The Morphology And Function Of Astrocytes Cultured On Water-repellent Fractal Tripalmitin Surface

Objective:In the CNS, astrocytes play an essential role with their multiple functions and sophisticated structure, as surrounded by a fractal environment which hasn’t been available in our traditional cell culture. We sought to investigate whether a water-repellent fractal nanomaterial surface made by tripalmitin (PPP), could provide the cultured primary astrocytes with an improved closer-to-natural environment for experimental assessment of glial structure and functions.Methods:Tripalmitin is a hydrophobic triglyceride derived from palmitic acid with good biocompatibility and can form water-repellent fractal structure during the phase transition from the metastable a-form to the stable β-crystalline form. We examined morphology and biochemical characterization of astrocytes cultured 3 days on poly-1-lysine (control) and PPP surfaces with contact angles of 105°～115°(non-fractal but water-repellent),125°～135°(fractal and water-repellent) and 150°～160°(fractal and super water-repellent).Results:We found that (1) water-repellent fractal PPP surface can induce astrocytes to display differentiated morphology with smaller size of cell area, longer and finer filopodium-like processes, and higher morphological complexity revealed by fractal analysis. The super water-repellent fractal PPP surface with water contact angle of 150°～160° produced the maximal effects compared with other surfaces at lower water contact angle. (2) The trends of characteristic protein expression, including that of nestin, vimentin, GFAP and glutamine synthetase, for astrocytes cultured in super water-repellent fractal PPP surface approximated more to in vivo pattern compared with those in conventional cell culture surface. (3) This super water-repellent PPP surface also rendered astrocytes to perform more pronounced promotion of neurogenesis by increasing the release of nerve growth factor in a co-culture system.Conclusion:Our results suggest that super water-repellency fractal PPP surface facilitates the astrocytes to mimic their in vivo performance in respect of differentiated morphology and biochemical characterization as well as increased functions in promoting neurogenesis. Thus this surface is particularly suitable for two-dimensional cell culture to provide biomaterial properties closely mimicking that in vivo.