Changes in fractal dimension and lacunarity as early markers of UV-induced apoptosis.

The aim of our study was to employ fractal analysis for evaluation of ultrastructural changes during early stages of apoptosis. Apoptosis was induced in U251 human glioma cell line by exposure to UVB light. The cells were visualized by optical phase-contrast microscopy and photographed before the UV treatment, immediately after the treatment, as well as at 30 min intervals during 5h observation period. For each of the 32 cells analyzed, cellular and nuclear fractal dimension, as well as nuclear lacunarity, were determined at each time point. Our data demonstrate that cellular ultrastructural complexity determined by fractal dimension and lacunarity significantly decreases after the UV irradiation, with the nuclear lacunarity being a particularly sensitive parameter in detecting early apoptosis. Importantly, fractal analysis was able to detect cellular apoptotic changes earlier than conventional flow cytometric analysis of phosphatidylserine exposure, DNA fragmentation and cell membrane permeabilization. These results indicate that fractal analysis might be a powerful and affordable method for non-invasive early identification of apoptosis in cell cultures.

[1]  G. Häcker,et al.  Apoptosis induced by direct triggering of mitochondrial apoptosis proceeds in the near-absence of some apoptotic markers , 2007, Apoptosis.

[2]  E. Ulukaya,et al.  Apoptosis: why and how does it occur in biology? , 2011, Cell biochemistry and function.

[3]  C D Woodworth,et al.  Cell surface as a fractal: normal and cancerous cervical cells demonstrate different fractal behavior of surface adhesion maps at the nanoscale. , 2011, Physical review letters.

[4]  Jan Ellenberg,et al.  Molecular crowding affects diffusion and binding of nuclear proteins in heterochromatin and reveals the fractal organization of chromatin , 2009, The EMBO journal.

[5]  Clarke F Millette,et al.  Fractal and Image Analysis of Morphological Changes in the Actin Cytoskeleton of Neonatal Cardiac Fibroblasts in Response to Mechanical Stretch , 2007, Microscopy and Microanalysis.

[6]  The fractal dimension of cell membrane correlates with its capacitance: a new fractal single-shell model. , 2010, Chaos.

[7]  C. Heckman,et al.  Morphological Fractal Analysis of Shape in Cancer Cells Treated with Combinations of Microtubule-Polymerizing and -Depolymerizing Agents , 2010, Microscopy and Microanalysis.

[8]  T. Utsumi,et al.  Mechanisms of enhanced apoptosis in HL-60 cells by UV-irradiated n-3 and n-6 polyunsaturated fatty acids. , 2003, Free radical biology & medicine.

[9]  Katharina D'Herde,et al.  Apoptosis and necrosis: detection, discrimination and phagocytosis. , 2008, Methods.

[10]  A. Giuliani,et al.  Fractal analysis in a systems biology approach to cancer. , 2011, Seminars in cancer biology.

[11]  W. B. Marks,et al.  Fractal methods and results in cellular morphology — dimensions, lacunarity and multifractals , 1996, Journal of Neuroscience Methods.

[12]  D. Kulms,et al.  Molecular mechanisms of UV‐induced apoptosis , 2000, Photodermatology, photoimmunology & photomedicine.

[13]  Gabriele A. Losa,et al.  Ultrastructural Complexity of Nuclear Components During Early Apoptotic Phases in Breast Cancer Cells , 2001, Analytical cellular pathology : the journal of the European Society for Analytical Cellular Pathology.

[14]  Nacim Betrouni,et al.  Fractal and multifractal analysis: A review , 2009, Medical Image Anal..

[15]  D. Lebedev,et al.  Fractal nature of chromatin organization in interphase chicken erythrocyte nuclei: DNA structure exhibits biphasic fractal properties , 2005, FEBS letters.

[16]  M. Eshraghi,et al.  Apoptosis and cancer: mutations within caspase genes , 2009, Journal of Medical Genetics.

[17]  W. Lambert,et al.  Identification of early apoptosis in feulgen-stained cultured cells in situ by computerized image analysis. , 1998, Cytometry.

[18]  Ye Zhang,et al.  Repression of hsp90β Gene by p53 in UV Irradiation-induced Apoptosis of Jurkat Cells* , 2004, Journal of Biological Chemistry.

[19]  Adam Wax,et al.  Light scattering measurements of subcellular structure provide noninvasive early detection of chemotherapy-induced apoptosis. , 2009, Cancer research.

[20]  S. V. Muniandy,et al.  Modelling of chromatin morphologies in breast cancer cells undergoing apoptosis using generalized Cauchy field , 2008, Comput. Medical Imaging Graph..

[21]  Gabriele A. Losa,et al.  Nuclear patterns of human breast cancer cells during apoptosis: characterisation by fractal dimension and co-occurrence matrix statistics , 2005, Cell and Tissue Research.

[22]  V. Trajković,et al.  Novel platinum(IV) complexes induce rapid tumor cell death in vitro , 2005, International journal of cancer.

[23]  I. Amit,et al.  Comprehensive mapping of long range interactions reveals folding principles of the human genome , 2011 .

[24]  D. Xing,et al.  Inhibition of the JNK/Bim pathway by Hsp70 prevents Bax activation in UV‐induced apoptosis , 2010, FEBS letters.

[25]  Judith Sandbank,et al.  Lymphoma and Leukemia Cells Possess Fractal Dimensions That Correlate with Their Biological Features , 2008, Acta Haematologica.

[26]  B. Sobel,et al.  Morphological and cytochemical determination of cell death by apoptosis , 2007, Histochemistry and Cell Biology.

[27]  Herbert F Jelinek,et al.  Quantitative analysis of dendritic morphology of the α and δ retinal ganglion cells in the rat: a cell classification study. , 2009, Journal of theoretical biology.

[28]  B. Kaina,et al.  How DNA lesions are turned into powerful killing structures: insights from UV-induced apoptosis. , 2009, Mutation research.

[29]  M. A. Barracco,et al.  MORPHOLOGICAL AND CYTOCHEMICAL STUDIES OF THE , 1992 .

[30]  Alessandro Giuliani,et al.  Metabolism and cell shape in cancer: a fractal analysis. , 2011, The international journal of biochemistry & cell biology.

[31]  N. Shinomiya,et al.  Role of G1 phase in the UV-induced apoptosis of EL-4 mouse lymphoma cells , 1999, Apoptosis.