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Background Neuregulin‐1β ( NRG ‐1β) is a growth factor critical for cardiac development and repair with therapeutic potential for heart failure. We previously showed that the glial growth factor 2 ( GGF 2) isoform of NRG ‐1β improves cardiac function in rodents after myocardial infarction ( MI ), but its efficacy in a large animal model of cardiac injury has not been examined. We therefore sought to examine the effects of GGF 2 on ventricular remodeling, cardiac function, and global transcription in post‐ MI swine, as well as potential mechanisms for anti‐remodeling effects. Methods and Results MI was induced in anesthetized swine (n=23) by intracoronary balloon occlusion. At 1 week post‐ MI , survivors (n=13) received GGF 2 treatment (intravenous, biweekly for 4 weeks; n=8) or were untreated (n=5). At 5 weeks post‐ MI , fractional shortening was higher (32.8% versus 25.3%, P =0.019), and left ventricular ( LV ) end‐diastolic dimension lower (4.5 versus 5.3 cm, P =0.003) in GGF 2‐treated animals. Treatment altered expression of 528 genes, as measured by microarrays, including collagens, basal lamina components, and matricellular proteins. GGF 2‐treated pigs exhibited improvements in LV cardiomyocyte mitochondria and intercalated disk structures and showed less fibrosis, altered matrix structure, and fewer myofibroblasts (myoFbs), based on trichrome staining, electron microscopy, and immunostaining. In vitro experiments with isolated murine and rat cardiac fibroblasts demonstrate that NRG ‐1β reduces myoFbs, and suppresses TGF β‐induced phospho‐ SMAD 3 as well as α SMA expression. Conclusions These results suggest that GGF 2/ NRG ‐1β prevents adverse remodeling after injury in part via anti‐fibrotic effects in the heart.

Using an established rat peripheral nerve regeneration model, we investigated the role of glial growth factor (GGF) in nerve regeneration in combination with a novel bioresorbable poly(lactic-co-glycolic) acid (PLGA) guide in vivo. Schwann cells, established from a 1-cm segment of excised rat sciatic nerve, were isolated and seeded onto nerve guides with or without GGF (n = 24/group). Living nerve guides were re-established in these animals, and nerve regeneration was assessed over a period of 12 weeks. Histological studies revealed a reduction in the total axon count and the number of myelinated axons in the presence of exogenously added Schwann cells compared to saline controls. In contrast, the addition of GGF alone enhanced the total number of axons and significantly increased the number of blood vessels. Although combining GGF with Schwann cells negated the enhanced numbers of axons and blood vessels seen with GGF alone, this combination resulted in the highest myelination index and the fastest conduction velocities recorded. The PLGA guide material did not trigger any histologically detectable host response and was permissive for nerve regeneration in this animal model. The results from this study demonstrate the potential utility of this guide in vivo and establish a promotional role for GGF in nerve regeneration.

The work performed under this grant evaluated the efficacy of Glial Growth Factor 2 (GGF2), a member for the neuregulin family, as a spinal cord injury (SCI) therapeutic. The research expanded on previous work and extended these studies to determine if GGF2 should be advanced into human clinical studies for SCI. GGF2 s optimal dosage was examined using a model of rodent SCI and testing several dose levels delivered either subcutaneously (SC) or intravenously (IV). Optimized dosing was determined to be by a SC route, and subsequent studies evaluated recovery of function by monitoring bladder function, muscle volume changes, and motor function in SCI rodent models of various severities. Additionally, safety and tolerability was explored in naive canines, and followed by a clinical trial for safety in dogs with SCI.

It is widely thought that mammalian Schwann cells do not express P 0 , the major glycoprotein in peripheral myelin, unless they are induced to do so by axonal signals that can be mimicked by agents that trigger cAMP signaling pathways. In contrast, we find that cultured Schwann cells make large amounts of P 0 without the addition of any axonal-like signal, provided they have not been exposed to serum during the culture process. We also report that glial growth factor/neuregulin inhibits this constitutive P 0 expression. Myelin basic protein is regulated in a similar way. We suggest that expression of P 0 by Schwann cells before the onset of myelination may be prevented by inhibitory signals within the nerve, rather than by the absence of a positive signal from axons.

Neu-differentiation factor (glial growth factor) has been established as an important regulator of early Schwann cell development, and the lineage relationship between immature Schwann cells and the neural crest has been clarified by the identification of the Schwann cell precursor. Progress has been made in identifying transcription factors that control Schwann cell development and in defining molecules that positively and negatively regulate myelin differentiation pathways. The tetraspan group has emerged as a set of proteins with prominent functions in Schwann cell biology.

