Erythropoietin enhances the regeneration of traumatized tissue after combined muscle-nerve injury

Investigation into effects of tocilizumab and epoetin beta in rats with experimental sciatic nerve injury model

OBJECTIVE

To investigate the effects of tocilizumab (TCZ), epoetin beta (EPO), and their combination on nerve regeneration in a sciatic nerve injury model.

MATERIALS AND METHOD

Male Sprague-Dawley rats were divided into (-) negative control, sham, TCZ, EPO ((+) positive control), and TCZ+EPO groups. The TCZ group received TCZ (8 mg/kg intraperitoneal) immediately after surgery. On day 14th, the EPO group received EPO (5000 IU/kg, intraperitoneal); the TCZ+EPO group received TCZ (8 mg/kg, intraperitoneal), EPO (5000 IU/kg, intraperitoneal), and TCZ (8 mg/kg, intraperitoneal) post-surgery. Motor and sensory functions were assessed pre and post-surgery. Lipid peroxidation and oxidative stress parameters were evaluated biochemically in the serum, and sciatic nerve tissue was evaluated histopathologically using haematoxylin-Eosin and Masson trichrome staining.

CONCLUSIONS

TCZ and EPO decreased nerve injury effects by increasing motor and sensory conduction velocities of the sciatic nerve. Biochemically, TCZ and EPO significantly increased Superoxide Dismutase, Catalase, and Glutathione peroxidase 4 levels while decreasing Lipid Peroxidation levels (p=0.001). Histopathologically, neuronal degeneration following nerve injury was decreased in the groups receiving TCZ and EPO (p=0.001). EPO and TCZ attenuate the adverse effects of nerve injury. However, the TCZ+EPO treatment favoured biochemical activities over tissue and functional activities. This has been confirmed functionally, biochemically, and histopathologically.

Effects of 4-Aminopyridine on Combined Nerve and Muscle Injury and Bone Loss

PURPOSE

Musculoskeletal injuries are common, and peripheral nerve injury (PNI) causes significant muscle and bone loss within weeks. After PNI, 4-aminopyridine (4-AP) improves functional recovery and muscle atrophy. However, it is unknown whether 4-AP has any effect on isolated traumatic muscle injury and PNI-induced bone loss.

METHODS

A standardized crush injury was performed on the sciatic nerve and muscles in mice, and the mice were assigned to receive normal saline or 4-AP treatment daily for 21 days. The postinjury motor and sensory function recovery was assessed, injured muscles were processed for histomorphometry, and the tibial bone was scanned for bone density.

RESULTS

4-Aminopyridine significantly accelerated the postinjury motor and sensory function recovery, improved muscle histomorphometry, increased muscle satellite cell numbers, and shifted muscle fiber types after combined nerve and muscle injury. Importantly, the 4-AP treatment significantly reduced PNI-induced bone loss. In contrast, in the case of isolated muscle injury, 4-AP had no effect on functional recovery and bone density, but it improved muscle-specific histomorphometry to a limited extent.

CONCLUSIONS

These findings demonstrate the potential beneficial effects of 4-AP on the recovery of muscle morphology and bone density after combined muscle and nerve injury.

CLINICAL RELEVANCE

Nerve injuries frequently involve muscle and result in rapid muscle and bone atrophy. In this scenario, 4-AP, in addition to accelerating nerve functional recovery, might work as an adjunctive agent to improve the recovery of injured muscle and attenuate PNI-induced bone loss.

Needling on trigger point promotes muscle regeneration after bupivacaine injection induced injury

Dry needling treatment has a promising relieving effect on Myofascial Pain Syndrome (MPS). In China, acupuncture practitioners use acupuncture needle instead to insert the "A-Shi" acupoint to treat MPS which is defined as the same as the trigger point of dry needling. This method has been applied for thousands of years in China. In this study, bupivacaine injection induced gastrocnemius muscle injury in mice. We applied the clinical improved needling method on animal model by making the angle between the skin and needle less than 30 degree. Animals got needling treatment 24 h later at the point where the bupivacaine was injected. Results of muscle H.E. staining showed that, compared to bupivacaine injection group without needling, acupuncture treatment group showed more intact muscle fibers, less inflammatory cell infiltration and fractured muscle fibers. By RNA sequencing analysis, our work firstly demonstrated that the physical stimulation of needling changed the gene expression of muscle tissue to accelerate the muscular regeneration process. Therefore, our study proved that simple needling at "A-Shi" acupoint promoted muscle regeneration and revealed underlying mechanisms of the beneficial effects of acupuncture and dry needle treatments.

