Platelet secretion during clot retraction

Abstract

The precise route serving as the pathway for extrusion of products contained in platelet storage organelles following cell activation has been controversial for many years. Some workers believe that the granules and dense bodies fuse together to form secretion vacuoles that move to the exposed cell surface, fuse with it and extrude contained products to the outside. Others suggest that the organelles fuse with channels of the open canalicular system (OCS) and deposit their contents which are subsequently secreted to the exterior. The controversy has been difficult to resolve because nearly all workers have used platelets in suspension to arrive at diverse conclusions. The present study has used ethylenediamine tetracetic acid (EDTA)-treated platelets and isometric clot retraction as a model system, and either polylysine or tannic acid to define the pathway used for secretion. Results indicate that secretion takes place in EDTA platelets under isometric tension by fusion of granules to OCS channels and passage of products through these conduits to the cell exterior. There is no evidence to suggest the organelles form secretion vacuoles or extrude their products by fusion with the inside of the exposed surface membrane.

Ultrastructure of hybrid chitosan–glycerol phosphate blood clots by environmental scanning electron microscopy

“…A specific chitosan-GP solution (called BST-CarGel TM ) can be mixed with autologous blood to form viscous chitosan-GP/blood mixtures that solidifies in about 10 min, in part due to the thrombogenicity of chitosan . A whole blood clot quickly looses a great extent of its volume via clot retraction; a platelet-mediated contractile process that exudes serum (Cohen et al, 1982;Morgenstern et al, 1990;White, 2000). In contrast, chitosan-GP/blood clots do not retract, but rather maintain their volume after coagulation .…”

Platelet membrane variations and their effects on δ-granule secretion kinetics and aggregation spreading among different species

“…This structure has been shown to help localize granules within the cell for easier export of their contents and is involved in the activation-initiated change in platelet morphology widely known as spreading. [6–9]…”

Chitosan–glycerol phosphate/blood implants increase cell recruitment, transient vascularization and subchondral bone remodeling in drilled cartilage defects

“…Since marrow-stimulation alone does not reproducibly lead to the formation of hyaline repair cartilage, it may be concluded that these procedures do not generate an optimal setting for effective cartilage repair. One potential limitation of these procedures is that the resident blood clot resulting from marrow-stimulation retracts to a small percentage of its original volume via a platelet-mediated process 8,9 and may be subsequently removed by fluid irrigation. Stabilizing this critical blood clot in the cartilage lesion could improve cartilage repair by providing a physical and chemical environment suitable for migration of progenitor cells and synthesis of repair tissue.…”