Signals that alter cell fate are probably crucial in metazoan development. Glial growth factor may play such a role in the mammalian neural crest, by regulating the generation of neurons and Schwann cells.

Neuregulins are a family of growth factors essential for normal cardiac and nervous system development. The EGF-like domain of neuregulins contains the active site which binds and activates signaling cascades through ErbB receptors. A neuregulin-1 gene EGF-like fragment demonstrated neuroprotection in the transient middle cerebral artery occlusion (MCAO) stroke model and drastically reduced infarct volume (Xu et al., 2004). Here we use a permanent MCAO rat model to initially compare two products of the neuregulin-1 gene and also assess levels of recovery with acute versus delayed time to treatment. In the initial study full-length glial growth factor 2 (GGF2) and an EGF-like domain fragment were compared with acute intravenous delivery. In a second study GGF2 only was delivered starting at 24h, 3 days or 7 days after permanent ischemia was induced. In both studies daily intravenous administration continued for 10 days. Recovery of neurological function was assessed using limb placing and body swing tests. GGF2 had similar functional improvements compared to the EGF-like domain fragment at equimolar doses, and a higher dose of GGF2 demonstrated more robust functional improvements compared to a lower dose. GGF2 improved sensorimotor recovery with all treatment paradigms, even enhancing recovery of function with a delay of 7 days to treatment. Histological assessments did not show any associated reduction in infarct volume at either 48 h or 21 days post-ischemic event. Neurorestorative effects of this kind are of great potential clinical importance, given the difficulty of delivering neuroprotective therapies within a short time after an ischemic event in human patients. If confirmed by additional work including additional data on mechanism(s) of improved outcome with verification in other stroke models, one can make a compelling case to bring GGF2 to clinical trials as a neurorestorative approach to improving outcome following stroke injury.

Many students understand the electrical properties of neurons and can adequately describe the creation and transmission of electrical impulses. However, students often have difficulty when it comes to understanding how neurons have an equally important role in cell signaling. This latter function is crucial in the establishment of proper cell fate during regeneration. I have devised a lab that includes in its goals: 1) an investigation into the cell signaling role of neurons, 2) experience with non-lethal invasive surgery, 3) an opportunity for student-collected data, and 4) the chance to work with charismatic animals. In addition, the exercise provides insight into development because development and regeneration follow similar pathways. The lab also introduces the topic of stem cells. Finally, the eventual regeneration of the denervated limb can provide an opportunity to discuss the mechanisms of nerve repair. A critical event in urodele limb regeneration is the formation of a blastema. This event requires an intact nerve supply. Nerves secrete a substance called the neurotrophic growth factor(s) that appear to stimulate the reentry of blastema cells into the cell cycle, through a complex series of signaling events. In this laboratory exercise, students examine this effect by amputating both front limbs, but denervating only one. They then compare limb regeneration under and exempt from nerve control within the same animal. Students control for denervation using a behavioral assay, and monitor limb growth for six weeks. All sixteen of the surgeries were successful, and all showed the expected difference between the denervated and the control limb.

Two to four cm nerve gaps in the rabbit common peroneal nerve were bridged with poly-3-hydroxybutyrate (PHB) conduits containing either glial growth factor (GGF) (PHB-GGF) or alginate matrix (PHB-ALG), and with empty PHB conduit (E-PHB). PHB-GGF significantly increased nerve regeneration up to 63 days following repair of long nerve gaps and the regeneration was sustained long term leading to motor organ reinnervation. At 120 days postoperatively, GGF addition significantly increased the quantity of Schwann cell and axonal regeneration compared to those in control conduits. In PHB-GGF conduits there were more minifascicles of myelinated fibres compared to the controls. The distal nerve of PHB-GGF and E-PHB conduits showed greater regeneration than that of PHB-ALG grafts, although all distal nerves contained fewer myelinated fibres than grafted conduits. Consistently, PHB-GGF conduits significantly reduced the muscle mass percentage loss compared to controls. In conclusion, GGF-containing conduits promoted sustained axonal regeneration and improved target muscle reinnervation.

