ABSTRACT
Several studies have reported functional improvement after transplantation of neural stem cells into injured spinal cord. We now provide evidence that grafting of adult neural stem cells into a rat thoracic spinal cord weight-drop injury improves motor recovery but also causes aberrant axonal sprouting associated with allodynia-like hypersensitivity of forepaws. Transduction of neural stem cells with neurogenin-2 before transplantation suppressed astrocytic differentiation of engrafted cells and prevented graft-induced sprouting and allodynia. Transduction with neurogenin-2 also improved the positive effects of engrafted stem cells, including increased amounts of myelin in the injured area, recovery of hindlimb locomotor function and hindlimb sensory responses, as determined by functional magnetic resonance imaging. These findings show that stem cell transplantation into injured spinal cord can cause severe side effects and call for caution in the consideration of clinical trials.
Subject(s)
Neurons/physiology , Recovery of Function/physiology , Spinal Cord Injuries/therapy , Stem Cell Transplantation/methods , Stem Cells/physiology , Analysis of Variance , Animals , Basic Helix-Loop-Helix Transcription Factors , Behavior, Animal , Brain/blood supply , Brain/physiopathology , Bromodeoxyuridine/metabolism , Calcitonin Gene-Related Peptide/metabolism , Cell Count , Disease Models, Animal , Female , Functional Laterality/physiology , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Hindlimb/innervation , Hindlimb/physiopathology , Immunohistochemistry/methods , Laminin/classification , Laminin/metabolism , Magnetic Resonance Imaging/methods , Motor Activity/physiology , Myelin Sheath/metabolism , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Neural Pathways/metabolism , Neurofilament Proteins/metabolism , Oligopeptides/metabolism , Oxygen/blood , Pain/etiology , Pain/physiopathology , Pain Measurement , Phosphopyruvate Hydratase/metabolism , Rats , Rats, Sprague-Dawley , Receptors, Atrial Natriuretic Factor/metabolism , Spinal Cord/metabolism , Spinal Cord/physiopathology , Spinal Cord Injuries/physiopathology , Stem Cell Transplantation/adverse effects , Time Factors , Transduction, Genetic/methods , Tubulin/metabolismABSTRACT
The cochlear sensory epithelium and spiral ganglion neurons (SGNs) in the adult mammalian inner ear do not regenerate following severe injury. To replace the degenerated SGNs, neural stem cell (NSC) is an attractive alternative for substitution cell therapy. In this study, adult mouse NSCs were transplanted into normal and deafened inner ears of guinea pigs. To more efficiently drive the implanted cells into a neuronal fate, NSCs were also transduced with neurogenin 2 (ngn2) before transplantation. In deafened inner ears and in animals transplanted with ngn2-transduced NSCs, surviving cells expressed the neuronal marker neural class III beta-tubulin. Transplanted cells were found close to the sensory epithelium and adjacent to the SGNs and their peripheral processes. The results illustrate that adult NSCs can survive and differentiate in the injured inner ear. It also demonstrates the feasibility of gene transfer to generate specific progeny for cell replacement therapy in the inner ear.
Subject(s)
Cell Differentiation/physiology , Cochlea/physiology , Graft Survival/physiology , Hearing Loss, Sensorineural/therapy , Neurons/transplantation , Stem Cell Transplantation/methods , Animals , Basic Helix-Loop-Helix Transcription Factors , Biomarkers , Cell Lineage/genetics , Cochlea/cytology , Cochlea/surgery , Gene Transfer Techniques , Guinea Pigs , Hair Cells, Auditory/cytology , Hair Cells, Auditory/physiology , Mice , Mice, Transgenic , Nerve Regeneration/physiology , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Neurons/cytology , Neurons/physiology , Spiral Ganglion/cytology , Spiral Ganglion/physiology , Transplantation, Heterologous , Treatment Outcome , Tubulin/metabolismABSTRACT
Neural stem cells may present an ideal route for gene therapy as well as offer new possibilities for the replacement of neurons lost to injury or disease. However, it has proved difficult to express ectopic genes in stem cells. We report methods to introduce genes into adult neural stem cells using viral and nonviral vectors in vitro and in vivo. Adenoviral and VSV-G-pseudotyped retroviral vectors are more efficient than plasmid transfection or VSV-G lentiviral transduction in vitro. We further show that adult neural stem cells can be directed to a neuronal fate by ectopic expression of neurogenin 2 in vitro. Plasmids can be delivered in vivo when complexed with linear polyethyleneimine, and gene expression can be targeted specifically to neural stem or progenitor cells by the use of specific promoters. These techniques may be utilized both to study the function of various genes in the differentiation of neural stem cells to specific cell fates and, ultimately, for gene therapy or to generate specific differentiated progeny for cell transplantation.
