Development of a Relevant Pre-Clinical Animal Model as a Tool to Evaluate Human Stem Cell-Derived Replacement Therapies for Motor Neuron Injuries and Degenerative Diseases
In the present project, our research team is investigating the possibility of using motor neurons that have been developed from human embryonic stem cells to replace lost motor neurons in the spinal cord of a large mammal. The project is of importance for better understanding of the translation of promising cell survival studies in rodents to a research model that more closely mimics the human condition. The findings may help the development of cellular treatments for injuries that affect both the spinal cord and spinal nerve roots as well as degenerative conditions that affect spinal cord motor neurons.
During the first year of the project, we have obtained the necessary institutional approvals for experimental studies and and use of human stem cells. the planned studies at both UCLA and UC Davis as well as obtained additional infrastructure and equipment. We have also further developed our in vitro protocols for the production of larger volumes of motor neurons from human embryonic stem cell. These studies have shown that we can grow human embryonic stem cells to develop into motor neurons in vitro and that these cells maintain motor neuron-like properties, such as being able to develop connections with muscle cells in a tissue culture setting. The tissue cultures also show reliable growth and robust differentiation of a large portion of cells to early forms of motor neurons and motor neurons with more differentiated features.
Survival of transplanted human cells in experimental models can be challenging and dependent on immuno-suppressive treatments. Based on recent advancements in the the field of transplant biology, we have adjusted our planned immuno-suppressive treatment plan to allow for longer study periods and reduce the risk of any medication-related side effects. In addition, we have refined our surgical methods for minimally invasive spine surgery to perform nerve root injuries and nerve root repairs, and these methods will be used when the addition of stem cell treatments to this new research model. In addition, we have developed and refined a series of imaging and functional outcome measures that are part of our new research tool in the form of improved magnetic resonance imaging techniques for correct identification of spinal cord levels prior to nerve root injury and stem cell injections into the spinal cord. We have also developed urodynamic study protocols as well as electromyography recordings from muscles cells of the pelvic floor and sphincters that are important for bladder and rectal function. These clinically relevant outcome measures are integrated into the research model to help determine the potential benefit from stem cell treatments. A series of 4 research manuscripts related to the present project have been submitted during the first year, and 2 of the manuscripts are presently accepted for publication/In Press.
Reporting Period:
Year 3
The present project aims at developing a large animal model to test new stem cell therapies for neurological conditions that cause loss of motor neurons. Such conditions include spinal cord injury to the sacral portion of the spinal cord, also known as the conus medullaris, and amyotrophic lateral sclerosis (ALS). For this purpose, we are developing techniques to inject human embryonic stem cells into the spinal cord of non-human primates. The cells have first been cultured in petri dishes to develop properties of motor neurons. The animals also are treated with a new protocol for immunosuppression that has eliminated the needs for oral medications and instead are injected intravenously or under the skin. The injectable anti-rejection medications are able to result in more stable blood levels of the medications and are better tolerated as they can reduce side effects such as nausea. The project is progressing well. Initial studies have shown ability to inject cells into the appropriate target areas of the spinal cord where motor neurons normally reside. The subjects have demonstrated treatment levels of immuno-suppression in the blood, and transplanted cells have survived and integrated well in the spinal cord. We are presently performing longer-term studies to evaluate the ability for the subjects to tolerate immuno-suppression administrated by injection over longer study periods periods and for cells to survive over longer time periods. We are also monitoring the subjects for potential adverse effects, including pain and tumor growth over several months. Our request for a o-cost time extesion will allow us to complete these studies and original goals. Next steps after the present project has been completed will aim to use this new research tool to evaluate for possible positive effect on neurological function in a larger group of non-human primates before translating this cellular treatment form to a human population in clinical studies.
