Insulin-like growth factor 1 prevents neuronal cell death and paraplegia in the rabbit model of spinal cord ischemia

Potential Role of Insulin-Like Growth Factors in Myofascial Pain Syndrome: A Narrative Review

ABSTRACT

Insulin-like growth factors have diverse functions in skeletal muscles by acting through multiple signaling pathways, including growth regulation and differentiation, anti-inflammation, and antioxidation. Insulin-like growth factors have anti-inflammatory effects and also play roles in nociceptive pathways, determining pain sensitivity, in addition to their protective role against ischemic injury in both the nervous system and skeletal muscle. In skeletal muscle, insulin-like growth factors maintain homeostasis, playing key roles in maintenance, accelerating muscle regeneration, and repair processes. As part of their maintenance role, increased levels of insulin-like growth factors may be required for the repair mechanisms after exercise. Although the role of insulin-like growth factors in myofascial pain syndrome is not completely understood, there is evidence from a recent study that insulin-like growth factor 2 levels in patients with myofascial pain syndrome are lower than those of healthy individuals and are associated with increased levels of inflammatory biomarkers. Importantly, higher insulin-like growth factor 2 levels are associated with increased pain severity in myofascial pain syndrome patients. This may suggest that too low or high insulin-like growth factor levels may contribute to musculoskeletal disorder process, whereas a midrange levels may optimize healing without contributing to pain hypersensitivity. Future studies are required to address the mechanisms of insulin-like growth factor 2 in myofascial pain syndrome and the optimal level as a therapeutic agent.

Histological Findings After Aortic Cross-Clamping in Preclinical Animal Models

Spinal cord ischemic injury and paralysis are devastating complications after open surgical repair of thoracoabdominal aortic aneurysms. Preclinical models have been developed to simulate the clinical paradigm to better understand the neuropathophysiology and develop therapeutic treatment. Neuropathological findings in the preclinical models have not been comprehensively examined before. This systematic review studies the past 40 years of the histological findings after open surgical repair in preclinical models. Our main finding is that damage is predominantly in the grey matter of the spinal cord, although white matter damage in the spinal cord is also reported. Future research needs to examine the neuropathological findings in preclinical models after endovascular repair, a newer type of surgical repair used to treat aortic aneurysms.

Dynamics of biomarkers across the stages of traumatic spinal cord injury - implications for neural plasticity and repair

BACKGROUND

Traumatic spinal cord injury (SCI) is a complex medical condition causing significant physical disability and psychological distress. While the adult spinal cord is characterized by poor regenerative potential, some recovery of neurological function is still possible through activation of neural plasticity mechanisms. We still have limited knowledge about the activation of these mechanisms in the different stages after human SCI.

OBJECTIVE

In this review, we discuss the potential role of biomarkers of SCI as indicators of the plasticity mechanisms at work during the different phases of SCI.

METHODS

An extensive review of literature related to SCI pathophysiology, neural plasticity and humoral biomarkers was conducted by consulting the PubMed database. Research and review articles from SCI animal models and SCI clinical trials published in English until January 2021 were reviewed. The selection of candidates for humoral biomarkers of plasticity after SCI was based on the following criteria: 1) strong evidence supporting involvement in neural plasticity (mandatory); 2) evidence supporting altered expression after SCI (optional).

RESULTS

Based on selected findings, we identified two main groups of potential humoral biomarkers of neural plasticity after SCI: 1) neurotrophic factors including: Brain derived neurotrophic factor (BDNF), Nerve growth factor (NGF), Neurotrofin-3 (NT-3), and Insulin-like growth factor 1 (IGF-1); 2) other factors including: Tumor necrosis factor-alpha (TNF-α), Matrix Metalloproteinases (MMPs), and MicroRNAs (miRNAs). Plasticity changes associated with these biomarkers often can be both adaptive (promoting functional improvement) and maladaptive. This dual role seems to be influenced by their concentrations and time-window during SCI.

CONCLUSIONS

Further studies of dynamics of biomarkers across the stages of SCI are necessary to elucidate the way in which they reflect the remodeling of neural pathways. A better knowledge about the mechanisms underlying plasticity could guide the selection of more appropriate therapeutic strategies to enhance positive spinal network reorganization.

Exosomes Derived from lncRNA TCTN2-Modified Mesenchymal Stem Cells Improve Spinal Cord Injury by miR-329-3p/IGF1R Axis

Mesenchymal stem cells (MSCs)-derived exosomes play significant roles in alleviating spinal cord injury (SCI). Previous study showed that long non-coding RNA tectonic family member 2 (TCTN2) was able to relieve SCI. Herein, whether TCTN2 exerted its roles in functional recovery after SCI via exosomes derived from MSCs was explored. The SCI model was established in rats, and the neurological function was evaluated using the Basso, Beattie, and Bresnahan (BBB) scoring. Lipopolysaccharide (LPS)-induced differentiated PC12 cells were used as an in vitro model for neurotoxicity research. The expression of genes and proteins was detected by qRT-PCR and Western blot. Exosomes were isolated by ultracentrifugation and qualified by TEM and Western blot. In vitro assays were performed using CCK-8 assay, EdU assay, and flow cytometry, respectively. Dual-luciferase reporter assay and RIP assay were used to confirm the target relationship between miR-329-3p and TCTN2 or insulin-like growth factor1 receptor (IGF1R). TCTN2 expression was down-regulated in SCI model rat and lipopolysaccharide (LPS)-stimulated PC12 cells. MSCs produced exosomes and could package TCTN2 into secreted exosomes. Tail vein injection of TCTN2 exosomes into rats significantly improved functional recovery of SCI. Meanwhile, TCTN2 exosomes treatment alleviated LPS-induced neuronal apoptosis, inflammation, and oxidative stress in vitro. Additionally, TCTN2 targeted miR-329-3p and subsequently regulated the expression of its target IGF1R. Rescue assays suggested that miR-329-3p/IGF1R axis mediated the beneficial effects of TCTN2 exosomes on LPS-treated PC12 cells. In all, exosomes derived from TCTN2-modified MSCs could improve functional recovery of SCI in vivo and attenuate LPS-induced neuronal apoptosis, inflammation, and oxidative stress in vitro via miR-329-3p/IGF1R axis, suggesting a novel insight into the development of MSC-exosomes-based therapy for SCI.