Functional recovery with histomorphometric analysis of nerves and muscles after combination treatment with erythropoietin and dexamethasone in acute peripheral nerve injury

Introduction

Peripheral nerve injury (PNI) often leads to significant functional loss in patients and poses a challenge to physicians since treatment options for improving functional outcomes are limited. Recent studies suggest that erythropoietin and glucocoticoids have beneficial effects as mediators of neuro-regenerative processes. We hypothesized that combination treatment with erythropoietin and glucocoticoids would have a synergistic effect on functional outcome after PNI.

Materials and methods

Sciatic nerve crush injury was simulated in ten-week-old male C57BL/6 mice. The mice were divided into four groups according to the type of drugs administered (control, erythropoietin, dexamethasone, and erythropoietin with dexamethasone). Motor functional recovery was monitored by walking track analysis at serial time points up to 28 days after injury. Morphological analysis of the nerve was performed by immunofluorescent staining for neurofilament (NF) heavy chain and myelin protein zero (P0) in cross-sectional and whole-mount nerve preparations. Additionally, morphological analysis of the muscle was performed by Hematoxylin and eosin staining.

Results

Combination treatment with erythropoietin and dexamethasone significantly improved the sciatic functional index at 3, 7, 14, and 28 days after injury. Fluorescence microscopy of cross sectional nerve revealed that the combination treatment increased the ratio of P0/NF-expressing axons. Furthermore, confocal microscopy of the whole-mount nerve revealed that the combination treatment increased the fluorescence intensity of P0 expression. The cross-sectional area and minimum Feret’s diameter of the muscle fibers were significantly larger in the mice which received combination treatment than those in the controls.

Conclusion

Our results demonstrated that combination treatment with erythropoietin and dexamethasone accelerates functional recovery and reduces neurogenic muscle atrophy caused by PNI in mice, which may be attributed to the preservation of myelin and Schwann cell re-myelination. These findings may provide practical therapeutic options for patients with acute PNI.

Effect of Apoptotic Neutrophils on the Production of Erythropoietin, MMP-9, and TIMP-1 in Cultures of Human Macrophages

We studied the effect of apoptotic neutrophils on the production of erythropoietin, MMP-9, and TIMP-1 by GM-CSF-induced human macrophages. GM-CSF-induced macrophages spontaneously produce erythropoietin and secrete MMP-9 and TIMP-1. Polarization of these macrophages towards the M2-like phenotype after exposure to apoptotic neutrophils considerably increased the production of erythropoietin; the MMP-9/TIMP-1 ratio tended to increase under these conditions due to a decrease in TIMP-1.

The refined biomimetic NeuroDigm GEL™ Model of neuropathic pain in the mature rat

Background:Many humans suffering with chronic pain have no clinical evidence of a lesion or disease. They are managed with a morass of drugs and invasive procedures. Opiates usually become less effective over time. In many, their persistent pain occurs after the healing of a soft tissue injury. Current animal models of neuropathic pain typically create direct neural damage with open surgeries using ligatures, neurectomies, chemicals or other forms of deliberate trauma. However, we have observed clinically that after an injury in humans, the naturally occurring process of tissue repair can cause chronic neural pain.Methods:We demonstrate how the refined biomimetic NeuroDigm GEL™ Model, in the mature male rat, gradually induces neuropathic pain behavior with a nonsurgical percutaneous implant of tissue-derived hydrogel in the musculo-fascial tunnel of the distal tibial nerve. Morphine, Celecoxib, Gabapentin and Duloxetine were each screened in the model three times each over 5 months after pain behaviors developed. A pilot study followed in which recombinant human erythropoietin was applied to the GEL neural procedure site.Results:The GEL Model gradually developed neuropathic pain behavior lasting months. Morphine, initially effective, had less analgesia over time. Celecoxib produced no analgesia, while gabapentin and duloxetine at low doses had profound analgesia at all times tested. The injected erythropoietin markedly decreased bilateral pain behavior that had been present for over 4 months. Histology revealed a site of focal neural remodeling, with neural regeneration, as in human biopsies.Conclusion:The refined NeuroDigm GEL™ Model induces localized neural remodeling resulting in robust neuropathic pain behavior. The analgesics responses in this model reflect known responses of humans with neuropathic pain. The targeted recombinant human erythropoietin appears to heal the ectopic focal neural site, as demonstrated by the extinguishing of neuropathic pain behavior present for over 4 months.

