Effect of local application of transforming growth factor-β at the nerve repair site following chronic axotomy and denervation on the expression of regeneration-associated genes. Laboratory investigation

The Role of Neuromodulation and Potential Mechanism in Regulating Heterotopic Ossification

Heterotopic ossification (HO) is a pathological process characterized by the aberrant formation of bone in muscles and soft tissues. It is commonly triggered by traumatic brain injury, spinal cord injury, and burns. Despite a wide range of evidence underscoring the significance of neurogenic signals in proper bone remodeling, a clear understanding of HO induced by nerve injury remains rudimentary. Recent studies suggest that injury to the nervous system can activate various signaling pathways, such as TGF-β, leading to neurogenic HO through the release of neurotrophins. These pathophysiological changes lay a robust groundwork for the prevention and treatment of HO. In this review, we collected evidence to elucidate the mechanisms underlying the pathogenesis of HO related to nerve injury, aiming to enhance our understanding of how neurological repair processes can culminate in HO.

Correlation between pulp sensibility and magnetic resonance signal intensity following regenerative endodontic procedures in mature necrotic teeth- a retrospective cohort study

BACKGROUND

With increasing studies being published on regenerative endodontic procedures (REPs) as a treatment modality for mature necrotic teeth, the assessment of outcomes following regenerative endodontic procedures has become more challenging and the demand for a better understanding of the regenerated tissues following this treatment is rising. The study aimed to correlate cold, electric pulp testing (EPT), and magnetic resonance imaging (MRI) signal intensity (SI) in mature necrotic teeth treated with regenerative endodontic procedures.

METHODOLOGY

This retrospective cohort study included eighteen adult patients who experienced tooth necrosis in mature maxillary anterior teeth recruited from the outpatient clinic, Conservative Dentistry Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt from July 2017 until December 2018 with 12 months of follow-up. regenerative endodontic procedures via blood clot were performed. The canals were instrumented by ProTaper Next (PTN) files until final sizes X3 or X5. Biodentine was used as cervical plug material. Pre and post-operative clinical follow-up was done where the patients' responses to cold and electric pulp testing were given a scoring system and were compared to the normal contralateral tooth. Pre and post-operative magnetic resonance imaging signal intensity of both the involved tooth and its contralateral at the middle and the apical thirds of the root canals were assessed after 3, 6, and 12 months. Data was analyzed using the ANOVA, Friedman and Bonferroni tests. Significance was set at a p-value < 0.05.

RESULTS

All 18 teeth scored a baseline score of "2" for cold and electric pulp testing. There was a significant difference between scores of the cold test at baseline and 12-month follow-up (p < 0.001). There was a significant difference between scores of the electric pulp testing of baseline and 12-month follow-up (p < 0.001). There was a moderately significant indirect (inverse) correlation between magnetic resonance imaging signal intensity and cold test in both the middle and apical thirds at 12 months. No significant correlations were detected between magnetic resonance imaging signal intensity and electric pulp testingat any of the time intervals (p > 0.05).

CONCLUSION

Magnetic resonance imaging is a successful non-invasive method to assess outcomes of regenerative endodontic procedures and correlating it with another reliable method of assessing pulpal responses, cold test, could validate these outcomes.

CLINICAL TRIAL REGISTRATION

The study was registered with ClinicalTrials.gov (ID: NCT03804450).

Role of transforming growth factor-β in peripheral nerve regeneration

Injuries caused by trauma and neurodegenerative diseases can damage the peripheral nervous system and cause functional deficits. Unlike in the central nervous system, damaged axons in peripheral nerves can be induced to regenerate in response to intrinsic cues after reprogramming or in a growth-promoting microenvironment created by Schwann cells. However, axon regeneration and repair do not automatically result in the restoration of function, which is the ultimate therapeutic goal but also a major clinical challenge. Transforming growth factor (TGF) is a multifunctional cytokine that regulates various biological processes including tissue repair, embryo development, and cell growth and differentiation. There is accumulating evidence that TGF-β family proteins participate in peripheral nerve repair through various factors and signaling pathways by regulating the growth and transformation of Schwann cells; recruiting specific immune cells; controlling the permeability of the blood-nerve barrier, thereby stimulating axon growth; and inhibiting remyelination of regenerated axons. TGF-β has been applied to the treatment of peripheral nerve injury in animal models. In this context, we review the functions of TGF-β in peripheral nerve regeneration and potential clinical applications.

