Transplantation of brain cells assembled around a programmable synthetic microenvironment.

Cell therapy is a promising method for treatment of hematopoietic disorders, neurodegenerative diseases, diabetes, and tissue loss due to trauma. Some of the major barriers to cell therapy have been partially addressed, including identification of cell populations, in vitro cell proliferation, and strategies for immunosuppression. An unsolved problem is recapitulation of the unique combinations of matrix, growth factor, and cell adhesion cues that distinguish each stem cell microenvironment, and that are critically important for control of progenitor cell differentiation and histogenesis. Here we describe an approach in which cells, synthetic matrix elements, and controlled-release technology are assembled and programmed, before transplantation, to mimic the chemical and physical microenvironment of developing tissue. We demonstrate this approach in animals using a transplantation system that allows control of fetal brain cell survival and differentiation by pre-assembly of neo-tissues containing cells and nerve growth factor (NGF)-releasing synthetic particles.