Reporting Period:
NCE Year 4
The present project aimed at developing a tool and technology in the form of a large animal model to evaluate the potential utility and safety of transplanting motor neurons derived from human embryonic stem cells into the spinal cord of an in vivo research model. The studies used a nerve root injury model that results in loss of motor neurons in the spinal cord, thereby mimicking the effects of a spinal cord injury affecting the most caudal part of the spinal cord or motor neuron disorders such as amyotrophic lateral sclerosis (ALS). Embryonic human stems cell were used to growth early forms of motor neurons in cultures, and the cells were injected into the motor neuron area of the lumbar spinal cord after an avulsion injury of lumbosacral nerve roots. A surgical repair of lumbar nerve roots with surgical re-attachments of the roots to the spinal cord was also performed. In addition, all subjects received treatment with a new combination of immuno-suppression medications to allow for improved survival of human cells in the in vivo research model spinal cord. Animals were evaluated at both 2 and 7 months after the injury, surgical root repair, and transplantation of human motor neurons into the in vivo research model spinal cord spinal cord. All subjects showed excellent survival of human cells, and many of the transplanted cells had also developed synaptic contacts with host nerve cells in the in vivo research model spinal cord spinal cord. Some of the cells also showed nerve transmitter expression suggestive of a motor neuron profile and extension of nerve processes into the repaired ventral roots. Recordings from pelvic floor muscles and bladder pressure recordings confirmed injury effects from the initial nerve root injury but absence of any detectable functional adverse effects. The development of the large animal tool and technology was successful. In future studies, this new tool and technology may be used to assess potential utility and safety of emerging human stem cell therapies to replace degenerating motor neurons.
Grant Application Details
Application Title:
Development of a Relevant Pre-Clinical Animal Model as a Tool to Evaluate Human Stem Cell-Derived Replacement Therapies for Motor Neuron Injuries and Degenerative Diseases
Public Abstract:
Motor neurons degenerate and die as a consequence of many conditions, including trauma to the spinal cord and its nerve roots and degenerative diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy. Paralysis and in many cases death may result from a loss of motor neurons. No effective treatments are available for these patients. Most cellular therapy studies for motor neuron disorders are done in rodents. However, because of the dramatic differences between the rodent and human spinal cord, translation of these studies to humans is difficult. In particular, the development of new stem cell based treatments is limited by the lack of large animal models to test promising candidate therapies.
This bottleneck will be addressed by developing a new research tool in which human embryonic stem cell-derived motor neurons are transplanted into the spinal cord of rhesus macaques after injury and surgical repair of motor nerve roots. This injury and repair model mimic many features of motor neuron degeneration in humans. Microscopic studies will determine survival and tissue integration of transplanted human cells in the primate spinal cord tissues. Evaluations of walking, muscle and bladder function, sensation and magnetic resonance imaging (MRI) will test for possible benefits and potential adverse effects. This new research tool will be available for future pre-clinical testing of additional stem cell-based therapies that target motor neuron loss.
Statement of Benefit to California:
Paralysis resulting from motor neuron loss after cauda equina and conus medullaris forms of spinal cord injury and from neurodegenerative conditions, such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA), are devastating and affects thousands of patients and their families in California (CA). These conditions also create a significant financial burden on the state of CA. No effective treatments are available for these underserved patients. Development of a clinically relevant research tool is proposed to evaluate emerging stem cell-based motor neuron replacement therapies in translational studies. No such models are presently available to the global research community. As a result, the proposed research tool, which will remain based in CA, may attract interest across the United States and abroad, potentially being able to tap into a global translational research market of stem cell-based therapies and contribute to a positive revenue flow to CA.
Future benefits to people in CA include: 1) Development and translation of a new CA-based research tool to facilitate and expedite clinical realization of emerging stem cell-based therapies for devastating neurological conditions affecting motor neurons; 2) Reduction of health care costs and care giver costs for chronic motor neuron conditions with paralysis; 3) Potential for revenue from intellectual properties related to new cellular treatments entering clinical trials and human use.
