An assessment of the long-term effects of simulated microgravity on cranial neural crest cells in zebrafish embryos with a focus on the adult skeleton

It is becoming increasingly important to address the long-term effects of exposure to simulated microgravity as the potential for space tourism and life in space become prominent topics amongst the World's governments. There are several studies examining the effects of exposure to simulated microgravity on various developmental systems and in various organisms; however, few examine the effects beyond the juvenile stages. In this study, we expose zebrafish embryos to simulated microgravity starting at key stages associated with cranial neural crest cell migration. We then analyzed the skeletons of adult fish. Gross observations and morphometric analyses show that exposure to simulated microgravity results in stunted growth, reduced ossification and severe distortion of some skeletal elements. Additionally, we investigated the effects on the juvenile skull and body pigmentation. This study determines for the first time the long-term effects of embryonic exposure to simulated microgravity on the developing skull and highlights the importance of studies investigating the effects of altered gravitational forces.

A quick whole-mount staining protocol for bone deposition and resorption

Osteoblasts and osteoclasts, two cell types important in bone development, are associated with enzymes capable of hydrolyzing phosphate groups. These enzymes are important for their function of bone deposition and resorption. Alkaline phosphatase (AP) activity is associated with the cell surface of osteoblasts, while osteoclasts secrete tartrate-resistant acid phosphatase (TRAP). Due to their shared enzymatic properties, we were able to develop a simple whole-mount staining protocol to stain for both enzymes (TRAP and AP) within the same teleostean tissue sample. In addition, we were able to perform each reaction individually. Further, AP and TRAP stains were maintained through decalcification, embedding, and sectioning procedures. Staining can also be conducted after sectioning depending on the question under investigation. These rapid staining protocols can thus be used to observe the processes involved in bone remodeling in whole teleost specimens, and/or the location of the stain can be determined through sectioning. The ability to observe bone deposition and resorption in such a capacity will significantly advance our understanding of bone remodeling throughout the life history of organisms and also within particular skeletal elements.