Nonviral HVJ (hemagglutinating virus of Japan) liposome-mediated retrograde gene transfer of human hepatocyte growth factor into rat nervous system promotes functional and histological recovery of the crushed nerve

Advanced Gene-Targeting Therapies for Motor Neuron Diseases and Muscular Dystrophies

Gene therapy is a revolutionary, cutting-edge approach to permanently ameliorate or amend many neuromuscular diseases by targeting their genetic origins. Motor neuron diseases and muscular dystrophies, whose genetic causes are well known, are the frontiers of this research revolution. Several genetic treatments, with diverse mechanisms of action and delivery methods, have been approved during the past decade and have demonstrated remarkable results. However, despite the high number of genetic treatments studied preclinically, those that have been advanced to clinical trials are significantly fewer. The most clinically advanced treatments include adeno-associated virus gene replacement therapy, antisense oligonucleotides, and RNA interference. This review provides a comprehensive overview of the advanced gene therapies for motor neuron diseases (i.e., amyotrophic lateral sclerosis and spinal muscular atrophy) and muscular dystrophies (i.e., Duchenne muscular dystrophy, limb-girdle muscular dystrophy, and myotonic dystrophy) tested in clinical trials. Emphasis has been placed on those methods that are a few steps away from their authoritative approval.

Gene therapy for diabetic peripheral neuropathy: A randomized, placebo-controlled phase III study of VM202, a plasmid DNA encoding human hepatocyte growth factor

VM202 is a plasmid DNA encoding two isoforms of hepatocyte growth factor (HGF). A previous phase II study in subjects with painful diabetic peripheral neuropathy (DPN) showed significant reductions in pain. A phase III study was conducted to evaluate the safety and efficacy of VM202 in DPN. The trial was conducted in two parts, one for 9 months (DPN 3-1) with 500 subjects (VM202: 336 subjects; and placebo: 164) and a preplanned subset of 101 subjects (VM202: 65 subjects; and placebo: 36) with a noninterventional extension to 12 months (DPN 3-1b). VM202 or placebo was administered to calf muscles on days 0 and 14, and on days 90 and 104. The primary end point in DPN 3-1 was change from baseline in the mean 24-h Numerical Rating Scale (NRS) pain score. In DPN 3-1b, the primary end point was safety, whereas the secondary efficacy end point was change in the mean pain score. VM202 was well-tolerated in both studies without significant adverse events. VM202 failed to meet its efficacy end points in DPN 3-1. In DPN 3-1b, however, VM202 showed significant and clinically meaningful pain reduction versus placebo. Pain reduction in DPN 3-1b was even greater in subjects not receiving gabapentin or pregabalin, confirming an observation noted in the phase II study. In DPN 3-1b, symptomatic relief was maintained for 8 months after the last injection suggesting that VM202 treatment might change disease progression. Despite the perplexing discrepancy between the two studies, the safety and long-lasting pain-relieving effects of VM202 observed in DPN 3-1b warrant another rigorous phase III study. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Current therapies for painful diabetic peripheral neuropathy (DPN) are palliative and do not target the underlying mechanisms. Moreover, symptomatic relief is often limited with existing neuropathic pain drugs. Thus, there is a great medical need for safer and effective treatments for DPN. WHAT QUESTION DID THIS STUDY ADDRESS? Can nonviral gene delivery of hepatocyte growth factor reduce pain in patients with DPN and potentially modify progression of the disorder? WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? Nonviral gene therapy can be used safely and practically to treat DPN. HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? As the first gene medicine to enter advanced clinical trials for the treatment of DPN, this study provides the proof of concept of an entirely new potential approach to the disorder.

