Platelet-derived growth factor-b expression induced after rat peripheral nerve injuries

Single-cell RNA sequencing of neurofibromas reveals a tumor microenvironment favorable for neural regeneration and immune suppression in a neurofibromatosis type 1 porcine model

Neurofibromatosis Type 1 (NF1) is one of the most common genetically inherited disorders that affects 1 in 3000 children annually. Clinical manifestations vary widely but nearly always include the development of cutaneous, plexiform and diffuse neurofibromas that are managed over many years. Recent single-cell transcriptomics profiling efforts of neurofibromas have begun to reveal cell signaling processes. However, the cell signaling networks in mature, non-cutaneous neurofibromas remain unexplored. Here, we present insights into the cellular composition and signaling within mature neurofibromas, contrasting with normal adjacent tissue, in a porcine model of NF1 using single-cell RNA sequencing (scRNA-seq) analysis and histopathological characterization. These neurofibromas exhibited classic diffuse-type histologic morphology and expected patterns of S100, SOX10, GFAP, and CD34 immunohistochemistry. The porcine mature neurofibromas closely resemble human neurofibromas histologically and contain all known cellular components of their human counterparts. The scRNA-seq confirmed the presence of all expected cell types within these neurofibromas and identified novel populations of fibroblasts and immune cells, which may contribute to the tumor microenvironment by suppressing inflammation, promoting M2 macrophage polarization, increasing fibrosis, and driving the proliferation of Schwann cells. Notably, we identified tumor-associated IDO1 +/CD274+ (PD-L1) + dendritic cells, which represent the first such observation in any NF1 animal model and suggest the role of the upregulation of immune checkpoints in mature neurofibromas. Finally, we observed that cell types in the tumor microenvironment are poised to promote immune evasion, extracellular matrix reconstruction, and nerve regeneration.

The Effect of Leukocyte- and Platelet-Rich Fibrin on Central and Peripheral Nervous System Neurons-Implications for Biomaterial Applicability

Leukocyte- and Platelet-Rich Fibrin (L-PRF) is a second-generation platelet concentrate that is prepared directly from the patient's own blood. It is widely used in the field of regenerative medicine, and to better understand its clinical applicability we aimed to further explore the biological properties and effects of L-PRF on cells from the central and peripheral nervous system. To this end, L-PRF was prepared from healthy human donors, and confocal, transmission, and scanning electron microscopy as well as secretome analysis were performed on these clots. In addition, functional assays were completed to determine the effect of L-PRF on neural stem cells (NSCs), primary cortical neurons (pCNs), and peripheral dorsal root ganglion (DRG) neurons. We observed that L-PRF consists of a dense but porous fibrin network, containing leukocytes and aggregates of activated platelets that are distributed throughout the clot. Antibody array and ELISA confirmed that it is a reservoir for a plethora of growth factors. Key molecules that are known to have an effect on neuronal cell functions such as brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) were slowly released over time from the clots. Next, we found that the L-PRF secretome had no significant effect on the proliferative and metabolic activity of NSCs, but it did act as a chemoattractant and improved the migration of these CNS-derived stem cells. More importantly, L-PRF growth factors had a detrimental effect on the survival of pCNs, and consequently, also interfered with their neurite outgrowth. In contrast, we found a positive effect on peripheral DRG neurons, and L-PRF growth factors improved their survival and significantly stimulated the outgrowth and branching of their neurites. Taken together, our study demonstrates the positive effects of the L-PRF secretome on peripheral neurons and supports its use in regenerative medicine but care should be taken when using it for CNS applications.

Peripheral nerve regeneration in rats using nerve graft in a vein conduit pre-filled with platelet-rich fibrin (PRF)

Treatment of peripheral nerve injury is not always satisfactory. To improve results, specific adjuvant methods have been used, such as platelet-rich fibrin (PRF) and vein conduits. The goal of this study was to assess whether use of PRF and vein conduits after nerve suture improves nerve regeneration as measured by a functional score and histomorphometry analysis. Ten isogenic spontaneously hypertensive rats were randomly assigned to 4 experimental procedures: 1) Sham group (n = 10); 2) Nerve graft (NG) group (n = 10); 3) Nerve graft covered with a vein conduit (NGVC) (n = 10); and 4) Nerve graft covered with a vein conduit pre-filled with PRF (NGVCP) (n = 10). Nerve repair results were evaluated on: sciatic functional index (SFI) at 0, 30, 60 and 90 days; morphometric and morphologic analysis of the distal nerve; and histological analysis of Fluoro-Gold® stained motor neurons in the anterior horn of the spinal cord. Compared to the Sham control group, the NGVC and NGVCP groups exhibited lower SFI on all measures. The NGVC group showed improvement in SFI at day 90, which was significant compared to the NG group. Fiber and axon diameters were comparable in the NGVC and NGVCP groups, which were both significantly lower than in the Sham and NG groups. Significant improvement was expected with PRF, but in fact the release of factors from this substance was not as effective as hoped.

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.

The potential therapeutic effect of platelet-rich plasma in the treatment of post-COVID-19 parosmia

Background

COVID-19-related olfactory dysfunction is an emerging problem with a significant impact on the quality of life of affected individuals. Different lines of treatment have been used with varying results. This study aimed to assess the potential therapeutic effect of PRP in the treatment of post-COVID olfactory dysfunction. This work aimed to assess the potential therapeutic effect of platelet-rich plasma (PRP) in treating post-COVID-19 parosmia. A pilot study was conducted on 60 patients with post-COVID parosmia without responding to a 3-month course of olfactory training, topical corticosteroids, omega-three, vitamin B12, and zinc supplementation. The patients were distributed randomly and equally among 2 groups. The case group was subjected to three PRP injections in the olfactory cleft at 3 weeks intervals. The control group continued the pre-study treatment protocol for 6 weeks. The degree of parosmia was assessed before and after treatment subjectively using a visual analog scale (VAS) from 0 to 10. Reaching 0–1 on the visual analog scale was a complete improvement. The primary outcome was assessing the post-treatment score for parosmia 1 month after the third injection in the case group. The second outcome was the comparison between both groups regarding the degree of improvement 1 month after cessation of treatment.

Results

There was a highly significant improvement in VAS for parosmia (p < 0.00001) in the case group and a significant improvement in VAS for parosmia in the control group (p = P = 0.00148). There was a significant difference between both groups regarding the degree of improvement favoring the case group (p = 0.002).

Conclusion

Platelet-rich plasma injection in the olfactory cleft offers a therapeutic option for treating patients with post-COVID-19 olfactory parosmia who failed to respond to traditional conservative treatment.

Effects of chitosan and platelet-rich plasma on facial nerve regeneration in an animal model

PURPOSE

There is still no widely-accepted local agent proven to be effective in nerve regeneration. We aimed to investigate the effects of chitosan gel and platelet-rich plasma MATERIALS AND METHODS: Electrophysiological measurements were performed before and immediately after injury. The injured nerves were covered with spongostan impregnated with the following agents: Group 1 (Control Group): Saline at a dose of 50 µl; Group 2: Chitosan (CHT) at a dose of 50 µl; Group 3: PRP at a dose of 50 ml; and Group 4: a solution of CHT with PRP (1:1). The final measurements were performed after 3 weeks and the injured nerve of each rat was removed.

