Abstract

DO.09.03

Biomechanical features of Müller cells

Yanors Yandiev1, Yun-be Lu2, Thomas Pannicke2, Kristian Franze2, Andreas Bringmann1, Peter Wiedemann1, Josef Käs2, Andreas Reichenbach2
1Klinik und Poliklinik für Augenheilkunde, Universitätsklinikum Leipzig, Leipzig; 2Paul-Flechsig-Institut für Hirnforschung, Universität Leipzig, Leipzig

Objective
Recently, we investigated the biomechanical properties of individual cells from brain and retina (Lu et al., 2006, PNAS 103:17759-64). Although neurons are very soft, the glial cells are even softer than neurons. However, alterations in the cytoskeleton may change these properties in cases of reactive gliosis and glial scar formation. Müller cells in normal retinae express the intermediate filament vimentin. In virtually all retinal diseases, Müller cells upregulate vimentin and express another intermediate filament, glial fibrillary acidic protein (GFAP). Thus, the present study intended to compare the biomechanical properties of normal and reactive Müller cells.
Methods
Transient ischemia was induced in retinae of adult Long-Evans rats by elevation of the intraocular pressure for 60 min. At 7 days after ischemia, Müller cells were acutely isolated and used in biophysical measurements with scanning force microscopy.
Results
Müller cells from postischemic retinae showed a pronounced gliosis, as revealed by the increased expression of the intermediate filaments GFAP and vimentin. To characterize the local mechanical properties of Müller cells, we recorded the Young's modulus in a defined range of deforming frequencies (30, 100 Hz) using a scanning force microscope. We separately measured the endfoot, the adjacent inner stem process, and the bulged soma with the nucleus. Both the endfoot and the inner process were significantly stiffer in gliotic Müller cells as compared to controls. No significant difference was seen in the soma region.
Conclusions

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