A novel mouse-driven ex vivo flow chamber for the study of leukocyte and platelet function

Ali Hafezi-Moghadam, Kennard L. Thomas, Christian Cornelssen
2004 American Journal of Physiology - Cell Physiology  
Hafezi-Moghadam, Ali, Kennard L. Thomas, and Christian Cornelssen. A novel mouse-driven ex vivo flow chamber for the study of leukocyte and platelet function. Am J Physiol Cell Physiol .-Various in vitro and in vivo techniques exist for study of the microcirculation. Whereas in vivo systems impress with their physiological fidelity, in vitro systems excel in the amount of reduction that can be achieved. Here we introduce the autoperfused ex vivo flow chamber designed to study murine leukocytes
more » ... murine leukocytes and platelets under well-defined hemodynamic conditions. In our model, the murine heart continuously drives the blood flow through the chamber, providing a wide range of physiological shear rates. We used a balance of force approach to quantify the prevailing forces at the chamber walls. Numerical simulations show the flow characteristics in the chamber based on a shear-thinning fluid model. We demonstrate specific rolling of wild-type leukocytes on immobilized P-selectin, abolished by a blocking MAb. When uncoated, the surfaces having a constant shear rate supported individual platelet rolling, whereas on areas showing a rapid drop in shear platelets interacted in previously unreported grapelike conglomerates, suggesting an influence of shear rate on the type of platelet interaction. In summary, the ex vivo chamber amounts to an external vessel connecting the arterial and venous systems of a live mouse. This method combines the strengths of existing in vivo and in vitro systems in the study of leukocyte and platelet function. autoperfused flow chamber; intravital microscopy; inflammation; thrombus formation PROPER IMMUNE FUNCTION REQUIRES recruitment of leukocytes to various sites of an organism (56). Leukocyte recruitment is a complex process, orchestrated by various signals, chemicals, and specialized molecules (i.e., adhesion molecules) (11, 57). Analogously, the growth of a thrombus requires the recruitment of platelets and plasma components at sites of vascular injury (22, 27, 45) . To understand the details of these events cell interactions are studied in vivo and in vitro under flow conditions (12, 41). Previously we introduced (29) the local catheter technique, which expands the capabilities of intravital microscopy of the mouse cremaster muscle by allowing the upstream insertion of reagents directly into the microcirculation. However, despite the advancement of this technique, it shares the limitations of most in vivo models, which derive from having all blood components and the full complexity of the vascular wall. Therefore, we discuss here the existing in vivo and in vitro models and the need for an ex vivo model that would bridge the Prevailing Shear Forces To have a proficient model, quantitative knowledge of the shear forces is necessary. Shear stresses in a system manifest themselves in two ways: they cause pressure loss and are related to the shear rates of the flow, which, in turn, are kinematically determined by the Fig. 5. Non-Newtonian flow characteristics. II. Simulated steady flow of a shear-thinning fluid with viscosity parameters o ϭ 73.8 cP, ϱ ϭ 5 cP, ⌳ ϭ 13.42 s through a rectangular cross section of size a ϫ b ϭ 0.4 mm ϫ 0.04 mm, from the same series as used in Fig. 4. A: magnitude of the shear rate: at the boundaries it coincides with the wall shear rate. B: magnitude of the shear stress: at the boundaries it coincides with the wall shear stress. Top: Ϫ⌬p/⌬x ϭ 20 dyn/cm 3 . Middle: Ϫ⌬p/⌬x ϭ 200 dyn/cm 3 . Bottom: Ϫ⌬p/⌬x ϭ 10,000 dyn/cm 3 . C884 THE AUTOPERFUSED MURINE FLOW CHAMBER
doi:10.1152/ajpcell.00500.2003 pmid:14668262 fatcat:b2s7w7c7infipcx5owm6mezole