Evaluation of Vascular Endothelial Growth Factor (VEGF) and Its Family Member Expression After Peripheral Nerve Regeneration and Denervation

The effects of anti-lung cancer in nude mice by a fully human single-chain antibody against associated antigen Ts7TMR between A549 cells and Trichinella spiralis

Lung cancer is a dangerous disease that is lacking in an ideal therapy. Here, we evaluated the anti-lung cancer effect in nude mice of a fully human single-chain antibody (scFv) against the associated antigen 7 transmembrane receptor (Ts7TMR), which is also called G protein-coupled receptor, between A549 cells and Trichinella spiralis (T. spiralis). Our data showed that anti-Ts7TMR scFv could inhibit lung cancer growth in a dose-dependent manner, with a tumour inhibition rate of 59.1%. HE staining did not reveal any obvious tissue damage. Mechanistically, immunohistochemical staining revealed that the scFv down-regulated the expression of PCNA and VEGF in tumour tissues. Overall, this study found that anti-Ts7TMR scFv could inhibit A549 lung cancer growth by suppressing cell proliferation and angiogenesis, which may provide a new strategy for treating lung cancer.

Enhancing therapeutic potential: Human adipose-derived mesenchymal stem cells modified with recombinant adeno-associated virus expressing VEGF165 gene for peripheral nerve injury

This study aimed to investigate the therapeutic potential of human adipose-derived mesenchymal stem cells (hADSCs) modified with recombinant adeno-associated virus (rAAV) carrying the vascular endothelial growth factor 165 (VEGF165) gene in peripheral nerve injury (PNI). The hADSCs were categorized into blank, control (transduced with rAAV control vector), and VEGF165 (transduced with rAAV VEGF165 vector) groups. Subsequently, Schwann cell differentiation was induced, and Schwann cell markers were assessed. The sciatic nerve injury mouse model received injections of phosphate-buffered saline (PBS group), PBS containing hADSCs (hADSCs group), rAAV control vector (control-hADSCs group), or rAAV VEGF165 vector (VEGF165-hADSCs group) into the nerve defect site. Motor function recovery, evaluated through the sciatic function index (SFI), and nerve regeneration, assessed via toluidine blue staining along with scrutiny of Schwann cell markers and neurotrophic factors, were conducted. Modified hADSCs exhibited enhanced Schwann cell differentiation and elevated expression of Schwann cell markers [S100 calcium-binding protein B (S100B), NGF receptor (NGFR), and glial fibrillary acidic protein (GFAP)]. Mice in the VEGF165-hADSCs group demonstrated improved motor function recovery compared to those in the other three groups, accompanied by increased fiber diameter, axon diameter, and myelin thickness, as well as elevated expression of Schwann cell markers (S100B, NGFR, and GFAP) and neurotrophic factors [mature brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF)] in the distal nerve segment. rAAV-VEGF165 modification enhances hADSC potential in PNI, promoting motor recovery and nerve regeneration. Elevated Schwann cell markers and neurotrophic factors underscore therapy benefits, providing insights for nerve injury strategies.

Peripheral Mechanism of Cancer-Induced Bone Pain

Cancer-induced bone pain (CIBP) is a type of ongoing or breakthrough pain caused by a primary bone tumor or bone metastasis. CIBP constitutes a specific pain state with distinct characteristics; however, it shares similarities with inflammatory and neuropathic pain. At present, although various therapies have been developed for this condition, complete relief from CIBP in patients with cancer is yet to be achieved. Hence, it is urgent to study the mechanism underlying CIBP to develop efficient analgesic drugs. Herein, we focused on the peripheral mechanism associated with the initiation of CIBP, which involves tissue injury in the bone and changes in the tumor microenvironment (TME) and dorsal root ganglion. The nerve-cancer and cancer-immunocyte cross-talk in the TME creates circumstances that promote tumor growth and metastasis, ultimately leading to CIBP. The peripheral mechanism of CIBP and current treatments as well as potential therapeutic targets are discussed in this review.

