Stem cell autotomy and niche interaction in different systems

Figure 10 Thrombopoiesis (platelet formation) in mammal bone marrow (schematized). Platelets are produced by a most spectacular form of cell autotomy performed by the megakaryocyte (MK). Maturation and fragmentation of the megakaryocyte is orchestrated by the vascular niche which consists of the endothelial cells (EC) of sinusoids and the extracellular matrix (MA) of the endothelium. The megakaryocyte is located at the outer surface of the sinusoid epithelium and sends pseudopods through the pores of the endothelium into the lumen of the sinusoids (arrows). The pseudopods branch and form proplatelets (PPL). These are released into the sinusoids (rPPL) followed by the release of platelets (PL). Nu, polyploidy nucleus of the megakaryocyte (Adapted from Patel et al[115]).