Skeletal tissue growth, differentiation and mineralization in the NASA Rotating Wall Vessel

The NASA Rotating Wall Vessel (RWV) is a device that creates a unique environment that supports three-dimensional tissue growth, a heightened level of cell differentiation and randomizes the position of the downward gravitational force on cells. Embryonic bone formation encompasses a cascade of chondrogenic and osteogenic events, which can be altered by changes in gravitational loading. These studies were conducted to determine if the chondrogenic cascade in bone formation would be enhanced or hindered in the unique culture environment of the RWV. Embryonic mouse pre-bone tissues were placed in the RWV at one of four different stages of chondrogenesis, ranging from undifferentiated mesenchyme cells to chondrocytes on the verge of undergoing terminal chondrocyte differentiation. After culture, tissues were analyzed for their size, the amount of alkaline phosphatase (ALP) activity and their ability to form a mineralized matrix. Tissue consisting of cells at the early phase of chondrogenesis grew very little and did not differentiate or mineralize when cultured in the RWV. Some tissues were cultured for short periods in the RWV then cultured in standard culture dishes (SCD). Following this culture regime, the cartilage grew only a small amount, but alkaline phosphatase activity increased, and some mineralized regions formed. The pattern of mineralization was abnormal, with two mineralized zones at each end of the cartilage instead of a single central zone. Tissues that were at the three more advanced stages of chondrogenesis when placed in the RWV showed substantial growth, differentiation and mineralization. Mineralization patterns in these older tissues was normal. Tissues at the oldest stage of chondrogenesis showed more growth and as much or more mineralization as tissue cultured only in SCD. These data suggest that exposure to the RWV at early stages of chondrogenesis severely limits the ability for cartilage growth and yields abnormal downstream morphogenesis. However, at later stages of chondrogenesis, the RWV environment may be beneficial and enhance growth and development. Future studies to characterize intercellular signaling molecules and gene expression activities of chondrocytes in the RWV will be valuable for understanding the mechanism of skeletogenesis.