Year 2

Injuries to the lowest portion of the spine and the spinal cord commonly results in paralysis and impairment of bladder , bowel, and sexual functions. These injuries are usually referred to as conus medullaris and cauda equina forms of spinal cord injuries. Presently, no treatments are available to reverse the neurological deficits that result from these injuries.
In this project, we aim to reverse neurological deficits, including bladder function, in a rat model of spinal cord injury, which affects the lowermost portion of the spinal cord. This part of the spinal cord and the associated nerve roots are called the conus medullaris and cauda equina. In our experimental model, nerve roots carrying fibers that control muscle function and pelvic organs, such as the bladder and bowel, are injured at the surface of the spinal cord. This injury mimics many of the neurological deficits encountered in human cases.
For treatment purposes, we transplant human derived embryonic stem cells, which have been prepared to acquire properties of motor neurons, into the lowermost portion of the rat spinal cord after injury and surgical repair of nerve roots carrying motor fibers. The studies will evaluate both acute and delayed transplantation of human embryonic stem cells, which have acquired properties of motor neurons.
During the second year of the studies, we have developed improved protocols to increase our ability to produce large number of motor neurons from human embryonic stem cells. We have also developed improved methods to detect motor neurons during the neuron production process by using fluorescent reporters inside of the cells. The latter development is of great help when sorting and preparing cells with desired properties for transplantation studies. In addition, we have refined our surgical methods to make it less invasive, using a one-sided injury model instead of lesions on both sides of the spinal cord in rats. Specifically, bladder dysfunction can be assessed after a one sided injury of nerve roots and be evaluated using a combination of bladder pressure recordings and electrical recordings referred to as electromyography (EMG) from muscles along the urethra. The revised procedure is well tolerated by the rats and is a suitable approach for studies of chronic injury and cell-based long-term treatments. A research manuscript describing this improved experimental method and refinement has been published. The experimental refinement will greatly assist with our long-term studies on the effects of transplanted motor neurons derived from human embryonic stem cells. We have also performed transplantations of embryonic human stem cell derived motor neurons into the rat spinal cord and demonstrated surgical feasibility as well as survival of large numbers of neurons in the rat spinal cord. Some of the transplanted cells also demonstrate anatomical markers for motor neurons after transplantation.