Beyond Trophic Factors: Exploiting the Intrinsic Regenerative Properties of Adult Neurons

Injuries and diseases of the peripheral nervous system (PNS) are common but frequently irreversible. It is often but mistakenly assumed that peripheral neuron regeneration is robust without a need to be improved or supported. However, axonal lesions, especially those involving proximal nerves rarely recover fully and injuries generally are complicated by slow and incomplete regeneration. Strategies to enhance the intrinsic growth properties of reluctant adult neurons offer an alternative approach to consider during regeneration. Since axons rarely regrow without an intimately partnered Schwann cell (SC), approaches to enhance SC plasticity carry along benefits to their axon partners. Direct targeting of molecules that inhibit growth cone plasticity can inform important regenerative strategies. A newer approach, a focus of our laboratory, exploits tumor suppressor molecules that normally dampen unconstrained growth. However several are also prominently expressed in stable adult neurons. During regeneration their ongoing expression “brakes” growth, whereas their inhibition and knockdown may enhance regrowth. Examples have included phosphatase and tensin homolog deleted on chromosome ten (PTEN), a tumor suppressor that inhibits PI3K/pAkt signaling, Rb1, the protein involved in retinoblastoma development, and adenomatous polyposis coli (APC), a tumor suppressor that inhibits β-Catenin transcriptional signaling and its translocation to the nucleus. The identification of several new targets to manipulate the plasticity of regenerating adult peripheral neurons is exciting. How they fit with canonical regeneration strategies and their feasibility require additional work. Newer forms of nonviral siRNA delivery may be approaches for molecular manipulation to improve regeneration.

Conditioned Medium of Bone Marrow-Derived Mesenchymal Stromal Cells as a Therapeutic Approach to Neuropathic Pain: A Preclinical Evaluation

Neuropathic pain is a type of chronic pain caused by injury or dysfunction of the nervous system, without effective therapeutic approaches. Mesenchymal stromal cells (MSCs), through their paracrine action, have great potential in the treatment of this syndrome. In the present study, the therapeutic potential of MSC-derived conditioned medium (CM) was investigated in a mouse model of neuropathic pain induced by partial sciatic nerve ligation (PSL). PSL mice were treated by endovenous route with bone marrow-derived MSCs (1 × 10⁶), CM, or vehicle. Gabapentin was the reference drug. Twelve hours after administration, neuropathic mice treated with CM exhibited an antinociceptive effect that was maintained throughout the evaluation period. MSCs also induced nonreversed antinociception, while gabapentin induced short-lasting antinociception. The levels of IL-1β, TNF-α, and IL-6 were reduced, while IL-10 was enhanced on sciatic nerve and spinal cord by treatment with CM and MSCs. Preliminary analysis of the CM secretome revealed the presence of growth factors and cytokines likely involved in the antinociception. In conclusion, the CM, similar to injection of live cells, produces a powerful and long-lasting antinociceptive effect on neuropathic pain, which is related with modulatory properties on peripheral and central levels of cytokines involved with the maintenance of this syndrome.

Signal transduction cascades in axon regeneration: insights from C. elegans

Axon regeneration after nerve injury is a conserved biological process in many animals, including humans. The nematode Caenorhabditis elegans (C. elegans) has recently emerged as a genetically tractable model for studying regenerative responses in neurons. Extensive studies over several years using this organism have revealed a number of intrinsic and extrinsic signal transduction cascades that regulate axon regeneration, and these are found to be conserved from worms to humans. Further studies have demonstrated that these cascades consist of several signaling networks that ultimately merge into the c-Jun N-terminal kinase (JNK) cascade. In this review, we describe some recent insights into the signaling cascades controlling axon regeneration in C. elegans and describe their conserved roles in other organisms including mammals.

Double-blind, placebo-controlled study of HGF gene therapy in diabetic neuropathy

OBJECTIVE

To evaluate the safety and efficacy of a plasmid (VM202) containing two human hepatocyte growth factor isoforms given by intramuscular injections in patients with painful diabetic neuropathy.