Motor Neuron Diseases and Neuroprotective Peptides: A Closer Look to Neurons

Motor neurons (MNs) are specialized neurons responsible for muscle contraction that specifically degenerate in motor neuron diseases (MNDs), such as amyotrophic lateral sclerosis (ALS), spinal and bulbar muscular atrophy (SBMA), and spinal muscular atrophy (SMA). Distinct classes of MNs degenerate at different rates in disease, with a particular class named fast-fatigable MNs (FF-MNs) degenerating first. The etiology behind the selective vulnerability of FF-MNs is still largely under investigation. Among the different strategies to target MNs, the administration of protective neuropeptides is one of the potential therapeutic interventions. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide with beneficial effects in many neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, and more recently SBMA. Another neuropeptide that has a neurotrophic effect on MNs is insulin-like growth factor 1 (IGF-1), also known as somatomedin C. These two peptides are implicated in the activation of neuroprotective pathways exploitable in the amelioration of pathological outcomes related to MNDs.

Insulin-like growth factor-1 improves postoperative cognitive dysfunction following splenectomy in aged rats

Postoperative cognitive dysfunction (POCD) is a serious complication following anesthesia and operations in aged patients undergoing surgical intervention. It is characterized by temporary or permanent cognitive decline, memory impairment and deterioration in language comprehension and social adaption ability. Therefore, the development of POCD prevention and treatment tools has become an area of interest. The current study assessed the therapeutic effects of insulin-like growth factor-1 (IGF-1) on POCD in aged rats and explored the underlying mechanisms. Model rats underwent splenectomy under 1.5-2% isoflurane and mechanical ventilation. IGF-1 (50 µg/kg) was diluted in normal saline and administered by abdominal hypodermic injection daily from the operation to day 7 post-operation. Following splenectomy, the animals showed marked cognitive impairment as determined by the Morris water maze test. Hippocampal protein levels of amyloid precursor protein (APP), β-site APP-cleaving enzyme-1 (BACE-1), amyloid-β (Aβ), capase3, Bax and Bcl-2 were assessed by immunoblotting. Neuronal apoptosis in the hippocampus was analyzed using a TUNEL assay. The results demonstrated that the levels of APP, BACE-1, Aβ, caspase3 and Bax were increased following splenectomy, while the levels of Bcl2 were reduced at days 1, 3 and 7 post-operation in aged rats. However, IGF-1 downregulated APP, BACE-1, Aβ, capase3 and Bax, and upregulated Bcl2 at these time points following splenectomy. TUNEL staining revealed that administration of IGF-1 significantly reduced neuronal apoptosis in the hippocampal CA1 region following splenectomy. These results indicated that IGF-1 decreased Aβ-protein production and inhibited neuronal apoptosis in the hippocampus following splenectomy, subsequently alleviating POCD.

The combination of insulin-like growth factor 1 and erythropoietin protects against ischemic spinal cord injury in rabbits

INTRODUCTION

Insulin-like growth factor 1 (IGF-1) and erythropoietin (EPO) have been reported to independently protect against ischemic spinal cord injury in rabbits. In the present study, we investigated whether the combination of IGF-1 and EPO protects against ischemic spinal cord injury in rabbits.

METHODS

Animals were assigned to 1 of 4 groups (n = 6 in each): a control group (saline), an IGF-1 group (IGF-1 0.3 mg/kg), an EPO group (EPO 800 U/kg), or an IGF-1 + EPO group (IGF-1 0.3 mg/kg + EPO 800 U/kg). Spinal cord ischemia was produced by occluding the abdominal aorta for 15 min. Saline, IGF-1, and EPO were administered intravenously just after the start of reperfusion. Hindlimb motor function was assessed daily for 7 days, after which histopathological evaluation was performed. To analyze phosphorylation of signal transduction molecules, animals were assigned to 1 of the 4 groups (n = 8 in each). Spinal cord ischemia and the treatment were the same as those described above. The spinal cords were removed at 15 or 30 min after reperfusion and used to analyze phosphorylation of signal transduction molecules. Four animals served as the preischemic control, and the spinal cord was removed just before the start of ischemia.

RESULTS

In the IGF-1 + EPO group, both neurological and histopathological outcomes were significantly improved as compared to the control group, which was consistent with the increase of Janus kinase-2 (JAK2) phosphorylation.

CONCLUSIONS

The combination of IGF-1 and EPO protects against ischemic spinal cord injury in rabbits. JAK2 might contribute to the protective effect.

The effects of testosterone and insulin-like growth factor 1 on motor system form and function

In this perspective article, we review the effects of selected anabolic hormones on the motoric system and speculate on the role these hormones may have on influencing muscle and physical function via their impact on the nervous system. Both muscle strength and anabolic hormone levels decline around middle age into old age over a similar time period, and several animal and human studies indicate that exogenously increasing anabolic hormones (e.g., testosterone and insulin-like growth factor-1 (IGF-1)) in aged subjects is positively associated with improved muscle strength. While most studies in humans have focused on the effects of anabolic hormones on muscle growth, few have considered the impact these hormones have on the motoric system. However, data from animals demonstrate that administering either testosterone or IGF-1 to cells of the central and peripheral motor system can increase cell excitability, attenuate atrophic changes, and improve regenerative capacity of motor neurons. While these studies do not directly indicate that changes in anabolic hormones contribute to reduced human performance in the elderly (e.g., muscle weakness and physical limitations), they do suggest that additional research is warranted along these lines.

