Extended Data Fig. 7: Ultrastructural characterization of cell–cell contacts between lining macrophages.
From: Locally renewing resident synovial macrophages provide a protective barrier for the joint
a, Representative CLSM of macrophages (tdTomato, red) within the synovial membrane of knee joints of Cx3cr1creERR26-tdTomato mice, visualizing the tight-junction protein ZO-1/TJP1 (white). Phalloidin, green; DAPI, blue. Scale bars, 5 µm. b, Transmission electron microscopy (TEM) images of the synovial membrane of a healthy knee joint showing tight junctions (tj), adherens junctions (aj), desmosomes (ds) and interdigitations connecting synovial lining macrophages. c, TEM micrograph showing synovial lining macrophages (red) constituting a dense physical barrier segregating the synovial fluid from sublining interstitial tissue containing synovial fibroblasts (cyan), endothelial cells (purple) embedded into the extracellular matrix (beige). d, TEM micrograph demonstrating synovial macrophages (red) forming the uppermost cell layer covering the layer of synovial fibroblasts (cyan). e, f, TEM micrographs of an inflamed synovial membrane two days after induction of K/BxN STA, showing the disruption of the covering synovial macrophage (red) layer and a reorientation of synovial macrophages (red) and synovial fibroblasts (cyan) directed to the synovial cavity. g, A TEM micrograph of an inflamed synovial membrane two days after the induction of STA reveals the emergence of macrophages containing large amounts of vacuoles filled with phagocytosed material. h, i, Recruited monocytes and granulocytes as well as free DNA of neutrophil extracellular traps (blue) within the synovial cavity of knee joints two days after the induction of STA. Filled arrowheads point at an exemplary monocyte engulfing free DNA.