Burn Injury-related Growth Factor Expressions and Their Potential Roles in Burn-related Neuropathies

In the context of burn injury, growth factors (GFs) play a significant role in mediating the complex local and systematic processes that occur. Among the many systemic complications that arise following a burn injury, peripheral neuropathy remains one of the most common. Despite the broad understanding of the effects GFs have on multiple tissues, their potential implications in both wound healing and neuropathy remain largely unexplored. Therefore, this review aims to investigate the expression patterns of GFs prominent during the burn wound healing process and explore the potential contributions these GFs have on the development of burn-related peripheral neuropathy.

Pulsed Electromagnetic Fields Improved Peripheral Nerve Regeneration After Delayed Repair of One Month

The goal of this study was to determine if postoperative pulsed electromagnetic fields (PEMFs) could improve the neuromuscular rehabilitation after delayed repair of peripheral nerve injuries. Thirty-six Sprague-Dawley rats were randomly divided into sham group, control group, and PEMFs group. The sciatic nerves were transected except for the control group. One month later, the nerve ends of the former two groups were reconnected. PEMFs group of rats was subjected to PEMFs thereafter. Control group and sham group received no treatment. Four and 8 weeks later, morphological and functional changes were measured. Four and eight weeks postoperatively, compared to sham group, the sciatic functional indices (SFIs) of PEMFs group were higher. More axons regenerated distally in PEMFs group. The fiber diameters of PEMFs group were larger. However, the axon diameters and myelin thicknesses were not different between these two groups. The brain-derived neurotrophic factor and vascular endothelial growth factor expressions were higher in PEMFs group after 8 weeks. Semi-quantitative IOD analysis for the intensity of positive staining indicated that there were more BDNF, VEGF, and NF200 in PEMFs group. It's concluded that PEMFs have effect on the axonal regeneration after delayed nerve repair of one month. The upregulated expressions of BDNF and VEGF may play roles in this process. © 2023 Bioelectromagnetics Society.

Tumor-Induced T Cell Polarization by Schwann Cells

Nerve-cancer crosstalk resulting in either tumor neurogenesis or intratumoral neurodegeneration is critically controlled by Schwann cells, the principal glial cells of the peripheral nervous system. Though the direct stimulating effect of Schwann cells on malignant cell proliferation, motility, epithelial-mesenchymal transition, and the formation of metastases have been intensively investigated, the ability of Schwann cells to affect the effector and regulatory immune cells in the tumor environment is significantly less studied. Here, we demonstrated that tumor cells could stimulate Schwann cells to produce high levels of prostaglandin E, which could be blocked by COX-2 inhibitors. This effect was mediated by tumor-derived TGF-β as neutralization of this cytokine in the tumor-conditioned medium completely blocked the inducible prostaglandin E production by Schwann cells. Similar protective effects were also induced by the Schwann cell pretreatment with TGF-βR1/ALK4/5/7 and MAPK/ERK kinase inhibitors of the canonical and non-canonical TGF-β signaling pathways, respectively. Furthermore, prostaglandin E derived from tumor-activated Schwann cells blocked the proliferation of CD3/CD28-activated T cells and upregulated the expression of CD73 and PD-1 on both CD4+ and CD8+ T cells, suggesting T cell polarization to the exhausted phenotype. This new pathway of tumor-induced T cell inhibition via the activation of neuroglial cells represents new evidence of the importance of nerve-cancer crosstalk in controlling tumor development and progression. A better understanding of the tumor-neuro-immune axis supports the development of efficient targets for harnessing this axis and improving the efficacy of cancer therapy.

