Background-Arteriogenesis serves as an efficient mechanism for flow restoration after arterial occlusion. This process is associated with inflammatory mediators such as tumor necrosis factor-␣ (TNF-␣), although their role in arteriogenesis remains unclear. We hypothesized that arteriogenesis is reduced in mice lacking functional TNF-␣ or p55 receptor. To test this hypothesis, we developed a novel microsphere-based murine model of hindlimb perfusion measurement. Methods and Results-Unilateral femoral arteries of nude (nϭ9), TNF-␣ Ϫ/Ϫ (nϭ9), TNF-␣ receptor p55 Ϫ/Ϫ (nϭ8), and p75 Ϫ/Ϫ (nϭ8) mice as well as their appropriate genetic background controls were occluded. The nude mice underwent laser Doppler hindlimb flux measurements preoperatively, postoperatively, and after 7 days. Seven days after ligation, all animals underwent tissue perfusion determinations using fluorescent microspheres. Laser Doppler findings confirmed acute decrease in flux with falsely normal values after 1 week. Microsphere results from control mice showed perfusion restoration to values Ϸ50% of normal within 7 days. Key Words: collateral circulation Ⅲ inflammation Ⅲ microspheres Ⅲ blood flow Ⅲ remodeling A rteriogenesis (remodeling of preexistent arteriolar collateral networks into large collateral conductance arteries) serves as the most efficient mechanism to restore flow after arterial occlusion. 1 Perivascular inflammation and monocyte/macrophage accumulation accompany this process. 2 Tumor necrosis factor-␣ (TNF-␣) is an important proximal mediator of inflammation. Most prototypical inflammatory TNF-␣ signaling occurs by TNF-␣ binding to its p55 receptor. 3 Previous studies have associated TNF-␣ with arteriogenesis. 2 We hypothesized that arteriogenesis proceeds by way of TNF-␣ signaling via the p55 receptor. Specifically, we hypothesized that arteriogenesis is reduced in mice lacking functional TNF-␣ or p55 receptor. We developed and validated a novel model of perfusion measurement in the mouse hindlimb to test this hypothesis. Methods Animal ModelThis study conforms to the Guide for the Care and Use of Laboratory Animals (NIH publication No. 85-23, revised 1996). Nine athymic nude, 8 TNF-␣ receptor p55Ϫ/Ϫ3,4 (N5 backcross onto C57BL/6J, maintained by brother/sister matings) and 9 TNF-␣ Ϫ/Ϫ5(on B6x129 F1 background, maintained by sister/brother matings) (both provided by Dr Carl K. Edwards III, Amgen, Inc, Thousand Oaks, Calif), 8 TNF-␣ receptor p75 Ϫ/Ϫ , 7 B6x129, and 9 C57BL/6J (Jackson Laboratory, Bar Harbor, Maine) mice underwent unilateral femoral artery ligation. The right femoral artery was ligated immediately distal to the inguinal ligament. Because collateral arteries develop from preexisting arteriolar connections spanning from the profunda femoris and circumflexa femoris to the genualis and saphena parva arteries, 4 the femoral artery was not excised to leave these vessels intact. In rabbits, this technique does not lead to ischemia in the region of collateral artery growth or distal to the site of ligation. 5 Wounds were cl...

Accelerated intimal hyperplasia in response to altered flow environment is critical to the process of vein bypass graft failure. Lack of a reproducible animal model for dissecting the mechanisms of vein graft (VG) remodeling has limited progress toward solving this clinically significant problem. Combining a cuffed anastomotic technique with other surgical manipulations, we developed a well-defined, more robust method for studying hemodynamic factors in VG arterialization. VG with fistula placement, complete occlusion, or partial distal branch ligation (DBL) was performed in the carotid artery of 56 rabbits. Extensive hemodynamic and physiological analyses were performed to define the hemodynamic forces and histological adaptations of the wall at 1-28 days. Anastomotic time averaged 12 min, with 100% patency of bilateral grafts and unilateral grafts plus no adjunct or delayed fistula. Bilateral VG-DBL resulted in an immediate disparity in wall shear (0.8 +/- 0.1 vs. 12.4 +/- 1.1 dyn/cm2, ligated vs. contralateral graft). Grafts exposed to low shear stress responded primarily through enhanced intimal thickening (231 +/- 35 vs. 36 +/- 18 microm, low vs. high shear). High-shear-stress grafts adapted through enhanced outward remodeling, with a 24% increase in lumen diameter at 28 days (3.0 +/- 0.1 vs. 3.7 +/- 0.2 mm, low vs. high shear). We have taken advantage of the cuffed anastomotic technique and combined it with a bilateral VG-DBL model to dissect the impact of hemodynamic forces on VG arterialization. This novel model offers a robust, clinically relevant, statistically powerful small animal model for evaluation of high- and low-shear-regulated VG remodeling.