Generation of cortical neurons from human induced-pluripotent stem cells by biodegradable polymeric microspheres loaded with priming factors.

Ischemic stroke is often associated with loss of cortical neurons leading to various neurological deficits. A cell replacement based on stem cell transplantation to repair the damaged brain requires the generation of specific neuronal subtypes. Recently, induced pluripotent stem cells have been used to generate various subtypes of neurons in vitro for transplantation in stroke-damaged brains. However, whether these cells can be primed as neuronal precursors to become cortical projection neurons by means of biomaterials releasing differentiation factors is not known. Here, we report that microspheres of biodegradable poly(ester-amide) composed of adipic acid, L-phenyl-alanine and 1,4-butanediol, loaded with differentiation factors, can be used to fate human induced pluripotent stem cell-derived long-term expandable neuroepithelial-like stem cells to cortical projection neurons. The three factors, Wnt3A, BMP4 and cyclopamine, were released from loaded microspheres over at least one month following biphasic dynamic time course, promoting cortical differentiation of the cells in vitro. Microspheres did not evoke significant inflammatory response after transplantation into intact rodent brain. Our study shows the potential of biodegradable polymer microspheres to promote neuronal differentiation by continuous release of factors, thereby creating the appropriate microenvironment. This new strategy may improve the efficacy of stem cell-based therapeutic approaches.