Pulsed electromagnetic field-assisted reduced graphene oxide composite 3D printed nerve scaffold promotes sciatic nerve regeneration in rats

Peripheral nerve injuries can lead to sensory or motor deficits that have a serious impact on a patient's mental health and quality of life. Nevertheless, it remains a major clinical challenge to develop functional nerve conduits as an alternative to autologous grafts. We applied reduced graphene oxide (rGO) as a bioactive conductive material to impart electrophysiological properties to a 3D printed scaffold and the application of a pulsed magnetic field to excite the formation of microcurrents and induce nerve regeneration.In vitrostudies showed that the nerve scaffold and the pulsed magnetic field made no effect on cell survival, increased S-100βprotein expression, enhanced cell adhesion, and increased the expression level of nerve regeneration-related mRNAs.In vivoexperiments suggested that the protocol was effective in promoting nerve regeneration, resulting in functional recovery of sciatic nerves in rats, when they were damaged close to that of the autologous nerve graft, and increased expression of S-100β, NF200, and GAP43. These results indicate that rGO composite nerve scaffolds combined with pulsed magnetic field stimulation have great potential for peripheral nerve rehabilitation.

Exploring the molecular pathways and therapeutic implications of angiogenesis in neuropathic pain

Recently, much attention has been paid to chronic neuro-inflammatory condition underlying neuropathic pain. It is generally linked with thermal hyperalgesia and tactile allodynia. It results due to injury or infection in the nervous system. The neuropathic pain spectrum covers a variety of pathophysiological states, mostly involved are ischemic injury viral infections associated neuropathies, chemotherapy-induced peripheral neuropathies, autoimmune disorders, traumatic origin, hereditary neuropathies, inflammatory disorders, and channelopathies. In CNS, angiogenesis is evident in inflammation of neurons and pain in bone cancer. The role of chemokines and cytokines is dualistic; their aggressive secretion produces detrimental effects, leading to neuropathic pain. However, whether the angiogenesis contributes and exists in neuropathic pain remains doubtful. In the present review, we elucidated summary of diverse mechanisms of neuropathic pain associated with angiogenesis. Moreover, an overview of multiple targets that have provided insights on the VEGF signaling, signaling through Tie-1 and Tie-2 receptor, erythropoietin pathway promoting axonal growth are also discussed. Because angiogenesis as a result of these signaling, results in inflammation, we focused on the mechanisms of neuropathic pain. These factors are mainly responsible for the activation of post-traumatic regeneration of the PNS and CNS. Furthermore, we also reviewed synthetic and herbal treatments targeting angiogenesis in neuropathic pain.

Morphological Methods to Evaluate Peripheral Nerve Fiber Regeneration: A Comprehensive Review

Regeneration of damaged peripheral nerves remains one of the main challenges of neurosurgery and regenerative medicine, a nerve functionality is rarely restored, especially after severe injuries. Researchers are constantly looking for innovative strategies for tackling this problem, with the development of advanced tissue-engineered nerve conduits and new pharmacological and physical interventions, with the aim of improving patients' life quality. Different evaluation methods can be used to study the effectiveness of a new treatment, including functional tests, morphological assessment of regenerated nerve fibers and biomolecular analyses of key factors necessary for good regeneration. The number and diversity of protocols and methods, as well as the availability of innovative technologies which are used to assess nerve regeneration after experimental interventions, often makes it difficult to compare results obtained in different labs. The purpose of the current review is to describe the main morphological approaches used to evaluate the degree of nerve fiber regeneration in terms of their usefulness and limitations.

Effects of Olfactory Mucosa Stem/Stromal Cell and Olfactory Ensheating Cells Secretome on Peripheral Nerve Regeneration

Cell secretome has been explored as a cell-free technique with high scientific and medical interest for Regenerative Medicine. In this work, the secretome produced and collected from Olfactory Mucosa Mesenchymal Stem Cells and Olfactory Ensheating Cells was analyzed and therapeutically applied to promote peripheral nerve regeneration. The analysis of the conditioned medium revealed the production and secretion of several factors with immunomodulatory functions, capable of intervening beneficially in the phases of nerve regeneration. Subsequently, the conditioned medium was applied to sciatic nerves of rats after neurotmesis, using Reaxon^® as tube-guides. Over 20 weeks, the animals were subjected to periodic functional assessments, and after this period, the sciatic nerves and cranial tibial muscles were evaluated stereologically and histomorphometrically, respectively. The results obtained allowed to confirm the beneficial effects resulting from the application of this therapeutic combination. The administration of conditioned medium from Olfactory Mucosal Mesenchymal Stem Cells led to the best results in motor performance, sensory recovery, and gait patterns. Stereological and histomorphometric evaluation also revealed the ability of this therapeutic combination to promote nervous and muscular histologic reorganization during the regenerative process. The therapeutic combination discussed in this work shows promising results and should be further explored to clarify irregularities found in the outcomes and to allow establishing the use of cell secretome as a new therapeutic field applied in the treatment of peripheral nerves after injury.

