Bas Blits

Poor survival of cells transplanted into the CNS is a widespread problem and limits their therapeutic potential. Whereas substantial loss of transplanted cells has been described, the extent of acute cell loss has not been quantified previously. To assess the extent and temporal profile of transplanted cell death, and the contributions of necrosis and apoptosis to this cell death following spinal cord injury, different concentrations of Schwann cells (SCs), lentivirally transduced to express green fluorescent protein (GFP), were transplanted into a 1-week-old moderate contusion of the adult rat thoracic spinal cord. In all cases, transplanted cells were present from 10 min to 28 days. There was a 78% reduction in SC number within the first week, with no significant decrease thereafter. Real-time polymerase chain reaction showed a similar 80% reduction in GFP-DNA within the first week, confirming that the decrease in SC number was due to death rather than decreased GFP transgene expr...

Stem cells represent an attractive source for cell replacement therapy in neurological disorders due to their self-renewal and multi-potency. Genetic manipulation of these cells may allow controlled release of therapeutic proteins, suppress immune rejection, or produce essential neurotransmitters. Furthermore, when the expression cassette is incorporated into the host genome ex vivo, this technique also may be used as a method to trace cells following implantation into tissues of interest. We explored the possibility of transducing pluripotent fetal rat cortical neural progenitor cells (NPCs) using lentiviral vectors encoding the green fluorescent protein (GFP) or neurotrophic factors (BDNF, CNTF, D15A, GDNF, MNT and NT-3) prior to implanting these cells into the contused spinal cord or injured brain. In vitro staining of these cells for neural markers (such as nestin, GFAP, Tuj-1 and RIP) after transduction did not reveal any significant difference from non-transduced cells. When t...

Injuries to the adult mammalian spinal cord often lead to severe damage to both ascending (sensory) pathways and descending (motor) nerve pathways without the perspective of complete functional recovery. Future spinal cord repair strategies should comprise a multi-factorial approach addressing several issues, including optimalization of survival and function of spared central nervous system neurons in partial lesions and the modulation of trophic and inhibitory influences to promote and guide axonal regrowth. Neurotrophins have emerged as promising molecules to augment neuroprotection and neuronal regeneration. Although intracerebroventricular, intrathecal and local protein delivery of neurotrophins to the injured spinal cord has resulted in enhanced survival and regeneration of injured neurons, there are a number of drawbacks to these methods. Viral vector-mediated transfer of neurotrophin genes to the injured spinal cord is emerging as a novel and effective strategy to express neu...

The present study uniquely combines olfactory ensheathing glia (OEG) implantation with ex vivo adenoviral (AdV) vector-based neurotrophin gene therapy in an attempt to enhance regeneration after cervical spinal cord injury. Primary OEG were transduced with AdV vectors encoding rat brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), or bacterial marker protein beta-galactosidase (LacZ) and subsequently implanted into adult Fischer rats directly after unilateral transection of the dorsolateral funiculus. Implanted animals received a total of 2 x 105 OEG that were subjected to transduction with neurotrophin-encoding AdV vector, AdV-LacZ, or no vector, respectively. At 4 months after injury, lesion volumes were smaller in all OEG implanted rats and significantly reduced in size after implantation of neurotrophin-encoding AdV vector-transduced OEG. All OEG grafts were filled with neurofilament-positive axons, and AdV vector-mediated expression of BDNF by implanted cells sign...

In this review, recent studies using pharmacological treatment, cell transplantation, and gene therapy to promote regeneration of the injured spinal cord in animal models will be summarized. Pharmacological and cell transplantation treatments generally revealed some degree of effect on the regeneration of the injured ascending and descending tracts, but further improvements to achieve a more significant functional recovery are necessary. The use of gene therapy to promote repair of the injured nervous system is a relatively new concept. It is based on the development of methods for delivering therapeutic genes to neurons, glia cells, or nonneural cells. Direct in vivo gene transfer or gene transfer in combination with (neuro)transplantation (ex vivo gene transfer) appeared powerful strategies to promote neuronal survival and axonal regrowth following traumatic injury to the central nervous system. Recent advances in understanding the cellular and molecular mechanisms that govern neu...