RESULTS

There were statistically-significant differences between the groups regarding the measurements of the after-treatment values of stimulus threshold (p < 0.05). The best improvement in electrophysiological measurement and histopathological evaluation was found in Group 4 (CHT-PRP).

CONCLUSION

Chitosan gel has a positive effect on nerve healing and applying it along with PRP can enhance the effect of chitosan.

Effects and mechanism of platelet-rich plasma on military drill injury: a review

Military drill injury is a significant part of military medical research. The increase of training intensity and changes in training methods lead to differences in injury types. The ideal therapeutic modality should allow rapid healing at a reasonable cost and minimize impact on patients' life. Platelet -rich plasma (PRP), a platelet concentrate, is rich in a variety of growth factors and widely used clinically as a minimally invasive treatment. It plays an important role in injury repair and rehabilitation. In this article, we review the therapeutic role of PRP in military drill injury and its possible underlying mechanisms, with a focus on plantar fasciitis, stress fractures and other common injuries, in order to provide basic support for military reserve.

The Effectiveness of Platelet-Rich Plasma and Radial Extracorporeal Shock Wave Compared with Platelet-Rich Plasma in the Treatment of Moderate Carpal Tunnel Syndrome

OBJECTIVES

To evaluate the combination effect of platelet-rich plasma (PRP) and extracorporeal shock wave therapy (ESWT) for moderate carpal tunnel syndrome (CTS), compared with PRP alone.

DESIGN

A randomized, double-blinded, placebo-controlled trial.

SETTING

A single medical center in Taiwan.

PATIENTS

Patients diagnosed with moderate CTS.

INTERVENTIONS

All subjects were administered one dose of ultrasound-guided PRP injection at baseline. After two weeks, one session of rESWT was completed in the intervention group, whereas the control group received one session of sham rESWT. Evaluations were performed at baseline and one, three, and six months post-PRP injection.

OUTCOME MEASURES

The Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) was measured as the primary outcome. Electrophysiological study and cross-sectional area (CSA) of the median nerve were used as secondary outcomes.

RESULTS

All 40 enrolled subjects (male/female: 4/36) completed the study, resulting in an analysis of 32 wrists per group (total: N = 64 wrists). Compared with the control group, the intervention group did not show statistically significantly superior outcomes, except in BCTQs at one month (mean change ± SE = -11.47 ± 1.18 vs -7.06 ± 1.26, P = 0.013) and distal motor latency at three months (mean change ± SE = -0.59 ± 0.09 vs -0.30 ± 0.09, P = 0.031).

CONCLUSIONS

Combined PRP and one-session rESWT was not superior to PRP alone in treating moderate CTS. Further studies with multiple sessions of ESWT and longer follow-up periods are needed to verify the clinical efficacy of ESWT.

Revisiting the Regenerative Therapeutic Advances Towards Erectile Dysfunction

Erectile dysfunction (ED) is an inability to attain or maintain adequate penile erection for successful vaginal intercourse, leading to sexual and relationship dissatisfaction. To combat ED, various surgical and non-surgical approaches have been developed in the past to restore erectile functions. These therapeutic interventions exhibit significant impact in providing relief to patients; however, due to their associated adverse effects and lack of long-term efficacy, newer modalities such as regenerative therapeutics have gained attention due to their safe and prolonged efficacy. Stem cells and platelet-derived biomaterials contained in platelet-rich plasma (PRP) are thriving as some of the major therapeutic regenerative agents. In recent years, various preclinical and clinical studies have evaluated the individual, as well as combined of stem cells and PRP to restore erectile function. Being rich in growth factors, chemokines, and angiogenic factors, both stem cells and PRP play a crucial role in regenerating nerve cells, myelination of axons, homing and migration of progenitor cells, and anti-fibrosis and anti-apoptosis of damaged cavernous nerve in corporal tissues. Further, platelet-derived biomaterials have been proven to be a biological supplement for enhancing the proliferative and differentiation potential of stem cells towards neurogenic fate. Therefore, this article comprehensively analyzes the progresses of these regenerative therapies for ED.

Efficacy of platelet-rich plasma as an adjuvant to surgical carpal ligament release: a prospective, randomized controlled clinical trial

The purpose of this study is to evaluate the efficiency of local platelet-rich plasma (PRP) injection as an adjuvant treatment after carpal ligament release. We conducted a prospective randomized, triple-blinded, controlled trial. Fifty participants with mild to extreme carpal tunnel syndrome (CTS) were randomly assigned either to the PRP (n = 25) or the platelet-poor plasma (PPP, n = 25) group. After performing open surgical release of the carpal ligament, the inside of the carpal tunnel was irrigated with 3 mL of PRP or PPP according to each participant’s group allocation. The primary outcome was hand grip strength (HGS). Secondary outcomes were the time taken off work after surgery (in days) and scores on the Wong–Baker Faces Scale, Boston Carpal Tunnel Questionnaire, and Southampton Wound Assessment Scale. We evaluated patients before treatment and at 6-weeks. As expected, the pain levels, symptom severity, and functional status improved in all the patients after surgery. However, intragroup analysis revealed that only the participants in the PRP group had regained their pre-operative HGS levels at 6-weeks follow-up. These findings indicate that PRP is an effective adjuvant treatment in patients with mild to severe CTS who require surgery.

Corneal Cells: Fine-tuning Nerve Regeneration

The cornea is a transparent outermost structure of the eye anterior segment comprising the highest density of innervated tissue. In the process of corneal innervation, trigeminal ganglion originated corneal nerves diligently traverse different corneal cell types in different corneal layers including the corneal stroma and epithelium. While crossing the stromal and epithelial cell layers during innervation, due to the existing physical contacts, close interactions occur between stromal keratocytes, epithelial cells, resident immune cells and corneal nerves. Furthermore, by producing various trophic and growth factors corneal cells assist in maintaining the growth and function of corneal nerves. Similarly, corneal nerve generated growth factors critically modify the corneal cell function in all the corneal layers. Due to their close association and contacts, on-going cross-communication between these cell types and corneal nerves play a vital role in the modulation of corneal nerve function, regeneration during wound healing. The present review highlights the influence of different corneal cell types and growth factors released from these cells on corneal nerve regeneration and function.

