Learn more about our ongoing projects.

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OPUS 2019-2022

Does DREADD and TrkB gene transfer targeted to selected motoneurons following spinal cord injury bring recovery of motor functions? Dependence between chemogenetic and neurotrophic activation and synaptic changes in motoneurons

The aim of the study is to explore whether enrichment of selected populations of hindlimb α-motor neurons (MNs) in genes encoding membrane receptors and their subsequent stimulation aimed to increase MN activity, leads to recovery of motor functions following spinal cord transection (SCT). Our goal is to solve a problem, which accompanies the majority of experimental therapies implemented following SCI, which do not take into account demands of functionally different MN groups for stimulation. Although paradigms of activation of the whole network lead to moderate improvement of motor functions, they do not restore the functional equilibrium between different groups of MNs and muscles. We showed that this equilibrium is heavily distorted between the ankle extensor and flexor MNs. Also, changes in neurotransmitter receptor expression and muscle responses to SCT and locomotor training are different between these MN groups. These observations led us to formulate the hypothesis, that targeting the proposed gene constructs selectively to a population of MNs with innervation deficits should lead to the recovery of equilibrium in innervation and signaling between MNs of antagonistic muscles. If so, we expect that the resulting restoration of motor functions will be superior to those achieved with general network activation.



Pharmacologically controlled BDNF gene therapy: a novel approach of optimized neurotrophin delivery for spinal cord injury

The project is devoted to a better understanding of the molecular background and drawbacks of brain derived neurotrophic factor (BDNF) gene therapy to treat anatomical deficits and functional impairment after spinal cord injury. BDNF regulates synaptic plasticity and neurotransmission and was shown to enhance recovery at the molecular and functional level in spinal animals, but also to produce signs of overstimulation. The main question is how the spinal cord transection and BDNF, in conditions of its overexpression in the spinal tissue, affect the excitability of motoneurons (MNs) which innervate hindlimb muscles crucial for locomotion. The answer to this question is functionally important owing to the fact, that in paraplegic subjects, including humans, spasticity tends to develop after spinalization. To increase understanding of underlying phenomena, we focus on AMPA and NMDA ionotropic glutamatergic receptors, which mediate excitatory signaling and study them in two groups of MNs innervating the ankle flexor (Tibialis anterior) and extensor (Soleus; Gastrocnemius lateralis) muscles at different time after lesion. The use of laser capture microdissection to dissect MNs has allowed us to selectively examine gene expression levels. Combined with tracing, immunohistochemistry and confocal imaging further allowed us to detect subunit composition and phosphorylation state of AMPA and NMDA receptors on the surface of spinal cord α-MNs in rats and to answer the question of whether increased BDNF levels in spinal animals change these receptors. Results may provide us clinical indications on the pharmacological manipulation of BDNF signaling after spinal cord injury.

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PRELUDIUM 2018-2020

The impact of locomotor training and electrical stimulation of the tibial nerve on
organization of perineuronal nets surrounding alpha-motoneurons in rats with complete
spinal cord transection

Perineuronal nets (PNNs) are well-organized, specialized lattice-like structures of extracellular matrix in the central nervous system (CNS), which are formed during development. In the spinal cord, they encapsulate the cell body and proximal dendrites of many neurons. The damage to the CNS structures, including the spinal cord, causes changes in the expression of PNN and their components – chondroitin sulfate proteoglycan (CSPG). Increased PNN production causes limitations in the reorganization of the neuronal network and reinnervation after injury.
Based on our study results we made an assumption that PNNs limit morphological plasticity of the mature spinal cord after spinal cord transection (SCT). Preliminary experiments showed that after SCT, a significant decrease of the number of cholinergic terminals abutting α- motoneurons (MN), which provide inputs to extensor muscles of the ankle joints is paralleled by changes in PNNs enwrapping MN. The analysis also showed a twofold increase in the level of the PNN component of CSPG-phosphacan. Further research revealed that (1) locomotor training, which stimulates the whole network, and (2) electrical stimulation of a peripheral nerve, securing application of physiological stimuli to MN, leads to an increase in α-MN innervation. These results are the presumption to verify the hypothesis that using the same stimuli pattern we will be able to change the organization of the PNN within motor nuclei, particularly of those surrounding spinal MNs.


PRELUDIUM 2019-2021

The impact of complete spinal cord transection and BDNF overexpression on the subunit composition and phosphorylation state of AMPAR and NMDAR on MNs innervating ankle flexor and extensor muscles

AMPAR and NMDAR are two important ionotropic glutamate receptors, both in the brain and spinal cord, which mediate synaptic plasticity. The biophysical properties and trafficking of the two receptors are critically dependent on their subunit composition as well as posttranslational modifications. In the spinal cord, both AMPAR and NMDAR were detected on α-motoneurons (MNs) involved in the neuronal circuit controlling locomotion. Injury of the spinal cord causes changes in their expressions and posttranslational state. Thus, the molecular quantification of the synaptic composition of AMPAR and NMDAR and their posttranslational modifications are crucial for the understanding of mechanisms underlying their trafficking and synaptic plasticity in the spinal cord in response to injury. Brain-derived neurotrophic factor (BDNF) can regulate AMPAR and NMDAR mediated synaptic plasticity and transmission and enhance recovery processes in the adult spinal animal. Based on our preliminary studies we hypothesize that BDNF treatment will counteract the changes of subunit composition and phosphorylation state of AMPAR and NMDAR on the two pools of MNs caused by spinal cord transection (SCT). To verify this hypothesis quantification of transcript levels in isolated MN and visualization of protein distribution will be carried on.

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PRELUDIUM 2020-2022

Molecular and ultrastructural changes

in neuromuscular junction after complete spinal cord transection and spinal BDNF overexpression

The aim of the project is to provide an insight into the structural and molecular changes in peripheral
synapses of motoneurons (MN) in hindlimb muscles, that are occurring after complete spinal cord transection
(SCT) and treatment with brain-derived neurotrophic factor (BDNF). In a previous study, we found (1) better preservation of neuromuscular junctions (NMJ) integrity in muscles after BDNF treatment, (2) differential response of flexor and extensor muscles to injury and treatment, and (3) differential neurotrophic demands of these muscles.

In the project, we ask questions on the mechanisms which may contribute to BDNF-related maintenance of peripheral synapse. Our hypothesis is that better integrity of NMJ is the result of improved signaling at the MN central synapses, which results in better maintenance and increased activity of MN. This may result in the facilitated release of neurotransmitters and neurotrophins, with signaling to the accompanying non-myelinating Schwann cells,
surrounding the NMJ. The second hypothesis is that postsynaptic response also contributes to the processes of synapse maintenance, with the involvement of enhanced secretory activity of muscles and changes in muscle