Hyaluronic acid-based scaffolds for repair strategies after spinal cord injury: A behavioral study 1 The University of Texas at Austin, Department of Biomedical Engineering 2 The University of Texas at Austin, Department of Psychology Zin Z. Khaing 1, Sydney A. Geissler 1, Sandra V. Aguilar 1, Timothy Schallert 2 and Christine E. Schmidt 1

Hyaluronic Acid (HA)  Extracellular and cell surface-associated  Highly viscous and hydrophilic  Can modulate cell behavior (development, inflammation axonal growth)  Vital role in scar-free wound healing

Other Applications Dermal Filler (Restylane ® ), Adhesion Barrier (Seprafilm®) Hyaluronic Acid Materials Images from healon.com and synvisc.com Vitreous substitute (Healon ® ) Viscosupplementation (Synvisc ® ) In Our Group

After Acute Spinal Cord Injury  Cell death  Axonal damage  Local hemorrhage  Inflammation and edema Acute Phase Sub-acute Phase  Expansion of injured area during secondary phase  Activation of microglia and macrophages  Astrocyte activation  Scar formation (involve fibroblasts, meningial cells, infiltrating progenitors and astrocytes) production of glial scar including CSPGs

HA after SCI Previous studies from our lab showed that the presence of high MW HA hydrogel can  Limit macrophage and microglia infiltration after SCI  Limit astrocyte response in vivo and astrocyte proliferation in vitro  Can alter the amount of CSPG deposition  Support axonal outgrowth after SCI

HA hydrogels after SCI Spinal Cord Injury Model:Cervical lateral hemisection at C3/C4 The most clinically relevant model (63% of human SCI are at the cervical level) Rodents mainly use their forelimbs, therefore, behavioral deficits and improvements can be assessed more readily in an accurate manner Hydrogels Used: GMHA, LN/GMHA, LN/gelfoam, gelfoam, and laminectomy (n=6 in each group) Analysis: (a) Behavioral (b) Histological

Behavioral Tests 1.Forelimb Locomotor Score (FLS)  General forelimb usage during locomotion will be scored.  Non-linear scale from Cylinder  Forelimb exploration will be assessed.  The numbers of forelimb contacts (left, right, and both) with the cylinder walls were counted and expressed as a percentage of total placements. 3. Forelimb placing  Forelimb placing tests response to sensorimotor/proprioceptive detection of edge of table with capacity vibrissae (whiskers) 4. Adhesive removal (Sensory bias)  Small adhesive backed (sticky) labels are placed on the distal–radial aspect of both forelimbs  Contact and removal times are recorded  Tests preference for responding sensory stimuli as well as motor coordination

Forelimb Function

Behavioral Tests 1.Forelimb Locomotor Score (FLS)  General forelimb usage during locomotion will be scored.  Non-linear scale from Cylinder  Forelimb exploration will be assessed.  The numbers of forelimb contacts (left, right, and both) with the cylinder walls were counted and expressed as a percentage of total placements. 3. Forelimb placing  Forelimb placing tests response to sensorimotor/proprioceptive detection of edge of table with capacity vibrissae (whiskers) 4. Adhesive removal (Sensory bias)  Small adhesive backed (sticky) labels are placed on the distal–radial aspect of both forelimbs  Contact and removal times are recorded  Tests preference for responding sensory stimuli as well as motor coordination

Cylinder Height LN-soaked gelfoam implants showed the most improved behavior

Paw Preference (Cylinder) Implanted animals showed some increase in affected limb usage at 12 week post surgery.

Behavioral Tests 1.Forelimb Locomotor Score (FLS)  General forelimb usage during locomotion will be scored.  Non-linear scale from Cylinder  Forelimb exploration will be assessed.  The numbers of forelimb contacts (left, right, and both) with the cylinder walls were counted and expressed as a percentage of total placements. 3. Forelimb placing  Forelimb placing tests response to sensorimotor/proprioceptive detection of edge of table with capacity vibrissae (whiskers) 4. Adhesive removal (Sensory bias)  Small adhesive backed (sticky) labels are placed on the distal–radial aspect of both forelimbs  Contact and removal times are recorded  Tests preference for responding sensory stimuli as well as motor coordination

Acknowledgements  Dr. Christine Schmidt  Sydney Geissler  Entire Schmidt lab Collaborators  Dr. Timothy Schallert, UT-Austin  Raymond Grill, UT-Houston Supported By Texas Paralysis Foundation David Van Wagner Foundation Gillson Longenbough Foundation

Thank You!