Neutrophil elastase inhibition effectively rescued angiopoietin-1 decrease and inhibits glial scar after spinal cord injury

After spinal cord injury (SCI), neutrophil elastase (NE) released at injury site disrupts vascular endothelium integrity and stabilization. Angiopoietins (ANGPTs) are vascular growth factors that play an important role in vascular stabilization. We hypothesized that neutrophil elastase is one of the key determinants of vascular endothelium disruption/destabilization and affects angiopoietins expression after spinal cord injury. To test this, tubule formation and angiopoietins expression were assessed in endothelial cells exposed to different concentrations of recombinant neutropil elastase. Then, the expression of angiopoietin-1, angiopoietin-2, and neutrophil elastase was determined at 3 h and at 1, 3, 5, 7, 14, 21, and 28 days in a clinically relevant model of moderate compression (35 g for 5 min at T10) spinal cord injury. A dichotomy between the levels of angiopoietin-1 and angiopoietin-2 was observed; thus, we utilized a specific neutrophil elastase inhibitor (sivelestat sodium; 30 mg/kg, i.p., b.i.d.) after spinal cord injury. The expression levels of neutropil elastase and angiopoietin-2 increased, and that of angiopoietin-1 decreased after spinal cord injury in rats. The sivelestat regimen, optimized via a pharmacokinetics study, had potent effects on vascular stabilization by upregulating angiopoietin-1 via the AKT pathway and preventing tight junction protein degradation. Moreover, sivelestat attenuated the levels of inflammatory cytokines and chemokines after spinal cord injury and hence subsequently alleviated secondary damage observed as a reduction in glial scar formation and the promotion of blood vessel formation and stabilization. As a result, hindlimb locomotor function significantly recovered in the sivelestat-treated animals as determined by the Basso, Beattie, and Bresnahan scale and footprint analyses. Furthermore, sivelestat treatment attenuated neuropathic pain as assessed by responses to von Frey filaments after spinal cord injury. Thus, our result suggests that inhibiting neutropil elastase by administration of sivelestat is a promising therapeutic strategy to inhibit glial scar and promote functional recovery by upregulating angiopoietin-1 after spinal cord injury.

Platelet-rich plasma injections for carpal tunnel syndrome: a systematic and comprehensive review

A series of clinical trials focused on the use of ultrasound-guided platelet-rich plasma (PRP) infusions for the treatment of patients with carpal tunnel syndrome (CTS) were published over the last few years. However, the role of PRP for CTS remains unclear. We performed a systematic review according to Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. Two reviewers independently conducted the search using multiple databases: MEDLINE/PubMed, SCOPUS, Cochrane Database, and Web of Science. These databases were searched using terms "platelet" AND "rich" AND "plasma" AND "carpal" AND "tunnel". To maximize the search, backward chaining of references from retrieved papers was also undertaken. From the initial 19 studies, only five met our eligibility criteria. These articles included one randomized controlled double-blind study, one randomized controlled single-blind study, one randomized controlled non-blind study, one case-control study, and one case report. The vast majority of the included studies supported that PRP infusion improved the clinical condition of the patients and that PRP infusion was beneficial for patients with mild-to-moderate CTS. Therefore, PRP seems to be an interesting alternative for the treatment of mild-to-moderate CTS which, still, has not been thoroughly investigated. However, despite the promising results of the present studies, PRP has to be further tested before we reach to a definite conclusion regarding its therapeutic value.

Identification of Dysregulated microRNA Networks in Schwann Cell-Like Cultures Exposed to Immune Challenge: Potential Crosstalk with the Protective VIP/PACAP Neuropeptide System

Following peripheral nerve injury, dysregulations of certain non-coding microRNAs (miRNAs) occur in Schwann cells. Whether these alterations are the result of local inflammation and/or correlate with perturbations in the expression profile of the protective vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase-activating polypeptide (PACAP) system is currently unknown. To address these issues, we aimed at profiling the expression of selected miRNAs in the rat RT4 Schwann cell line. Cells exposed to lipopolysaccharide (LPS), to mimic the local inflammatory milieu, were appraised by real-time qPCR, Western blot and ELISAs. We found that upon LPS treatment, levels of pro-inflammatory cytokines (IL-1β, -6, -18, -17A, MCP-1 and TNFα) increased in a time-dependent manner. Unexpectedly, the expression levels of VIP and PACAP were also increased. Conversely, levels of VPAC1 and VPAC2 receptors were reduced. Downregulated miRNAs included miR-181b, -145, -27a, -340 and -132 whereas upregulated ones were miR-21, -206, -146a, -34a, -155, -204 and -29a, respectively. Regression analyses revealed that a subset of the identified miRNAs inversely correlated with the expression of VPAC1 and VPAC2 receptors. In conclusion, these findings identified a novel subset of miRNAs that are dysregulated by immune challenge whose activities might elicit a regulatory function on the VIP/PACAP system.

Cavernous nerve reconstruction with autologous vein graft and platelet-derived growth factors

In this study, we investigated the feasibility of using autologous vein graft and platelet-derived growth factors to bridge transected cavernous nerve in a rat model. A short defect in the bilateral cavernous nerve was created and repaired with vein graft from the right jugular vein or vein graft plus platelet-derived growth factors. The 32 rats were divided into four groups, namely Group 1 - no repair as a negative control, Group 2 - vein graft alone, Group 3 - vein graft plus platelet-derived growth factors, and Group 4 - sham operation as a positive control. We evaluated nerve regeneration and functional recovery using retrograde tracing study with FluoroGold, Toluidine blue staining of cavernous nerve, and the intracavernous pressure at 3 months. Three months after surgery, rich FluoroGold-positive cells were observed in the sham and vein graft plus platelet-derived growth factors group, but very few were found in the no repair group. The number of myelinated axons of regenerated cavernous nerve and intracavernous pressure were increased obviously in the two vein graft groups, especially in the vein graft plus platelet-derived growth factors group. These findings confirm the feasibility of using autologous vein as guides for cavernous nerve regeneration, and the regeneration can be further enhanced when the vein is filled with platelet-derived growth factors.

Injury-activated glial cells promote wound healing of the adult skin in mice

Cutaneous wound healing is a complex process that aims to re-establish the original structure of the skin and its functions. Among other disorders, peripheral neuropathies are known to severely impair wound healing capabilities of the skin, revealing the importance of skin innervation for proper repair. Here, we report that peripheral glia are crucially involved in this process. Using a mouse model of wound healing, combined with in vivo fate mapping, we show that injury activates peripheral glia by promoting de-differentiation, cell-cycle re-entry and dissemination of the cells into the wound bed. Moreover, injury-activated glia upregulate the expression of many secreted factors previously associated with wound healing and promote myofibroblast differentiation by paracrine modulation of TGF-β signalling. Accordingly, depletion of these cells impairs epithelial proliferation and wound closure through contraction, while their expansion promotes myofibroblast formation. Thus, injury-activated glia and/or their secretome might have therapeutic potential in human wound healing disorders.

Inside-out and standard vein grafts associated with platelet-rich plasma (PRP) in sciatic nerve repair. A histomorphometric study

Purpose:

To evaluated the tubulization technique with standard and inside-out vein, filled or not with platelet-rich plasma (PRP), in sciatic nerve repair.

Methods:

Seventy male Wistar rats were randomly divided into five groups: IOVNF (Inside-Out Vein with No Filling); IOVPRP (Inside-Out Vein filled with PRP); SVNF (Standard Vein with No Filling); SVPRP (Standard Vein filled with PRP); Sham (Control). The left external jugular vein was used as graft in a 10 mm nervous gap.

Results:

In the morphological analysis of all groups, myelinated nerve fibers with evident myelin sheath, neoformation of the epineurium and perineurium, organization of intraneural fascicles and blood vessels were observed. In the morphometry of the distal stump fibers, SVPRP group had the highest means regarding fiber diameter (3.63±0.42 μm), axon diameter (2.37±0.31 μm) and myelin sheath area (11.70±0.84 μm2). IOVPRP group had the highest means regarding axon area (4.39±1.16 μm2) and myelin sheath thickness (0.80±0.19 μm). As for values of the fiber area, IOVNF group shows highest means (15.54±0.67 μm2), but are still lower than the values of the Sham group.

