TITLE:
Mineral Fabrication and Golgi Apparatus Activity in Spirostomum ambiguum: A Primordial Paradigm of the Stressed Bone Cell?
AUTHORS:
Valerie Fallon, Philippa E. Garner, Jean E. Aaron
KEYWORDS:
Golgi-Directed Calcification, Mechanosensing Protozoan, Osteocyte Model, Tetracycline Fluorochrome for Bone Mineral, GFP Fluorochrome for Golgi Apparatus
JOURNAL NAME:
Journal of Biomedical Science and Engineering,
Vol.10 No.10,
October
27,
2017
ABSTRACT: The histological basis for acute osteocyte mechanosensitivity remains uncertain. A novel bone cell model of mechanotransduction and inorganic trafficking may be the powerful, silt-burrowing protozoan Spirostomum ambiguum which when being physically challenged fabricates within vesicles populations of bone-like calcium phosphate microspheres, about 1 μm in diameter. These not only attribute considerable compression-resilience but also resemble the Golgi-directed mineral assemblies we recently reported in osteocytes. Advantageously, calcification in the protozoan (confirmed by ultramicroscopy with EDX elemental microanalysis) enabled Golgi comparison under overt, natural phases of both high (i.e. silt-tunnelling) and low (i.e free-swimming) stress. Established hard-tissue microscopy techniques previously positive in bone cells included quantitative fluorescent tetracycline labelling for bone salt together with the same metazoan Golgi body marker (Green Fluorescent Protein-tagged mannosidase II construct). Organellar modulation was monitored by transfection of live organisms in situ (some post-stained with red nuclear fluorochrome TOPRO-3). Results showed that GFP-tagged Golgi fluorescence increased from swimmers (mean 74.5 ± SD 6.7 AU) to burrowers (mean 104.6 ± SD 2.7; p