Gravity has an important role in both the development and maintenance of bone mass. This is most evident in the rapid and intense bone loss observed in both humans and animals exposed to extended periods of microgravity in spaceflight. Here, cohabitating 9-week-old male C57BL/6 mice resided in spaceflight for ~4 weeks. A skeletal survey of these mice was compared to both habitat matched ground controls to determine the effects of microgravity and baseline samples in order to determine the effects of skeletal maturation on the resulting phenotype. We hypothesized that weight-bearing bones would experience an accelerated loss of bone mass compared to non-weight-bearing bones, and that spaceflight would also inhibit skeletal maturation in male mice. As expected, spaceflight had major negative effects on trabecular bone mass of the following weight-bearing bones: femur, tibia, and vertebrae. Interestingly, as opposed to the bone loss traditionally characterized for most weight-bearing skeletal compartments, the effects of spaceflight on the ribs and sternum resembled a failure to accumulate bone mass. Our study further adds to the insight that gravity has site-specific influences on the skeleton.
In academia, manuscripts serve as an important component of career development. The past several years have seen heightened evaluation of the role of the gender gap in career advancement, as well as other bibliometric changes in publications. We therefore analyzed authorship and publication trends in the Annals of Biomedical Engineering over the past three decades (one complete year of manuscripts for each decade; 1986, 1996, 2006, and 2016). The variables analyzed were number of authors per manuscript, numerical position of the corresponding author, number of collaborating institutions and countries, number of references, and number of citations per manuscript. The gender of both the first and corresponding authors was identified and analyzed over time and by region. Globally, the percentage of female first and corresponding authors significantly increased from 0% in 1986 to 28.6% (p = 0.003) and 20.4% (p = 0.0009) respectively, in 2016. Although there were significant differences regarding female first and corresponding author over time, they did not vary by region of origin (p = 0.5 and 0.2, respectively). Overall, these findings highlight the improvements made and the challenges that still exist related to publishing within the bioengineering field.
Exosomes have attracted attention due to their ability to promote intercellular communication leading to enhanced cell recruitment, lineage-specific differentiation, and tissue regeneration. The object of this study was to determine the effect of exosomes on cell homing and angiogenic differentiation for pulp regeneration. Exosomes (DPSC-Exos) were isolated from rabbit dental pulp stem cells cultured under a growth (Exo-G) or angiogenic differentiation (Exo-A) condition. The characterization of exosomes was confirmed by nanoparticle tracking analysis and an antibody array. DPSC-Exos significantly promoted cell proliferation and migration when treated with 5 Γ 108/mL exosomes. In gene expression analysis, DPSC-Exos enhanced the expression of angiogenic markers including vascular endothelial growth factor A (VEGFA), Fms-related tyrosine kinase 1 (FLT1), and platelet and endothelial cell adhesion molecule 1 (PECAM1). Moreover, we identified key exosomal microRNAs in Exo-A for cell homing and angiogenesis. In conclusion, the exosome-based cell homing and angiogenic differentiation strategy has significant therapeutic potential for pulp regeneration.
Background and Hypothesis: Soft tissue injury surrounding tibia fractures is a key determinant of surgical care decisions and healing outcomes. We have established a porcine tibia fracture model with a corresponding volumetric muscle loss (VML) injury in the adjacent peroneus tertius (PT) muscle. Herein, we test the hypothesis that tibia fracture without VML induces an initial strength deficit that recovers within three months post-injury, while VML injuries present chronic strength deficits.
Background/Hypothesis: Few large animal bone injury models exist. We present a porcine tibial model of metacritical and critical sized bone defects for the simulation of traumatic bone injuries. Project Methods: 16 pigs were used in this study. The pigs were divided into 3 groups (n=4-8/group). In 12 pigs, a 25 mm osteotomy was created in the tibia and the space was filled with a 25 mm scaffold. 8 of the 25 mm scaffolds were secured with an intramedullary (IM) nail and 4 of the scaffolds were secured with plates. In 4 pigs a 40 mm osteotomy was created, filled with a 40 mm scaffold, and secured with plates. Fracture healing was assessed 3 months post-operatively using the Radiographic Union Score for Tibial Fractures (RUST) criteria. Results: For the 25 mm IM group, none of the 8 pigs achieved cortical bone union at 3 months post-op. In contrast, cortical union was observed in all of the 25 mm defects secured with plates. None of the 40 mm defects secured with plates achieved cortical union. Conclusion/Potential Impact: The failure of the 25 mm defect secured with an IM nail and the 40 mm defect secured with plates demonstrates that these are critical sized defect models. However, because the 25 mm defect secured with bridge plates did heal, we have termed this a metacritical sized defect. Identification of a defect size that can heal or not heal based on the fixation technique is a powerful translational model for testing therapies.
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