Institute of Neurological Sciences and Psychiatry, Hacettepe University, Ankara, Turkey; Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Université de Montréal, Montréal, Québec, Canada; Department of Neuroscience, Université de Montréal, Montréal, Québec, Canada
Sinem Yilmaz-Ozcan
Institute of Neurological Sciences and Psychiatry, Hacettepe University, Ankara, Turkey
Institute of Neurological Sciences and Psychiatry, Hacettepe University, Ankara, Turkey; Department of Neurology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
Jesse Schallek
Center for Visual Science, University of Rochester, New York, United States; Flaum Eye Institute, University of Rochester, New York, United States
Kıvılcım Kılıç
Institute of Neurological Sciences and Psychiatry, Hacettepe University, Ankara, Turkey
Alp Can
Department of Histology and Embryology, School of Medicine, Ankara University, Ankara, Turkey
Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Université de Montréal, Montréal, Québec, Canada; Department of Neuroscience, Université de Montréal, Montréal, Québec, Canada
Institute of Neurological Sciences and Psychiatry, Hacettepe University, Ankara, Turkey; Department of Neurology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
Recent evidence suggests that capillary pericytes are contractile and play a crucial role in the regulation of microcirculation. However, failure to detect components of the contractile apparatus in capillary pericytes, most notably α-smooth muscle actin (α-SMA), has questioned these findings. Using strategies that allow rapid filamentous-actin (F-actin) fixation (i.e. snap freeze fixation with methanol at −20°C) or prevent F-actin depolymerization (i.e. with F-actin stabilizing agents), we demonstrate that pericytes on mouse retinal capillaries, including those in intermediate and deeper plexus, express α-SMA. Junctional pericytes were more frequently α-SMA-positive relative to pericytes on linear capillary segments. Intravitreal administration of short interfering RNA (α-SMA-siRNA) suppressed α-SMA expression preferentially in high order branch capillary pericytes, confirming the existence of a smaller pool of α-SMA in distal capillary pericytes that is quickly lost by depolymerization. We conclude that capillary pericytes do express α-SMA, which rapidly depolymerizes during tissue fixation thus evading detection by immunolabeling.
