Extracellular Vimentin/VWF (von Willebrand Factor) Interaction Contributes to VWF String Formation and Stroke Pathology.

Background and Purpose- VWF (von Willebrand factor) strings mediate spontaneous platelet adhesion in the vascular lumen, which may lead to microthrombi formation and contribute to stroke pathology. However, the mechanism of VWF string attachment at the endothelial surface is unknown. We tested the novel hypothesis that VWF strings are tethered to the endothelial surface through an interaction between extracellular vimentin and the A2 domain of VWF. We further explored the translational value of blocking this interaction in a model of ischemic stroke. Methods- Human endothelial cells and pressurized cerebral arteries were stimulated with histamine to elicit VWF string formation. Recombinant proteins and antibodies were used to block VWF string formation. Mice underwent transient middle cerebral artery occlusion with reperfusion. Just before recanalization, mice were given either vehicle or A2 protein (recombinant VWF A2 domain) to disrupt the vimentin/VWF interaction. Laser speckle contrast imaging was used to monitor cortical perfusion. Results- Pressurized cerebral arteries produced VWF strings following histamine stimulation, which were reduced in arteries from Vim KO (vimentin knockout) mice. VWF string formation was significantly reduced in endothelial cells incubated with A2 protein or antivimentin antibodies. Lastly, A2 protein treatment significantly improved cortical reperfusion after middle cerebral artery occlusion. Conclusions- We provide the first direct evidence of cerebral VWF strings and demonstrate that extracellular vimentin significantly contributes to VWF string formation via A2 domain binding. Lastly, we show that pharmacologically targeting the vimentin/VWF interaction through the A2 domain can promote improved reperfusion after ischemic stroke. Together, these studies demonstrate the critical role of VWF strings in stroke pathology and offer new therapeutic targets for treatment of ischemic stroke.

Risk factors for early symptomatic femoroacetabular impingement following in situ fixation of slipped capital femoral epiphysis.

In situ fixation of slipped capital femoral epiphysis (SCFE) results in residual deformity that can cause femoroacetabular impingement (FAI). It is unknown what factors could help differentiate patients who are more likely to become symptomatic. We performed a retrospective review of 55 hips treated with in situ pinning for SCFE and subsequent secondary deformity correction procedure for symptomatic FAI and compared them to 39 asymptomatic hips with SCFE deformity using multivariable analysis. Case patients were slightly older than controls (12.6 vs 11.3 years, p = 0.0002) but had similar BMI. The mean epiphyseal-diaphyseal angle was 56° in cases versus 44° in controls (p = 0.0019). Cases were significantly more likely to have obligate external rotation with hip flexion, external foot progression, flexion <90°, antalgic limp, and Trendelenburg lurch. On radiographs, most cases had a head-neck offset ≤0 mm, a distinct metaphyseal corner prominence, acetabular retroversion, and an alpha angle ≥60°. Most controls also had head-neck offset ≤0 mm. Pre-pinning, older age (OR = 1.98 per year, p = 0.0016) and initial epiphyseal-diaphyseal angle (OR = 1.04 per degree, p = 0.018) significantly increased the odds of having symptomatic FAI. Post-pinning, external foot progression increased the odds of symptomatic FAI by 10.48 (p = 0.017), and an alpha angle ≥60° resulted in 11.4 times higher odds of symptomatic FAI (p = 0.011). The linear correlation between epiphyseal-diaphyseal and alpha angle was poor (r = 0.28). Older age and initial epiphyseal-diaphyseal pre-pinning mildly increased the odds of eventual symptomatic FAI. This information can help the surgeon to predict which patients may develop symptomatic FAI.

A low-cost mouse cage warming system provides improved intra-ischemic and post-ischemic body temperature control - Application for reducing variability in experimental stroke studies.

BACKGROUND: Brain temperature is a strong determinant of ischemic stroke injury. For this reason, tight management of brain or body temperature (Tcore) in experimental rodent stroke models is recommended to improve the rigor and reproducibility of outcomes. However, methods for managing Tcore during and after stroke vary widely in approach and effectiveness. NEW METHOD: We developed a low-cost warm ambient air cage (WAAC) system to provide improved temperature control during the intra-ischemic and post-ischemic recovery periods. The system is incorporated into standard holding cages for maintaining Tcore during the intra-ischemic period as well as for several hours into the recovery period. RESULTS AND COMPARISON WITH EXISTING METHODS: We compared the WAAC system with a commonly used heat support method, consisting of a cage on a heating pad. Both heat support systems were evaluated for the middle cerebral artery occlusion (MCAo) stroke model in mice. The WAAC system provided improved temperature control (more normothermic Tcore and less Tcore variation) during the intra- ischemic period (60 min) and post-ischemic period (3 h). Mean infarct volume was not statistically different by heat support system, however, standard deviation was 54 % lower in the WAAC system group. CONCLUSIONS: Mice and other small rodents are highly vulnerable to heat loss during and after the MCAo procedure. The WAAC system provides more precise and controlled Tcore maintenance compared with frequently used induction heating methods in mice undergoing the MCAo stroke model. The improved temperature control should enhance experimental rigor and reduce the number of experimental animals needed.