Disuse osteopenia: altered gene expression of small leucine-rich proteoglycans biglycan (BGN) and decorin (DCN)

Disuse osteopenia is a significant reduction in bone mineral density that results from a loss of functional loading. This disorder is particularly prevalent in individuals returning from space flight and those subjected to prolonged periods of bed rest, where in the former, changes in bone mineral density can approach -1.6% per month. In order to better understand the causes of bone loss, the complex molecular signaling mechanisms that are likely responsible for this process need further examination. Previous experiments have shown that the loss of the bone extracellular matrix (ECM) found in disuse osteopenia is accompanied by the downregulation of several important ECM genes. In the current study, gene expression profiles of two small leucine-rich proteoglycans (SLRPs), biglycan (BGN) and decorin (DCN), were explored in RNA that was previously extracted from the whole proximal tibia of mice that experienced four days of unloading. The primary objective of this experiment was to confirm microarray results from previous experiments. Expression levels of BGN were significant downregulation (-49%), which was generally consistent with microarray data, while DCN expression levels were downregulation (-34%), albeit not significant. These results highlight the importance of relatively unexplored non-collagenous ECM proteins in the molecular signaling process of disuse osteopenia