Regeneration of injured axons following injury depends on a delicate balance between growth-promoting and growth-inhibiting factors. Overexpression of neurotrophin genes seems a promising strategy to promote regeneration. Trophic genes can be overexpressed at the site of injury at the axonal stumps, or at the perikaryal level of the injured neuron. Transduction of the neural cells can be achieved by applying adenoviral vectors, either directly in vivo or-in the case of neurotransplantation as an ex vivo approach. In both cases it would create a more permissive environment for axonal growth and therefore in functional regeneration. In this article, the feasibility of the use of adenoviral vectors in several neuroregeneration models--in particularly in spinal cord lesion models and the biological clock transplantation model--is illustrated. The results show that the adenoviral vectors can be a powerful tool to study the effects of overexpression of genes in an in vivo paradigm of nerv...

Frequently, mtDNA with pathogenic mutations coexist with wild-type genomes (mtDNA heteroplasmy). Mitochondrial dysfunction and disease ensue only when the proportion of mutated mtDNAs is high, thus a reduction in this proportion should provide an effective therapy for these disorders. We developed a system to decrease specific mtDNA haplotypes by expressing a mitochondrially targeted restriction endonuclease, ApaLI, in cells of heteroplasmic mice. These mice have two mtDNA haplotypes, of which only one contains an ApaLI site. After transfection of cultured hepatocytes with mitochondrially targeted ApaLI, we found a rapid, directional, and complete shift in mtDNA heteroplasmy (2-6 h). We tested the efficacy of this approach in vivo, by using recombinant viral vectors expressing the mitochondrially targeted ApaLI. We observed a significant shift in mtDNA heteroplasmy in muscle and brain transduced with recombinant viruses. This strategy could prevent disease onset or reverse clinical symptoms in patients harboring certain heteroplasmic pathogenic mutations in mtDNA.

ABSTRACT Transplantation of exogenous cells into the injured central nervous system and subsequent examination of how these cells survive, integrate and perform physiological functions within the host environment requires that the cells be clearly identifiable from host cells. As many of the cells used for transplantation studies are derived from cultures of cells indistinguishable from the host using immunochemical approaches, numerous dyes or genetic markers have been devised and used for this purpose. These markers used to label and track these transplanted cells need to be specific, reliable, resistant to leakage or cellular transfer, and remain chemically stable once inside the host to allow long-term tracking. In the current study we compared two labeling methods for long-term tracking of cells following transplantation into the injured rat spinal cord; lentiviral vector transduction with green fluorescent protein (GFP) and DNA in situ hybridization for the Y chromosome after male cell transplantation in female rats. Examination of labeled cells at 12 wk post-injury demonstrated that both labels did not exhibit significant fading or loss of the signal due to instability over time. The visualization procedure for the DNA in situ reaction product was significantly more labor intensive than simple identification of GFP by fluorescent microscopy. Y chromosome positive cells were, however, easier to definitely count for assessment of cell survival than GFP labeled cells, due to the presence of the label as a single point within the nucleus rather than diffuse labeling throughout the entirety of the cell. The limited presence of the signal in Y chromosome positive cells though, made examination of their ability to integrate within the injured spinal cord, migrate and associate with axons impossible without additional immunochemical methods for labeling the entire cell. The combination of immunochemistry with DNA in situ however proved to be unsuccessful with the many antibody combinations tested. In conclusion GFP delivery by lentiviral vectors was far superior to DNA in situ detection of the Y chromosome for labeling of transplanted cells due to its rapid visualization and its applicability to a wide range of assessment techniques.

