A Novel Quantitative Volumetric Spreading Index Definition and Assessment of Astrocyte Spreading In Vitro

Abstract

A novel quantitative volumetric spreading index (VSI) is defined that depends on the total distance between object voxels and the contact surface plane in three-dimensional (3D) space. The VSI, which ranges from 0 to 1, is rotationally invariant around the zaxis. VSI can be used to quantify the degree of individual cell spreading, which is important for analysis of cell interactions with their environment. The VSIs of astrocytes cultured on a nanofibrillar surface and three different comparative planar surfaces have been calculated from confocal laser scanning microscope z-series images, and the effects of both culture surface and immunoreactivity on the degree of cell spreading were investigated. VSI calculations indicated a statistical correlation between increased reactivity, based on immunolabeling for glial fibrillary acidic protein, and decreased cell spreading. Further results provided a quantitative measure for the increased spreading of quiescent-like and reactive-like astrocytes on planar substrates functionalized with poly-L-lysine.