Promoting tissue repair and functional recovery after spinal cord injury by targeting the microtubule regulatory protein Fidgetin-like 2: Supplement for Imaging System

Abstract Text Traumatic spinal cord injuries (SCI) impact hundreds of thousands of people, and there are no therapies available which can promote regeneration and clinical meaningful improvements in sensory, motor, or autonomic function. 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. We have 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. Based on these data, MicroCures has developed a siRNA nanoparticle- encapsulated formulation to target FL2 after SCI, which can be applied onto the dura or injected intrathecally. In pilot studies using rodent SCI models, we found that local depletion of FL2 from the injury site using a nanoparticle-encapsulated FL2 siRNA improved recovery of locomotor function. Here, we will conduct proof-of-feasibility studies to determine the efficacy of MicroCures’ nanoparticle formulation in promoting healing using a rat contusion model. In Specific Aim 1, we will repeat our pilot study in a larger cohort of animals, assessing efficacy through evaluating recovery of hindlimb locomotor function as well as expanding our assessments to include bladder, sexual, and sensory function. In Aim 2, we will characterize structural and morphological changes at the lesion with treatment through a combination of MRI/DTI imaging and immunohistochemistry analyses. In Aim 3, we will conduct a discovery-level toxicity study to characterize the safety profile of our therapeutic using a subset of the animals from Aim 1. Completion of these studies will provide strong evidence of whether our therapeutic formulation, called SiFi2, is an effective and safe therapeutic for treating SCI, and whether it should be further tested and developed in IND-enabling studies. FL2 acts through mechanisms considerably different from other genes/proteins/factors currently being investigated as treatments for SCI; to our knowledge, these studies would represent the first reported success of promoting healing after SCI through an siRNA-based targeting of a microtubule regulatory protein.