Designer PGs for CNS Injury

In the adult mammalian brain and spinal cord, neuronal injury results in failed regeneration, in part due to the upregulation of chondroitin sulfate proteoglycans (CSPGs). The majority of CSPGs originate from reactive astrocytes of the glial scar surrounding the lesion. The glial scar is beneficial for the recovering nervous system and thus should not be “excised”, but rather, axonal growth could be promoted if the expression of specific inhibitory portions of astrocyte-expressed CSPGs could be targeted selectively. This is consistent with previous data from our lab indicating that neuronal inhibition is due to specific CSPG microheterogeneities and to the specific configurations of CSPGs predicted by their structure and by the molecules to which they bind.

Sensory Growth Cone Behaviors

Analysis of the Effects of Designer PGs on Sensory Growth Cone Behaviors. Representative growth cone image (40x) of a single time lapse frame taken prior to contact with Designer PGs (zone 1; control) demonstrating the measurement of growth cone area, length, width, number of filopodia, filopodial length, and vector.

With our recent support from NIH (NINDS, R01-NS053470, “Designer PGs for Spinal Cord Injury), our goal is to identify the most significant of these CSPG motifs with respect to neurite inhibition and regeneration, and specifically, to manipulate these moieties to promote regeneration. To this end, we and our collaborators (Dr. Thomas Hering and lab at Case Western Reserve University, Cleveland, OH) have engineered 1) an array of CSPG isoforms and mutants we call “Designer PGs”, 2) a variety of unique bioassays to express CSPGs, including a novel model of the glial scar in vitro, and 3) new imaging methods to measure subtle features of neuronal responses to CSPGs. Using our Designer PGs, we are determining the inhibitory potential for specific CSPG postranslational modifications or core protein domains. Part of this effort involves the use of a novel system, which assigns an inhibitory quotient (IQ) to each Designer CSPG based on overt as well as subtle responses of adult neurons in vitro. Statistical analyses then predict the CSPG microheterogeneities that result in the greatest degree of inhibition. It is these domains that will be experimentally targeted in future studies.

The long term goal of this study is to identify the mechanism(s) of CSPG-induced inhibition following brain and spinal cord injury. The significance of the studies lies in the tremendous potential for translational application through the manipulation of specific CSPG motifs in injured patients, providing a therapeutic avenue to stimulate neuronal plasticity, facilitate re-connectivity of injured neurons, and accomplish restoration of function.