Application of neurotrophic and proangiogenic factors as therapy after peripheral nervous system injury

The intrinsic ability of peripheral nerves to regenerate after injury is extremely limited, especially in case of severe injury. This often leads to poor motor function and permanent disability. Existing approaches for the treatment of injured nerves do not provide appropriate conditions to support survival and growth of nerve cells. This drawback can be compensated by the use of gene therapy and cell therapy-based drugs that locally provide an increase in the key regulators of nerve growth, including neurotrophic factors and extracellular matrix proteins. Each growth factor plays its own specific angiotrophic or neurotrophic role. Currently, growth factors are widely studied as accelerators of nerve regeneration. Particularly noteworthy is synergy between various growth factors, that is essential for both angiogenesis and neurogenesis. Fibroblast growth factor 2 and vascular endothelial growth factor are widely known for their proangiogenic effects. At the same time, fibroblast growth factor 2 and vascular endothelial growth factor stimulate neural cell growth and play an important role in neurodegenerative diseases of the peripheral nervous system. Taken together, their neurotrophic and angiogenic properties have positive effect on the regeneration process. In this review we provide an in-depth overview of the role of fibroblast growth factor 2 and vascular endothelial growth factor in the regeneration of peripheral nerves, thus demonstrating their neurotherapeutic efficacy in improving neuron survival in the peripheral nervous system.

Implantable Biomaterials for Peripheral Nerve Regeneration-Technology Trends and Translational Tribulations

The use of autografted nerve in surgical repair of peripheral nerve injuries (PNI) is severely limited due to donor site morbidity and restricted tissue availability. As an alternative, synthetic nerve guidance channels (NGCs) are available on the market for surgical nerve repair, but they fail to promote nerve regeneration across larger critical gap nerve injuries. Therefore, such injuries remain unaddressed, result in poor healing outcomes and are a limiting factor in limb reconstruction and transplantation. On the other hand, a myriad of advanced biomaterial strategies to address critical nerve injuries are proposed in preclinical literature but only few of those have found their way into clinical practice. The design of synthetic nerve grafts should follow rational criteria and make use of a combination of bioinstructive cues to actively promote nerve regeneration. To identify the most promising NGC designs for translation into applicable products, thorough mode of action studies, standardized readouts and validation in large animals are needed. We identify design criteria for NGC fabrication according to the current state of research, give a broad overview of bioactive and functionalized biomaterials and highlight emerging composite implant strategies using therapeutic cells, soluble factors, structural features and intrinsically conductive substrates. Finally, we discuss translational progress in bioartificial conduits for nerve repair from the surgeon's perspective and give an outlook toward future challenges in the field.

The Role of c-Jun and Autocrine Signaling Loops in the Control of Repair Schwann Cells and Regeneration

After nerve injury, both Schwann cells and neurons switch to pro-regenerative states. For Schwann cells, this involves reprogramming of myelin and Remak cells to repair Schwann cells that provide the signals and mechanisms needed for the survival of injured neurons, myelin clearance, axonal regeneration and target reinnervation. Because functional repair cells are essential for regeneration, it is unfortunate that their phenotype is not robust. Repair cell activation falters as animals get older and the repair phenotype fades during chronic denervation. These malfunctions are important reasons for the poor outcomes after nerve damage in humans. This review will discuss injury-induced Schwann cell reprogramming and the concept of the repair Schwann cell, and consider the molecular control of these cells with emphasis on c-Jun. This transcription factor is required for the generation of functional repair cells, and failure of c-Jun expression is implicated in repair cell failures in older animals and during chronic denervation. Elevating c-Jun expression in repair cells promotes regeneration, showing in principle that targeting repair cells is an effective way of improving nerve repair. In this context, we will outline the emerging evidence that repair cells are sustained by autocrine signaling loops, attractive targets for interventions aimed at promoting regeneration.

