Title

Viral vector-mediated transduction of Schwann cells expressing a bifunctional neurotrophin facilitates myelination and axon growth after spinal cord injury

Date of Award

2005

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Neuroscience

First Committee Member

Mary Bartlett Bunge, Committee Chair

Abstract

Schwann cells (SCs) implanted into the injured spinal cord provide an environment conducive for axon growth and myelination. Growth of supraspinal axons into SC grafts, however, does not occur without additional manipulations. In the current study, viral transduction of SCs ex vivo was employed with either adenoviral (AdV) vectors or lentiviral (LV) vectors containing a gene encoding for a bifunctional neurotrophin molecule that mimics the actions of both neurotrophin-3 and brain-derived neurotrophic factor to promote supraspinal axon growth and enhance myelination. SCs (2 x 106 in 5muL) were implanted into the injury epicenter 1 week after a moderate thoracic (T8) spinal cord contusion in female Fischer rats. ELISAs were performed on tissue containing the injury/graft for assessment of neurotrophin production at 2 d, 1 wk, 3 wk, or 6 wk post-implantation. The implants of neurotrophin-secreting SCs contained significantly higher levels of neurotrophin (8,237 +/- 1548 and 4359 +/- 1202 pg NT-3 for AdV and LV vectors, respectively) for up to 1 wk post-implantation, when compared to non-transduced SCs and AdV/GFP and LV/GFP SC controls (107 +/- 22, 194 +/- 53 and 113 +/- 11 pg NT-3, respectively). Analysis of axon profiles was performed at 6 wk post-implantation. Supraspinal [corticospinal, raphespinal (5-HT), reticulospinal and coerulospinal (DbetaH)] and ascending sensory (CGRP+) axon growth was quantified following anterograde tracing or immunohistochemistry. Myelinated axon counts, myelinated to unmyelinated axon ratios and total axon estimates at the center of the graft were performed on semithin or ultrathin sections. Neurotrophin-secreting SC grafts exhibited increases in graft volume (5-fold), SC number (five-fold), myelinated axons (5-fold), myelinated to unmyelinated axon ratios (3-fold), 5-HT, DbetaH, and CGRP axon growth within the graft (up to 5-fold), demonstrating the efficacy of secreted neurotrophins for axon growth and myelination. This combination strategy demonstrates the therapeutic potential for genetically engineered SCs in a clinically relevant spinal cord contusion injury.

Keywords

Biology, Neuroscience; Biology, Animal Physiology

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3185009