Clinical neurorestorative cell therapies for stroke

Positive and negative cell therapy in randomized control trials for central nervous system diseases

Neurorestorative cell therapies have been tested to treat patients with nervous system diseases for over 20 years. Now it is still hard to answer which kinds of cells can really play a role on improving these patients' quality of life. Non-randomized clinical trials or studies could not provide strong evidences in answering this critical question. In this review, we summarized randomized clinical trials of cell therapies for central nervous diseases, such as stroke, spinal cord injury, cerebral palsy (CP), Parkinson's disease (PD), multiple sclerosis (MS), brain trauma, amyotrophic lateral sclerosis (ALS), etc. Most kinds of cell therapies demonstrated negative results for stoke, brain trauma and amyotrophic lateral sclerosis. A few kinds of cell therapies showed neurorestorative effects in this level of evidence-based medicine, such as olfactory ensheating cells for chronic ischemic stroke. Some kinds of cells showed positive or negative effects from different teams in the same or different diseases. We analyzed the possible failed reasons of negative results and the cellular bio-propriety basis of positive results. Based on therapeutic results of randomized control trials and reasonable analysis, we recommend: (1) to further conduct trials for successful cell therapies with positive results to increase neurorestorative effects; (2) to avoid in repeating failed cell therapies with negative results in same diseases because it is nonsense for them to be done with similar treatment methods, such as cell dosage, transplanting way, time of window, etc. Furthermore, we strongly suggest not to do non-randomized clinical trials for cells that had shown negative results in randomized clinical trials.

Advances in Neurorestoratology-Current status and future developments

Neurorestoratology constitutes a novel discipline aimed at the restoration of damaged neural structures and impaired neurological functions. This area of knowledge integrates and compiles all concepts and strategies dealing with the neurorestoration. Although currently, this discipline has already been well recognized by physicians and scientists throughout the world, this article aimed at broadening its knowledge to the academic circle and the public society. Here we shortly introduced why and how Neurorestoratology was born since the fact that the central nervous system (CNS) can be repaired and the subsequent scientific evidence of the neurorestorative mechanisms behind, such as neurostimulation or neuromodulation, neuroprotection, neuroplasticity, neurogenesis, neuroregeneration or axonal regeneration or sprouting, neuroreplacement, loop reconstruction, remyelination, immunoregulation, angiogenesis or revascularization, and others. The scope of this discipline is the improvement of therapeutic approaches for neurological diseases and the development of neurorestorative strategies through the comprehensive efforts of experts in the different areas and all articulated by the associations of Neurorestoratology and its journals. Strikingly, this article additionally explores the "state of art" of the Neurorestoratology field. This includes the development process of the discipline, the achievements and advances of novel neurorestorative treatments, the most efficient procedures exploring and evaluating outcome after the application of pioneer therapies, all the joining of a multidisciplinary expert associations and the specialized journals being more and more impact. We believe that in a near future, this discipline will evolve fast, leading to a general application of cell-based comprehensive neurorestorative treatments to fulfill functional recovery demands for patients with neurological deficits or dysfunctions.

Clinical results of neurorestorative cell therapies and therapeutic indications according to cellular bio-proprieties

Cell therapies have been explored to treat patients with nervous diseases for over 20 years. Even though most kinds of cell therapies demonstrated neurorestorative effects in non-randomized clinical trials; the effects of the majority type cells could not be confirmed by randomized controlled trials. In this review, clinical therapeutic results of neurorestorative cell therapies according to cellular bio-proprieties or cellular functions were introduced. Currently it was demonstrated from analysis of this review that some indications of cell therapies were not appropriate, they might be reasons why their neurorestorative effects could not be proved by multicenter, randomized, double blind, placebo-controlled clinical trials. Theoretically if one kind of cell therapy has neurorestorative effects according to its cellular bio-proprieties, it should have appropriate indications. The cell therapies with special bio-properties is promising if the indication selections are appropriate, such as olfactory ensheathing cells for chronic ischemic stroke, and their neurorestorative effects can be confirmed by higher level clinical trials of evidence-based medicine.

Why is olfactory neuroepithelium?

Currently, most cellular therapeutic effects for nervous diseases cannot be proven in a multicenter, randomized, double-blind placebo-control clinical trials, except for a few kinds of cells such as olfactory ensheathing cells. These cells show significant improvements in functional recovery and quality of life for patients with chronic ischemic stroke. Also, olfactory neuron transplantation has promising neurorestorative effects on patients with vascular dementia. Human olfactory neuroepithelium can spontaneously and sustainably regenerate or produce new olfactory neurons and glial cell types for decades or a lifetime. The neurorestorative mechanisms of olfactory ensheathing cells are well known; however, little is known about the neurorestorative mechanisms of olfactory neurons. Therefore, I hypothesize that the neurorestorative mechanisms of olfactory neurons after transplantation: (1) can well migrate where they are needed and become local functional neurons, as they need to compensate or replace; (2) must be regulated by some special molecular factors to elongate their axons, modulate or direct synapses to correctly recognize and connect the target cells, and integrate functions. Based on olfactory neuroepithelium cells displaying the special characterization, neurorestorative mechanisms, clinical therapeutic achievements, and hypotheses of effective mechanisms, they (olfactory ensheathing cells and olfactory neurons) may be the most efficient instruments of neurorestoration.