An in vivo characterization of trophic factor production following neural precursor cell or bone marrow stromal cell transplantation for spinal cord injury

Cellular transplantation strategies for repairing the injured spinal cord have shown consistent benefit in preclinical models, and human clinical trials have begun. Interactions between transplanted cells and host tissue remain poorly understood. Trophic factor secretion is postulated a primary or supplementary mechanism of action for many transplanted cells, however, there is little direct evidence to support trophin production by transplanted cells in situ. In the present study, trophic factor expression was characterized in uninjured, injured-untreated, injured-treated with transplanted cells, and corresponding control tissue from the adult rat spinal cord. Candidate trophic factors were identified in a literature search, and primers were designed for these genes. We examined in vivo trophin expression in 3 paradigms involving transplantation of either brain or spinal cord-derived neural precursor cells (NPCs) or bone marrow stromal cells (BMSCs). Injury without further treatment led to a significant elevation of nerve growth factor (NGF), leukemia inhibitory factor (LIF), insulin-like growth factor-1 (IGF-1), and transforming growth factor-β1 (TGF-β1), and lower expression of vascular endothelial growth factor isoform A (VEGF-A) and platelet-derived growth factor-A (PDGF-A). Transplantation of NPCs led to modest changes in trophin expression, and the co-administration of intrathecal trophins resulted in significant elevation of the neurotrophins, glial-derived neurotrophic factor (GDNF), LIF, and basic fibroblast growth factor (bFGF). BMSCs transplantation upregulated NGF, LIF, and IGF-1. NPCs isolated after transplantation into the injured spinal cord expressed the neurotrophins, ciliary neurotrophic factor (CNTF), epidermal growth factor (EGF), and bFGF at higher levels than host cord. These data show that trophin expression in the spinal cord is influenced by injury and cell transplantation, particularly when combined with intrathecal trophin infusion. Trophins may contribute to the benefits associated with cell-based repair strategies for spinal cord injury.

In vitro characterization of trophic factor expression in neural precursor cells

In cellular transplantation strategies for repairing the injured central nervous system, interactions between transplanted neural precursor cells (NPCs) and host tissue remain incompletely understood. Although trophins may contribute to the benefits observed, little research has explored this possibility. Candidate trophic factors were identified, and primers were designed for these genes. Template RNA was isolated from 3 NPC sources, and also from bone marrow stromal cells (BMSCs) and embryonic fibroblasts as comparative controls. Quantitative polymerase chain reaction was performed to determine the effect of cell source, passaging, cellular differentiation, and environmental changes on trophin factor expression in NPCs. Results were analyzed with multivariate statistical analyses. NPCs, BMSCs, and fibroblasts each expressed trophic factors in unique patterns. Trophic factor expression was similar among NPCs whether harvested from rat or mouse, brain or spinal cord, or their time in culture. The expression of neurotrophin NT-3, NT-4/5, glial-derived neurotrophic factor, and insulin-like growth factor-1 decreased with time in culture. Induced differentiation of NPCs led to a marked and statistically significant increase in the expression of trophic factors. Culture conditions and environmental changes were also associated with significant changes in trophin expression. These results suggest that trophins could contribute to the benefits associated with transplantation of NPCs as well as BMSCs. Trophic factor expression changes with NPC differentiation and environmental conditions, which could have important implications with regard to their behavior after in vivo transplantation.

Perspectives and challenges in regenerative medicine using plasma rich in growth factors

Plasma rich in growth factors (PRGF-Endoret) is an endogenous therapeutic technology that is gaining interest in regenerative medicine due to its potential to stimulate and accelerate tissue healing and bone regeneration. This autologous biotechnology is designed for the in situ delivery of multiple cellular modulators and the formation of a fibrin scaffold, thereby providing different formulations that can be widely used in numerous medical and scientific fields including dentistry, oral implantology, orthopedics, ulcer treatment and tissue engineering among others. Here we discuss the important progress that has been accomplished in this field. Furthermore, a comprehensive outlook of the intriguing therapeutic applications of this technology is presented.

Temporal and regional changes in IGF-1/IGF-1R signaling in the mouse brain after traumatic brain injury

Although neurotrophic factors such as nerve growth factor, basic fibroblast growth factor, brain-derived neurotrophic factor, and neurotrophin 4/5 are elevated after traumatic brain injury (TBI), little is known about the endogenous response of insulin-like growth factor-1 (IGF-1). We evaluated IGF-1, IGF-1 receptor (IGF-1R), and total and phosphorylated Akt (p-Akt), a known downstream mediator of IGF-1 signaling, using ELISA, Western blotting, and immunohistochemistry at 1, 6, 24, 48, and 72 h following 0.5-mm controlled cortical impact brain injury in adult mice. IGF-1 was transiently upregulated in homogenates of injured cortex at 1 h, and cells with increased IGF-1 immunoreactivity were observed in and around the cortical contusion site up to 48 h. IGF-1R and total Akt levels in cortical homogenates were unchanged, although immunohistochemistry revealed regional changes. In contrast, serine p-Akt levels increased significantly in homogenates at 6 h post-injury. Interestingly, delayed increases in vascular IGF-1R, total Akt, and p-Akt immunostaining were observed in and around the cortical contusion. IGF-1 and its downstream mediators were also upregulated in the subcortical white matter. Our findings indicate that moderate TBI results in a brief induction of IGF-1 and its signaling components in the acute post-traumatic period. This may reflect an attempt at endogenous neuroprotection or repair.

The application of platelet-rich plasma may be a novel treatment for central nervous system diseases

As a potential biological product, platelet-rich plasma (PRP) has been widely utilized in the areas of oral and maxillofacial reconstruction, bone and soft tissue restoration and wound healing. A recent study reported that the application of PRP on interrupted sciatic nerve could promote remyelinization of peripheral nerve. This renovated a notion that the application of PRP might extend to the nervous system. Most central nervous system (CNS) diseases have a series of common pathological changes in the later period of diseases which induce neurons and glia apoptosis and aggravate neurological dysfunction. It has been demonstrated that the potent restorative function of PRP is mainly based on neurotrophic capacity of preparation rich in growth factors (PRGFs) and scaffolding effect of platelet-rich gel (PRG), all of which could be certified to ameliorate the pathological process of CNS diseases. In view of this, we propose a hypothesis that the application of PRP and its derivatives might provide a novel therapeutic approach for CNS diseases, especially for traumatic brain or spinal cord injury, autoimmune diseases and neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.

