Abstract-The structural characteristics of a healthy tendon are related to the anisotropic speckle patterns observed in ultrasonic images. This speckle orientation is disrupted upon damage to the tendon structure as observed in patients with tendinopathy. Quantification of the structural appearance of tendon shows promise in creating a tool for diagnosing, prognosing, or measuring changes in tendon organization over time. The current work describes a first step taken towards this goal-classification of Achilles tendon images into tendinopathy and control categories. Eight spatial frequency parameters were extracted from regions of interest on tendon images, filtered and classified using linear discriminant analysis. Resulting algorithms had better than 80% accuracy in categorizing tendon image kernels as tendinopathy or control. Tendon images categorized wrongly provided for an interesting clinical association between incorrect classification of tendinopathy kernels as control and the symptom and clinical time history based inclusion criteria. To assess intersession reliability of image acquisition, the first 10 subjects were imaged twice during separate sessions. Test-retest of repeated measures was excellent ( = 0 996 ICC (2 1) = 0 73 with one outlier) indicating a general consistency in imaging techniques.

Objective-Fluid shear stress plays a role in angiogenesis. Laminar shear stress (LS) promotes endothelial cell (EC) quiescence, whereas oscillatory shear stress (OS) promotes EC turnover and dysfunction, which could lead to pathological angiogenesis. We hypothesized that LS inhibits EC migration and tubule formation, 2 functions important in angiogenesis, by inhibiting the secretion of proangiogenic factors. Methods and Results-Human umbilical vein ECs (HUVECs), human microvascular ECs (HMECs), or bovine aortic ECs (BAECs) were subjected to either LS (15 dyn/cm 2 ) or OS (Ϯ5 dyn/cm 2 ) for 24 hours and used in Matrigel tubule formation or scratch migration assays. Exposure of HUVECs, HMECs, but not BAECs, to LS inhibited tubule formation compared with OS. LS also inhibited migration of HUVECs and BAECs compared with OS. Angiopoietin-2 (Ang2), a known angiogenic protein, was found to be downregulated by LS both in cultured ECs and mouse aortas. Using Ang2 siRNA, Ang2 knockdown blocked OS-mediated migration and tubule formation and the LS-inhibited tubule formation was partially rescued by recombinant Ang2. Conclusions-Our data suggests that Ang2 produced by OS in ECs plays a critical role in migration and tubule formation, and may play an important role in diseases with disturbed flow and angiogenesis. (Arterioscler Thromb Vasc Biol. 2007;27:2150-2156.)Key Words: shear stress Ⅲ endothelial cells Ⅲ angiogenesis Ⅲ angiopoietin-2 F luid shear stress, the dragging force created by flow through blood vessels, is sensed by the endothelium and plays an important role in normal physiological responses as well as disease pathologies. In particular, shear stress is thought to play a role in angiogenesis, or the formation of new blood vessels from preexisting blood vessels. 1-3 At the cellular and molecular level, unidirectional laminar shear stress (LS) is thought to promote endothelial cell (EC) quiescence; laminar sheared ECs are antiproliferative, antiapoptotic, and antithrombotic. 4 However, oscillatory shear stress (OS), a type of disturbed shear stress implicated in diseases such as atherosclerosis, is thought to promote EC dysfunction; oscillatory sheared ECs are proproliferative, promigratory, prothrombotic, and secrete growth factors that stimulate smooth muscle cell proliferation and migration. 4 The secretion of growth factors from dysfunctional ECs exposed to OS could also play a role in blood vessel remodeling and angiogenesis.There are several diseases associated with both angiogenesis and disturbed flow, such as atherosclerosis, aortic valve calcification, and arterial occlusion. In atherosclerosis, atherosclerotic plaques preferentially occur in areas of the arterial system exposed to disturbed flow and angiogenesis in the plaque is thought to promote the progression of atherosclerosis. 5,6 Disturbed flow is found in the aortic valve sinus and angiogenesis in the valve leaflet is associated with calcification. 7,8 In arterial occlusion, disturbed flow is found in the postocclusive site and angiogenesis is...