Long-Term Effects of Neural Precursor Cell Transplantation on Secondary Injury Processes and Functional Recovery after Severe Cervical Contusion-Compression Spinal Cord Injury

Abstract

Cervical spinal cord injury (SCI) remains a devastating event without adequate treatment options despite decades of research. In this context, the usefulness of common preclinical SCI models has been criticized. We, therefore, aimed to use a clinically relevant animal model of severe cervical SCI to assess the long-term effects of neural precursor cell (NPC) transplantation on secondary injury processes and functional recovery. To this end, we performed a clip contusion-compression injury at the C6 level in 40 female Wistar rats and a sham surgery in 10 female Wistar rats. NPCs, isolated from the subventricular zone of green fluorescent protein (GFP) expressing transgenic rat embryos, were transplanted ten days after the injury. Functional recovery was assessed weekly, and FluoroGold (FG) retrograde fiber-labeling, as well as manganese-enhanced magnetic resonance imaging (MEMRI), were performed prior to the sacrifice of the animals eight weeks after SCI. After cryosectioning of the spinal cords, immunofluorescence staining was conducted. Results were compared between the treatment groups (NPC, Vehicle, Sham) and statistically analyzed (p < 0.05 was considered significant). Despite the severity of the injury, leading to substantial morbidity and mortality during the experiment, long-term survival of the engrafted NPCs with a predominant differentiation into oligodendrocytes could be observed after eight weeks. While myelination of the injured spinal cord was not significantly improved, NPC treated animals showed a significant increase of intact perilesional motor neurons and preserved spinal tracts compared to untreated Vehicle animals. These findings were associated with enhanced preservation of intact spinal cord tissue. However, reactive astrogliosis and inflammation where not significantly reduced by the NPC-treatment. While differences in the Basso–Beattie–Bresnahan (BBB) score and the Gridwalk test remained insignificant, animals in the NPC group performed significantly better in the more objective CatWalk XT gait analysis, suggesting some beneficial effects of the engrafted NPCs on the functional recovery after severe cervical SCI.

Microneurotrophin BNN27 Reduces Astrogliosis and Increases Density of Neurons and Implanted Neural Stem Cell-Derived Cells after Spinal Cord Injury

“…NSC survival was lower when NSCs were transplanted in the acute phase of injury (1%) compared to the subacute one (6%) [ 48 , 49 ]. This deficiency could be caused by early immunoreaction events at the lesion site, which are toxic to implanted cells [ 50 , 51 ]. Strategies for protecting implanted NSCs from the harsh SCI lesion environment include delivering NSCs inside biomaterials (such as the PCS utilized in this study) and providing anti-apoptotic support via small molecule compounds or biologics.…”

“…Another major challenge of NSC-based SCI treatments is that NSCs differentiate mostly into glial cells and poorly towards neurons, as the lesion environment is unfavorable for neuronal differentiation [ 49 , 51 , 53 , 54 , 55 ]. Significant research has attempted to guide the fate of implanted NSCs using biomaterials and growth factors that enhance neuronal survival and differentiation [ 55 ].…”

The Sonic Hedgehog Pathway Modulates Survival, Proliferation, and Differentiation of Neural Progenitor Cells under Inflammatory Stress In Vitro

“…In the context of growing evidence for the relevance of endogenous NPCs in response to CNS injuries [ 10 , 38 , 39 ], Shh might thus have the potential to improve endogenous neuroregeneration by modulation of NPC niches in, e.g., the spinal cord. Moreover, given the recent interest in stem cell transplantation as a therapeutic option after SCI [ 26 , 40 , 41 , 42 ], whereby NPCs play a dominant role [ 13 , 21 , 43 , 44 ], a better understanding of the interactions between Shh and the proliferation/differentiation of NPCs might have implications for such cellular-based treatments as well. Of note, a common problem of current NPC-transplantation strategies is the low survival of the cell graft which might be improved by synergistic Shh-treatment [ 45 , 46 ].…”

Application and prospects of high-throughput screening for in vitro neurogenesis

“…Before clinical trials, studies of stem cell trans plantation were conducted on animal disease models to examine the safety and efficiency of stem cell therapy. Recently, various studies have been carried out using primary NS/PCs, neural precursors, immortalized neural stem cell lines, iPSC-derived NS/PCs, and directly reprogrammed neural precursor cells to treat spinal cord injury (SCI)[ 189 , 190 ], AD[ 191 , 192 ], PD[ 193 - 195 ], Huntington’s disease (HD)[ 196 , 197 ] and ALS[ 198 ] in animal models, and the symptoms of those diseases were relieved to some extent. For instance, the long-term selective stimulation of hM3Dq-expressing human iPSCs (hiPSCs)-derived NS/PCs enhanced their BDNF secretion, neuron-to-neuron interactions and synaptic activity in the surrounding host tissue in mouse SCI models, suggesting that enhancing neural activity and interactions with other cells in the neural circuit can be an effective way to improve the therapeutic effect of stem cell transplantation[ 199 ].…”