It is my great pleasure to join this conference. I want to thank Dr. Jha for his invitation. Today I'm going to discuss with you about post spinal cord injury therapeutic effects over human neural stem cells. As we all know, neural stem cell as a biological concept has existed for a long time. However, its potential to be translated to treat clinical neurological problems, including neurotrauma was only recognized after the discovery of adulthood neurogenesis in mammalian central nervous system in the 80s of the 20th century. As illustrated here, mammalian brain still possesses two primary neurogenic zone. One is a long lateral ventricle, the periventricular zone that produce neural stem cells that migrate along rostral migratory stream to go to olfactory bulb where they become fresh interneurons. Another neurogenic zone is in the hippocampal dentate gyrus in the subgranular zone where newborn neurons also take place. It has been appreciated that such ability remains very robust during infant phase of human development, but it may be drastically diminished in the adulthood. Nevertheless, this suggests if we could use such capacity to treat neurotrauma, such as a spinal cord injury, the overall scale of clinical efficacy would have been very different. Here is a strategic map showing us the current understanding about a clinically defined functional deficit after traumatic spinal cord injury. It has been recognized that such a state actually is formed by three sequential and parallel processes. That is the primary injury and the secondary injury such as excitotoxicity, oxidative damage inflammation, and the endogenous recovery mechanisms setting in motion by primary injury. From a clinical point of view, therapeutic windows thus exist in impeding secondary injury and booming recovery mechanism, including trophic factor expression, neural stem cell reactivation, et cetera. What happened during primary injury is largely beyond the management of physicians. In my own lab, I decided to integrate newly emerged technologies from new fields, such as stem cell biology, material science, synthetic materials, glial biology, and neuro-oncology to jointly integrate their strengths to investigate injured spinal cord. In other words, I decided to turn this table around to go back trying to define novel recovery neurobiology mechanisms that can be used as therapeutic targets. From there, eventually we'll be able to update our understanding about adult spinal cord neurobiology. This was done by a novel multimodal technology that I and my collaborators introduced, invented for the field, because back then in the late 90s and early 2000s, it has been well accepted that the acutely injured spinal cord epicenter, such as in this penetrating injury model and middle line segmental hemisection, the microenvironment is too hostile about supporting any survival of a donor cells. We decided to use synthetic biologically compatible and degradable polymers to scaffold neural stem cells and immediately transplanted into this freshly created lesion zone. And this model offers a whole variety of neuropathophysiology and neurobiology targets to be investigated. As we all know, this model exactly mimicked the clinical Brown-Seguire syndrome of clinical spinal cord trauma. What we found was that with such a treatment, the rats recovered robust hind limb locomotion because that was a lower thoracic injury on the affected side. As showing in this montage, that they restored consistent locomotion that can coordinate with front limb and bare body weight. That was in sharp contrast with lesion alone controls. We also got a bonus from that study. We found that polymer alone also had benefits, definitive benefits. In contrast, simply inject stem cell suspension into such an open lesion zone or even contusion injury epicenter would not help as much because donor cells did not survive very well. When we looked into mechanisms, we found that these red cells, they are donor marker N2, and they did not actually become new neurons or other neurotype cells such as otochondrocytes because the green neurofilament components did not have a red color suggesting there are host tissues. What we additionally uncovered was these donor cells survived long in the host spinal cord. These are eight, 10 weeks or even longer after spinal cord injury remained as neural stem cells. As you will see, they remained their own tricurb beta-gal positive, which was green, and also there were positive over nesting that was red. So these yellow cells were long surviving donor cells. These donor cells did not become astrocytes, and they were largely GFAP, which is green negative. Very encouragingly, we reported the first evidence that transplantation of neural stem cells could suppress reactive gliosis, which we know is a detrimental factor for post-spinal cord injury beneficial neuroplasticity, and relative to control groups, reactive gliosis, as indicated by GFAP level, was drastically reduced. And that led us to hypothesize in this paper published in New England J.A. Medicine as an education piece that some of the original hypothesis about neural stem cells possibility to become naturally, spontaneously, become new