Tazarotene gel promotes healing of deep tissue injury in mice

We investigated the efficacy and molecular mechanisms of tazarotene gel for healing deep tissue injury (DTI). We used male C57BL/6J mice to establish a DTI model. Animals were divided randomly into control, tazarotene gel and purilon gel groups. We injected 100 ul tazarotene gel, purilon gel or saline every 48 h for 20 days. Hematoxylin and eosin staining was used to observe pathological changes on days 14 and 21. The mRNA and protein expression of VEGF-α, TGF-β1 and HIF-1α were detected by qRT-PCR and western blot, respectively. Wound sites exhibited accelerated healing by 20 days in the tazarotene gel group. Fewer inflammatory cells and more granulation tissue were found in both experimental groups compared to controls. The mRNA and protein expression of VEGF-α and TGF-β1 in the experimental groups were increased compared to the control group by day 14. Expression of HIF-1α in the experimental groups was significantly less than in the controls. Tazarotene gel promoted wound healing independent of the HIF-1α/VEGF signalling pathway during tissue repair of DTI. Tazarotene and purilon gels exhibited similar macroscopic healing of wounds and expression of genes and proteins.

In vitro modulation of Schwann cell behavior by VEGF and PDGF in an inflammatory environment

Peripheral glial cell transplantation with Schwann cells (SCs) is a promising approach for treating spinal cord injury (SCI). However, improvements are needed and one avenue to enhance regenerative functional outcomes is to combine growth factors with cell transplantation. Vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) are neuroprotective, and a combination of these factors has improved outcomes in rat SCI models. Thus, transplantation of SCs combined with VEGF and PDGF may further improve regenerative outcomes. First, however, we must understand how the two factors modulate SCs. In this in vitro study, we show that an inflammatory environment decreased the rate of SC-mediated phagocytosis of myelin debris but the addition of VEGF and PDGF (alone and combined) improved phagocytosis. Cytokine expression by SCs in the inflammatory environment revealed that addition of PDGF led to significantly lower level of pro-inflammatory cytokine, TNF-α, but IL-6 and anti-inflammatory cytokines (TGF-β and IL-10), remained unaltered. Further, PDGF was able to decrease the expression of myelination associated gene Oct6 in the presence of inflammatory environment. Overall, these results suggest that the use of VEGF and/or PDGF combined with SC transplantation may be beneficial in SCI therapy.

Multi-Factorial Nerve Guidance Conduit Engineering Improves Outcomes in Inflammation, Angiogenesis and Large Defect Nerve Repair

Nerve guidance conduits (NGCs) are sub-optimal for long-distance injuries with inflammation and poor vascularization related to poor axonal repair. This study used a multi-factorial approach to create an optimized biomaterial NGC to address each of these issues. Through stepwise optimization, a collagen-chondroitin-6-sulphate (Coll-CS) biomaterial was functionalized with extracellular matrix (ECM) components; fibronectin, laminin 1 and laminin 2 (FibL1L2) in specific ratios. A snap-cooled freeze-drying process was then developed with optimal pore architecture and alignment to guide axonal bridging. Culture of adult rat dorsal root ganglia on NGCs demonstrated significant improvements in inflammation, neurogenesis and angiogenesis in the specific Fib:L1:L2 ratio of 1:4:1. In clinically relevant, large 15 mm rat sciatic nerve defects, FibL1L2-NGCs demonstrated significant improvements in axonal density and angiogenesis compared to unmodified NGCs with functional equivalence to autografts. Therefore, a multiparameter ECM-driven strategy can significantly improve axonal repair across large defects, without exogenous cells or growth factors.

Biocompatible Polyurethane Conduit Grafted with Vascular Endothelial Growth Factor-Loaded Hydrogel Repairs the Peripheral Nerve Defect in Rats

Artificial nerve guidance conduits (NGCs) can be potentially used to address the problems of peripheral nerve defects. The biomaterial polyurethane (PU) has already been used to construct NGCs. However, the use of a combination of PU-based NGCs and other bioactive cues, such as extracellular matrix proteins and growth factors, has not been reported yet. A PU conduit grafted with a vascular endothelial growth factor (VEGF)-loaded hydrogel (abbreviated as PU/Gel/VEGF conduit) is fabricated. The leachate generated during the use of the PU/Gel/VEGF conduit could facilitate the proliferation, migration, and expression of the neural marker S100β in RSC96 cells (in vitro). The walking track and target muscle are analyzed, and it is observed that PU/Gel/VEGF conduits promote the functional recovery of the injured side. Various histological staining analyses are carried out, and the results reveal that the PU/Gel/VEGF conduit effectively improves the extent of nerve regeneration achieved. The number of blood vessels developed during the regeneration of the axons in the PU/Gel/VEGF group (attributable to the pro-angiogenic effect of the functional NGC) is higher than the number of blood vessels developed in the PU/Gel conduit. Overall, the results indicate that PU/Gel/VEGF conduits could promote the process of peripheral nerve regeneration.

