Protective effects of osmolytes in cryopreserving adherent neuroblastoma (Neuro-2a) cells

A simple method to cryopreserve adherent monolayers of neuronal cells is currently not available, but the development of this technique could facilitate numerous applications in the field of biomedical engineering, cell line development, and drug screening. However, complex tissues of some exceptional animals survive freezing in nature. These animals are known to accumulate several small molecular weight solutes prior to freezing. Following a similar strategy, we investigated the effects of osmolytes such as trehalose, proline, and sucrose as additives to the traditional cryoprotectant dimethyl sulfoxide (Me2SO) in modulating the cryopreservation outcome of mouse neuroblastoma (Neuro-2a) cells. Neuro-2a cells adhered to cell culture plates were incubated for 24 h at varying concentrations of trehalose, proline, sucrose and combinations of these compounds. Cells were cryopreserved for 24 h and cell viability post-freezing and thawing was quantified by trypan blue exclusion assay. On average, only 13.5% of adherent cells survived freezing in the presence of 10% Me2SO alone (control). Pre-incubation of cells with medium containing both trehalose and proline severely decreased cell proliferation, but increased cell recovery to about 53% of control. Furthermore, characterization using Raman microspectroscopy revealed that the addition of both trehalose and proline to 10% Me2SO substantially increased the size, and altered the nature, of ice crystals formed during freezing. Our results suggest that pre-incubation of Neuro-2a cells with trehalose and proline in combination provides cell protection along with alterations of ice structure in order to increase cell survival post-freezing.