Long-term functional restoration by neural progenitor cell transplantation in rat model of cognitive dysfunction: co-transplantation with olfactory ensheathing cells for neurotrophic factor support

Neural progenitor cell transplantation has emerged as a promising approach for cell replacement therapy in the brain of neurodegenerative diseases. These are multipotent stem cells with self-renewal capabilities and can give rise to cells of all the three lineages of nervous system and can be maintained and differentiated to desirable neuronal subtypes in vitro with known trophic factors. However, like fetal cells, neural progenitor cells after differentiating to specific neuronal type also require continuous neurotrophic factor support for their long-term survival following transplantation. Recent reports suggest that olfactory ensheathing cells are capable of providing continuous neurotrophic factor to the transplanted neural progenitor cells for their long-term survival. In the present investigation, an attempt has been made to validate functional restoration in kainic acid lesioned rat model of cognitive dysfunction following co-transplantation of neural progenitor cells with olfactory ensheathing cells.Animals lesioned with kainic acid in CA3 subfield of hippocampal region were transplanted with neural progenitor cells, olfactory ensheathing cells or neural progenitor cells + olfactory ensheathing cells together. Twelve weeks post-transplantation functional restoration was assessed using neurobehavioral, neurochemical, and immunohistochemical approaches. Significant recovery in learning and memory (89%) was observed in co-transplanted group when compared to lesioned group. This was accompanied by significantly higher expression of choline acetyltransferase and restoration in cholinergic receptor binding in co-transplanted group (61%) over the animals transplanted either olfactory ensheathing cells or neural progenitor cells alone. Role of olfactory ensheathing cells in supplementing neurotrophic factors was further substantiated in vitro by pronounced differentiation of neural progenitor cells to choline acetyltransferase/acetylcholine esterase immunoreactive cells when co-cultured with olfactory ensheathing cells as compared to neural progenitor cells alone. The results strengthened the hypothesis that co-transplantation of olfactory ensheathing cells and neural progenitor cells may be a better approach for functional restoration in kainic acid induced rat model of cognitive dysfunction.