Therapeutic Effect of Neurotrophin-3 Treatment in an Injectable Collagen Scaffold Following Rat Spinal Cord Hemisection Injury.

Spinal cord injury (SCI) patients display varying quantities of spinal cord tissue damage with injuries that present as complete, incomplete or compressive. One theory proposed to repair the injured spinal cord and regain motor control is to regenerate axons through the lesion site. This study was designed to quantify the impact of a local injectable in situ forming hydrogel reservoir therapy following rat hemisection SCI. We investigated the effect of hydrogel only treatment following SCI in addition to hydrogels loaded with a neurotrophic factor, Neurotrophin-3 (NT-3), immediately following SCI. Functional recovery, assessed by Basso Beattie Bresnahan (BBB) locomotor test, and local healing mechanisms, including neuronal growth, glial scar formation, inflammation and collagen deposition were investigated one and 6 weeks postsurgery. Delivery of an injectable hydrogel significantly increased functional recovery at four and 6 weeks post injury. In addition, a significant reduction in the inhibitory glial scar and in inflammation was observed at the injury site. Similarly hydrogel + NT-3 delivered directly into the injury site significantly reduced glial scarring and collagen deposition. The hydrogel + NT-3 also resulted in a significant increase in neurons at 6 weeks post injury. This study represents a novel and effective therapy combining growth factor and a biomaterial based therapy following SCI.

The BCL-2 family protein Bid is critical for pro-inflammatory signaling in astrocytes.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the loss of motoneurons in the spinal cord, brainstem and motor cortex. Mutations in the superoxide dismutase 1 (SOD1) gene represent a frequent genetic determinant and recapitulate a disease phenotype similar to ALS when expressed in mice. Previous studies using SOD1(G93A) transgenic mice have suggested a paracrine mechanism of neuronal loss, in which cytokines and other toxic factors released from astroglia or microglia trigger motoneuron degeneration. Several pro-inflammatory cytokines activate death receptors and may downstream from this activate the Bcl-2 family protein, Bid. We here sought to investigate the role of Bid in astrocyte activation and non-cell autonomous motoneuron degeneration. We found that spinal cord Bid protein levels increased significantly during disease progression in SOD1(G93A) mice. Subsequent experiments in vitro indicated that Bid was expressed at relatively low levels in motoneurons, but was enriched in astrocytes and microglia. Bid was strongly induced in astrocytes in response to pro-inflammatory cytokines or exposure to lipopolysaccharide. Experiments in bid-deficient astrocytes or astrocytes treated with a small molecule Bid inhibitor demonstrated that Bid was required for the efficient activation of transcription factor nuclear factor-κB in response to these pro-inflammatory stimuli. Finally, we found that conditioned medium from wild-type astrocytes, but not from bid-deficient astrocytes, was toxic when applied to primary motoneuron cultures. Collectively, our data demonstrate a new role for the Bcl-2 family protein Bid as a mediator of astrocyte activation during neuroinflammation, and suggest that Bid activation may contribute to non-cell autonomous motoneuron degeneration in ALS.