title: An automated method to quantify microglia morphology and application to monitor activation state longitudinally in vivo.
abstract: Microglia are specialized immune cells of the brain. Upon insult, microglia initiate a cascade of cellular responses including a characteristic change in cell morphology. To study the dynamics of microglia immune response in situ, we developed an automated image analysis method that enables the quantitative assessment of microglia activation state within tissue based solely on cell morphology. Per cell morphometric analysis of fluorescently labeled microglia is achieved through local iterative threshold segmentation, which reduces errors caused by signal-to-noise variation across large volumes. We demonstrate, utilizing systemic application of lipopolysaccharide as a model of immune challenge, that several morphological parameters, including cell perimeter length, cell roundness and soma size, quantitatively distinguish resting versus activated populations of microglia within tissue comparable to traditional immunohistochemistry methods. Furthermore, we provide proof-of-concept data that monitoring soma size enables the longitudinal assessment of microglia activation in the mouse neocortex imaged via 2-photon in vivo microscopy. The ability to quantify microglia activation automatically by shape alone allows unbiased and rapid analysis of both fixed and in vivo central nervous system tissue.
authors.affiliation: Department of Biomedical Imaging and Department of Neuroscience, Genentech, Inc., South San Francisco, California, USA. kozlowski.cleopatra@gene.com
authors.forename: Cleopatra
authors.initials: C
authors.lastname: Kozlowski
authors.forename: Robby M
authors.initials: RM
authors.lastname: Weimer
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D000073883:CX3C Chemokine Receptor 1; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002490:Central Nervous System / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry / Q000379:methods*; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008840:Microfilament Proteins / Q000378:metabolism; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018613:Microscopy, Confocal / Q000379:methods*; D018121:Receptors, Cytokine / Q000235:genetics / Q000378:metabolism; D015728:Receptors, HIV / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000073883:CX3C Chemokine Receptor 1; D002135:Calcium-Binding Proteins; D049452:Green Fluorescent Proteins; D008070:Lipopolysaccharides; D008840:Microfilament Proteins; D018121:Receptors, Cytokine; D015728:Receptors, HIV; C491049:Aif1 protein, mouse; C067980:CD68 antigen, human; D000097382:CD68 Molecule