An artificial three-dimensional matrix promotes ramification in the microglial cell-line, BV-2

Three-dimensional (3D) cell culture yields strikingly different cell phenotypes compared to two-dimensional (2D) cell culture. Since microglia, monocyte derived immune cells in the brain, exist in a variety of cell shapes ranging from amoeboid to ramified, we evaluated the impact of 2D versus 3D culture conditions on cell shape. The microglial cell-line, BV-2, was either cultured on poly-d-lysine coated dishes (2D culture conditions) or in a BD Pura Matrix Peptide Hydrogel (3D culture conditions) in the absence or presence of the extracellular matrix proteins, fibronectin and collagen type I, respectively. We identified five distinct morphological phenotypes (amoeboid, bipolar, tripolar, multipolar, ramified) and compared the frequency distribution of these phenotypes under different culture conditions using a χ2 test. Culture of BV-2 cells in an inert 3D matrix shifted the frequency distribution from an amoeboid dominated population, which is typical for BV-2 cells cultured under conventional 2D conditions, to a population dominated by multipolar phenotypes. Fibronectin or collagen type I significantly suppressed matrix-induced ramification. These cell culture experiments illustrate the dependency of cell shape on spatial distribution of potential adhesion sites.