METHODS

In a double-blind, placebo-controlled study, patients were randomized to receive injections of 8 or 16 mg VM202 per leg or placebo. Divided doses were administered on Day 0 and Day 14. The prospective primary outcome was change in the mean pain score measured by a 7 day pain diary. Secondary outcomes included a responder analysis, quality of life and pain measures, and intraepidermal nerve fiber density.

RESULTS

There were no significant adverse events attributable to VM202. Eighty-four patients completed the study. Patients receiving 8 mg VM202 per leg improved the most in all efficacy measures including a significant (P = 0.03) reduction at 3 months in the mean pain score and continued but not statistically significant reductions in pain at 6 and 9 months. Of these patients, 48.4% experienced a ≥50% reduction in pain compared to 17.6% of placebo patients. There were also significant improvements in the brief pain inventory for patients with diabetic peripheral neuropathy and the questionnaire portion of the Michigan Neuropathy Screening Instrument. Patients not on pregabalin or gabapentin had the largest reductions in pain.

INTERPRETATION

VM202 was safe, well tolerated and effective indicating the feasibility of a nonviral gene therapy approach to painful diabetic neuropathy. Two days of treatment were sufficient to provide symptomatic relief with improvement in quality of life for 3 months. VM202 may be particularly beneficial for patients not taking gabapentin or pregabalin.

Therapeutic effect of exendin-4, a long-acting analogue of glucagon-like peptide-1 receptor agonist, on nerve regeneration after the crush nerve injury

Glucagon-like peptide-1 (GLP-1) is glucose-dependent insulinotropic hormone secreted from enteroendocrine L cells. Its long-acting analogue, exendin-4, is equipotent to GLP-1 and is used to treat type 2 diabetes mellitus. In addition, exendin-4 has effects on the central and peripheral nervous system. In this study, we administered repeated intraperitoneal (i.p.) injections of exendin-4 to examine whether exendin-4 is able to facilitate the recovery after the crush nerve injury. Exendin-4 injection was started immediately after crush injury and was repeated every day for subsequent 14 days. Rats subjected to sciatic nerve crush exhibited marked functional loss, electrophysiological dysfunction, and atrophy of the tibialis anterior muscle (TA). All these changes, except for the atrophy of TA, were improved significantly by the administration of exendin-4. Functional, electrophysiological, and morphological parameters indicated significant enhancement of nerve regeneration 4 weeks after nerve crush. These results suggest that exendin-4 is feasible for clinical application to treat peripheral nerve injury.

Critical role of p38 MAPK for regeneration of the sciatic nerve following crush injury in vivo

BACKGROUND

The physiological function of p38α, which is an isoform of p38 MAPK, has been investigated previously in several studies using pharmacological inhibitors. However, the results regarding whether p38α promotes or inhibits nerve regeneration in vivo have been controversial.

METHODS

We generated novel p38α mutant mice (sem mice) with a point mutation in the region encoding the p38α substrate-docking-site, which serves as a limited loss-of-function model of p38α. In the present study, we utilized sem mice and wild-type littermates (wt mice) to investigate the physiological role of p38α in nerve regeneration following crush injuries.

RESULTS

At four weeks after crush injury, the average axon diameter and the average axon area in sem mice were significantly smaller than those in wt mice. The average myelin sheath thickness in sem mice was reduced compared to wt mice, but no significant difference was observed in the G-ratio between the two groups. The sciatic functional index value demonstrated that functional nerve recovery in sem mice following crush injury was delayed, which is consistent with the histological findings. To investigate the underlying mechanisms of these findings, we examined inflammatory responses of the sciatic nerve by immunohistochemistry and western blotting. At an early phase following crush injury, sem mice showed remarkably lower expression of inflammatory cytokines, such as TNF-α and IL-1β, than wt mice. The expression of Caspase-3 and Tenascin-C were also lower in sem mice. Conversely, at a late phase of the response, sem mice showed considerably higher expression of TNF-α and of IL-1β with lower expression of S-100 than wt mice.