Translational bioengineering strategies for peripheral nerve regeneration: opportunities, challenges, and novel concepts

Peripheral nerve injuries remain a challenging problem in need of better treatment strategies. Despite best efforts at surgical reconstruction and postoperative rehabilitation, patients are often left with persistent, debilitating motor and sensory deficits. There are currently no therapeutic strategies proven to enhance the regenerative process in humans. A clinical need exists for the development of technologies to promote nerve regeneration and improve functional outcomes. Recent advances in the fields of tissue engineering and nanotechnology have enabled biomaterial scaffolds to modulate the host response to tissue repair through tailored mechanical, chemical, and conductive cues. New bioengineered approaches have enabled targeted, sustained delivery of protein therapeutics with the capacity to unlock the clinical potential of a myriad of neurotrophic growth factors that have demonstrated promise in enhancing regenerative outcomes. As such, further exploration of combinatory strategies leveraging these technological advances may offer a pathway towards clinically translatable solutions to advance the care of patients with peripheral nerve injuries. This review first presents the various emerging bioengineering strategies that can be applied for the management of nerve gap injuries. We cover the rationale and limitations for their use as an alternative to autografts, focusing on the approaches to increase the number of regenerating axons crossing the repair site, and facilitating their growth towards the distal stump. We also discuss the emerging growth factor-based therapeutic strategies designed to improve functional outcomes in a multimodal fashion, by accelerating axonal growth, improving the distal regenerative environment, and preventing end-organs atrophy.

Role of Transforming Growth Factor Beta in Peripheral Nerve Regeneration: Cellular and Molecular Mechanisms

Peripheral nerve injury (PNI) is one of the most common concerns in trauma patients. Despite significant advances in repair surgeries, the outcome can still be unsatisfactory, resulting in morbidities such as loss of sensory or motor function and reduced quality of life. This highlights the need for more supportive strategies for nerve regrowth and adequate recovery. Multifunctional cytokine transforming growth factor-β (TGF-β) is essential for the development of the nervous system and is known for its neuroprotective functions. Accumulating evidence indicates its involvement in multiple cellular and molecular responses that are critical to peripheral nerve repair. Following PNI, TGF-β is released at the site of injury where it can initiate a series of phenotypic changes in Schwann cells (SCs), modulate immune cells, activate neuronal intrinsic growth capacity, and regulate blood nerve barrier (BNB) permeability, thus enhancing the regeneration of the nerves. Notably, TGF-β has already been applied experimentally in the treatment of PNI. These treatments with encouraging outcomes further demonstrate its regeneration-promoting capacity. Herein, we review the possible roles of TGF-β in peripheral nerve regeneration and discuss the underlying mechanisms, thus providing new cues for better treatment of PNI.

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.

Regenerative Endodontic Procedures for the Treatment of Necrotic Mature Teeth: A Preliminary Randomised Clinical Trial

AIM

This preliminary randomised, prospective, controlled trial aimed to compare the clinical and radiographic outcomes of two regenerative endodontic procedures (REPs), revitalisation and a platelet-rich fibrin (PRF)-based technique, in the treatment of mature permanent teeth with necrotic pulps.

METHODOLOGY

The trial has been reported according to the Preferred Reporting Items for Randomised Trials in Endodontics 2020 guidelines. The study protocol was registered at the clinical trial registry (ClinicalTrials.gov) with identifier number NCT04158232. Twenty patients with mature necrotic anterior teeth with large periapical lesions were randomly allocated into two groups (n=10): group I, treated with revitalisation with the blood clot (BC) technique, and Group II, treated with a PRF-based technique. The follow-up was for 12 months. Periradicular healing was assessed using standardised radiographs taken at baseline, and at 6 and 12 months after treatment. An electric pulp tester was used to assess whether pulp sensibility had been regained during the follow-up period. Statistical analysis was conducted using Mann-Whitney test and Wilcoxon test for non-parametric data. For parametric data, repeated measures analysis of variance was used. The significance level was set at P≤0.05.

RESULTS

There was a significant increase in periradicular healing in both groups at 6 and 12 months, compared to that at baseline, with no significant difference between the studied groups after 12 months (P=0.143). There was a significant difference between the tooth sensibility readings at baseline, 6-month, and 12-month follow-up timepoints (P<0.001).

CONCLUSIONS

The findings of this preliminary trial indicate the potential for using REPs, such as revitalisation or PRF-based techniques, as treatment options for mature teeth with necrotic pulps. A higher level of evidence obtained through adequately powered clinical trials and longer follow-up periods are required to conclusively validate the different outcomes of REPs.

