In the beginning of the ERC project we investigated whether CDNF had a neuroprotective effect in vivo in the SOD1-G93A mouse, an ALS in vivo animal model where chronic ER stress response in the corresponding MNs has been previously reported in many studies. To this end, we utilized a single injection of CDNF, which in PD animal models effectively counteracted dopamine neuron degeneration [Lindholm et al., 2007]. As proof-of principle, we first validated that CDNF and 125I-labelled CDNF injected in the brain lateral ventricle efficiently diffuse to different areas of the brain, including cortex, striatum, and substantia nigra, and to the lumbar spinal cord. Moreover, we found that CDNF specifically co-localizes with lumbar MNs. Early symptomatic SOD1-G93A mice and WT littermates of 13 weeks of age received a single i.c.v. injection of 10 μg of human CDNF or phosphate buffered saline (PBS) as vehicle and were examined twice a week to follow changes in symptoms and motor behavior until the final stage of paralysis. At the time of treatment, SOD1-G93A mice displayed measurable tremors in the hind limbs. Upon a single CDNF injection, mutant mice developed gait impairment and paralysis symptoms significantly more slowly than PBS-treated mutant littermates, and survival was increased in both female and male SOD1 mice. Along with this, their balance and motor behavior performance were significantly ameliorated by CDNF treatment. One week after CDNF or PBS injection, the CDNF group showed an increased ability to run on the smallest 8 mm rod in the multiple static rods experimental paradigm for females and on the 21 and 11 mm rods for males, compared to the PBS group. These gender differences in the experimental tasks are in accordance with previous observations that males develop major symptoms approximately one week earlier than female littermates. In the accelerating rotarod, CDNF-treated mice showed an increased latency to fall compared to vehicle treated-mice. No statistical difference was found in CDNF or vehicle-injected WT littermates over time.
In the open field, SOD1-G93A mice exhibited a decreased number of rearings compared to WT mice, which is associated with less strength in the hind limb muscles, and CDNF treatment increased the number of rearings compared to PBS controls at 16 weeks. To correlate the improvement of motor behavior to MN survival, we examined the lumbar spinal cord, which revealed a significantly higher number of MNs present in the CDNF-treated compared to PBS-treated mice. The results showing that intracerebroventricularly injected CDNF protects spinal motoneurons in 3 different transgenic rodent models of ALS were published in Brain 2023.
In the ERC StG project we tested the effect of CDNF and CDNF fragment in continuous cells, primary Motoneuron and DA neuron cultures and in several animal models of ALS (SOD1 and TDP-43 rodent ) and PD (6-OHDA and MPTP toxin models ).
We were able to see efficacy after single or chronic intracerebroventraicular administration of CDNF and CDNF fragment in SOD1-G93A mouse model of ALS. We were also able to show neuroprotection after CDNF and CDNF fragment icv infusion in TDP-43 rat model of ALS, in which no other research group has ever reported positive effects with drug candidates. The experiments were carried out as planned