CONCLUSIONS

This is the first study of the physiological role of p38 MAPK in nerve regeneration that does not rely on the use of pharmacological inhibitors. Our results indicate that p38α insufficiency may cause an inflammatory disorder, resulting in a delay of histological and functional nerve recovery following crush injury. We conclude that p38 MAPK has an important physiological role in nerve regeneration and may be important for controlling both initiation of inflammation and recovery from nerve injury.

Critical role of p38 MAPK for regeneration of the sciatic nerve following crush injury in vivo

Background

The physiological function of p38α, which is an isoform of p38 MAPK, has been investigated previously in several studies using pharmacological inhibitors. However, the results regarding whether p38α promotes or inhibits nerve regeneration in vivo have been controversial.

Methods

We generated novel p38α mutant mice (sem mice) with a point mutation in the region encoding the p38α substrate-docking-site, which serves as a limited loss-of-function model of p38α. In the present study, we utilized sem mice and wild-type littermates (wt mice) to investigate the physiological role of p38α in nerve regeneration following crush injuries.

Results

At four weeks after crush injury, the average axon diameter and the average axon area in sem mice were significantly smaller than those in wt mice. The average myelin sheath thickness in sem mice was reduced compared to wt mice, but no significant difference was observed in the G-ratio between the two groups. The sciatic functional index value demonstrated that functional nerve recovery in sem mice following crush injury was delayed, which is consistent with the histological findings. To investigate the underlying mechanisms of these findings, we examined inflammatory responses of the sciatic nerve by immunohistochemistry and western blotting. At an early phase following crush injury, sem mice showed remarkably lower expression of inflammatory cytokines, such as TNF-α and IL-1β, than wt mice. The expression of Caspase-3 and Tenascin-C were also lower in sem mice. Conversely, at a late phase of the response, sem mice showed considerably higher expression of TNF-α and of IL-1β with lower expression of S-100 than wt mice.

Conclusions

This is the first study of the physiological role of p38 MAPK in nerve regeneration that does not rely on the use of pharmacological inhibitors. Our results indicate that p38α insufficiency may cause an inflammatory disorder, resulting in a delay of histological and functional nerve recovery following crush injury. We conclude that p38 MAPK has an important physiological role in nerve regeneration and may be important for controlling both initiation of inflammation and recovery from nerve injury.

Hepatocyte growth factor protects retinal ganglion cells by increasing neuronal survival and axonal regeneration in vitro and in vivo

Hepatocyte growth factor (HGF) is known to promote the survival and foster neuritic outgrowth of different subpopulations of CNS neurons during development. Together with its corresponding receptor c-mesenchymal-epithelial transition factor (Met), it is expressed in the developing and the adult murine, rat and human CNS. We have studied the role of HGF in paradigms of retinal ganglion cell (RGC) regeneration and cell death in vitro and in vivo. After application of recombinant HGF in vitro, survival of serum-deprived RGC-5 cells and of growth factor-deprived primary RGC was significantly increased. This was shown to be correlated to the phosphorylation of c-Met and subsequent activation of serine/threonine protein kinase Akt and MAPK downstream signalling pathways involved in neuronal survival. Furthermore, neurite outgrowth of primary RGC was stimulated by HGF. In vivo, c-Met expression in RGC was up-regulated after optic nerve axotomy lesion. Here, treatment with HGF significantly improved survival of axotomized RGC and enhanced axonal regeneration after optic nerve crush. Our data demonstrates that exogenously applied HGF has a neuroprotective and regeneration-promoting function for lesioned CNS neurons. We provide strong evidence that HGF may represent a trophic factor for adult CNS neurons, which may play a role as therapeutic target in the treatment of neurotraumatic and neurodegenerative CNS disorders.

