Clinical relevance of microparticles from platelets and megakaryocytes

Abstract

Purpose of review: Platelet microparticles were identified more than 40 years ago and are the most abundant circulating microparticle subtype. Yet fundamental questions about their formation and role in human disease are just beginning to be understood at the cellular and molecular level. This review will address mechanisms of platelet microparticle generation and evaluate our current understanding of their clinical relevance.

Recent findings: New evidence indicates that the majority of CD41 microparticles circulating in healthy individuals derive directly from megakaryocytes. CD41 microparticles also form from activated platelets upon loss of cytoskeleton-membrane adhesion, which occurs in a multitude of disease states characterized by elevated platelet microparticle levels. More recent studies have demonstrated that platelet microparticles function as a transport and delivery system for bioactive molecules, participating in hemostasis and thrombosis, inflammation, malignancy infection transfer, angiogenesis, and immunity. The mechanism of platelet microparticle participation in specific disease entities such as rheumatoid arthritis has been elucidated.

Summary: Continued research into how platelet microparticles are generated and function as a transcellular delivery system will advance our basic understanding of microparticle physiology and may enable new strategies for treatment of select disease entities.

Figure 1. Microparticle generation from mouse megakaryocytes

Thin-section electron micrograph showing the surface of a mouse megakaryocyte. Multiple, small projections were observed emanating from the surface. Blebs at various stages are visualized along the plasma membrane. Scale bar, 500 microns.