| Description |
Spinal cord injury is debilitating and patients have historically had little hope for functional recovery. Astrocytes forming the scar tissue and producing chondroitin sulfate proteoglycan (CSPG) were often identified as the chief culprits for inhibiting neuronal regeneration. However, as the complex role of astrocytes in spinal cord injury are increasingly understood, the benefits they provide for healing have become valuable tools towards promoting recovery. Inducing aligned astrocyte populations in the wound site may promote functional recovery outcomes. Many approaches have been researched for restoring signaling after spinal cord injury, but artificial nerve guidance devices are particularly interesting as they can provide lasting directional cues to the injury site. The goal of this research was to demonstrate and measure the impact of surface protein patterns on astrocyte reactivity in an effort to reduce their neuroninhibitory CSPG production. By quantifying CSPG expression as measure of astrocyte reactivity, no change in reactivity was seen with varying amounts of fibrinogen surface coverage. However, astrocytes were found to selectively remove adsorbed fibrinogen from glass surfaces from amongst other proteins and also secrete CSPG onto surfaces. To mitigate protein pattern removal, a cross-linked patterning method based on microcontact printing was developed to attach protein patterns to collagen gels. Protein patterns were first created on glass and transferred to collagen by gelling collagen directly on top of the pattern. This construct was then peeled off from glass to create free standing collagen sheets with one patterned surface. Stripe patterns of various extracellular matrix molecules were thus patterned and found to align astrocytes on collagen gel surfaces and reduced astrocyte CSPG expression. To understand how astrocytes interact with surface patterns, astrocyte morphology was measured in real time. This revealed that astrocytes prefer adhesion to laminin over aggrecan and will shift their cell bodies accordingly. Astrocytes initially extend multiple processes upon attachment and span the largest distances when presented with mixed adhesion cues, up to 150 micrometers. Collectively, this research demonstrates the importance of surface protein patterns in biasing astrocyte behavior and provides a new technique for further modifications of collagen hydrogels for use as nerve guidance materials. |
