Unique secretory dynamics of tissue plasminogen activator and its modulation by plasminogen activator inhibitor-1 in vascular endothelial cells

We analyzed the secretory dynamics of tissue plasminogen activator (tPA) in EA.hy926 cells, an established vascular endothelial cell (VEC) line producing GFP-tagged tPA, using total internal reflection fluorescence (TIR-F) microscopy. tPA-GFP was detected in small granules in EA.hy926 cells, the distribution of which was indistinguishable from intrinsically expressed tPA. Its secretory dynamics were unique, with prolonged (>5min.) retention of the tPA-GFP on the cell surface, appearing as fluorescent spots in two-thirds of the exocytosis events. The rapid disappearance (mostly by 250ms) of a domain-deletion mutant of tPA-GFP possessing only the signal peptide and catalytic domain indicates that the amino-terminal heavy chain of tPA-GFP is essential for binding to the membrane surface. The addition of PAI-1 dose-dependently facilitated the dissociation of membrane-retained tPA and increased the amounts of tPA-PAI-1 high molecular weight complexes in the medium. Accordingly, suppression of PAI-1 synthesis in EA.hy926 cells by siRNA prolonged the dissociation of tPA-GFP, whereas a catalytically inactive mutant of tPA-GFP not forming complexes with PAI-1 remained on the membrane even after PAI-1 treatment. Our results provide new insights into the relationship between exocytosed, membrane-retained tPA and PAI-1, which would modulate cell surface-associated fibrinolytic potential

Accuracy of Acetabular Cup Implantation, as a Function of Body Mass Index and Soft-tissue Thickness, with a Mechanical Intraoperative Support Device: A Retrospective Observational Study

HipCOMPASS, a mechanical intraoperative support device used in total hip arthroplasty (THA), improves the cup-alignment accuracy. However, the alignment accuracy achieved by HipCOMPASS has not been specifically examined in obese patients. In this study, we retrospectively evaluated the relation between alignment accuracy and several obesity-related parameters in 448 consecutive patients who underwent primary THA using HipCOMPASS. We used computed tomography (CT) to measure the preoperative soft-tissue thickness of the anterior-superior iliac spine (ASIS) and pubic symphysis and the differences between preoperative and postoperative cup angle based on the cup-alignment error. We found significant correlations between the absolute value of radiographic anteversion difference and body mass index (r = 0.205), ASIS thickness (r = 0.419), and pubic symphysis thickness (r = 0.434). The absolute value of radiographic inclination difference was significantly correlated with ASIS (r = 0.257) and pubic symphysis thickness (r = 0.202). The receiver operating characteristic curve showed a pubic symphysis thickness of 37.2 mm for a ≥ 5° implantation error in both radiographic inclination and anteversion simultaneously. The cup-alignment error for HipCOMPASS was large in patients whose pubic symphysis thickness was ≥ 37.2 mm on preoperative CT. Our results indicate that methods other than HipCOMPASS, including computed tomography-based navigation systems, might be preferable in obese patients

Multidisciplinary Approach to Reduce Postoperative Complications and Improve the Activity of Patients with Hip Fracture: A 24-month Follow-up Survey

Multidisciplinary approaches such as fracture liaison services (FLS) have been introduced in some countries to reduce medical complications and secondary fractures in patients with fragility hip fracture. We aimed to investigate outcomes in patients with fragility hip fracture following the introduction of FLS. Patients > 50 years old who experienced fragility hip fractures between January 1, 2015 and December 31, 2017 were enrolled, and divided into a control group (without FLS; 94 patients) and FLS group (373 patients). We found that the time from injury to surgery decreased significantly from 2.42 to 1.83 days (p = 0.003), the proportion of patients who underwent surgery within 36 h of injury increased significantly (p = 0.014), and the number of cases with complications after admission decreased significantly (p = 0.004) in the FLS group. Patients with a Barthel index ≥ 80 were more common in the FLS than the control group at 6 , 12, and 24 months following injury (p = 0.046 , 0.018, and 0.048, respectively). Multiple logistic regression analysis revealed the factors associated with postoperative complications and death within 12 or 24 months after injury. Our results indicate that FLS contributed to earlier recovery, rehabilitation following surgery and rehabilitation of medical complications following admission; improved patient activity; and decreased secondary hip fractures