Characterization of schwann cells in self-assembled sheets from thermoresponsive substrates

Schwann cells are the vital glial cells in the development and regeneration of the peripheral nervous system (PNS). Recently, Schwann cell transplantation has emerged as one of the attractive candidates in treating demyelinating diseases resulting from the PNS and central nervous system injuries. Schwann cells are usually injected as cell suspensions or transplanted after being seeded on extracellular matrix proteins or biodegradable polymeric scaffolds. In these approaches, the adherens junctions between Schwann cells present in vivo are not readily replicated as Schwann cells dispersed as individual cells. Here we describe a procedure to grow a large amount of Schwann cells in a sheet architecture that can be either transplanted or injected and provide some insights into the influence of a sheet-like cell organization on the function of Schwann cells, including their viability, proliferation, alignment, and migration. The Schwann cell sheet was successfully generated through coating the culture plate surfaces by layer-by-layer self-assembly of the thermoresponsive polymer poly-(N-isopropylacrylamide) (PNIPAAM). Further characterization of the Schwann cell sheet showed that Schwann cells in sheet were highly viable, but maintained a lower proliferation rate than individual Schwann cells. The levels of nerve growth factor and glial cell-derived neurotrophic factor were also maintained in Schwann cell sheets. The protein level of a cyclin-dependent kinase inhibitor, p27, was upregulated in the Schwann cell sheet. Both alignment with axon-like nanofibers and migration of Schwann cells are not significantly different between Schwann cells in a sheet-like organization and as individual cells. We conclude that Schwann cell sheet engineering presents a promising method for cell-based nerve injury therapy, as well as a model to study the control of Schwann cell proliferation in response to intercellular organization.