Conclusion:

The graft filled with platelet-rich plasma, with use standard (SVPRP) or inside-out vein (IOVPRP), promoted the improvement in axonal regeneration on sciatic nerve injury.

Six-month efficacy of platelet-rich plasma for carpal tunnel syndrome: A prospective randomized, single-blind controlled trial

Recently, a few small reports with short follow-up period have shown clinical benefits of platelet-rich plasma (PRP) for peripheral neuropathy including one pilot study and one small, non-randomized trial in patients with carpal tunnel syndrome (CTS). Therefore, we conducted a randomized, single-blind, controlled trial to assess the 6-month effect of PRP in patients with CTS. Sixty patients with unilateral mild-to-moderate CTS were randomized into two groups of 30, namely the PRP and control groups. In the PRP group, patients were injected with one dose of 3 mL of PRP using ultrasound guidance and the control group received a night splint through the study period. The primary outcome measure was the visual analog scale (VAS) and secondary outcome measures included the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) score, the cross-sectional area (CSA) of the median nerve (MN), electrophysiological findings of the MN, and finger pinch strength. The evaluation was performed before treatment and at 1, 3, and 6 months post-injection. The PRP group exhibited a significant reduction in the VAS score, BCTQ score, and CSA of MN compared to the those of control group 6 months post-treatment (p < 0.05). Our study demonstrates that PRP is a safe modality that effectively relieves pain and improves disability in the patients with CTS.

Mechanisms of PDGF siRNA-mediated inhibition of bone cancer pain in the spinal cord

Patients with tumors that metastasize to bone frequently suffer from debilitating pain, and effective therapies for treating bone cancer are lacking. This study employed a novel strategy in which herpes simplex virus (HSV) carrying a small interfering RNA (siRNA) targeting platelet-derived growth factor (PDGF) was used to alleviate bone cancer pain. HSV carrying PDGF siRNA was established and intrathecally injected into the cavum subarachnoidale of animals suffering from bone cancer pain and animals in the negative group. Sensory function was assessed by measuring thermal and mechanical hyperalgesia. The mechanism by which PDGF regulates pain was also investigated by comparing the differential expression of pPDGFRα/β and phosphorylated ERK and AKT. Thermal and mechanical hyperalgesia developed in the rats with bone cancer pain, and these effects were accompanied by bone destruction in the tibia. Intrathecal injection of PDGF siRNA and morphine reversed thermal and mechanical hyperalgesia in rats with bone cancer pain. In addition, we observed attenuated astrocyte hypertrophy, down-regulated pPDGFRα/β levels, reduced levels of the neurochemical SP, a reduction in CGRP fibers and changes in pERK/ERK and pAKT/AKT ratios. These results demonstrate that PDGF siRNA can effectively treat pain induced by bone cancer by blocking the AKT-ERK signaling pathway.

Does glioblastoma cyst fluid promote sciatic nerve regeneration?

Glioblastoma cyst fluid contains growth factors and extracellular matrix proteins which are known as neurotrophic and neurite-promoting agents. Therefore, we hypothesized that glioblastoma cyst fluid can promote the regeneration of injured peripheral nerves. To validate this hypothesis, we transected rat sciatic nerve, performed epineural anastomosis, and wrapped the injured sciatic nerve with glioblastoma cyst fluid- or saline-soaked gelatin sponges. Neurological function and histomorphological examinations showed that compared with the rats receiving local saline treatment, those receiving local glioblastoma cyst fluid treatment had better sciatic nerve function, fewer scars, greater axon area, counts and diameter as well as fiber diameter. These findings suggest that glioblastoma cyst fluid can promote the regeneration of injured sciatic nerve and has the potential for future clinical application in patients with peripheral nerve injury.

Improved peripheral nerve regeneration using acellular nerve allografts loaded with platelet-rich plasma

Acellular nerve allografts (ANAs) behave in a similar manner to autografts in supporting axonal regeneration in the repair of short peripheral nerve defects but fail in larger defects. The objective of this article is to evaluate the effect of ANA supplemented with platelet-rich plasma (PRP) to improve nerve regeneration after surgical repair and to discuss the mechanisms that underlie this approach. Autologous PRP was obtained from rats by double-step centrifugation and was characterized by determining platelet numbers and the release of growth factors. Forty-eight Sprague-Dawley rats were randomly divided into 4 groups (12/group), identified as autograft, ANA, ANA loaded with PRP (ANA+PRP), and ANA loaded with platelet-poor plasma (PPP, ANA+PPP). All grafts were implanted to bridge long-gap (15 mm) sciatic nerve defects. We found that PRP with a high platelet concentration exhibited a sustained release of growth factors. Twelve weeks after surgery, the autograft group displayed the highest level of reinnervation, followed by the ANA+PRP group. The ANA+PRP group showed a better electrophysiology response for amplitude and conduction velocity than the ANA and ANA+PPP groups. Based on histological evaluation, the ANA+PRP and autograft groups had higher numbers of regenerating nerve fibers. Quantitative real-time polymerase chain reaction (qRT-PCR) demonstrated that PRP boosted expression of neurotrophins in the regenerated nerves. Moreover, the ANA+PRP and autograft groups showed excellent physiological outcomes in terms of the prevention of muscle atrophy. In conclusion, ANAs loaded with PRP as tissue-engineered scaffolds can enhance nerve regeneration and functional recovery after the repair of large nerve gaps nearly as well as autografts.

Platelet-Rich Plasma Promotes Axon Regeneration, Wound Healing, and Pain Reduction: Fact or Fiction

Platelet-rich plasma (PRP) has been tested in vitro, in animal models, and clinically for its efficacy in enhancing the rate of wound healing, reducing pain associated with injuries, and promoting axon regeneration. Although extensive data indicate that PRP-released factors induce these effects, the claims are often weakened because many studies were not rigorous or controlled, the data were limited, and other studies yielded contrary results. Critical to assessing whether PRP is effective are the large number of variables in these studies, including the method of PRP preparation, which influences the composition of PRP; type of application; type of wounds; target tissues; and diverse animal models and clinical studies. All these variables raise the question of whether one can anticipate consistent influences and raise the possibility that most of the results are correct under the circumstances where PRP was tested. This review examines evidence on the potential influences of PRP and whether PRP-released factors could induce the reported influences and concludes that the preponderance of evidence suggests that PRP has the capacity to induce all the claimed influences, although this position cannot be definitively argued. Well-defined and rigorously controlled studies of the potential influences of PRP are required in which PRP is isolated and applied using consistent techniques, protocols, and models. Finally, it is concluded that, because of the purported benefits of PRP administration and the lack of adverse events, further animal and clinical studies should be performed to explore the potential influences of PRP.

Fingolimod induces the transition to a nerve regeneration promoting Schwann cell phenotype

Successful regeneration of injured peripheral nerves is mainly attributed to the plastic behavior of Schwann cells. Upon loss of axons, these cells trans-differentiate into regeneration promoting repair cells which provide trophic support to regrowing axons. Among others, activation of cJun was revealed to be involved in this process, initiating the stereotypic pattern of Schwann cell phenotype alterations during Wallerian degeneration. Nevertheless, the ability of Schwann cells to adapt and therefore the nerve's potential to regenerate can be limited in particular after long term denervation or in neuropathies leading to incomplete regeneration only and thus emphasizing the need for novel therapeutic approaches. Here we stimulated primary neonatal and adult rat Schwann cells with Fingolimod/FTY720P and investigated its impact on the regeneration promoting phenotype. FTY720P activated a number of de-differentiation markers including cJun and interfered with maturation marker and myelin expression. Functionally, FTY720P treated Schwann cells upregulated growth factor expression and these cells enhanced dorsal root ganglion neurite outgrowth on inhibitory substrates. Our results therefore provide strong evidence that FTY720P application supports the generation of a repair promoting cellular phenotype and suggest that Fingolimod could be used as treatment for peripheral nerve injuries and diseases.