There is considerable evidence that peripheral nerves have the potential to regenerate in an appropriate microenvironment. We have developed a novel artificial nerve guide composed of poly 3-hydroxybutyrate (PHB) filled with glial growth factor (GGF) suspended in alginate hydrogel. Gaps of 2-4 cm in rabbit common peroneal nerve were bridged using a PHB conduit containing either GGF in alginate hydrogel (GGF) or alginate alone (Alginate), or with an empty PHB conduit (Empty). Tissues were harvested 21, 42 and 63 days post-operatively. Schwann cell and axonal regeneration were assessed using quantitative immunohistochemistry. At 21 days, addition of GGF increased significantly the distance of axonal and Schwann cells regeneration in comparison with that observed in Alginate and Empty conduits for both gap lengths. The axons bridged the 2-cm GGF conduits gap by 63 days, with a comparable rate of regeneration seen in 4-cm conduits. Schwann cells and axonal regeneration quantity was similar for both gap lengths in each group. However, at all time points the quantity of axonal and Schwann cells regeneration in GGF grafts was significantly greater than in both Alginate and Empty conduits, the latter showing better regeneration than Alginate conduits. The results indicate an inhibitory effect of alginate on regeneration, which is partially reversed by the addition of GGF to the conduits. In conclusion, GGF stimulates a progressive and sustainable regeneration increase in long nerve gap conduits.

Peripheral nerve trauma is a common cause of considerable functional morbidity, and healthcare expenditure. Particularly in the ~15% of injuries unsuitable for primary repair, standard clinical management results in inadequate sensory restitution in the majority of cases, despite the rigorous application of complex microsurgical techniques. This can largely be explained by the failure of surgical management to adequately address the neurobiological hurdles to optimal regeneration. Most significant of these is the extensive sensory neuronal death that follows injury, and which is accompanied by a reduction in the regenerative potential of axotomised neurons, and in the supportive capacity of the Schwann cell population if nerve repair is delayed. The present study aimed to accurately delineate the timecourse of neuronal death, in order to identify a therapeutic window during which clinically applicable neuroprotective strategies might be adopted. It then proceeded to investigate means to increase the regenerative capacity of chronically axotomised neurons, and to augment the Schwann cells’ ability to promote that regenerative effort. Unilateral sciatic nerve transection in the rat was the model used, initially assessing neuronal death within the L4&5 dorsal root ganglia by a combination of morphology, TdT uptake nick-end labelling (TUNEL), and statistically unbiased estimation of neuronal loss using the stereological optical disector technique. Having identified 2 weeks, and 2 months post-axotomy as the most biologically relevant timepoints to study, the effect upon neuronal death of systemic treatment with acetyl-L-carnitine (ALCAR 10, or 50mg/kg/day) or N-acetyl-cysteine (NAC 30, or 150mg/kg/day) was determined. A model of secondary nerve repair was then adopted; either 2 or 4 months after unilateral sciatic nerve division, 1cm gap repairs were performed using either reversed isografts, or poly-3-hydroxybutyrate (PHB) conduits containing an alginate-fibronectin hydrogel. Six weeks later nerve regeneration and the Schwann cell population were quantified by digital image analysis of frozen section immunohistochemistry. Sensory neuronal death begins within 24 hours of injury, but takes 1 week to translate into significant neuronal loss. The rate of neuronal death peaks 2 weeks after injury, and neuronal loss is essentially complete by 2 months post-axotomy. Nerve repair is incompletely neuroprotective, but the earlier it is performed the greater the benefit. Two clinically safe pharmaceutical agents, ALCAR & NAC, were found to virtually eliminate sensory neuronal death after peripheral nerve transection. ALCAR also enhanced nerve regeneration independently of its neuroprotective role. Plain PHB conduits were found to be technically simple to use, and supported some regeneration, but were not adequate in themselves. Leukaemia inhibitory factor enhanced nerve regeneration, though cultured autologous Schwann cells (SC’s) were somewhat more effective. Both were relatively more efficacious after a 4 month delay in nerve repair. The most profuse regeneration was found with recombinant glial growth factor (rhGGF-2) in repairs performed 2 months after axotomy, with results that were arguably better than were obtained with nerve grafts. A similar conclusion can be drawn from the result found using both rhGGF-2 and SC’s in PHB conduits 4 months after axotomy. In summary, these findings reinforce the significance of sensory neuronal death in peripheral nerve trauma, and the possibility of its` limitation by early nerve repair. Two agents for the adjuvant therapy of such injuries were identified, that can virtually eliminate neuronal death, and enhance regeneration. Elements in the creation of a bioartificial nerve conduit to replace, or surpass autologous nerve graft for secondary nerve repair are presented.