Beneficial effect of the oxygen free radical scavenger amifostine (WR-2721) on spinal cord ischemia/reperfusion injury in rabbits

Background

Paraplegia is the most devastating complication of thoracic or thoraco-abdominal aortic surgery. During these operations, an ischemia-reperfusion process is inevitable and the produced radical oxygen species cause severe oxidative stress for the spinal cord. In this study we examined the influence of Amifostine, a triphosphate free oxygen scavenger, on oxidative stress of spinal cord ischemia-reperfusion in rabbits.

Methods

Eighteen male, New Zealand white rabbits were anesthetized and spinal cord ischemia was induced by temporary occlusion of the descending thoracic aorta by a coronary artery balloon catheter, advanced through the femoral artery. The animals were randomly divided in 3 groups. Group I functioned as control. In group II the descending aorta was occluded for 30 minutes and then reperfused for 75 min. In group III, 500 mg Amifostine was infused into the distal aorta during the second half-time of ischemia period. At the end of reperfusion all animals were sacrificed and spinal cord specimens were examined for superoxide radicals by an ultra sensitive fluorescent assay.

Results

Superoxide radical levels ranged, in group I between 1.52 and 1.76 (1.64 ± 0.10), in group II between 1.96 and 2.50 (2.10 ± 0.23), and in group III (amifostine) between 1.21 and 1.60 (1.40 ± 0.19) (p = 0.00), showing a decrease of 43% in the Group of Amifostine. A lipid peroxidation marker measurement ranged, in group I between 0.278 and 0.305 (0.296 ± 0.013), in group II between 0.427 and 0.497 (0.463 ± 0.025), and in group III (amifostine) between 0.343 and 0.357 (0.350 ± 0.007) (p < 0.00), showing a decrease of 38% after Amifostine administration.

Conclusion

By direct and indirect methods of measuring the oxidative stress of spinal cord after ischemia/reperfusion, it is suggested that intra-aortic Amifostine infusion during spinal cord ischemia phase, significantly attenuated the spinal cord oxidative injury in rabbits.

Prevention, identification, and treatment of perioperative spinal cord injury

OBJECT

In this report, the authors suggest evidence-based approaches to minimize the chance of perioperative spinal cord injury (POSCI) and optimize outcome in the event of a POSCI.

METHODS

A systematic review of the basic science and clinical literature is presented.

RESULTS

Authors of clinical studies have assessed intraoperative monitoring to minimize the chance of POSCI. Furthermore, preoperative factors and intraoperative issues that place patients at increased risk of POSCI have been identified, including developmental stenosis, ankylosing spondylitis, preexisting myelopathy, and severe deformity with spinal cord compromise. However, no studies have assessed methods to optimize outcomes specifically after POSCIs. There are a number of studies focussed on the pathophysiology of SCI and the minimization of secondary damage. These basic science and clinical studies are reviewed, and treatment options outlined in this article.

CONCLUSIONS

There are a number of treatment options, including maintenance of mean arterial blood pressure > 80 mm Hg, starting methylprednisolone treatment preoperatively, and multimodality monitoring to help prevent POSCI occurrence, minimize secondary damage, and potentially improve the clinical outcome of after a POSCI. Further prospective cohort studies are needed to delineate incidence rate, current practice patterns for preventing injury and minimizing the clinical consequences of POSCI, factors that may increase the risk of POSCI, and determinants of clinical outcome in the event of a POSCI.

Insulin-like growth factors in the peripheral nervous system

IGF-I and -II are potent neuronal mitogens and survival factors. The actions of IGF-I and -II are mediated via the type I IGF receptor (IGF-IR) and IGF binding proteins regulate the bioavailability of the IGFs. Cell viability correlates with IGF-IR expression and intact IGF-I/IGF-IR signaling pathways, including activation of MAPK/phosphatidylinositol-3 kinase. The expression of IGF-I and -II, IGF-IR, and IGF binding proteins are developmentally regulated in the central and peripheral nervous system. IGF-I therapy demonstrates mixed therapeutic results in the treatment of peripheral nerve injury, neuropathy, and motor neuron diseases such as amyotrophic lateral sclerosis. In this review we discuss the role of IGFs during peripheral nervous system development and the IGF signaling system as the potential therapeutic target for the treatment of nerve injury and motor neuron diseases.

Tight glycemic control by insulin, started in the preischemic, but not postischemic, period, protects against ischemic spinal cord injury in rabbits

BACKGROUND

It is not well established whether insulin protects against ischemic spinal cord injury. We examined the effects of a single dose of insulin that corrects mild hyperglycemia on the outcome after transient spinal cord ischemia in rabbits.

METHODS

We assigned rabbits to four groups (n = 8 in each); untreated control (C) group, preischemic insulin (Pre-I) group, preischemic insulin with glucose (GI) group (glucose concentrations were maintained at levels similar to the C group by the administration of glucose), and postischemic insulin (Post-I) group. Insulin (0.5 IU/kg) was administered 30 min before ischemia in the Pre-I and GI groups, and just after reperfusion in the Post-I group. Spinal cord ischemia was produced by occluding the abdominal aorta for 13 min. Neurologic and histopathologic evaluations were performed 7 days after ischemia.

RESULTS

The mean blood glucose concentration before ischemia in the Pre-I group (118 mg/dL) was significantly lower than in the other three groups (158-180 mg/dL) and those of 30 min after reperfusion in the Pre-I (92 mg/dL) and Post-I (100 mg/dL) groups were significantly lower than in the C (148 mg/dL) and GI (140 mg/dL) groups. The motor function score and number of normal neurons in the anterior lumbar spinal cord in the Pre-I group were significantly greater than in the other three groups.