Does the combination of erythropoietin and tapered oral corticosteroids improve recovery following iatrogenic nerve injury?

INTRODUCTION

The reported prognosis for recovery after peripheral nerve injury is remarkably poor. Deficits may persist for years, resulting in significant functional disability. Both corticosteroids and Erythropoietin have been investigated as neuroprotective agents; however, their efficacy in total hip and knee arthroplasty is not known. The purpose of this study was to evaluate the effect of systemically-administered Erythropoietin and tapered oral corticosteroids on the recovery of postoperative nerve palsies in the setting of total hip and knee arthroplasty.

METHODS

Eleven patients sustaining postoperative peripheral nerve injuries after total hip or knee arthroplasty were treated acutely with Erythropoietin and tapered oral steroids. Motor and sensory function was assessed clinically pre- and postoperatively until complete motor recovery or for a minimum of 1 year.

RESULTS

Motor loss was complete in seven (64%) patients and partial in four (36%). Seven (64%) patients' symptoms affected the common peroneal nerve distribution and four (36%) had concomitant tibial nerve involvement. Eight (73%) patients experienced full motor recovery at an average of 39 days (range: 3-133 days), and three (27%) had near-complete motor recovery. At final follow up, no patient required assistive devices for ambulation.

CONCLUSIONS

Administration of Erythropoietin coupled with oral tapered steroids for patients sustaining iatrogenic nerve injuries in total hip and knee arthroplasty demonstrated faster and more complete recovery of motor and sensory function compared to previous reports in the literature. This study highlights the importance of further investigation to define the role of each in the setting of acute postoperative nerve palsies.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Erythropoietin Does Not Enhance Skeletal Muscle Protein Synthesis Following Exercise in Young and Older Adults

Purpose: Erythropoietin (EPO) is a renal cytokine that is primarily involved in hematopoiesis while also playing a role in non-hematopoietic tissues expressing the EPO-receptor (EPOR). The EPOR is present in human skeletal muscle. In mouse skeletal muscle, EPO stimulation can activate the AKT serine/threonine kinase 1 (AKT) signaling pathway, the main positive regulator of muscle protein synthesis. We hypothesized that a single intravenous EPO injection combined with acute resistance exercise would have a synergistic effect on skeletal muscle protein synthesis via activation of the AKT pathway.

Methods: Ten young (24.2 ± 0.9 years) and 10 older (66.6 ± 1.1 years) healthy subjects received a primed, constant infusion of [ring-₁₃C⁶] L-phenylalanine and a single injection of 10,000 IU epoetin-beta or placebo in a double-blind randomized, cross-over design. 2 h after the injection, the subjects completed an acute bout of leg extension resistance exercise to stimulate skeletal muscle protein synthesis.

Results: Significant interaction effects in the phosphorylation levels of the members of the AKT signaling pathway indicated a differential activation of protein synthesis signaling in older subjects when compared to young subjects. However, EPO offered no synergistic effect on vastus lateralis mixed muscle protein synthesis rate in young or older subjects.

Conclusions: Despite its ability to activate the AKT pathway in skeletal muscle, an acute EPO injection had no additive or synergistic effect on the exercise-induced activation of muscle protein synthesis or muscle protein synthesis signaling pathways.

The role and regulation of erythropoietin (EPO) and its receptor in skeletal muscle: how much do we really know?

Erythropoietin (EPO) primarily activates erythroid cell proliferation and growth and is active in several types of non-hematopoietic cells via its interaction with the EPO-receptor (EPO-R). This review focuses on the role of EPO in skeletal muscle. The EPO-R is expressed in skeletal muscle cells and EPO may promote myoblast differentiation and survival via the activation of the same signaling cascades as in hematopoietic cells, such as STAT5, MAPK and Akt. Inconsistent results exist with respect to the detection of the EPO-R mRNA and protein in muscle cells, tissue and across species and the use of non-specific EPO-R antibodies contributes to this problem. Additionally, the inability to reproducibly detect an activation of the known EPO-induced signaling pathways in skeletal muscle questions the functionality of the EPO-R in muscle in vivo. These equivocal findings make it difficult to distinguish between a direct effect of EPO on skeletal muscle, via the activation of its receptor, and an indirect effect resulting from a better oxygen supply to the muscle. Consequently, the precise role of EPO in skeletal muscle and its regulatory mechanism/s remain to be elucidated. Further studies are required to comprehensively establish the importance of EPO and its function in skeletal muscle health.