Certain nervous system injuries, autoimmune diseases affecting the central or peripheral nervous system, and neurodegenerative diseases are characterized by loss of specific cells, or abnormal functions of existing nerve cells, which cause the patient to present with different neurological signs and symptoms and potentially irreversible loss of neurological functions.  As one example only, some patients suffering stroke, spinal cord injury, or other neural injury and degeneration experience loss of functioning cell types, or neurological conditions like Parkinson's disease and Alzheimer's disease which in turn results in loss of or abnormal function of system function.  Currently therapeutic options for treating and restoring such cell and system functions are limited.  Thus, a need remains for methods, systems, and compositions to promote additional therapies, including therapies addressed to replacement of missing or damaged nervous system cells, tissues, and functions.