FL2 siRNA as a Novel Therapeutic Option to Induce Spinal Cord Regeneration Following Injury

ABSTRACT Fidgetin-like 2 (FL2) is a microtubule (MT) regulatory protein that modulates MT dynamics through its putative MT-severing activity, regulating cell motility and axonal growth and guidance. Recently, we identified FL2 as a negative regulator of axonal growth, and demonstrated that targeted depletion of FL2 following peripheral nerve injury enhances functional nerve regeneration in rats. Our preliminary studies show that following injury FL2 is upregulated at the injury site in several adult tissues including the spinal cord. In pilot studies using rodent SCI models, we similarly found that local depletion of FL2 from the injury site using FL2 siRNA embedded in nanoparticles (SiFi2) improved recovery of locomotor and bladder function after thoracic contusion and compression injury. We hypothesize that FL2 negatively regulates axonal regeneration after SCI, and that downregulation of FL2 after SCI will improve functional recovery. We aim to test this hypothesis with 3 specific aims. The first aim will determine the extent and duration of FL2 silencing following SiFi2 treatment. The second aim will evaluate the functional effects of SiFi2 treatment after SCI by exploring hindlimb locomotor and sensory function after SiFi2 administration. The third aim will evaluate molecular and histological changes at the spinal cord lesion site following SiFi2 treatment by examining axonal regeneration, glial scar formation, and inflammatory response in the spinal cord tissue from Aim 2. These studies will be the first to evaluate FL2 regulation of the central nervous system (CNS) injury response, and the first to assess the therapeutic potential of using RNAi to transiently downregulate FL2 expression in order to improve functional recovery after CNS injury. While this proposal focuses specifically on SCI as a therapeutic application, we anticipate the data generated from these studies will have broader implications as they will characterize the role of a previously unstudied regulator of CNS traumatic injury response, one which can potentially be targeted to enhance regeneration following a wide range of CNS injuries.