Parallels between the Developing Vascular and Neural Systems: Signaling Pathways and Future Perspectives for Regenerative Medicine

Neurovascular disorders, which involve the vascular and nervous systems, are common. Research on such disorders usually focuses on either vascular or nervous components, without looking at how they interact. Adopting a neurovascular perspective is essential to improve current treatments. Therefore, comparing molecular processes known to be involved in both systems separately can provide insight into promising areas of future research. Since development and regeneration share many mechanisms, comparing signaling molecules involved in both the developing vascular and nervous systems and shedding light to those that they have in common can reveal processes, which have not yet been studied from a regenerative perspective, yet hold great potential. Hence, this review discusses and compares processes involved in the development of the vascular and nervous systems, in order to provide an overview of the molecular mechanisms, which are most promising with regards to treatment for neurovascular disorders. Vascular endothelial growth factor, semaphorins, and ephrins are found to hold the most potential, while fibroblast growth factor, bone morphogenic protein, slits, and sonic hedgehog are shown to participate in both the developing vascular and nervous systems, yet have not been studied at the neurovascular level, therefore being of special interest for future research.

In vitro, In vivo and Ex vivo Models for Peripheral Nerve Injury and Regeneration

Peripheral Nerve Injuries (PNI) frequently occur secondary to traumatic injuries. Recovery from these injuries can be expectedly poor, especially in proximal injuries. In order to study and improve peripheral nerve regeneration, scientists rely on peripheral nerve models to identify and test therapeutic interventions. In this review, we discuss the best described and most commonly used peripheral nerve models that scientists have and continue to use to study peripheral nerve physiology and function.

Angiogenesis and nerve regeneration induced by local administration of plasmid pBud-coVEGF165-coFGF2 into the intact rat sciatic nerve

Vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2) are well-known growth factors involved in the regeneration of various tissues and organs, including peripheral nerve system. In the present study, we elucidated the local and systemic effects of plasmid construct рBud-coVEGF165-coFGF2 injected into the epineurium of intact rat sciatic nerve. Results of histological examination of sciatic nerve and multiplex immunoassays of serum showed the absence of immunogenicity and biosafety of plasmid рBud-coVEGF165-coFGF2. Moreover, local administration of plasmid DNA construct resulted in significantly decreased levels of pro-inflammatory cytokines in the peripheral blood, including tumor necrosis factor α (TNFα) and interleukin-12, and significantly increased levels of cytokines and chemokines including Regulated upon Activation, Normal T Cell Expressed and Presumably Secrete (RANTES), epidermal growth factor, interleukin-2, and monocyte chemoattractant protein 1. These changes in the peripheral blood on day 7 after injection of plasmid construct рBud-coVEGF165-coFGF2 show that the plasmid construct has systemic effects and may modulate immune response. At the same time, reverse transcription-polymerase chain reaction revealed transient expression of coFGF2, coVEGF165, ratFGF2 and ratVEGFA with direct transport of transcripts from distal part to proximal part of the sciatic nerve. Immunohistochemical staining revealed prolonged presence of VEGFA in sciatic nerve till 14 days post-injection. These findings suggest that local administration of plasmid construct рBud-coVEGF165-coFGF2 at a concentration of 30 ng/µL results in the formation of pro-angiogenic stimuli and, and the plasmid construct, used as a drug for gene therapy, might potentially facilitate regeneration of the sciatic nerve. The study was approved by the Animal Ethics Committee of Kazan Federal University, procedures were approved by the Local Ethics Committee (approval No. 5) on May 27, 2014.