An inside-out vein graft filled with platelet-rich plasma for repair of a short sciatic nerve defect in rats

Platelet-rich plasma containing various growth factors can promote nerve regeneration. An inside-out vein graft can substitute nerve autograft to repair short nerve defects. It is hypothesized that an inside-out vein graft filled with platelet-rich plasma shows better effects in the repair of short sciatic nerve defects. In this study, an inside-out vein autograft filled with platelet-rich plasma was used to bridge a 10 mm-long sciatic nerve defect in rats. The sciatic nerve function of rats with an inside-out vein autograft filled with platelet-rich plasma was better improved than that of rats with a simple inside-out vein autograft. At 6 and 8 weeks, the sciatic nerve function of rats with an inside-out vein autograft filled with platelet-rich plasma was better than that of rats undergoing nerve autografting. Compared with the sciatic nerve repaired with a simple inside-out vein autograft, the number of myelinated axons was higher, axon diameter and myelin sheath were greater in the sciatic nerve repaired with an inside-out vein autograft filled with platelet-rich plasma and they were similar to those in the sciatic nerve repaired with nerve autograft. These findings suggest that an inside-out vein graft filled with platelet-rich plasma can substitute nerve autograft to repair short sciatic nerve defects.

Platelet-rich plasma and the elimination of neuropathic pain

Peripheral neuropathic pain typically results from trauma-induced nociceptive neuron hyperexcitability and their spontaneous ectopic activity. This pain persists until the trauma-induced cascade of events runs its full course, which results in complete tissue repair, including the nociceptive neurons recovering their normal biophysical properties, ceasing to be hyperexcitable, and stopping having spontaneous electrical activity. However, if a wound undergoes no, insufficient, or too much inflammation, or if a wound becomes stuck in an inflammatory state, chronic neuropathic pain persists. Although various drugs and techniques provide temporary relief from chronic neuropathic pain, many have serious side effects, are not effective, none promotes the completion of the wound healing process, and none provides permanent pain relief. This paper examines the hypothesis that chronic neuropathic pain can be permanently eliminated by applying platelet-rich plasma to the site at which the pain originates, thereby triggering the complete cascade of events involved in normal wound repair. Many published papers claim that the clinical application of platelet-rich plasma to painful sites, such as muscle injuries and joints, or to the ends of nerves evoking chronic neuropathic pain, a process often referred to as prolotherapy, eliminates pain initiated at such sites. However, there is no published explanation of a possible mechanism/s by which platelet-rich plasma may accomplish this effect. This paper discusses the normal physiological cascade of trauma-induced events that lead to chronic neuropathic pain and its eventual elimination, techniques being studied to reduce or eliminate neuropathic pain, and how the application of platelet-rich plasma may lead to the permanent elimination of neuropathic pain. It concludes that platelet-rich plasma eliminates neuropathic pain primarily by platelet- and stem cell-released factors initiating the complex cascade of wound healing events, starting with the induction of enhanced inflammation and its complete resolution, followed by all the subsequent steps of tissue remodeling, wound repair and axon regeneration that result in the elimination of neuropathic pain, and also by some of these same factors acting directly on neurons to promote axon regeneration thereby eliminating neuropathic pain.

Identification of VHY/Dusp15 as a regulator of oligodendrocyte differentiation through a systematic genomics approach

Multiple sclerosis (MS) is a neuroinflammatory disease characterized by a progressive loss of myelin and a failure of oligodendrocyte (OL)-mediated remyelination, particularly in the progressive phases of the disease. An improved understanding of the signaling mechanisms that control differentiation of OL precursors may lead to the identification of new therapeutic targets for remyelination in MS. About 100 mammalian Protein Tyrosine Phosphatases (PTPs) are known, many of which are involved in signaling both in health and disease. We have undertaken a systematic genomic approach to evaluate PTP gene activity in multiple sclerosis autopsies and in related in vivo and in vitro models of the disease. This effort led to the identification of Dusp15/VHY, a PTP previously believed to be expressed only in testis, as being transcriptionally regulated during OL differentiation and in MS lesions. Subsequent RNA interference studies revealed that Dusp15/VHY is a key regulator of OL differentiation. Finally, we identified PDGFR-beta and SNX6 as novel and specific Dusp15 substrates, providing an indication as to how this PTP might exert control over OL differentiation.

Expression of activating transcription factor 3 (ATF 3) and caspase 3 in Schwann cells and axonal outgrowth after sciatic nerve repair in diabetic BB rats

The aim of this study was to evaluate nerve regeneration in relation to the transcription factor, Activating Transcription Factor 3 (ATF 3), and an apoptotic marker, caspase 3, in the Schwann cells of diabetic BB rats (i.e. display type 1 diabetes phenotype). Sciatic nerves in healthy Wistar rats and in diabetic BB rats were transected and immediately repaired. Axonal outgrowth (neurofilament staining) and expression of ATF 3 and caspase 3 were quantified by immunohistochemistry after six days. There was no difference in axonal outgrowth between healthy and diabetic rats. However, the sciatic nerve in the diabetic rats exhibited a larger number of ATF 3 expressing Schwann cells at the site of the lesion and also a higher number of caspase 3 expressing Schwann cells. Similar differences were observed in the distal nerve segment between the healthy and diabetic rats. There were no correlations between the number of Schwann cells expressing ATF 3 and caspase 3. Thus, diabetic BB rats display an increased activation of ATF 3 and also a rise in apoptotic caspase 3 expressing Schwann cells, but with no discrepancy in length of axonal outgrowth after nerve injury and repair at six days. Knowledge about signal transduction mechanisms in diabetes after stress may provide new insights into the development of diabetic neuropathy and neuropathic pain.

Effects of insulin-like growth factor-I and platelet-rich plasma on sciatic nerve crush injury in a rat model

OBJECT

Local administration of insulin-like growth factor-I (IGF-I) has been shown to increase the rate of axon regeneration in crush-injured and freeze-injured rat sciatic nerves. Local administration of platelet-rich plasma (PRP) has been also shown to have a measurable effect on facial nerve regeneration after transection in a rat model. The objective of the study was to compare the effects of locally administered IGF-I and PRP on the parameters of the Sciatic Function Index (SFI), sensory function (SF), axon count, and myelin thickness/axon diameter ratio (G-ratio) in a rat model of crush-injured sciatic nerves.

METHODS

The right sciatic nerve of Wistar albino rats (24 animals) was crushed using a Yasargil-Phynox aneurysm clip for 45 minutes. All animals were randomly divided into 3 groups: Group 1 (control group) was treated with saline, Group 2 was treated with IGF-I, and Group 3 was treated with PRP. Injections were performed using the tissue expander's injection port with a connecting tube directed at the crush-injured site. Functional recovery was assessed with improvement in the SFI. Recovery of sensory function was using the pinch test. Histopathological examination was performed 3 months after the injury.

