Structural changes in blood platelet activation visualized by scanning transmission electron tomography

Authors

• RD Leapman
• JD Hoyne
• GN Calco
• BC Kuo
• MA Aronova
• Q He
• G Zhang
• ID Pokrovskaya
• JA Kamykowski
• AA Prince

Abstract

Electron tomography in the scanning transmission electron microscope (STEM) enables visualization of 3D ultrastructure in entire small eukaryotic cells. This is made possible because, unlike the conventional transmission electron microscope (TEM), the STEM has no imaging lenses after the specimen, thus avoiding degradation of spatial resolution due to chromatic aberration effects. Furthermore, we have shown that by restricting the probe convergence angle in the acquisition of STEM tilt-series images, it is feasible to achieve a spatial resolution of a few nanometers in the resulting tomograms. We have applied STEM tomography to help elucidate the 3D ultrastructure of human blood platelets, which play an essential role in hemostasis by aggregating to seal leaks at sites of vascular injury. Platelet malfunction is implicated in the pathology of atherosclerosis and other diseases. Of particular interest are the morphological changes that occur in alpha-granules, which contain important proteins released on activation. Tomographic reconstructions revealed changes in ultrastructure that occur when platelets are activated, including release of alpha granules through channels connecting to the plasma membrane.

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