Intrathecal coelectrotransfer of a tetracycline-inducible, three-plasmid-based system to achieve tightly regulated antinociceptive gene therapy for mononeuropathic rats

Emerging role of nanomedicine in the treatment of neuropathic pain

Neuropathic pain (NeP) is a complex chronic pain condition associated with nerve injury. Approximately, 7-10% of the general population across the globe is suffering from this traumatic condition, but the existing treatment strategies are inadequate to deliver pain relief and are associated with severe adverse effects. To overcome these limitations, lot of research is focussed on developing new molecules with high potency and fewer side effects, novel cell and gene-based therapies and modification of the previously approved drugs by different formulation aspects. Nanomedicine has attracted a lot of attention in the treatment of many diverse pathological conditions because of their unique physiochemical and biological properties. In this manuscript, we highlighted the emerging role of nanomedicine in different therapies (drug, cell and gene), also we emphasised on the challenges associated with nanomedicine such as development of well-characterised nanoformulation, scaling of batches with reproducible results and toxicity along with this we discussed about the future of nanomedicine in the treatment of neuropathic pain.

Nonviral vector plasmid DNA encoding human proenkephalin gene attenuates inflammatory and neuropathic pain-related behaviors in mice

Inflammatory pain and neuropathic pain are major clinical health issues that represent considerable social and economic burden worldwide. In the present study, we investigated the anti-nociceptive efficacy of delivery of human proenkephalin gene by a plasmid DNA vector (pVAX1-PENK) on complete Freund's adjuvant (CFA) induced inflammatory pain and spared nerve injury (SNI) induced neuropathic pain in mice. Mice were intramuscularly or intrathecally administered pVAX1 or pVAX1-PENK, respectively. Pain thresholds in the pVAX1-PENK treated mice were significantly higher at day 3, then reached a peak at day 7 and lasted until day 28 after gene transfer, and the analgesic effect of pVAX1-PENK was blocked with naloxone hydrochloride. In contrast, pVAX1 treated mice did not significantly improve pain thresholds. These results indicate that peripheral or spinal delivery of a plasmid encoding human proenkephalin gene provides a potential therapeutic strategy for inflammatory pain and neuropathic pain.

Gene therapy for the treatment of chronic peripheral nervous system pain

Chronic pain is a major health concern affecting 80 million Americans at some time in their lives with significant associated morbidity and effects on individual quality of life. Chronic pain can result from a variety of inflammatory and nerve damaging events that include cancer, infectious diseases, autoimmune-related syndromes and surgery. Current pharmacotherapies have not provided an effective long-term solution as they are limited by drug tolerance and potential abuse. These concerns have led to the development and testing of gene therapy approaches to treat chronic pain. The potential efficacy of gene therapy for pain has been reported in numerous pre-clinical studies that demonstrate pain control at the level of the spinal cord. This promise has been recently supported by a Phase-I human trial in which a replication-defective herpes simplex virus (HSV) vector was used to deliver the human pre-proenkephalin (hPPE) gene, encoding the natural opioid peptides met- and leu-enkephalin (ENK), to cancer patients with intractable pain resulting from bone metastases (Fink et al., 2011). The study showed that the therapy was well tolerated and that patients receiving the higher doses of therapeutic vector experienced a substantial reduction in their overall pain scores for up to a month post vector injection. These exciting early clinical results await further patient testing to demonstrate treatment efficacy and will likely pave the way for other gene therapies to treat chronic pain.

Reversible immortalization of Nestin-positive precursor cells from pancreas and differentiation into insulin-secreting cells

Pancreatic stem cells or progenitor cells posses the ability of directed differentiation into pancreatic β cells. However, these cells usually have limited proliferative capacity and finite lifespan in vitro. In the present study, Nestin-positive progenitor cells (NPPCs) from mouse pancreas that expressed the pancreatic stem cells or progenitor cell marker Nestin were isolated to obtain a sufficient number of differentiated pancreatic β cells. Tet-on system for SV40 large T-antigen expression in NPPCs was used to achieve reversible immortalization. The reversible immortal Nestin-positive progenitor cells (RINPPCs) can undergo at least 80 population doublings without senescence in vitro while maintaining their biological and genetic characteristics. RINPPCs can be efficiently induced to differentiate into insulin-producing cells that contain a combination of glucagon-like peptide-1 (GLP-1) and sodium butyrate. The results of the present study can be used to explore transplantation therapy of type I diabetes mellitus.

Electroporation and ultrasound enhanced non-viral gene delivery in vitro and in vivo

Non-viral vectors are less efficient than the use of viral vectors for delivery of genetic material to cells in vitro and especially in vivo. However, viral vectors involve the use of foreign proteins that can stimulate both the innate and acquired immune response. In contrast, plasmid DNA can be delivered without carrier proteins and is non-immunogenic. Plasmid gene delivery can be enhanced by the use of physical methods that aid the passage of the plasmid through the cell membrane. Electroporation and microbubble-enhanced ultrasound are two of the most effective physical delivery methods and these can be applied to a range of different cell types in vitro and a broad range of tissues in vivo. Both techniques also have the advantage that, unlike viral vectors, they can be used to target specific tissues with systemic delivery. Although electroporation is often the more efficient of the two, microbubble-enhanced ultrasound causes less damage and is less invasive. This review provides an introduction to the methodology and summarises the range of cells and tissues that have been genetically modified using these techniques.