Enhanced neuronal Met signalling levels in ALS mice delay disease onset

Signalling by receptor tyrosine kinases (RTKs) coordinates basic cellular processes during development and in adulthood. Whereas aberrant RTK signalling can lead to cancer, reactivation of RTKs is often found following stress or cell damage. This has led to the common belief that RTKs can counteract degenerative processes and so strategies to exploit them for therapy have been extensively explored. An understanding of how RTK stimuli act at cellular levels is needed, however, to evaluate their mechanism of therapeutic action. In this study, we genetically explored the biological and functional significance of enhanced signalling by the Met RTK in neurons, in the context of a neurodegenerative disease. Conditional met-transgenic mice, namely Rosa26^{LacZ−stop−Met}, have been engineered to trigger increased Met signalling in a temporal and tissue-specific regulated manner. Enhancing Met levels in neurons does not affect either motor neuron (MN) development or maintenance. In contrast, increased neuronal Met in amyotrophic lateral sclerosis (ALS) mice prolongs life span, retards MN loss, and ameliorates motor performance, by selectively delaying disease onset. Thus, our studies highlight the properties of RTKs to counteract toxic signals in a disease characterized by dysfunction of multiple cell types by acting in MNs. Moreover, they emphasize the relevance of genetically assessing the effectiveness of agents targeting neurons during ALS evolution.

Dynamic plasticity of axons within a cutaneous milieu

The skin is a repository of sensory axons immersed within the turnover of epidermal, follicular, and dermal cellular constituents. We show that epidermal and perifollicular axons within intact hairy skin of mice possess a remarkable dynamic plasticity linked to their microenvironment. For example, the majority of epidermal axons express the growth protein GAP43. Unexpectedly, we induced new cutaneous axogenesis by simple and noninvasive hair clipping, a response linked to a series of changes in their cutaneous neighbors. In thy-1 YFP transgenic mice with fluorescent axons, superficial epidermal and perifollicular cells newly acquired YFP, indicating diffuse activation by clipping despite the absence of skin injury. At 48 h after clipping, this activation was accompanied by a rise in the number of epidermal cells, transient rises in mRNA of Sox2, a marker of follicular stem cells, and a rise in mRNA of glial fibrillary acidic protein, a marker of glial cells. Axons responded with rises in their numbers in the epidermis and around dermal hair follicles. Linking these responses were early, large, and selective rises in hepatic growth factor (HGF) mRNA, with its protein identified in epidermal cells, perifollicular cells, and sensory axons. Moreover, these elements also expressed the HGF receptor c-Met, especially in small caliber sensory neurons. Finally, we identified concurrent rises in Rac1 activation, a downstream target of ligated c-Met. Together, these results confirm critical linkages between sensory axons and their cutaneous milieu. We believe that the plasticity is provoked by follicular-originating cutaneous activation with HGF and Rac1 signaling, allowing cross talk and axonal remodeling.

Percutaneous nonviral delivery of hepatocyte growth factor in an osteotomy gap promotes bone repair in rabbits: a preliminary study

Hepatocyte growth factor (HGF) was initially identified in cultured hepatocytes and subsequently reported to induce angiogenic, morphogenic, and antiapoptotic activity in various tissues. These properties suggest a potential influence of HGF on bone healing. We asked if gene transfer of human HGF (hHGF) into an osteotomy gap with a hemagglutinating virus of Japan-envelope (HVJ-E) vector promotes bone healing in rabbits. HVJ-E that contained either hHGF or control plasmid was percutaneously injected into the osteotomy gap of rabbit tibias on Day 14. The osteotomy gap was evaluated by radiography, pQCT, mechanical tests, and histology at Week 8. The expression of hHGF was evaluated by reverse transcriptase-polymerase chain reaction and immunohistochemistry at Week 3. Radiography, pQCT, and histology suggested the hHGF group had faster fracture healing. Mechanical tests demonstrated the hHGF group had greater mechanical strength. The injected tissues at 3 weeks expressed hHGF mRNA by reverse transcriptase-polymerase chain reaction. hHGF-positive immunohistochemical staining was observed in various cells at the osteotomy gap at Week 3. The data suggest delivery of hHGF plasmid into the osteotomy gap promotes fracture repair, and HGF could become a novel agent for fracture treatment.

