine cell positivity and positive exocrine duct cells was discussed. Acetylated α-tubulin (AT) was restricted to axons of the nerve fibres and was located within the connective tissue accompanying intralobular and inter-lobular ducts, and between secretory acini in close contact with secretory cells.

Betacellulin regulates peripheral nerve regeneration by affecting Schwann cell migration and axon elongation

BackgroundGrowth factors execute essential biological functions and affect various physiological and pathological processes, including peripheral nerve repair and regeneration. Our previous sequencing data showed that the mRNA coding for betacellulin (Btc), an epidermal growth factor protein family member, was up-regulated in rat sciatic nerve segment after nerve injury, implying the potential involvement of Btc during peripheral nerve regeneration.MethodsExpression of Btc was examined in Schwann cells by immunostaining. The function of Btc in regulating Schwann cells was investigated by transfecting cultured cells with siRNA segment against Btc or treating cells with Btc recombinant protein. The influence of Schwann cell-secreted Btc on neurons was determined using a co-culture assay. The in vivo effects of Btc on Schwann cell migration and axon elongation after rat sciatic nerve injury were further evaluated.ResultsImmunostaining images and ELISA outcomes indicated that Btc was present in and secreted by Schwann cells. Transwell migration and wound healing observations showed that transfection with siRNA against Btc impeded Schwann cell migration while application of exogenous Btc advanced Schwann cell migration. Besides the regulating effect on Schwann cell phenotype, Btc secreted by Schwann cells influenced neuron behavior and increased neurite length. In vivo evidence supported the promoting role of Btc in nerve regeneration after both rat sciatic nerve crush injury and transection injury.ConclusionOur findings demonstrate the essential roles of Btc on Schwann cell migration and axon elongation and imply the potential application of Btc as a regenerative strategy for treating peripheral nerve injury.

Aldose Reductase and the Polyol Pathway in Schwann Cells: Old and New Problems.

Aldose reductase (AR) is a member of the reduced nicotinamide adenosine dinucleotide phosphate (NADPH)-dependent aldo-keto reductase superfamily. It is also the rate-limiting enzyme of the polyol pathway, catalyzing the conversion of glucose to sorbitol, which is subsequently converted to fructose by sorbitol dehydrogenase. AR is highly expressed by Schwann cells in the peripheral nervous system (PNS). The excess glucose flux through AR of the polyol pathway under hyperglycemic conditions has been suggested to play a critical role in the development and progression of diabetic peripheral neuropathy (DPN). Despite the intensive basic and clinical studies over the past four decades, the significance of AR over-activation as the pathogenic mechanism of DPN remains to be elucidated. Moreover, the expected efficacy of some AR inhibitors in patients with DPN has been unsatisfactory, which prompted us to further investigate and review the understanding of the physiological and pathological roles of AR in the PNS. Particularly, the investigation of AR and the polyol pathway using immortalized Schwann cells established from normal and AR-deficient mice could shed light on the causal relationship between the metabolic abnormalities of Schwann cells and discordance of axon-Schwann cell interplay in DPN, and led to the development of better therapeutic strategies against DPN.

Liposomes embedded within fibrin gels facilitate localized macrophage manipulations within nerve

BackgroundUnderstanding the role of macrophages at discrete spatial locations during nerve regeneration after injury is important. But, methodologies that systemically manipulate macrophages can obscure their roles within discrete spatial locations within nerve. New methodLiposomes were embedded within fibrin gels to construct a delivery system that facilitated macrophage-specific manipulations at a sole spatial region, as macrophages accumulated within the fibrin. Clodronate liposomes were characterized for their toxicity to specific cells composing nerve in vitro, then tested for macrophage-specific depletion in vivo. This delivery system using clodronate liposomes was used to repair a mouse sciatic nerve gap to evaluate its efficacy and effects. ResultClodronate liposomes showed specific toxicity to macrophages without affecting dorsal root ganglia (DRG)-derived neurons, endothelial cells, or Schwann cells in culture. The delivery system demonstrated sustained release of liposomes for more than 7 days while still retaining liposomes within the fibrin. In vivo, the delivery system demonstrated macrophages were targeted by liposomes, and the use of clodronate liposomes minimized macrophage accumulation within fibrin, while not affecting macrophage accumulation within DRG. Nerve regeneration across the nerve gap repaired using this delivery system was associated with decreased angiogenesis, Schwann cell accumulation, axon growth, and reinnervation of affected muscle. Comparison with existing methodsThis delivery system allowed specific perturbation of macrophages locally in nerve. This method could be applicable across species without the need for genetic manipulations or systemic pharmaceuticals. ConclusionLiposomes embedded within fibrin gels locally target macrophages at the site of nerve injury, which enables greater precision in conclusions regarding their roles in nerve.