RESULTS

The SFI showed an improved functional recovery in the IGF-I-treated animals (Group 2) compared with the saline-treated animals (Group 1) 30 days after the injury. In IGF-I-treated rats, sensory function returned to the baseline level significantly faster than in saline-treated and PRP-treated rats as shown in values between SF-2 and SF-7. The G-ratios were found to be significantly higher in both experimental groups than in the control group.

CONCLUSIONS

This study suggests that the application of IGF-I to the crush-injured site may expedite the functional recovery of paralyzed muscle by increasing the rate of axon regeneration.

Trophic responsiveness of purified postnatal and adult rat retinal ganglion cells

Central neurons lose the ability for axonal re-growth during development and typically do not regenerate their axons following axotomy once they become mature unless given a growth-permissive environment i.e. peripheral nerve graft. In the present study, the growth responsiveness of purified retinal ganglion cells (RGCs) at different ages to neurotrophic factors and Schwann cell (SC)-secreted factors were examined directly. The purity of adult RGCs was 97% as assessed by retrograde labelling with 4,6-diamidino-2-phenylindole. The stability of cultures were demonstrated by long-term survival (30 days) in medium contained brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF) and forskolin (F) (BCF). RGCs from postnatal (P) (P0, P4, P8, P21) and adult (P90) rats showed decreasing levels of survival and neuritogenesis when grown in BCF. In contrast, the opposite was observed in SC-conditioned medium (CM)-treated P0-P8 RGCs which were increasingly responsive. SCCM induced maximal neurite outgrowth in P8 RGCs via the activation of extracellular regulated kinase 1/2 (Erk1/2). Inhibition of mitogen-activated protein kinase-Erk1/2 signaling using an Erk1/2-specific inhibitor (UO126) abolished SCCM-induced Erk1/2 phosphorylation and neuritogenesis completely. Although both SCCM and BCF failed to sustain the same levels of growth in P21 or P90 cultures as observed in P8 cultures, SCCM promoted higher survival and neuritogenesis than BCF-treated adult RGCs. This study is the first report of adult rat RGC purification and demonstrates that mature RGCs need multiple factors for survival and neurite outgrowth.

Cellular origin and developmental mechanisms during the formation of skin melanocytes

Melanocytes are derived from the neural crest (NC), which are transient multipotent cells arising by delamination from the developing dorsal neural tube. During recent years, signaling systems and molecular mechanisms of melanocyte development have been studied in detail, but the exact diversification of the NC into melanocytes and how they migrate, expand and disperse in the skin have not been fully understood. The recent finding that Schwann cell precursors (SCPs) of the growing nerve represents a stem cell niche from which various cell types, including Schwann cells, endoneural fibroblasts and melanocytes arise has exposed new knowledge on the cellular basis for melanocyte development. This opens for the identification of new factors and reinterpretation of old data on cell fate instructive, proliferative, survival and cell homing factors participating in melanocyte development.

Intrathecal delivery of PDGF produces tactile allodynia through its receptors in spinal microglia

Neuropathic pain is a debilitating pain condition that occurs after nerve damage. Such pain is considered to be a reflection of the aberrant excitability of dorsal horn neurons. Emerging lines of evidence indicate that spinal microglia play a crucial role in neuronal excitability and the pathogenesis of neuropathic pain, but the mechanisms underlying neuron-microglia communications in the dorsal horn remain to be fully elucidated. A recent study has demonstrated that platelet-derived growth factor (PDGF) expressed in dorsal horn neurons contributes to neuropathic pain after nerve injury, yet how PDGF produces pain hypersensitivity remains unknown. Here we report an involvement of spinal microglia in PDGF-induced tactile allodynia. A single intrathecal delivery of PDGF B-chain homodimer (PDGF-BB) to naive rats produced a robust and long-lasting decrease in paw withdrawal threshold in a dose-dependent manner. Following PDGF administration, the immunofluorescence for phosphorylated PDGF β-receptor (p-PDGFRβ), an activated form, was markedly increased in the spinal dorsal horn. Interestingly, almost all p-PDGFRβ-positive cells were double-labeled with an antibody for the microglia marker OX-42, but not with antibodies for other markers of neurons, astrocytes and oligodendrocytes. PDGF-stimulated microglia in vivo transformed into a modest activated state in terms of their cell number and morphology. Furthermore, PDGF-BB-induced tactile allodynia was prevented by a daily intrathecal administration of minocycline, which is known to inhibit microglia activation. Moreover, in rats with an injury to the fifth lumbar spinal nerve (an animal model of neuropathic pain), the immunofluorescence for p-PDGFRβ was markedly enhanced exclusively in microglia in the ipsilateral dorsal horn. Together, our findings suggest that spinal microglia critically contribute to PDGF-induced tactile allodynia, and it is also assumed that microglial PDGF signaling may have a role in the pathogenesis of neuropathic pain.

The effect of platelet-rich plasma on cavernous nerve regeneration in a rat model

The aim of this study was to investigate the effect of platelet-rich plasma (PRP) on cavernous nerve (CN) regeneration and functional status in a nerve-crush rat model. Twenty-four Sprague-Dawley male rats were randomly divided into three equal groups: eight had a sham operation, eight underwent bilateral nerve crushing with no further intervention and eight underwent bilateral nerve crushing with an immediate application of PRP on the site of injury. Erectile function was assessed by CN electrostimulation at 3 months and nerve regeneration was assessed by toluidine blue staining of CN and nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining of penile tissue. Three months after surgery, in the group that underwent bilateral nerve crushing with no further intervention, the functional evaluation showed a lower mean maximal intracavernous pressure (ICP) and maximal ICP per mean arterial pressure (MAP) with CN stimulation than those in the sham group. In the group with an immediate application of PRP, the mean maximal ICP and maximal ICP/MAP were significantly higher than those in the injured control group. Histologically, the group with the application of PRP had more myelinated axons of CNs and more NADPH-diaphorase-positive nerve fibres than the injured control group but fewer than the sham group. These results show that the application of PRP to the site of CN-crush injury facilitates nerve regeneration and recovery of erectile function. Our research indicates that clinical application of PRP has potential repairing effect on CN and peripheral nerves.

Changes in PDGF expression in spared dorsal root ganglia and associated spinal dorsal horns in cats subjected to partial dorsal root ganglionectomy

Changes in the platelet derived growth factor (PDGF) in the spared dorsal root ganglia (DRG) and associated spinal dorsal horns were evaluated in cats subjected to unilateral removal of L1-L5 and L7-S2 DRG, sparing the L6 DRG. The number of PDGF immunopositive neurons and protein expression decreased significantly in the spared DRG and associated dorsal horns of the L3 and L6 cord segments at 3 days post-operation (dpo). It bottomed to the lowest level at 7 dpo in the DRG, then returned to the control level at 14 dpo; while in the L6 dorsal horn, it rapidly increased at 7 dpo and exceeded the control level at 14 dpo. This showed a significant upregulation in the spared DRG and associated spinal dorsal horns, especially in the L6 cord segment following a transient decrease. Meanwhile, a significant upregulation of PDGF mRNA was also seen in L6 DRG and L3 and L6 dorsal horns at 3 dpo. The upregulation of the endogenous PDGF in the said structures indicated a potential role of this factor in spinal cord plasticity after partial dorsal root ganglia removal in cats.