Transforming Growth Factor Beta 1 Regulates Fibroblast Growth Factor 7 Expression in Schwann Cells

Background: Our previous work demonstrated that application of transforming growth factor beta 1 (TGF-β1) and forskolin to the repair site after chronic denervation and axotomy has a mitogenic effect, reactivates Schwann cells (SCs), and supports axonal regeneration. We found decreased expression of fibroblast growth factor 7 (FGF-7), a factor involved in synaptic organization and maintenance. Using an in vitro system, we examined the molecular mechanism of TGF-β1 and forskolin on the regulation of FGF-7 expression in SCs. Methods: SCs were prepared from the sciatic nerve and stimulated with forskolin (0.5 μM), TGF-β1 (1 ng/mL), or TGF-β1 + forskolin for 6 or 24 hours. SCs were also pretreated with LY2109761 (0.5 μM), a TGF-β receptor inhibitor, prior to stimulation with TGF-β1 + forskolin for 6 hours. Real-time TaqMan quantitative polymerase chain reaction analyses for FGF-7, myelin basic protein, and peripheral myelin protein 22 expression were performed. Cycle threshold (Ct) data were normalized to a reference gene, and fold changes relative to untreated SCs were determined using the 2^-ΔΔCt method. Statistical analysis was done using t test (P<0.05). Results: TGF-β1 alone or in combination with forskolin for 24 hours resulted in a 3.3- and 2.8-fold decrease in FGF-7 expression in SCs, respectively. No change in FGF-7 expression was found with forskolin alone. TGF-β1 + forskolin treatment for 6 hours resulted in a 4.0-fold decrease in FGF-7 expression, while the addition of LY2109761 resulted in a 2.7-fold decrease in FGF-7 expression. Conclusion: We showed that SC expression of FGF-7 is regulated by TGF-β1. The positive effect of TGF-β1 and forskolin on SC reactivation and axonal regeneration may involve modulation of FGF-7 expression and activity in SCs.

Nerve growth factor and substance P may be involved in moist exposed burn ointment-mediated chronic refractory wound healing

Moist exposed burn ointment (MEBO) is becoming increasingly popular in China as it shortens wound-healing time and reduces scar formation. However, its exact mechanism in mediating the wound-healing process is not yet clear. In the present study a total of 90 healthy adult male Wistar rats of specific-pathogen-free grade were divided equally into a control group, wound group, MEBO group, recombinant bovine basic fibroblast growth factor (rb-bFGF) group and sham operation group. Wound healing was observed from the extracted granulation tissues and recorded at three time points on 3, 7 and 14 days. Different levels of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) in tissue homogenate were detected using ELISA. Western blot analysis and quantitative PCR were used to detect the expression of nerve growth factor (NGF), substance P (SP) as well as tyrosine kinase A (TrkA) receptor protein and the corresponding mRNA levels in granulation tissue. It was observed that the wound healing progressed faster in the MEBO and rb-bFGF groups compared with the wound group (P<0.01). TNF-α and IL-6 had an upward-downward trend at three time points, with the wound group demonstrating the most obvious increase (P<0.01). NGF and SP mRNA and protein levels in granulation tissue in MEBO, rb-bFGF and sham operation groups reached their highest levels on day 7 and then decreased on day 14. The expression level of TrkA was also measured simultaneously and its expression pattern was similar to that of NGF and SP. These results suggested that MEBO may promote nerve repair and accelerate wound healing through mediating the expression levels of NGF and SP, as well as TrkA.

Combined Rosiglitazone and Forskolin Have Neuroprotective Effects in SD Rats after Spinal Cord Injury

The peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist rosiglitazone inhibits NF-κB expression and endogenous neural stem cell differentiation into neurons and reduces the inflammatory cascade after spinal cord injury (SCI). The aim of this study was to explore the mechanisms underlying rosiglitazone-mediated neuroprotective effects and regulation of the balance between the inflammatory cascade and generation of endogenous spinal cord neurons by using a spinal cord-derived neural stem cell culture system as well as SD rat SCI model. Activation of PPAR-γ could promote neural stem cell proliferation and inhibit PKA expression and neuronal formation in vitro. In the SD rat SCI model, the rosiglitazone + forskolin group showed better locomotor recovery compared to the rosiglitazone and forskolin groups. MAP2 expression was higher in the rosiglitazone + forskolin group than in the rosiglitazone group, NF-κB expression was lower in the rosiglitazone + forskolin group than in the forskolin group, and NeuN expression was higher in the rosiglitazone + forskolin group than in the forskolin group. PPAR-γ activation likely inhibits NF-κB, thereby reducing the inflammatory cascade, and PKA activation likely promotes neuronal cell regeneration.

