Intrathecal injection of a therapeutic gene-containing polyplex to treat spinal cord injury

Abstract

Spinal cord injury (SCI) is a serious clinical problem that suddenly deprives patients of neurologic function and drastically diminishes their quality of life. Gene introduction has the potential to be effective for various pathological states of SCI because various proteins can be produced just by modifying nucleic acid sequences. In addition, the sustainable protein expression allows to maintain its concentration at an effective level at the target site in the spinal cord. Here we propose an approach using a polyplex system composed of plasmid DNA (pDNA) and a cationic polymer, poly{N'-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} [PAsp(DET)], that has high capacity to promote endosome escape and the long-term safety by self-catalytically degrading within a few days. We applied brain-derived neurotrophic factor (BDNF)-expressing pDNA for SCI treatment by intrathecal injection of PAsp(DET)/pDNA polyplex. A single administration of polyplex for experimental SCI provided sufficient therapeutic effects including prevention of neural cell death and enhancement of motor function recovery. This lasted for a few weeks after SCI, demonstrating the capability of this system to express BDNF in a safe and responsible manner for treatment of various pathological states in SCI.

RhoA knockdown by cationic amphiphilic copolymer/siRhoA polyplexes enhances axonal regeneration in rat spinal cord injury model

“…To our knowledge, this is the first study to show that polyplexes exhibit increased residence time after local injection into spinal cord lesion site relative to naked siRNA. Several studies have used intrathecal injection and Otsuku et al reported preferential uptake of chemically-modified siRNA at the injury site, presumably due to increased penetration in injured tissue [51] [55]. In the future, we will investigate the delivery of PgP/siRhoA polyplexes to the injured spinal cord by the intrathecal route.…”

Experimental Spinal Cord Injury Models in Rodents: Anatomical Correlations and Assessment of Motor Recovery

“…The CatWalk™ system has been used in the following SCI models: thoracic CST Tx, RST Tx, and dorsal Hx [8,103]; thoracic contusion [101,102]; pyramidotomy models [22]; and lateral cervical spinal cord contusion [104,105], and in recent studies assessing the effects of training and gene therapy [106,107]. The CatWalk™ can furthermore be combined with the horizontal ladder test by placing the ladder above the glass plate, so that footslips light up because the animal touches the glass plate [108].…”

Gene Delivery Strategies to Promote Spinal Cord Repair

“…Compared to their viral counterparts, nonviral gene delivery methods are significantly less efficient; however, many researchers have focused on improving vector stability and cell internalization of delivered genes. 123 , 124 As with viral vectors, designing strategies to avoid detection by the immune system has also been a major goal. Generally, nonviral delivery strategies seek to complex nucleic acids with various polymers, biomolecules, nanoparticles, lipid vesicles, and other materials that serve to protect naked plasmid and carry it across cell membranes so the nucleic acid payload is released in the cytosol ( Fig.…”

“…Non-integrating vectors may be able to achieve higher levels of expression per transfected cell at early times after vector administration, because multiple plasmid copies encoding the therapeutic transgene can be incorporated into a single cell. 123 However, episomal nucleic acids are eventually degraded 124 ( Fig. 3B,C ), while integrating vectors, such as AAV or lentivirus, can achieve steady levels of transgene expression over periods of weeks to years ( Fig.…”

“…Many materials can be used to make polyplexes, but PEI carriers are the most widely used carriers due to their efficient vector delivery and buffering environment. 124 , 126 Other base materials used to create nanoparticle polyplexes for nucleic acid delivery to the CNS have include inorganic nanoparticles (eg, silica), natural polymers (eg, chitosan), PEI, liposomes, dendrimers, and carbon-based nanoparticles. These materials are reviewed in detail by Pérez-Martínez et al 125 and Yin et al 126 One group reported the use of polyplexes formed by a knotted single-chain polymer of cyclized 2-(dimethylamino) ethyl methacrylate.…”