Canadian Association of Neurosciences review: regulation of myelination by trophic factors and neuron-glial signaling

Myelination in the nervous system is a tightly regulated process that is mediated by both soluble and non-soluble factors acting on axons and glial cells. This process is bi-directional and involves a variety of neurotrophic and gliotrophic factors acting in paracrine and autocrine manners. Neuron-derived trophic factors play an important role in the control of early proliferation and differentiation of myelinating glial cells. At later stages of development, same molecules may play a different role and act as inducers of myelination rather than cell survival signals for myelinating glial cells. In return, myelinating glial cells provide trophic support for axons and protect them from injury. Chronic demyelination leads to secondary axonal degeneration that is responsible for long-term disability in primary demyelinating diseases such as multiple sclerosis and inherited demyelinating peripheral neuropathies. A better understanding of the molecular mechanisms controlling myelination may yield novel therapeutic targets for demyelinating nervous system disorders.

Effects of Electro-acupuncture on PDGF Expression in Spared Dorsal Root Ganglion and Associated Dorsal Horn Subjected to Partial Dorsal Root Ganglionectomy in Cats

The effects of electro-acupuncture (EA) on the expression of platelet derived growth factor (PDGF) in spared dorsal root ganglion (DRG) and associated dorsal horns were evaluated in cats subjected to bilateral removal of L1-L5 and L7-S2 DRG, while sparing L6 DRG and were demonstrated using Immunohistochemistry, Western blot and RT-PCR techniques. On the acupunctured side, there was a significant increase in the total number of PDGF positive neurons. Large neurons of the L6 DRG at 7 days post operation (dpo), and small to medium-sized neurons at 14 dpo, as well as in the lamina II of the L6 spinal cord at 14 dpo was observed. The expression of PDGF protein increased significantly in the L6 DRG at 7 and 14 dpo and in the dorsal horn of the L6 spinal cord at 14 dpo while the upregulation of PDGF mRNA was seen at 3 dpo in the L6 DRG and the dorsal horn of the L3 and L6 spinal cord. These findings demonstrate that intrinsic PDGF has been upregulated in cats subjected to partial dorsal root ganglionectomy following EA, indicating endogenous PDGF is involved in promoting spinal plasticity following EA.

Effect of Platelet Rich Plasma and Fibrin Sealant on Facial Nerve Regeneration in a Rat Model

OBJECTIVE

To investigate the effects of platelet rich plasma (PRP) and fibrin sealant (FS) on facial nerve regeneration.

STUDY DESIGN

Prospective, randomized, and controlled animal study.

METHODS

Experiments involved the transection and repair of facial nerve of 49 male adult rats. Seven groups were created dependant on the method of repair: suture; PRP (with/without suture); platelet poor plasma (PPP) (with/without suture); and FS (with/without suture) groups. Each method of repair was applied immediately after the nerve transection. The outcomes measured were: 1) observation of gross recovery of vibrissae movements within 8-week period after nerve transection and repair using a 5-point scale and comparing the left (test) side with the right (control) side; 2) comparisons of facial nerve motor action potentials (MAP) recorded before and 8 weeks after nerve transection and repair, including both the transected and control (untreated) nerves; 3) histologic evaluation of axons counts and the area of the axons.

RESULTS

Vibrissae movement observation: the inclusion of suturing resulted in overall improved outcomes. This was found for comparisons of the suture group with PRP group; PRP with/without suture groups; and PPP with/without suture groups (P < .05). The PRP without suture group had a significantly greater degree of recovery than the PPP without suture group (P < .05), but it did not have better performance than suture group (P > .05). The movement recovery of the suture group was significantly better than the FS group (P = .014). The recovery of function of the PRP groups was better than that of the FS groups, although this did not reach statistical significance (P = .09). Electrophysiologic testing: there was a significantly better performance of the suture group when compared with the PRP and PPP without suture groups in nerve conduction velocity (P < .05). The PRP with suture group had the best results when compared with the suture as well as the PPP with suture groups in duration and latency-2 of MAP (P < .05). For the FS groups, no results were found demonstrating a biological effect. The PRP with suture group demonstrated the best performance in the latency-2 and the area under the curve of MAP when compared with the suture and FS with suture groups (P < .05). Histomorphometric analysis: PRP with suture demonstrated the greatest increase in axon counts when compared with suture, FS with suture, and PPP with suture groups (P < .05). There was no statistically significant difference seen in axon diameter.

CONCLUSION

The best results for the return of function in our rat facial nerve axotomy models occurred when the nerve ends were sutured together. At the same time, the data demonstrated a measurable neurotrophic effect when PRP was present, with the most favorable results seen with PRP added to suture. There was an improved functional outcome with the use of PRP in comparison with FS or no bioactive agents (PPP). FS showed no benefit over conventional suturing in facial nerve regeneration. Our study provides the potential of a new clinical application for PRP in peripheral nerve regeneration.

Platelet-derived growth factors in the developing avian heart and maturating coronary vasculature

Platelet-derived growth factors (PDGFs) are important in embryonic development. To elucidate their role in avian heart and coronary development, we investigated protein expression patterns of PDGF-A, PDGF-B, and the receptors PDGFR-alpha and PDGFR-beta using immunohistochemistry on sections of pro-epicardial quail-chicken chimeras of Hamburger and Hamilton (HH) 28-HH35. PDGF-A and PDGFR-alpha were expressed in the atrial septum, sinus venosus, and throughout the myocardium, with PDGFR-alpha retreating to the trabeculae at later stages. Additionally, PDGF-A and PDGFR-alpha were present in outflow tract cushion mesenchyme and myocardium, respectively. Small cardiac nerves and (sub)epicardial cells expressed PDGF-B and PDGFR-beta. Furthermore, endothelial cells expressed PDGF-B, while vascular smooth muscle cells and interstitial epicardium-derived cells expressed PDGFR-beta, indicating a role in coronary maturation. PDGF-B is also present in ventricular septal development, in the absence of any PDGFR. Epicardium-derived cells in the atrioventricular cushions expressed PDGFR-beta. We conclude that all four proteins are involved in myocardial development, whereas PDGF-B and PDGFR-beta are specifically important in coronary maturation.