neurons and new oligodendrocytes to remodeling exons to form new neuroparachroma was indeed too naive. Instead, we found evidence that such a therapeutic effect was derived from neural stem cells' multiple functions that they can express trophic factors, they can impede inflammation and suppress a scar formation, reduce cavity, and they can also help to reignite intrinsic neural circuits. And perhaps by also hypothesize their effect, perhaps also involved their ability to nurture and reactivate distal spinal cords intrinsic neural circuits. Clearly, these are the things need more experimental evidence. In a more recent paper, we found that such multiple function not only can be carried out by neural stem cells, it can also be carried out by human mesenchymal stromal stem cells. In this study used the same strategy, same model. We observed a robust neurological recovery. We also observed such a recovery did not occur because of a long distance cortical spinal cord exon regeneration because below injury was no such green exon signals. It was also not due to rubral spinal exon regeneration because below injury in the recovered animals, they had no rubral spinal exon regeneration relative to segments above spinal cord lesion. What we observed was this very robust multifunction of stem cells that really enhanced the neurological integrity as indicated by synaptic markers in the intermediate gray neural network. It also helped to stabilize, maintain neuromuscular junction in the hind limb down through this multidimensional systemic neuromuscular tracing. Such approach enabled us to obtain this evidence. It also helped the existing proprio-spinal projection network to reach the lumbar spinal cord alpha motor neurons. Lastly, such treatment further augmented sprouting of serotonergic fibers in distal spinal cord. Evidently, previously existed a classic concept about stem cells, including neural stem cells could not be used to explain these novel actions we validated. So based on this evidence, I proposed a novel neurobiology concept about stem cells, that is a functional multipotency of stem cells that was first gleaned from neuroprosgenitor cells, such as neural stem cells, which illustrate this deep embedded innate biology of stem cells. In addition to their ability to become all three lineages of neural cells in developmental track, they can also process this innate developmental neurobiology capacity that is in interaction through censoring microenvironment need, they can activate developmental genes to produce neurotrophic factors, cytokines, including anti-inflammation cytokines, and shared exosomes. They could even form gap junctions with adjacent cells. And this allowed them not only possess the potential to become new neural cells, but more importantly, they can modify, regulate injury environment to impede secondary injury, augment endogenous recovery mechanism. And this actually can be a huge hope for the future critical medical treatment of acute neurotrauma, because as summarized in this more recent paper from my lab, we have recognized actually spinal cord injury is a systemic complex over different disorders involving many pivotal systems. Conventional treatment is such as a receptor specific agonist may improve specific functions such as respiration by 5-HT-A agonist, which was a patent by my lab. Biospar is a good example. Biospar can also specifically activate lumbar motor generator neurocircuits. It cannot cover the whole variety of treatment that are needed for instrument-facilitated neural rehab to eventually improve functional status of an individual living with STI condition. For this broad spectrum therapeutic effect, local and systemic neural stem cell therapy in the near future may offer true therapeutic potential. In a brief summary, the platform technology of a polymer scaffolding of stem cells enable the discovery of functional multipotency of stem cells, which resulted in more correct and more optimal applications of neural stem cells in basic and translational scientific research. Human neural stem cells-based multimodal effects enhanced the integrity of Rafi's spinal serotonergic re-innovation, proprio-spinal network, neuromuscular junction integrity, and a lumbar central patent generator. These multiple functions jointly could restore locomotion in mammalian species after a thoracic and even higher level spinal cord injury, as long as the locomotor circuitry in the lumbar enlargement itself is spared. The data collectively elucidate recovery neurobiology. The recovery neurobiology is another novel concept, which benefited from stem cell-based multimodal research that I put forward, but will not have time to go into details. Concisely, recovery neurobiology describes injured adult mammalian spinal cords may develop, may deploy polysynaptic neural circuits different from those of physiology for neural recovery. I want to acknowledge all the sponsors, especially my own lab team over years, my collaborators from different institutions. Their talent to work and contribution made my presentation possible. Thank you all very much.

neural stem cells

spinal cord injury

therapeutic effects

neurotrauma

functional multipotency