Facilitate Angiogenesis and Neurogenesis by Growth Factors Integrated Decellularized Matrix Hydrogel

Neurological functional recovery depends on the synergistic interaction between angiogenesis and neurogenesis after peripheral nerve injury (PNI). Decellularized nerve matrix hydrogels have drawn much attention and been considered as potential therapeutic biomaterials for neurovascularization, due to their intrinsic advantages in construction of a growth-permissive microenvironment, strong affinity to multiple growth factors (GFs), and promotion of neurite outgrowth. In the present study, nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) were incorporated into porcine decellularized nerve matrix hydrogel (pDNM-gel) for PNI treatment. Both GFs bound strongly to pDNM-gel and underwent a controlled release manner, which showed facilitated axonal extension and vascular-like tube formation in vitro. Especially, a companion growth was identified when human umbilical vein endothelial cells and neurons were cocultured on the GFs containing pDNM-gel. In a crushed rat sciatic nerve model, the incorporated NGF and VEGF appeared to contribute for axonal growth and neovascularization correspondingly but separately. Both GFs were equally important in improving nerve functional recovery after in situ administration. These findings indicate that pDNM-gel is not only a bioactive hydrogel-based material that can be used alone, but also serves as suitable carrier of multiple GFs for promoting an effective PNI repair. Impact statement Decellularized matrix hydrogel derived from nerve tissue has demonstrated its effectiveness in promoting nerve reinnervation, remyelination, and functionalization. Meanwhile, angiogenesis is highly desirable for treatment of long-distance peripheral nerve defects. To this end, we incorporated both vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) into porcine decellularized nerve matrix hydrogel (pDNM-gel) to induce neovascularization and neuroregeneration. At the cellular level, the pDNM-gel with both growth factors (GFs) exhibited significant capability in promoting axonal elongation, Schwann cell proliferation and migration, as well as vessel/nerve interaction. In crushed peripheral nerve injury (PNI) rat model, the integrated VEGF was more favorable for angiogenesis, whereas NGF mainly contributed to neurogenesis. However, the combination of both GFs in pDNM-gel highly facilitated motor functional recovery, highlighting the therapeutic promise of decellularized matrix hydrogel for growth factor delivery toward neuroprotection and neuroregeneration after PNI.

Modification of tubular chitosan-based peripheral nerve implants: applications for simple or more complex approaches

Surgical treatment of peripheral nerve injuries is still a major challenge in human clinic. Up to now, none of the well-developed microsurgical treatment options is able to guarantee a complete restoration of nerve function. This restriction is also effective for novel clinically approved artificial nerve guides. In this review, we compare surgical repair techniques primarily for digital nerve injuries reported with relatively high prevalence to be valuable attempts in clinical digital nerve repair and point out their advantages and shortcomings. We furthermore discuss the use of artificial nerve grafts with a focus on chitosan-based nerve guides, for which our own studies contributed to their approval for clinical use. In the second part of this review, very recent future perspectives for the enhancement of tubular (commonly hollow) nerve guides are discussed in terms of their clinical translatability and ability to form three-dimensional constructs that biomimick the natural nerve structure. This includes materials that have already shown their beneficial potential in in vivo studies like fibrous intraluminal guidance structures, hydrogels, growth factors, and approaches of cell transplantation. Additionally, we highlight upcoming future perspectives comprising co-application of stem cell secretome. From our overview, we conclude that already simple attempts are highly effective to increase the regeneration supporting properties of nerve guides in experimental studies. But for bringing nerve repair with bioartificial nerve grafts to the next level, e.g. repair of defects > 3 cm in human patients, more complex intraluminal guidance structures such as innovatively manufactured hydrogels and likely supplementation of stem cells or their secretome for therapeutic purposes may represent promising future perspectives.

The immunologic changes during different phases of intestinal anastomotic healing

Intestinal anatomosis is a complex and multicellular process that involving three overlapped phases: exudative phase, proliferative phase, and reparative phase. Undisturbed anastomotic healings are crucial for the recovery of patients after operations but unsuccessful healings are linked with a considerable mortality. This time, we concentrate on the immunologic changes during different phases of intestinal anastomotic healing and select several major immune cells and cytokines of each phase to get a better understanding of these immunologic changes in different phases, which will be significant for more precise therapy strategies in anastomoses.

Ex-Vivo Stimulation of Adipose Stem Cells by Growth Factors and Fibrin-Hydrogel Assisted Delivery Strategies for Treating Nerve Gap-Injuries

