Leukemia Inhibitory Factor as a late-stage treatment for delayed white matter loss in concussive head injury.

BACKGROUND

Leukemia Inhibitory Factor (LIF) is an injury-induced cytokine that peaks 48 hours after a traumatic brain injury (TBI). Juvenile LIF haplodeficient mice exhibit desynchronized glial responses, increased neurodegeneration, decreased axonal conductivity and behavioral deficits after a concussive head injury. Given the necessity of LIF during the acute recovery phase after injury, we hypothesized that intranasal (IN) LIF treatment would prevent neurodegeneration when administered during the chronic recovery period from a mild TBI (mTBI).

METHODS

Young adult male CD1 mice were subjected to a midline, closed-head frontal cortex injury using a flat metal impactor with a 3mm tip to induce a mTBI. In the 6-8 weeks post-mTBI, known to precede axonal atrophy in this mTBI model, two doses of 40 ng and 100 ng of LIF were administered twice daily, 5 days/week for two consecutive weeks. Sensorimotor functions were assessed at 4 and 8 weeks post mTBI, followed by ex-vivo brain magnetic resonance imaging at 9.4T and histopathology.

FINDINGS

mTBI mice showed sensorimotor deficits at 4 weeks, which worsened by 8 weeks post-injury. IN-LIF treatment prevented the progressive sensorimotor loss seen in the vehicle-treated controls. Increased mean diffusivity (MD) and decreased fractional anisotropy (FA) were observed in the corpus callosum and prefrontal cortex of mTBI brains. In a dose-dependent manner, IN-LIF prevented the mTBI-induced MD increase and FA decrease. Histologically, there was significantly less astrogliosis, microgliosis and axonal injury in the IN-LIF treated mice vs. controls.

INTERPRETATION

These results support the therapeutic potential of IN-LIF to reduce delayed neurodegeneration and improve neurological outcomes after mTBIs.

FUNDING

Supported by R21 NS125201, which was awarded to SWL, SK, and FH, and Rutgers Busch Biomedical Grant IRES 21-002946 to SWL and SK.

RESEARCH IN CONTEXT

Earlier studies had shown that LIF haplodeficient mice sustained worse outcomes after brain injury, which supported the hypothesis that LIF was an essential neuroprotective injury induced cytokine. Other studies had shown that acutely administered LIF was neuroprotective and glioprotective in mouse models of multiple sclerosis, neonatal hypoxia-ischemia and pediatric TBI. However, to date most pre-clinical studies for TBI have tested the efficacy of therapeutics delivered during the acute (primary) or sub-acute (secondary) recovery period. Few studies have focused on the mechanisms of delayed neurodegeneration (tertiary neurodegeneration) and therapeutics are entirely lacking. Therefore, we decided to test IN LIF during the chronic recovery period from TBI. With preliminary data, we submitted an NIH exploratory grant (R21) that was awarded to the senior investigators of this manuscript in October of 2021. That grant supported the majority of the studies contained in this submission.A pubmed search performed on Feb. 9th, 2025 using the search string "(traumatic brain injury) AND (axonal damage) AND (magnetic resonance imaging) AND intranasal AND neuroprotection" returned no references. The standard of care for individuals who have sustained head injuries is to treat their symptoms. They are provided medications to reduce seizures, decrease anxiety, reduce depression and reduce pain and other symptoms. However, none of these medications will prevent tertiary neurodegeneration. Given the number of individuals who have sustained head injuries, new therapeutics, especially therapeutics that can be easily administered, are needed. With the Superbowl having just taken place, there is once again increasing concern that many of these athletes who have sustained head injuries during the course of their careers will go on to develop chronic traumatic encephalopathy, for which there is no treatment.The studies we described herein are innovative as no other group has evaluated any of the cytokines related to LIF for their neuroprotective properties for mTBI and certainly not during the tertiary injury period. Moreover, a Pubmed database search that covered the period from 1966 to 2025 reveals that only a handful of other studies have used intranasal delivery of any compound to treat TBI, and all of these studies administered their therapeutic within 6 hours after an injury. Developing a long-lasting, CNS-targeted therapeutic that can be delivered as a simple nose spray will have a lasting impact on clinical medicine. Our studies presage future clinical trials to assess the therapeutic efficacy of intranasal LIF for individuals who have sustained mild TBIs.