CONCLUSIONS

These results suggest that a relatively small dose of preischemic insulin protects against ischemic spinal cord injury, and that the protective effects result from tight glycemic control before ischemia.

Intrathecal injection of bone marrow stromal cells attenuates neurologic injury after spinal cord ischemia

BACKGROUND

It has been shown that transplantation of bone marrow stromal cells (MSCs) into the ischemic brain improves functional outcome. We sought to investigate whether intrathecal injection of MSCs can attenuate neurologic injury of spinal cord ischemia.

METHODS

Rabbit MSCs were expanded in vitro and were pre-labeled with bromodeoxyuridine. Spinal cord ischemia was induced in rabbits by infrarenal aortic occlusion. Group A and control A were subjected to a 20-minute ischemia and the ischemic duration was extended to 30 minutes in group B and control B. Two days before spinal cord ischemia, 1 x 10(8) MSCs were intrathecally injected into groups A and B, whereas vehicle alone was injected into the control groups. Hind-limb motor function was assessed during a 14-day recovery period with Tarlov criteria, and then histologic examination was performed.

RESULTS

Marrow stromal cells survived and engrafted into the spinal cord 2 days after transplantation, and more MSCs were found in the lumbar spinal cord (ischemic segment) than in the thoracic spinal cord (nonischemic segment) at 14 days. Compared with their respective control groups, Tarlov scores were significantly higher in both groups A and B (p < 0.05, group A vs control A, at 2, 7, and 14 days; p < 0.05, group B vs control B, at 1, 2, 7, and 14 days, respectively). The number of intact motor neurons was much higher in the two experimental groups (p < 0.01 vs the corresponding control groups, respectively).

CONCLUSIONS

Intrathecal injection of MSCs attenuates ischemic injury of spinal cord.

Intraparenchymal spinal cord delivery of adeno-associated virus IGF-1 is protective in the SOD1G93A model of ALS

The potent neuroprotective activities of neurotrophic factors, including insulin-like growth factor 1 (IGF-1), make them promising candidates for treatment of amyotrophic lateral sclerosis (ALS). In an effort to maximize rate of motor neuron transduction, achieve high levels of spinal IGF-1 and thus enhance therapeutic benefit, we injected an adeno-associated virus 2 (AAV2)-based vector encoding human IGF-1 (CERE-130) into lumbar spinal cord parenchyma of SOD1(G93A) mice. We observed robust and long-term intraspinal IGF-1 expression and partial rescue of lumbar spinal cord motor neurons, as well as sex-specific delayed disease onset, weight loss, decline in hindlimb grip strength and increased animal survival.

Intravenous infusion of dihydroginsenoside Rb1 prevents compressive spinal cord injury and ischemic brain damage through upregulation of VEGF and Bcl-XL

Red ginseng root (Panax Ginseng CA Meyer) has been used clinically by many Asian people for thousands of years without any detrimental effects. One of the major components of Red ginseng root is ginsenoside Rb(1) (gRb1). Previously, we showed that intravenous infusion of gRb1 ameliorated ischemic brain damage through upregulation of an anti-apoptotic factor, Bcl-x(L) and that topical application of gRb1 to burn wound lesion facilitated wound healing through upregulation of vascular endothelial growth factor (VEGF). In the present study, we produced dihydroginsenoside Rb1 (dgRb1), a stable chemical derivative of gRb1, and showed that intravenous infusion of dgRb1 improved spinal cord injury (SCI) as well as ischemic brain damage. As we expected, the effective dose of dgRb1 was ten times lower than that of gRb1. Intravenous infusion of dgRb1 at this effective dose did not affect brain temperature, blood pressure or cerebral blood flow, suggesting that dgRb1 rescued damaged neurons without affecting systemic parameters. In subsequent in vitro studies that focused on dgRb1-induced expression of gene products responsible for neuronal death or survival, we showed that dgRb1 could upregulate the expression of not only Bcl-x(L), but also a potent angiogenic and neurotrophic factor, VEGF. We also showed that dgRb1-induced expression of bcl-x(L) and VEGF mRNA was HRE (hypoxia response element) and STRE (signal transducers and activators of transcription 5 (Stat5) response element) dependent, respectively.

The effects of prophylactic zinc and melatonin application on experimental spinal cord ischemia–reperfusion injury in rabbits: experimental study

STUDY DESIGN

Experimental study.

OBJECTIVES

To determine the neuroprotective effects of zinc and melatonin on spinal cord ischemia-reperfusion (I/R) injuries of rabbits.

SETTING

The Experimental Research Centre of Selçuk University, Konya, Turkey.

METHODS

Twenty-four male rabbits underwent spinal cord ischemia by clamping the thoraco-abdominal aorta for 20 min. Twenty minutes before the aortic clamping, animals received zinc, melatonin or a combination of both. Neurological examination of the animals was performed three times during reperfusion period. The animals were killed 24 h after reperfusion. Spinal cord samples were taken for biochemical and histopathological evaluation.

RESULTS

Pre-treated animals with zinc, melatonin or combination displayed better neurological outcomes than the I/R group (P<0.05). Zinc, melatonin and combined treatment prevented spinal cord injury by reducing apoptosis rate (P<0.05) and preserving intact ganglion cell numbers (P<0.05). Zinc pre-treatment protected spinal cord by preventing malondialdehyde (MDA) formation (P=0.002), increasing glutathione peroxidase (GPx) activity (P=0.002) and decreasing xanthine oxidase enzyme activity (P=0.026) at molecular level. Melatonin treatment also resulted with MDA formation (P=0.002), increased GPx activity (P=0.002) and decreased xanthine oxidase activity (P=0.026).

CONCLUSION

The results of the study showed that prophylactic zinc and melatonin use in spinal cord I/R not only suppressed lipid peroxidation by activating antioxidant systems but also had significant neuroprotective effects by specifically improving the neurological and histopathological situation.

