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Optimal surgical treatment of unstable sternal fractures is controversial. Wiring provides suboptimal fixation and adaptations of existing non-sternum specific plating systems may be dangerous when rapid sternal reentry is required. We present our experience with the sternal specific fixation system, SternaLock (Biomet Microfixation Inc, Jacksonville, FL), in the acute treatment of transverse sternal body fractures in 2 patients who sustained significant blunt anterior chest wall trauma. SternaLock provides the rigid sternal fixation necessary for reliable fracture healing while offering advantages over other systems with regards to ease of use and safety. [ABSTRACT FROM AUTHOR]

Summary: The first hematopoietic stem cells (HSCs) that engraft irradiated adult mice arise in the aorta-gonad-mesonephros (AGM) on embryonic day 11.5 (E11.5). However, at this stage, there is a discrepancy between the apparent frequency of HSCs depicted with imaging and their rarity when measured with limiting dilution transplant. We have attempted to reconcile this difference using neonatal recipients, which are more permissive for embryonic HSC engraftment. We found that embryonic HSCs from E9.5 and E10.5 preferentially engrafted neonates, whereas developmentally mature, definitive HSCs from E14.5 fetal liver or adult bone marrow (BM) more robustly engrafted adults. Neonatal engraftment was enhanced after treating adult BM-derived HSCs with interferon. Adult BM-derived HSCs preferentially homed to the liver in neonatal mice yet showed balanced homing to the liver and spleen in adults. These findings emphasize the functional differences between nascent and mature definitive HSCs. [Copyright &y& Elsevier]

Hematopoietic stem and progenitor cells (HSPCs), first specified from hemogenic endothelium (HE) in the ventral dorsal aorta (VDA), support lifelong hematopoiesis. Their de novo production promises significant therapeutic value; however, current in vitro approaches cannot efficiently generate multipotent long-lived HSPCs. Presuming this reflects a lack of extrinsic cues normally impacting the VDA, we devised a human dorsal aorta-on-a-chip platform that identified Yes-activated protein (YAP) as a cyclic stretch-induced regulator of HSPC formation. In the zebrafish VDA, inducible Yap overexpression significantly increased runx1 expression in vivo and the number of CD41+ HSPCs downstream of HE specification. Endogenous Yap activation by lats1/2 knockdown or Rho-GTPase stimulation mimicked Yap overexpression and induced HSPCs in embryos lacking blood flow. Notably, in static human induced pluripotent stem cell (iPSC)-derived HE culture, compound-mediated YAP activation enhanced RUNX1 levels and hematopoietic colony-forming potential. Together, our findings reveal a potent impact of hemodynamic Rho-YAP mechanotransduction on HE fate, relevant to de novo human HSPC production. • Biomechanical strain impacts human HSPC formation in vitro • YAP drives endothelial-to-hematopoietic transition downstream of blood flow in vivo • Rho-GTPase stimulation promotes HSPC production in vitro and in vivo via YAP activity Hemodynamic forces are required for embryonic hematopoietic stem and progenitor cell (HSPC) formation; however, transcriptional mediators of this process are unknown. Using in vitro microfluidics-mediated stimulation of human induced pluripotent stem cells and in vivo functional analyses in zebrafish embryos, Lundin et al. show cyclic stretch-mediated biophysical activation of YAP facilitates HSPC production. [ABSTRACT FROM AUTHOR]