The transplantation of Schwann cells (SCs) and olfactory ensheathing glia (OEG) have shown promise as therapeutic interventions for spinal cord injury (SCI) repair. The current study sought to identify novel sites of transplantation for these glial cells, as opposed to direct intraspinal cord injection, that would be less surgically invasive while permitting their migration to the location of SCI where

Due to their self-renewal and multi-potency, stem cells represent an attractive source for cell replacement therapy in neurological disorders. Genetic manipulation of these cells may allow controlled release of therapeutic proteins, suppress immune rejection, or produce essential neurotransmitters. Furthermore, when the expression cassette is incorporated into the host genome ex vivo, this technique also may be used as a method to trace cells following implantation into tissues of interest. We explored the possibility of transducing pluripotent fetal rat cortical neural progenitor cells using lentiviral vectors encoding either the green fluorescent protein (GFP) or neurotrophic factors (NT-3, BDNF, GDNF and CNTF) under control of the CMV promoter and the Woodchuck post-transcriptional regulatory element. Following isolation and expansion of the cells at clonal density on poly-ornithine-fibronectin-coated dishes in the presence of bFGF, cells were collected, infected and replated on the dishes. Staining of these cells for neural markers (such as nestin, GFAP, Tuj-1 and RIP) after transduction did not reveal any significant difference from non-transduced cells. However, when they were transduced with a vector encoding CNTF, cells started expressing GFAP. Cells continued to express the transgene, including when bFGF was withdrawn and when cells started to differentiate into GFAP positive cells. Following delayed (1 week) implantation into the lesion site of the moderately contused spinal cord, transduced cells survived well up to 4 weeks post-implantation (the longest time point currently examined). Migration of the cells was mainly restricted to white matter on either side of the lesion. Currently, the therapeutic and axonal growth stimulating properties of the implanted cells are being investigated in injured rats.

For regrowth of injured nerve fibers following spinal cord injury (SCI), the environment must be favorable for axonal growth. The delivery of a therapeutic gene, beneficial for axonal growth, into the central nervous system for repair can be accomplished in many ways. Perhaps the most simple and elegant strategy is the so-called direct gene therapy approach that uses a single injection for delivery of a gene therapy vehicle. Among the vectors that have been used to transduce neural tissue in vivo are non-viral, herpes simplex viral, adeno-associated viral, adenoviral, and lentiviral vectors, each with their own merits and limitations. Many studies have been undertaken using direct gene therapy, ranging from strategies for neuroprotection to axonal growth promotion at the injury site, dorsal root injury repair, and initiation of a growth-supporting genetic program. The limitations and successes of direct gene transfer for spinal cord repair are discussed in this review.

Retinal pigment epithelial cell malfunction is a causative feature of age-related macular degeneration, and transplantation of new retinal pigment epithelial cells is an attractive strategy to prevent further progression and visual loss. However, transplants have shown limited efficacy, mainly because transplanted cells fail to adhere and migrate onto pathological Bruch's membrane. Adhesion to Bruch's membrane is integrin-mediated. Ageing of Bruch's membrane leads to a decline in integrin ligands and, added to this, wet age-related macular degeneration leads to upregulation of anti-adhesive molecules such as tenascin-C. We have therefore investigated whether manipulation of integrin function in retinal pigment epithelial cells can restore their adhesion and migration on wet age-related macular degeneration-damaged Bruch's membrane. Using spontaneously immortalized human retinal pigment epithelial cells (adult retinal pigment epithelium-19), we show that adhesion and migration on the Bruch's membrane components is integrin-dependent and enhanced by integrin-activating agents manganese and TS2/16. These allowed cells to adhere and migrate on low concentrations of ligand, as would be found in aged Bruch's membrane. We next developed a method for stripping cells from Bruch's membrane so that adhesion and migration assays can be performed on its surface. Integrin activation had a moderate effect on enhancing retinal pigmented epithelial cell adhesion and migration on normal human and rat Bruch's membrane. However, on…