Wheel running and fluoxetine antidepressant treatment have differential effects in the hippocampus and the spinal cord

Exercise and antidepressants used independently have been shown to increase hippocampal brain-derived neurotrophic factor (BDNF) and neurogenesis. Despite the fact that patients with depression are often prescribed both, the effects of the exercise and fluoxetine antidepressant treatment used in combination are unknown. Using C57Bl/10 female mice, BDNF protein, insulin-like growth factor 1 (IGF-1) protein and neurogenesis were measured in the hippocampus after 21 days of wheel running, 21 days of fluoxetine antidepressant therapy (daily i.p. injections of 5 mg/kg, 10 mg/kg or 25 mg/kg) and the combination of the two. BDNF protein and cytogenesis/neurogenesis increased in the hippocampus with fluoxetine (high dose), but not wheel running. Hippocampal IGF-1 protein did not change with either treatment. There were no synergistic effects of combining exercise and fluoxetine treatment. Recent reports have also shown that exercise induces molecular mechanisms that benefit the spinal cord and can improve recovery after spinal cord injury (SCI); therefore, we repeated the assays in the spinal cord. Results showed that BDNF, IGF-1 and neurogenesis behave independently in the hippocampus and spinal cord. BDNF protein did not change in the spinal cord with either wheel running or fluoxetine treatment. Spinal cord IGF-1 protein did not change with wheel running, but it decreased with fluoxetine (high dose). Furthermore, spinal cord cytogenesis decreased with fluoxetine treatment. The combined wheel running and fluoxetine groups did not show synergistic results. Thus, the hippocampus and the spinal cord respond in distinct ways to wheel running and fluoxetine, and a prior induction of BDNF, IGF-1 or cytogenesis is unlikely to be the mechanism for wheel running providing a margin of protection against SCI.

Methylene blue decreases ischemia-reperfusion (I/R)-induced spinal cord injury: an in vivo study in an I/R rabbit model

OBJECTIVES

To evaluate the effects of intravenous methylene blue (MB) administration on ischemia-reperfusion (I/R) injury of the spinal cord (SC).

METHODS

16 rabbits were randomly assigned either to group M (n = 8; receiving MB, intervention group) or group C (n = 8; control group) and underwent a 30-min period of SC ischemia by clamping the abdominal aorta between the left renal artery and the aortic bifurcation. 15 min before clamping, rabbits received either intravenous MB (10 mg/kg; group M) or normal saline (group C). The two groups were compared 24 h postoperatively both histologically and for neurological function, using a Tarlov score. Measurements to determine levels of malondialdehyde (MDA) and glutathione (GSH) in the SC tissue were also performed.

RESULTS

Neurological impairment and spinal tissue MDA levels were significantly lower in animals treated with MB (p < 0.001). In contrast, spinal GSH levels were significantly higher in group M (p < 0.001). Histological examination revealed that the integrity of the SC was better preserved in the MB group, whereas cords from the control group exhibited evidence of acute neuronal injury.

CONCLUSIONS

The prophylactic use of MB reduces neurological injury and improves clinical outcomes in the rabbit SC I/R model. These effects are probably mediated by the drug's antioxidant properties.

The effects of cyclosporin A and insulin on ischemic spinal cord injury in rabbits

We examined the effects of cyclosporin A (CsA), a drug that inhibits mitochondrial permeability transition pore, and insulin on ischemic spinal cord damage in rabbits. We assigned rabbits to 5 groups (n = 6 in each); sham barrier-opened group (sham BO), barrier-opened group (BO), barrier-opened-CsA group (BO-CsA), barrier-opened-insulin group (BO-I), and barrier-opened-CsA-insulin group (BO-CsA-I). The blood-spinal cord barrier was opened to facilitate drug penetration by a mild injury to the lumber spinal cord on day 1. CsA (10 mg/kg per day IV) was administered on day 3 to day 5 (total 30 mg/kg). Insulin was administered 30 min before ischemia. In all groups, spinal cord ischemia was produced on day 5 by occluding the abdominal aorta for 13 min. Neurological and histopathological evaluations were performed 4 days after ischemia. In group BO-CsA, blood glucose concentrations were significantly larger compared with the other four groups, and no protection was observed. In contrast, hindlimb motor function in groups BO-I and Bo-CsA-I and histopathology in group BO-CsA-I were significantly better than in groups sham BO, BO, and BO-CsA. The results indicate that insulin protects against ischemic spinal cord injury, whereas the effect of CsA is, at best, minimal.

Re-growth of catecholaminergic fibers and protection of cholinergic spinal cord neurons in spinal repaired rats

The extent of re-growth of catecholaminergic fibers, the survival of cholinergic neurons and the degree of autonomic dysreflexia were assessed in complete spinal cord-transected adult rats that received a repair treatment of peripheral nerve grafts and acidic fibroblast growth factor (aFGF). The rats were randomly divided into three groups: (1) sham control group (laminectomy only); (2) spinal cord transection at T8 (transected group); and (3) spinal cord transection at T8, followed by aFGF treatment and peripheral nerve graft (repaired group). The spinal cords and brains of all rats were collected at 6 months post-surgery. Immunohistochemistry for tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH), and fluoro-gold (FG) retrograde tracing were used to evaluate axon growth across the damage site, and immunocytochemistry for choline acetyl transferase (ChAT) was used to evaluate cholinergic neuronal cell survival following the injury and treatment. When comparing with the transected group, the repaired group showed: (1) lower elevation of mean arterial pressure during colorectal distension; (2) retrogradely labeled neurons in the hypothalamus, zona incerta, subcoeruleus nuclei and rostral ventrolateral medulla following application of FG below the repair site; (3) the presence of TH- and DBH-labeled axons below the lesion site; (4) higher numbers of ChAT-positive neurons in ventral horn and intermediolateral column near the lesion site. We conclude that peripheral nerve graft and aFGF treatments facilitate the re-growth of catecholaminergic fibers, also protect sympathetic preganglionic neurons and spinal motor neurons, and reduce autonomic dysfunction in a T-8 spinal cord-transected rat model.