Single Local Application of TGF-β Promotes a Proregenerative State Throughout a Chronically Injured Nerve

BACKGROUND

The lack of nerve regeneration and functional recovery occurs frequently when injuries involve large nerve trunks because insufficient mature axons reach their targets in the distal stump and because of the loss of neurotrophic support, primarily from Schwann cells (SCs).

OBJECTIVE

To investigate whether a single application of transforming growth factor-beta (TGF-β) plus forskolin or forskolin alone can promote and support axonal regeneration through the distal nerve stump.

METHODS

Using a delayed repair rat model of nerve injury, we transected the tibial nerve. After 8 wk, end-to-end repair was done and the repair site was treated with saline, forskolin, or TGF- β plus forskolin. After 6 wk, nerve sections consisting of the proximal stump, distal to the site of repair, and the most distal part of the nerve stump were removed for nerve histology, axon counts, and immunohistochemistry for activated SCs (S100), macrophages (CD68), cell proliferation (Ki67), p75NGFR, and apoptosis (activated caspase-3).

RESULTS

TGF-β plus forskolin significantly increased the numbers of axons regenerated distal to the repair site and the most distal nerve sections. Both treatments significantly increased the numbers of axons regenerated in the most distal nerve sections compared to saline treated. Both treatments exhibited extended expression of regeneration-associated marker proteins.

CONCLUSION

TGF-β plus forskolin treatment of chronically injured nerve improved axonal regeneration and increased expression of regeneration-associated proteins beyond the repair site. This suggests that a single application at the site of repair has mitogenic effects that extended distally and may potentially overcome the decrease in regenerated axon over long distance.

Platelet-rich plasma for regeneration of neural feedback pathways around dental implants: a concise review and outlook on future possibilities

Along with the development of new materials, advanced medical imaging and surgical techniques, osseointegrated dental implants are considered a successful and constantly evolving treatment modality for the replacement of missing teeth in patients with complete or partial edentulism. The importance of restoring the peripheral neural feedback pathway and thus repairing the lack of periodontal mechanoreceptors after tooth extraction has been highlighted in the literature. Nevertheless, regenerating the nerve fibers and reconstructing the neural feedback pathways around osseointegrated implants remain a challenge. Recent studies have provided evidence that platelet-rich plasma (PRP) therapy is a promising treatment for musculoskeletal injuries. Because of its high biological safety, convenience and usability, PRP therapy has gradually gained popularity in the clinical field. Although much remains to be learned, the growth factors from PRP might play key roles in peripheral nerve repair mechanisms. This review presents known growth factors contributing to the biological efficacy of PRP and illustrates basic and (pre-)clinical evidence regarding the use of PRP and its relevant products in peripheral nerve regeneration. In addition, the potential of local application of PRP for structural and functional recovery of injured peripheral nerves around dental implants is discussed.

Effect of Spp1 on nerve degeneration and regeneration after rat sciatic nerve injury

BACKGROUND

Wallerian degeneration (WD) in injured peripheral nerves is associated with a large number of up- or down-regulated genes, but the effects of these changes are poorly understood. In our previous studies, we reported some key factors that are differentially expressed to activate nerve degeneration and regeneration during WD. Here, we determined the effects of secreted phosphoprotein 1 (Spp1) on WD after rat sciatic nerve injury.

RESULTS

Spp1 was upregulated from 6 h to 14 days after sciatic nerve injury. Altered expression of Spp1 in Schwann cells (SC) resulted in altered mRNA and protein expression levels for cytokines, c-Fos, PKCα and phospho-ERK/ERK and affected SC apoptosis in vitro. Silencing of Spp1 expression in SCs using siRNA technology reduced proliferation and promoted migration of SCs in vitro. By contrast, overexpression of Spp1 promoted proliferation and reduced migration in SCs in vitro. Differential expression of Spp1 after sciatic nerve injury in vivo altered the expression of cytokines, c-Fos, PKCα, and the p-ERK/ERK pathway.