Osteoactivin upregulates expression of MMP-3 and MMP-9 in fibroblasts infiltrated into denervated skeletal muscle in mice

In this study, we examined pathophysiological roles of osteoactivin, a functionally unknown type I membrane glycoprotein, in mouse skeletal muscle atrophied by denervation (sciatic neurectomy). Denervation increased the amounts of osteoactivin, vimentin, matrix metalloproteinase-3 (MMP-3), and MMP-9 in mouse gastrocnemius muscle. Interestingly, immunohistochemical analysis revealed that vimentin, MMP-3, and MMP-9 were mainly present in fibroblast-like cells infiltrated into denervated mouse gastrocnemius muscle, whereas osteoactivin was expressed in the sarcolemma of myofibers adjacent to the fibroblast-like cells. On the basis of these findings, we reasoned that osteoactivin in myocytes was involved in activation of the infiltrated fibroblasts. To address this issue, we examined effects of osteoactivin on expression of MMPs in fibroblasts in vitro and in vivo. Overexpression of osteoactivin in NIH-3T3 fibroblasts induced expression of MMP-3, but not in mouse C(2)C(12) myoblasts, indicating that osteoactivin might functionally target fibroblasts. Treatment with recombinant mouse osteoactivin increased the amounts of collagen type I, MMP-3, and MMP-9 in mouse NIH-3T3 fibroblasts. The upregulated expression of these fibroblast marker proteins was significantly inhibited by heparin, but not by an integrin inhibitor, indicating that a heparin-binding motif in the extracellular domain might be an active site of osteoactivin. In osteoactivin-transgenic mice, denervation further enhanced expression of MMP-3 and MMP-9 in fibroblasts infiltrated into gastrocnemius muscle, compared with wild-type mice. Our present results suggest that osteoactivin might function as an activator for fibroblasts infiltrated into denervated skeletal muscles and play an important role in regulating degeneration/regeneration of extracellular matrix.

Schwann cell lines derived from malignant peripheral nerve sheath tumors respond abnormally to platelet-derived growth factor-BB

Neurofibromatosis type 1 (NF1) is a genetic disease caused by the loss of neurofibromin, which can lead to formation of highly invasive malignant peripheral nerve sheath tumors (MPNST). We characterized platelet-derived growth factor-beta (PDGF-beta) receptor expression levels and signal transduction pathways in NF1 MPNST cell lines and compared them with the expression of PDGF-beta receptors in normal human Schwann cells (nhSC). As examined by Western blotting, PDGF-beta receptor expression levels were similar in nhSC and NF1 MPNST cell lines. MAPK and Akt also were phosphorylated in both cell types to a similar degree in response to PDGF B chains (PDGF-BB). However, increased intracellular calcium (Ca2+) levels in response to PDGF-BB were observed only in the NF1 MPNST cell lines; nhSC did not show any increase in intracellular calcium when stimulated with PDGF-BB. The calcium response in NF1 MPNST cell lines was blocked with thapsigargin, suggesting that the PDGF-BB-stimulated increases in intracellular calcium originated in the internal compartment of the cell rather than reflecting influx of calcium from the extracellular compartment. Calmodulin kinase II (CAMKII) is phosphorylated in response to PDGF-BB in the NF1 MPNST cell lines, whereas no phosphorylation of CAMKII was observed in nhSCs. The decreased growth of NF1 MPNST cell lines after treatment with a CAMKII inhibitor is consistent with the view that aberrant activation of the calcium-signaling pathway by PDGF-BB contributes to the formation of MPNST in NF1 patients.

Autologous fibrin glue in peripheral nerve regeneration in vivo

The activity of several growth factors on peripheral nerve regeneration is reported. Autologous fibrin glue contains a large number of platelets, which release significant quantities of growth factors. In order to understand the role of autologous fibrin glue in peripheral nerve regeneration, a 15-mm rabbit peroneal nerve defect was repaired using a vein graft filled with autologous fibrin glue. Axonal regeneration was examined using histological and electrophysiological methods. The extent of axonal regeneration was superior when treated with autologous fibrin glue. Our data suggest that fibrin nets formed by fibrinogen, in combination with growth factors present in autologous fibrin glue, might effectively promote peripheral nerve regeneration in nerve defects.

The neuroprotective role of inflammation in nervous system Injuries

The contribution of inflammation to the pathogenesis of several nervous system disorders has long been established. Other observations, however, indicate that both inflammatory cells and mediators may also have beneficial functions, assisting in repair and recovery processes. There is compelling evidence to indicate that in the injured nervous system, as in other tissues, macrophages are needed at an early stage after injury in order for healing to take place. Likewise, activated T cells of a particular specificity can reduce the spread of damage. This neuroprotective effect of T cells may be caused, at least in part, by the production of neurotrophic factors such as neurotrophin-3 or brain-derived neurotrophic factor. Interestingly, recent findings indicate that immune cells are able to produce a variety of neurotrophic factors which promote neuronal survival and may also mediate anti-inflammatory effects. Numerous cytokines are induced after nervous system injuries. Some cytokines, such as TNF-alpha, IL-1 and IFN-gamma, are well known for their promotion of inflammatory responses. However, these cytokines also have immunosuppressive functions and their subsequent expression also assists in repair or recovery processes, suggesting a dual role for some pro-inflammatory cytokines. This should be clarified, as it may be crucial in the design of therapeutic strategies to target specific cytokine(s). Finally, there is a growing body of evidence to show that autoreactive IgM antibodies may constitute an endogenous system of tissue repair, and therefore prove of value as a therapeutic strategy. Available evidence would appear to indicate that the inflammatory response observed in several neurological conditions is more complex than previously thought. Therefore, the design of more effective therapies depends on a clear delineation of the beneficial and detrimental effects of inflammation.

Homeobox gene expression in adult dorsal root ganglia during sciatic nerve regeneration: is regeneration a recapitulation of development?

After damage of the sciatic nerve, a regeneration process is initiated. Neurons in the dorsal root ganglion regrow their axons and functional connections. The molecular mechanisms of this neuronal regenerative process have remained elusive, but a relationship with developmental processes has been conceived. This chapter discusses the applicability of the developmental hypothesis of regeneration to the dorsal root ganglion; this hypothesis states that regeneration of dorsal root ganglion neurons is a recapitulation of development. We present data on changes in gene expression upon sciatic nerve damage, and the expression and function of homeobox genes. This class of transcription factors plays a role in neuronal development. Based on these data, it is concluded that the hypothesis does not hold for dorsal root ganglion neurons, and that regeneration-specific mechanisms exist. Cytokines and the associated Jak/STAT (janus kinase/signal transducer and activator of transcription) signal transduction pathway emerge as constituents of a regeneration-specific mechanism. This mechanism may be the basis of pharmacological strategies to stimulate regeneration.

Active Src expression is induced after rat peripheral nerve injury

The non-receptor-type Src tyrosine kinases are key components of intracellular signal transduction that are expressed at high levels in the nervous system. To improve understanding of the cascades of molecular events underlying peripheral nerve regeneration, we analyzed active Src expression in the crushed or cut rat sciatic nerves using a monoclonal antibody (clone 28) that recognizes the active form of Src tyrosine kinases, including c-Src and c-Fyn. Western blots showed that active Src expressed in the normal sciatic nerve transiently increased up to threefolds after both types of injury. Immunohistochemistry using clone 28 showed that axonal components are the primary sites of active Src expression in the normal sciatic nerve. Soon after both types of injury, active Src was abundantly expressed in Schwann cells of the segments distal to the injury site. The expression of active Src in the cells decreased with restoration of the axon-Schwann cell relationship and eventually became depleted to very low levels after crushing, but was sustained at high levels in the cut model until the end of the experiment. Regenerated axons consistently expressed active Src throughout nerve regeneration and these eventually became the major sites of active Src expression in the crushed nerve. Among the Src tyrosine kinases, active c-Src selectively increased after crushing according to immunoprecipitation and immunoblotting analyses. Due to its potent biological activity, the increased amounts of the active form of Src probably enhance axonal regrowth, the Schwann cell response, and axon-Schwann cell contact for peripheral nerve regeneration.