Metron factor-1 prevents liver injury without promoting tumor growth and metastasis

Hepatocyte growth factor (HGF) is the most powerful hepatotrophic factor identified so far. However, the ability of HGF to promote tumor cell "scattering" and invasion raises some concern about its therapeutic safety. We compared the therapeutic efficacy of HGF with that of Metron Factor-1 (MF-1), an engineered cytokine derived from HGF and the HGF-like factor macrophage stimulating protein (MSP), in mouse models of acute and chronic liver injury. At the same time, we tested the ability of HGF and MF-1 to promote tumor growth, angiogenesis, and invasion in several mouse models of cancer. We show that (1) MF-1 and HGF stimulate hepatocyte proliferation in vitro; (2) MF-1 and HGF protect primary hepatocytes against Fas-induced and drug-induced apoptosis; (3) HGF but not MF-1 induces scattering and matrigel invasion of carcinoma cell lines in vitro; (4) HGF but not MF-1 promotes migration and extracellular matrix invasion of endothelial cells in vitro; (5) MF-1 and HGF prevent CCl(4)-induced acute liver injury as measured by alanine aminotransferase (ALT) levels, histology, terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) analysis, and phospho-histone-3 immunostaining; (6) MF-1 and HGF attenuate liver fibrosis caused by chronic CCl(4) intoxication and promote regeneration as measured by Sirius red staining, alpha-smooth muscle actin immunostaining, and Ki-67 analysis; (7) HGF but not MF-1 promotes tumor growth, angiogenesis, and metastasis in a variety of xenograft models; (8) HGF but not MF-1 promotes intrahepatic dissemination of hepatocarcinoma cells injected orthotopically.

CONCLUSION

These data suggest that MF-1 is as effective as HGF at preventing liver injury and at promoting hepatocyte regeneration, but therapeutically safer than HGF because it lacks proangiogenic and prometastatic activity.

Nonviral gene transfer of hepatocyte growth factor attenuates neurologic injury after spinal cord ischemia in rabbits

OBJECTIVE

Paraplegia caused by spinal cord ischemia remains a serious complication after surgical repair of thoracoabdminal aortic aneurysms. Hepatocyte growth factor is a potent angiogenic and neurotrophic factor. We sought to investigate the neuroprotective effect of gene transfer of hepatocyte growth factor on spinal cord ischemia in rabbits.

METHODS

Human hepatocyte growth factor expression plasmid was combined with hemagglutinating virus of Japan envelope vector. Hemagglutinating virus of Japan envelope vector containing the hepatocyte growth factor gene was injected intrathecally into the experimental rabbits, whereas control vector or saline was given to the control animals. Five days later, spinal cord ischemia was induced by means of infrarenal aortic occlusion for 30 minutes. Hind-limb motor function was assessed during a 14-day recovery period with Tarlov criteria.

RESULTS

Human hepatocyte growth factor was detected in the cerebrospinal fluid 3 days after gene transfer, and the level peaked on day 5. Compared with the control animals, hepatocyte growth factor gene transfer significantly increased the capillary density in the gray matter and decreased the spinal cord edema. All rabbits pretreated with saline or control vector had hind-limb paraplegia (Tarlov score = 0) 14 days after spinal cord ischemia. However, previous transfection of the hepatocyte growth factor gene remarkably enhanced the Tarlov scores, and 8 of the 9 rabbits showed normal motor function (Tarlov score = 5) after a 14-day recovery period. Histologic examination showed that the intact motor neurons were preserved to a much greater extent in the rabbits transfected with the hepatocyte growth factor gene.

CONCLUSION

Gene transfer of hepatocyte growth factor attenuates neurologic injury after spinal cord ischemia.