Endogenous opiates and behavior: 2008

This paper is the 31st consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2008 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Immunogenicity of intrathecal plasmid gene delivery: cytokine release and effects on transgene expression

BACKGROUND

One method for the delivery of therapeutic proteins to the spinal cord is to inject nonviral gene vectors including plasmid DNA into the cerebrospinal fluid (CSF) that surrounds the spinal cord (intrathecal space). This approach has produced therapeutic benefits in animal models of disease and several months of protein expression; however, there is little information available on the immune response to these treatments in the intrathecal space, the relevance of plasmid CpG sequences to any plasmid-induced immune response, or the effect of this immune response on transgene expression.

METHODS

In the present study, coding or noncoding plasmids were delivered to the intrathecal space of the lumbar spinal region in rats. Lumbosacral CSF was then collected at various time points afterwards for monitoring of cytokines and transgene expression.

RESULTS

This work demonstrates, for the first time, increased tumor necrosis factor-alpha and interleukin-1 in response to intrathecal plasmid vector injection and provides evidence indicating that this response is largely absent in a CpG-depleted vector. Transgene expression in the CSF is not significantly affected by this immune response. Expression after intrathecal plasmid injection is variable across rats but correlates with the amount of tissue associated plasmid and is increased by disrupting normal CSF flow.

CONCLUSIONS

The data obtained in the present study indicate that plasmid immunogenicity may affect intrathecal plasmid gene therapy safety but not transgene expression in the CSF. Furthermore, the development of methods to prevent loss of plasmid via CSF flow out of the central nervous system through the injection hole and/or natural outflow routes may increase intrathecal plasmid gene delivery efficacy.

In vivo gene regulation using tetracycline-regulatable systems

Numerous preclinical studies have demonstrated the efficacy of viral gene delivery vectors, and recent clinical trials have shown promising results. However, the tight control of transgene expression is likely to be required for therapeutic applications and in some instances, for safety reasons. For this purpose, several ligand-dependent transcription regulatory systems have been developed. Among these, the tetracycline-regulatable system is by far the most frequently used and the most advanced towards gene therapy trials. This review will focus on this system and will describe the most recent progress in the regulation of transgene expression in various organs, including the muscle, the retina and the brain. Since the development of an immune response to the transactivator was observed following gene transfer in the muscle of nonhuman primate, focus will be therefore, given on the immune response to transgene products of the tetracycline inducible promoter.

Gene therapy for pain

BACKGROUND

Management of chronic pain remains a challenge in spite of the numerous drugs either approved or still in development. Apart from inadequacy of relief, there are concerns about adverse effects and addiction in the case of drugs such as opioids. Gene therapy is being investigated for improving management of pain.

OBJECTIVE

To addresses the rationale of gene therapy for treatment of pain and its advantages over drugs. The prospects of translation of these techniques from experimental animals to clinical use are discussed.

METHODS

The review is based on the available literature and is confined to experimental work, as there are no approved therapies in this category.

RESULTS/CONCLUSION

A number of promising gene therapies as well as antisense- and RNA interference-based approaches have been identified. These provide targeted approaches to delivery of antinociceptive molecules or interruption of pain pathways without subjecting the patient to systemic toxicity of drugs. Some of these approaches are aimed at correcting the underlying pathology of the diseases (e.g., treating degenerative joint diseases causing pain). Management of neuropathic pain is a challenge and a number of studies are addressing it. Overall the future of gene therapy for pain is promising.

Intrathecal injection of naked plasmid DNA provides long-term expression of secreted proteins

Therapeutic benefit has been reported to result from intrathecal (i.t.) injection of transgene vectors, including naked DNA. However, most studies using naked DNA have measured only the transgene expression of intracellular proteins. Here we demonstrate that i.t. injection of naked DNA can result in long-term expression of secreted proteins. Plasmids expressing either secreted alkaline phosphatase (SEAP) or human interleukin-10 (hIL-10) were injected into the i.t. space in rats, and transgene products were repeatedly measured in the cerebrospinal fluid (CSF). Both SEAP and hIL-10 were maximal at 1 and 2 days after the injection and still detectable at 4 months. The utilization of a plasmid having two features that are hypothesized to increase gene expression (matrix attachment regions (MARs) and lack of CpG dinucleotides) resulted in a significant increase in gene expression. Reinjection of SEAP or hIL-10 plasmids after 4 months significantly increased protein levels at 1 and 14 days after the reinjection. SEAP was uniformly distributed between the DNA delivery site (approximately vertebral level T13) and the lumbar puncture site (L5/L6 inter-vertebral space), was reduced at the cisterna magna, and was detectable, though at much lower levels, in serum. These data suggest that naked DNA has the potential to be used as a therapeutic tool for applications that require long-term release of transgenes into the CSF.