Dynamic Visualization of Thrombopoiesis Within Bone Marrow

Abstract

Platelets are generated from megakaryocytes (MKs) in mammalian bone marrow (BM) by mechanisms that remain poorly understood. Here we describe the use of multiphoton intravital microscopy in intact BM to visualize platelet generation in mice. MKs were observed as sessile cells that extended dynamic proplatelet-like protrusions into microvessels. These intravascular extensions appeared to be sheared from their transendothelial stems by flowing blood, resulting in the appearance of proplatelets in peripheral blood. In vitro, proplatelet production from differentiating MKs was enhanced by fluid shear. These results confirm the concept of proplatelet formation in vivo and are consistent with the possibility that blood flow-induced hydrodynamic shear stress is a biophysical determinant of thrombopoiesis.

Platelet bioreactor-on-a-chip

“…[11][12][13][14][15] Nearly 100% of human adult MKs must produce ;10 3 PLTs each to account for circulating PLT counts. 16 Although functional human PLTs were first grown in vitro in 1995, 17 to date only ;10% of human MKs initiate proPLT production in culture.…”

L’intégrine αIIbβ3

“…La mégacaryopoïèse, qui constitue une des voies de l'hématopoïèse, est le processus physiologique qui conduit à la libération des plaquettes dans le sang à partir des mégacaryocytes (MK) de la moelle osseuse [1]. Elle débute par la prolifération d'une cellule souche hématopoïétique multipotente qui va progressivement se différencier en progéniteurs mégacaryocytaires (Figure 1).…”

3D and 4D imaging of immune cells in vitro and in vivo

“…Two approaches are particularly useful to obtain this task. (1) By injection of Xuorescently labeled high-molecular weight dextran into the blood stream, blood Xow can be very nicely visualized (Junt et al 2007b). If a small organic dye such as Rhodamine 6G is used directly, it is possible to dye-label all cellular components in the blood stream as well as the peripheral cells surrounding the blood vessels, due to leakage of the dye into the embedding tissues (Niesner et al 2007).…”