Neuroprotective Effects of Activated Protein C Through Induction of Insulin-Like Growth Factor-1 (IGF-1), IGF-1 Receptor, and Its Downstream Signal Phosphorylated Serine-Threonine Kinase After Spinal Cord Ischemia in Rabbits

BACKGROUND AND PURPOSE

Activated protein C (APC) has beneficial effects on ischemia reperfusion injury in neuron. However, the possible mechanism of such beneficial effects is not fully understood. The aim of this study was to investigate the effects and possible mechanisms of APC on ischemic spinal cord damage.

METHODS

After induction of spinal cord ischemia, APC (group A) or vehicle (group I) was injected intravenously. Severity of ischemic damage was analyzed by counting the number of motor neurons. To investigate the mechanisms by which APC prevents ischemic spinal cord damage, we performed immunoreactivity and Western blotting of insulin-like growth factor 1 (IGF-1), IGF-1 receptor, and phosphorylated serine-threonine kinase (p-Akt).

RESULTS

APC eased the functional deficits and increased the number of motor neurons after ischemia. Immunoreactivity of IGF-1 in group A was stronger than in group I at 8 hours after reperfusion but was at the same level at 1 day. Induction of IGF-1 receptor and the downstream factor p-Akt was stronger and more prolonged in group A.

CONCLUSIONS

These results indicate that induction of IGF-1, IGF-1 receptor, and p-Akt might partially explain the neuroprotective effects of APC after transient spinal cord ischemia in rabbit.

Exogenous Bcl-xl fusion protein spares neurons after spinal cord injury

Spinal cord injury (SCI) induces neuronal death, including apoptosis, which is completed within 24 hr at and around the impact site. We identified early proapoptotic transcriptional changes, including upregulation of proapoptotic Bax and downregulation of antiapoptotic Bcl-xL, Bcl-2, and Bcl-w, using Affymetrix DNA microarrays. Because Bcl-xL is the most robustly expressed antiapoptotic Bcl-2 molecule in adult central nervous system, we decided to characterize better the effect of SCI on Bcl-xL expression. We found Bcl-xL expressed robustly throughout uninjured spinal cord in both neurons and glia cells. We also found Bcl-xL localized in different cellular compartments: cytoplasmic, mitochondrial, and nuclear. Bcl-xL protein levels decreased in the cytoplasm and mitochondria 2 hr after SCI and persisted for 24 hr. To test the contribution of proapoptotic decreases in Bcl-xL to neuronal death, we augmented endogenous Bcl-xL levels by administering Bcl-xL fusion protein (Bcl-xL FP) into injured spinal cords. Bcl-xL FP significantly increased neuronal survival, suggesting that SCI-induced changes in Bcl-xL contribute considerably to neuronal death. Because Bcl-xL FP increases survival of dorsal horn neurons and ventral horn motoneurons, it could become clinically relevant in preserving sensory and motor functions after SCI.

IGF-I induces DNA synthesis and apoptosis in rat liver hepatic stellate cells (HSC) but DNA synthesis and proliferation in rat liver myofibroblasts (rMF)

Several lines of evidence suggest a role of insulin-like growth factor I (IGF-I) in the regulation of apoptosis. Up to now its impact on many specific cells is unknown. We therefore studied the effect of IGF-I on two similar mesenchymal matrix-producing cell types of the liver, the hepatic stellate cells (HSC) and the myofibroblasts (rMF). The present study aimed to reveal the influence of IGF-I on cell cycle and apoptosis of HSC and rMF and to elucidate responsible signaling. While IGF-I significantly increased DNA synthesis in HSC, cell number decreased and apoptosis increased. In rMF IGF-I also increased DNA synthesis, which is, however, followed by proliferation. Blocking extracellular signal regulating kinase (ERK) revealed that in HSC, bcl-2 upregulation and bax downregulation are effected downstream of ERK, whereas downregulation of NFkappaB and consecutive of bcl-xL is mediated upstream. In the rMF upregulation of both, the antiapoptotic bcl-2 and bcl-xL is mediated upstream of ERK. The expression of the proapoptotic bax is not regulated by IGF-I in rMF. The studies demonstrate a completely different effect and signaling of IGF-I in two morphologically and functionally similar matrix-producing cells of the liver.

Resveratrol, a red wine polyphenol, protects spinal cord from ischemia-reperfusion injury

OBJECTIVE

The cardioprotective effect of red wine has been attributed to resveratrol. The resveratrol-induced protection against ischemia-reperfusion (I/R) injury has been documented in heart, kidney, and brain. Resveratrol scavenges free O(2) radicals and upregulates nitric oxide (NO). However, the presence of resveratrol-induced spinal cord protection against I/R injury has not been reported in the literature. The objective of this study was to evaluate the effects of resveratrol on neurologic functions, histopathologic changes, and NO metabolism following temporary spinal cord ischemia (SCI) in rabbits. Material and methods SCI was induced with occlusion of the infrarenal aorta in rabbits. In addition to the sham group (group S, n = 7), group C (n = 7) received vehicle 30 minutes before ischemia. Group R1 (n = 7) and R10 (n = 7) received 1 mg/kg and 10 mg/kg resveratrol instead of vehicle, respectively. Blood samples were taken to obtain nitrite/nitrate levels during the surgical procedure. After neurologic evaluation at the 48th hour of reperfusion, lumbar spinal cords were removed for histopathologic examination and malondialdehyde measurement as a marker of oxidative stress.

RESULTS

Five animals in group C had paraplegia while 5 in group R10 had normal neurologic functions. The average Tarlov score of group R10 was significantly higher than that the score of group C (4.1 +/- 1.2, vs 1.2 +/- 2.2; P =.014). Histopathologic examination revealed higher neuronal viability index in group R10 compared with that of group C (0.82 +/- 0.24 vs. 0.46 +/- 0.34; P =.018). Nitrite/nitrate levels decreased in group C (from 357 +/- 20.15 micromol/L to 281 +/- 47.9 micromol/L; P <.01) whereas they increased both in group R1 and group R10 (from 287+/-28 micromol/L to 310 +/- 33.9 micromol/L and from 296 +/- 106 micromol/L to 339 +/- 87 micromol/L, respectively) during SCI. Malondialdehyde levels of group R10 was lower than those of group C (55 +/- 12.9 nmol/mg protein vs 83.9 +/- 15.1 nmol/mg protein; P =.001, respectively).