CONCLUSIONS

Spp1 is a key regulatory factor that affects nerve degeneration and regeneration through c-Fos, PKCα and p-ERK/ERK pathways after rat sciatic nerve injury. These results shed new light on the role of Spp1 in nerve degeneration and regeneration during WD.

The Regulatory Effects of Transforming Growth Factor-β on Nerve Regeneration

Transforming growth factor-β (TGF-β) belongs to a group of pleiotropic cytokines that are involved in a variety of biological processes, such as inflammation and immune reactions, cellular phenotype transition, extracellular matrix (ECM) deposition, and epithelial-mesenchymal transition. TGF-β is widely distributed throughout the body, including the nervous system. Following injury to the nervous system, TGF-β regulates the behavior of neurons and glial cells and thus mediates the regenerative process. In the current article, we reviewed the production, activation, as well as the signaling pathway of TGF-β. We also described altered expression patterns of TGF-β in the nervous system after nerve injury and the regulatory effects of TGF-β on nerve repair and regeneration in many aspects, including inflammation and immune response, phenotypic modulation of neural cells, neurite outgrowth, scar formation, and modulation of neurotrophic factors. The diverse biological actions of TGF-β suggest that it may become a potential therapeutic target for the treatment of nerve injury and regeneration.

Transforming growth factor beta 1, a cytokine with regenerative functions

We review the biology and role of transforming growth factor beta 1 (TGF-β1) in peripheral nerve injury and regeneration, as it relates to injuries to large nerve trunks (i.e., sciatic nerve, brachial plexus), which often leads to suboptimal functional recovery. Experimental studies have suggested that the reason for the lack of functional recovery resides in the lack of sufficient mature axons reaching their targets, which is a result of the loss of the growth-supportive environment provided by the Schwann cells in the distal stump of injured nerves. Using an established chronic nerve injury and delayed repair animal model that accurately mimics chronic nerve injuries in humans, we summarize our key findings as well as others to better understand the pathophysiology of poor functional recovery. We demonstrated that 6 month TGF-β1 treatment for chronic nerve injury significantly improved Schwann cell capacity to support axonal regeneration. When combined with forskolin, the effect was additive, as evidenced by a near doubling of regenerated axons proximal to the repair site. We showed that in vivo application of TGF-β1 and forskolin directly onto chronically injured nerves reactivated chronically denervated Schwann cells, induced their proliferation, and upregulated the expression of regeneration-associated proteins. The effect of TGF-β1 and forskolin on old nerve injuries is quite impressive and the treatment regiment appears to mediate a growth-supportive milieu in the injured peripheral nerves. In summary, TGF-β1 and forskolin treatment reactivates chronically denervated Schwann cells and could potentially be used to extend and prolong the regenerative responses to promote axonal regeneration.

TGF-β1 is critical for Wallerian degeneration after rat sciatic nerve injury

Wallerian degeneration (WD) is a process of axonal degeneration distal to the injury site followed by a robust regenerative response. It involves degeneration and regeneration which can be directly induced by nerve injury and activated by transcription factors. Although WD has been studied extensively, the precise mechanisms of transcription factors regulating WD are still elusive. In this study, we reported the effect of transforming growth factor-β1 (TGF-β1) on WD after rat sciatic nerve injury. The data showed that TGF-β1 may express in injured rat sciatic nerve and cultured Schwann cells (SCs). Knock down of TGF-β1 expressions resulted in the reduction of SC proliferation and apoptosis, up regulation of cytokines and Smad2, 4. Enhanced expression of TGF-β1 could promote SC proliferation and apoptosis, down regulation of cytokines and Smad2, 4. Altered expressions of TGF-β1 may affect Smad and AKT but not c-Jun and extracellular regulated protein kinase (ERK) pathways. Our results revealed the role of TGF-β1 on WD and provided the basis for the molecular mechanisms of TGF-β1-regulated nerve degeneration and/or regeneration.