Closed circulatory systems (CCS) underlie the function of vertebrate organs, but in long bones their structure is unclear, although they constitute the exit route for bone marrow (BM) leukocytes. To understand neutrophil emigration from BM, we studied the vascular system of murine long bones. Here we show that hundreds of capillaries originate in BM, cross murine cortical bone perpendicularly along the shaft and connect to the periosteal circulation. Structures similar to these trans-cortical-vessels (TCVs) also exist in human limb bones. TCVs express arterial or venous markers and transport neutrophils. Furthermore, over 80% arterial and 59% venous blood passes through TCVs. Genetic and drug-mediated modulation of osteoclast count and activity leads to substantial changes in TCV numbers. In a murine model of chronic arthritic bone inflammation, new TCVs develop within weeks. Our data indicate that TCVs are a central component of the CCS in long bones and may represent an important route for immune cell export from the BM.
Introduction: The aim of this study was to evaluate the COVID-19 vaccination acceptance of emergency medical services (EMS) personnel as front-line health care workers (HCW) in Germany. Several studies have shown low willingness for vaccination (e.g., seasonal influenza) among HCWs and EMS personnel. Methods: We created a web-based survey. The questions were closed and standardized. Demographic data were collected (age, sex, federal state, profession). Experience with own COVID-19 infection, or infection in personal environment (family, friends) as well as willingness to vaccinate was queried. Results: The sample includes n = 1296 participants. A willingness to be vaccinated exists in 57%, 27.6% participants were undecided. Our results show a higher propensity to vaccinate among the following groups: male gender, higher medical education level, older age, own burden caused by the pandemic (p < 0.001). Conclusions: Due to the low overall acceptance of vaccination by HCWs, we recommend that the groups with vaccination hesitancy, in particular, be recruited for vaccination through interventions such as continuing education and awareness campaigns.
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