Expression data from cultured rat right ventricular papillary muscles

Several different mechanical signals have been proposed to control the extent and pattern of myocardial growth and remodeling, though this has largely been studied using in vitro model systems that are not representative of intact myocardium or in vivo models in which isolating the effects of individual candidate stimuli is exceedigly difficult. We used a unique tissue culture system that allows the simultaneous control of multiple mechanical inputs and other potentially confounding stimuli (e.g., hormonal). Following a 12 hour culture period under prescribed mechanics, we used microarrays to identify genes that are up- or down-regulated in response to different amounts of mean stretch and cyclic shortening. Muscles were dissected (one from each of 12 different male LBN-F1 rats) and cultured for 12 hours in a pseudo-sterile muscle culture system under one of four mechanical input schemes (i.e., three biological replicates per mechanical input group). We prescribed low or high values of both time averaged stretch and cyclic shortening. Specifically, we targeted 4% or 16% mean stretch (from slack length) and 4% of 16% cylic shortening (% of slack length) over the 12 hour culture period to give the following four groups: high mean stretch x high shortening (group A); high mean stretch x low shortening (group B); low mean stretch x low shortening (group C); low mean stretch x high shortening (group D). This 2 x 2 factorial design allowed us to identify individual genes and/or molecular pathways that might be regulated by one or both of these mechanical inputs indpendent from other candidate mechanical or hormonal stimuli.