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) which results in demyelination and axonal injury. Conventional therapy for MS is immune suppression in the absence of agents that promote neural and glial survival or remyelination. Neuregulins are a family of ligands that exert trophic effects on both neurons and glia. Using mice bearing a null mutation in the neuregulin gene, here we demonstrate that neuregulins are necessary for the normal development of oligodendrocytes. In addition, neuregulins are produced in the normal human CNS by astrocytes as well as neurons. Astrocyte-derived neuregulin is functionally active in bioassays and exists in secreted and membrane-associated β-isoforms. In active and chronic active MS lesions, however, the expression of astrocyte neuregulin is dramatically reduced. The absence of neuregulin in active MS lesions may contribute to the paucity of remyelination in MS.

Both cell growth (cell mass increase) and progression through the cell division cycle are required for sustained cell proliferation. Proliferating cells in culture tend to double in mass before each division, but it is not known how growth and division rates are co-ordinated to ensure that cell size is maintained. The prevailing view is that coordination is achieved because cell growth is rate-limiting for cell-cycle progression. Here, we challenge this view. We have investigated the relationship between cell growth and cell-cycle progression in purified rat Schwann cells, using two extracellular signal proteins that are known to influence these cells. We find that glial growth factor (GGF) can stimulate cell-cycle progression without promoting cell growth. We have used this restricted action of GGF to show that, for cultured Schwann cells, cell growth rate alone does not determine the rate of cell-cycle progression and that cell size at division is variable and depends on the concentrations of extracellular signal proteins that stimulate cell-cycle progression, cell growth, or both.

Glial Growth Factor 2 (GGF2) is a neuregulin peptide critical for myocardial function. GGF2 improves left ventricular function (LVF) in animal models of cardiac injury. We report echocardiographic findings in a first-in-man, double-blind, placebo controlled, escalating single dose study of

The ability to culture cells from the human nervous system provides new insight into the pathophysiology of neurological diseases and could be crucial to the development of gene replacement therapies and neural transplantation. We report that the proliferation of human Schwann cells isolated from paediatric and adult nerves is sustained in vitro by recombinant glial growth factor. Agents that increase intracellular cyclic cAMP were also mitogenic towards Schwann cells but suppress growth of contaminating fibroblasts. As the lifespan of highly enriched cultures can be extended for up to twelve population doublings, large numbers of cells can be generated from nerve biopsies.

Prion-related encephalopathies are characterized by the accumulation of an abnormal prion protein isoform (PrPSc) and the deposition of PrP amyloid in the brain. This process is accompanied by neuronal loss and astrogliosis. We recently showed that a synthetic peptide corresponding to residues 106–126 of human PrP is amyloidogenic and causes neuronal death by apoptosis in vitro. In the present study we investigated the effects of 1- and 14-day exposures of rat astroglial cultures to mtcromolar concentrations of this peptide as well as peptides homologous to other portions of PrP, a peptide corresponding to residues 25–35 of amyloid-β protein, and a scrambled sequence of PrP 106–126. No significant changes were observed after 1-day exposure of cultures to any peptide. Conversely, 14-day treatment with PrP 106–126 (50 μM) resulted in a 5-fold increase in glial fibrillary acidic protein (GFAP) expression, as evaluated by Northern and Western blot analyses, and a 1.5-fold increment in cell number. Light and electron microscopy immunohistochemistry showed an enlargement in size and density of astroglial processes, and an increase in GFAP-immunoreactive intermediate filaments. These changes were not observed after 14-day treatment of cultures with the other peptides, including PrP 106–126 scrambled. The increase in GFAP expression of astroglial cultures exposed to PrP 106–126 was quantitatively similar to that found in scrapie-infected hamster brains. These results suggest that the PrP region corresponding to residues 106–126 is biologically active, and that cerebral accumulation of peptides including this sequence might be responsible for both the neuronal degeneration and the astrogliosis that occur in prion-related encephalopathies.

Publisher Summary This chapter describes the preparation of rat Schwann cells and their purification by employing anti-Thy-1 antibodies to kill contaminating fibroblasts. Procedures for the Schwann cell DNA synthesis assay in microwells and the purification of glial growth factor (GGF) from the bovine pituitary are also provided in the chapter. GGF activity on the rat Schwann cell has only been detected in extracts of neural tissue, and it has been purified from the bovine pituitary. One area of the bovine brain—the caudate nucleus—has an even higher level than the pituitary and the properties of the partially purified caudate activity are indistinguishable from those of pituitary GGF as evidenced by chromatographic and immunochemical criteria. A similar molecule has been detected in extracts of the nervous system of all vertebrates investigated to date including human, bovine, rodent, chick, and amphibian sources. There is some evidence that GGF may be involved in the nerve dependence of amphibian limb regeneration.