Peripheral nerve injuries often result in lifelong disabilities despite advanced surgical interventions, indicating the urgent clinical need for effective therapies. In order to improve the potency of adipose-derived stem cells (ASC) for nerve regeneration, the present study focused primarily on ex-vivo stimulation of ASC by using growth factors, i.e., nerve growth factor (NGF) or vascular endothelial growth factor (VEGF) and secondly on fibrin-hydrogel nerve conduits (FNC) assisted ASC delivery strategies, i.e., intramural vs. intraluminal loading. ASC were stimulated by NGF or VEGF for 3 days and the resulting secretome was subsequently evaluated in an in vitro axonal outgrowth assay. For the animal study, a 10 mm sciatic nerve gap-injury was created in rats and reconstructed using FNC loaded with ASC. Secretome derived from NGF-stimulated ASC promoted significant axonal outgrowth from the DRG-explants in comparison to all other conditions. Thus, NGF-stimulated ASC were further investigated in animals and found to enhance early nerve regeneration as evidenced by the increased number of β-Tubulin III+ axons. Notably, FNC assisted intramural delivery enabled the improvement of ASC’s therapeutic efficacy in comparison to the intraluminal delivery system. Thus, ex-vivo stimulation of ASC by NGF and FNC assisted intramural delivery may offer new options for developing effective therapies.

Modern Trends for Peripheral Nerve Repair and Regeneration: Beyond the Hollow Nerve Guidance Conduit

Peripheral nerve repair and regeneration remains among the greatest challenges in tissue engineering and regenerative medicine. Even though peripheral nerve injuries (PNIs) are capable of some degree of regeneration, frail recovery is seen even when the best microsurgical technique is applied. PNIs are known to be very incapacitating for the patient, due to the deprivation of motor and sensory abilities. Since there is no optimal solution for tackling this problem up to this day, the evolution in the field is constant, with innovative designs of advanced nerve guidance conduits (NGCs) being reported every day. As a basic concept, a NGC should act as a physical barrier from the external environment, concomitantly acting as physical guidance for the regenerative axons across the gap lesion. NGCs should also be able to retain the naturally released nerve growth factors secreted by the damaged nerve stumps, as well as reducing the invasion of scar tissue-forming fibroblasts to the injury site. Based on the neurobiological knowledge related to the events that succeed after a nerve injury, neuronal subsistence is subjected to the existence of an ideal environment of growth factors, hormones, cytokines, and extracellular matrix (ECM) factors. Therefore, it is known that multifunctional NGCs fabricated through combinatorial approaches are needed to improve the functional and clinical outcomes after PNIs. The present work overviews the current reports dealing with the several features that can be used to improve peripheral nerve regeneration (PNR), ranging from the simple use of hollow NGCs to tissue engineered intraluminal fillers, or to even more advanced strategies, comprising the molecular and gene therapies as well as cell-based therapies.

The Median Nerve Injury Model in Pre-clinical Research - A Critical Review on Benefits and Limitations

The successful introduction of innovative treatment strategies into clinical practise strongly depends on the availability of effective experimental models and their reliable pre-clinical assessment. Considering pre-clinical research for peripheral nerve repair and reconstruction, the far most used nerve regeneration model in the last decades is the sciatic nerve injury and repair model. More recently, the use of the median nerve injury and repair model has gained increasing attention due to some significant advantages it provides compared to sciatic nerve injury. Outstanding advantages are the availability of reliable behavioural tests for assessing posttraumatic voluntary motor recovery and a much lower impact on the animal wellbeing. In this article, the potential application of the median nerve injury and repair model in pre-clinical research is reviewed. In addition, we provide a synthetic overview of a variety of methods that can be applied in this model for nerve regeneration assessment. This article is aimed at helping researchers in adequately adopting this in vivo model for pre-clinical evaluation of peripheral nerve reconstruction as well as for interpreting the results in a translational perspective.

Introduction: Thematic Papers Issue on Peripheral Nerve Regeneration and Repair

Injuries to the peripheral nerves result in loss of motor, sensory and autonomic functions in the denervated segments of the body, thus having strong impact in the quality of life of affected patients. Neurons are able to regenerate their injured axons in the peripheral nerves; however, the endogenous repair mechanisms usually do not allow for a satisfactory functional recovery, especially after severe nerve injuries. The interest on regeneration after peripheral nerve injuries has increased in the recent years due to the numerous advances derived from studies of neurobiology, cell therapy, and tissue engineering. This Thematic Papers Issue brings together a number of papers, authored by researchers in the field, which cover a wide spectrum of topics related to regeneration and repair of peripheral nerve injuries. The Issue proposal originated from the recent 4th International Symposium on Peripheral Nerve Regeneration (ISPNR2017) which was hosted by Xavier Navarro and the European Society for the Study of Peripheral Nerve Repair and Regeneration in Barcelona, Spain. Anat Rec, 301:1614-1617, 2018. © 2018 Wiley Periodicals, Inc.