Meeting Abstract
115.7 Tuesday, Jan. 7 11:45 Morphology and distribution of interlacunar canals in elasmobranch mineralized cartilage SHRIVASTAVA, R; SEIDEL, R; REPP, F; KOLLMANSBERGER, P; ZASLANSKY, P; DEAN, MN*; VIT University, India; MPI-Potsdam, Germany; MPI-Potsdam, Germany; ETH-Zürich, Switzerland; Charité-Universitätsmedizin, Germany; MPI-Potsdam, Germany mason.dean@mpikg.mpg.de
Connectivity among tetrapod bone cells is integral to tissue health and mechanosensing: osteocytes connect via tendril-like cell processes, passing through the mineralized matrix in long, narrow channels (canaliculi). Similar networks are lacking in tetrapod mineralized cartilage, as chondrocytes die during matrix mineralization. In shark and ray skeletons, however, chondrocytes remain alive despite encasement in mineralized tissue, their lacunae connected via short interlacunar canals. We examine this cellular network by monochromatic, high-resolution absorption synchrotron microCT tomography of stingray tesserae (mineralized tiles that comprise the calcified layer of the skeleton), using quantitative 3D image analysis to characterize orientation, density and morphology of the lacunae-canal system. Tesserae are as cell-dense as the underlying unmineralized cartilage, with a range of morphologically and locationally distinct lacunar types suggesting cells with different functional roles. Most prominent are long uni-directional “lacunar strings” formed from consecutive lacunar spaces linked by interlacunar canals. These radiate outward from the center of each tessera, with non-radial (i.e. vertical or circumferential) canals nearly non-existent. Lacunar strings are concentrated between wedge-shaped zones of higher mineral density, resulting in alternating cell-rich and mineral-dense zones. Although we have seen no cell processes physically linking chondrocytes, the high cell density, rich interlacunar network and lack of cell death in this tissue suggests cell communication is important and points to a level of parallelism in early chondrocyte and osteocyte evolution.
