Incidence of surgical rib fixation at chest wall injury society collaborative centers and a guide for expected number of cases (CWIS-CC1).

PURPOSE: Surgical stabilization of rib fractures (SSRF) improves outcomes in certain patient populations. The Chest Wall Injury Society (CWIS) began a new initiative to recognize centers who epitomize their mission as CWIS Collaborative Centers (CWIS-CC). We sought to describe incidence and epidemiology of SSRF at our institutions. METHODS: A retrospective registry evaluation of all patients (age > 15 years) treated at international trauma centers from 1/1/20 to 7/30/2021 was performed. Variables included: age, gender, mechanism of injury, injury severity score, abbreviated injury severity score (AIS), emergency department disposition, length of stay, presence of rib/sternal fractures, and surgical stabilization of rib/sternal fractures. Classification and regression tree analysis (CART) was used for analysis. RESULTS: Data were collected from 9 centers, 26,084 patient encounters. Rib fractures were present in 24% (n = 6294). Overall, 2% of all patients underwent SSRF and 8% of patients with rib fractures underwent SSRF. CART analysis of SSRF by AIS-Chest demonstrated a difference in management by age group. AIS-Chest 3 had an SSRF rate of 3.7, 7.3, and 12.9% based on the age ranges (16-19; 80-110), (20-49; 70-79), and (50-69), respectively (p = 0.003). AIS-Chest > 3 demonstrated an SSRF rate of 9.6, 23.3, and 39.3% for age ranges (16-39; 90-99), (40-49; 80-89), and (50-79), respectively (p = 0.001). CONCLUSION: Anticipated rate of SSRF can be calculated based on number of rib fractures, AIS-Chest, and age. The disproportionate rate of SSRF in patients age 50-69 with AIS-Chest 3 and age 50-79 with AIS-Chest > 3 should be further investigated, as lower frequency of SSRF in the other age ranges may lead to care inequalities.

Directed cell migration towards softer environments.

How cells sense tissue stiffness to guide cell migration is a fundamental question in development, fibrosis and cancer. Although durotaxis-cell migration towards increasing substrate stiffness-is well established, it remains unknown whether individual cells can migrate towards softer environments. Here, using microfabricated stiffness gradients, we describe the directed migration of U-251MG glioma cells towards less stiff regions. This 'negative durotaxis' does not coincide with changes in canonical mechanosensitive signalling or actomyosin contractility. Instead, as predicted by the motor-clutch-based model, migration occurs towards areas of 'optimal stiffness', where cells can generate maximal traction. In agreement with this model, negative durotaxis is selectively disrupted and even reversed by the partial inhibition of actomyosin contractility. Conversely, positive durotaxis can be switched to negative by lowering the optimal stiffness by the downregulation of talin-a key clutch component. Our results identify the molecular mechanism driving context-dependent positive or negative durotaxis, determined by a cell's contractile and adhesive machinery.

Specificities of exosome versus small ectosome secretion revealed by live intracellular tracking of CD63 and CD9.

Despite their roles in intercellular communications, the different populations of extracellular vesicles (EVs) and their secretion mechanisms are not fully characterized: how and to what extent EVs form as intraluminal vesicles of endocytic compartments (exosomes), or at the plasma membrane (PM) (ectosomes) remains unclear. Here we follow intracellular trafficking of the EV markers CD9 and CD63 from the endoplasmic reticulum to their residency compartment, respectively PM and late endosomes. We observe transient co-localization at both places, before they finally segregate. CD9 and a mutant CD63 stabilized at the PM are more abundantly released in EVs than CD63. Thus, in HeLa cells, ectosomes are more prominent than exosomes. By comparative proteomic analysis and differential response to neutralization of endosomal pH, we identify a few surface proteins likely specific of either exosomes (LAMP1) or ectosomes (BSG, SLC3A2). Our work sets the path for molecular and functional discrimination of exosomes and small ectosomes in any cell type.