CONCLUSIONS

In this model of SCI, resveratrol decreased oxidative stress, increased NO release, and protected spinal cord from I/R injury. Resveratrol-induced neuroprotection is probably mediated by its antioxidant and NO promoting properties. Before considering the clinical use of this natural antioxidant, further research is warranted about its mechanism of effects, timing, and optimum dose.

CLINICAL RELEVANCE

Paraplegia that results from spinal cord ischemia is a catastrophic complication of thoracic and thoracoabdominal aorta surgical procedures. Despite several surgical modifications and pharmacologic approaches, paraplegia has not been totally eliminated. On clinical grounds, the efficiency of currently used pharmacologic agents to prevent spinal cord injury during thoracic and thoracoabdominal aorta surgery is very limited and their benefit is controversial. Preischemic infusion of resveratrol protects the spinal cord from ischemia reperfusion injury in rabbits. Following clarification of the underlying protective mechanism, optimal dose, and timing, resveratrol may used in humans as an adjunct to eliminate this catastrophic complication.

Molecular evidence of repair and plasticity following spinal cord injury

Investigations into the genetic basis of neuronal damage following spinal cord injury have thus far been limited to the acute phase after the injury. Using microarray analysis, the present study compared the spinal-cord-injury-induced gene expression changes in adult rats at the epicenter and rostral segments of spinal cord at acute (12 h) and delayed (42 days) time points. We have previously reported that the acute response to spinal cord injury involves alterations in genes responsible for inflammation, cell cycle alteration, and altered receptor function. In contrast, the delayed response includes changes in the expression of HSP27, MAG, MAP-2, IGF-1 and ApoE. The alteration in expression of these genes suggests an ongoing repair process in animals whose functional recovery has reached a plateau.

Cell death in the nervous system: lessons from insulin and insulin-like growth factors

Programmed cell death is an essential process for proper neural development. Cell death, with its similar regulatory and executory mechanisms, also contributes to the origin or progression of many or even all neurodegenerative diseases. An understanding of the mechanisms that regulate cell death during neural development may provide new targets and tools to prevent neurodegeneration. Many studies that have focused mainly on insulin-like growth factor-I (IGF-I), have shown that insulin-related growth factors are widely expressed in the developing and adult nervous system, and positively modulate a number of processes during neural development, as well as in adult neuronal and glial physiology. These factors also show neuroprotective effects following neural damage. Although some specific actions have been demonstrated to be anti-apoptotic, we propose that a broad neuroprotective role is the foundation for many of the observed functions of the insulin-related growth factors, whose therapeutical potential for nervous system disorders may be greater than currently accepted.

Insulin-like growth factor-1 protects ischemic murine myocardium from ischemia/reperfusion associated injury

INTRODUCTION

Ischemia/reperfusion occurs in myocardial infarction, cardiac dysfunction during sepsis, cardiac transplantation and coronary artery bypass grafting, and results in injury to the myocardium. Although reperfusion injury is related to the nature and duration of ischemia, it is also a separate entity that may jeopardize viable cells and ultimately may impair cardiac performance once ischemia is resolved and the organ heals.

METHOD

The present study was conducted in an ex vivo murine model of myocardial ischemia/reperfusion injury. After 20 min of ischemia, isolated hearts were perfused for up to 2 hours with solution (modified Kreb's) only, solution plus insulin-like growth factor (IGF)-1, or solution plus tumor necrosis factor (TNF)-alpha. Cardiac contractility was monitored continuously during this period of reperfusion.

RESULTS

On the basis of histologic evidence, IGF-1 prevented reperfusion injury as compared with TNF-alpha; TNF-alpha increased perivascular interstitial edema and disrupted tissue lattice integrity, whereas IGF-1 maintained myocardial cellular integrity and did not increase edema. Also, there was a significant reduction in detectable creatine phosphokinase in the perfusate from IGF-1 treated hearts. By recording transduced pressures generated during the cardiac cycle, reperfusion with IGF-1 was accompanied by markedly improved cardiac performance as compared with reperfusion with TNF-alpha or modified Kreb's solution only. The histologic and functional improvement generated by IGF-1 was characterized by maintenance of the ratio of mitochondrial to nuclear DNA within heart tissue.

CONCLUSION

We conclude that IGF-1 protects ischemic myocardium from further reperfusion injury, and that this may involve mitochondria-dependent mechanisms.

N-methyl-D-aspartate receptors: transient loss of NR1/NR2A/NR2B subunits after traumatic brain injury in a rodent model

Hippocampal N-methyl-D-aspartate (NMDA) receptor subunits, by virtue of their involvement in excitotoxic injury as well as memory association, may play an important role in the pathophysiologic mechanisms of traumatic brain injury (TBI). In this study, temporal changes in NMDA receptor subunit (NR1, NR2A, and NR2B) levels in rat hippocampus after TBI were investigated by Western blot and mRNA expression levels by RT-PCR methods. Sprague-Dawley rats (250-350 g) were employed, and a controlled cortical impact injury device was used to produce the TBI in rodents. At different postinjury time points (2, 6, 12, 24, and 48 hr), the rat hippocampi were dissected out for protein and RNA preparation. Western blot analysis revealed significant decreases of NR1, NR2A, and NR2B subunit proteins at 6 and 12 hr postinjury in rat hippocampus. Complete recovery of NR1, NR2A, and NR2B subunit protein to the levels of sham controls was observed at 24 hr postinjury. However, RT-PCR analysis did not show any significant change in the mRNA levels at 2, 6, and 12 hr postinjury in comparison with sham controls, suggesting nontranscriptional change in the levels of these subunits. Thus, TBI can produce transient degradation of NMDA receptor subunits in the hippocampus, which might contribute to temporary memory impairment after injury.