Changes in morphology, gene expression and protein content in chondrocytes cultured on a random positioning machine

Abstract

Tissue engineering with chondrocytes on the random positioning machine (RPM) is a new strategy of cartilage regeneration. Using a three-dimensional RPM, a device designed to simulate microgravity on Earth, we investigated the early effects of RPM exposure on human chondrocytes of six different donors after 30 minutes, 2 h, 4 h, 16 h, 24 h and compared the achieved results with the corresponding static controls cultured under normal gravity conditions. Already 30 minutes of RPM exposure resulted in an increased expression of several genes for cell motility, structure and integrity (beta-actin), for control of cell growth, cell proliferation, cell differentiation and apoptosis (TGF-β1, osteopontin) and altered cytoskeletal components such as microtubules (beta-tubulin) and intermediate filaments (vimentin). After 4 hours of RPM exposure even disruptions in the vimentin network could be detected. These changes were less dramatic after 16 hours on the RPM when human chondrocytes appeared to reorganize their cytoskeleton. However, the gene expression and protein content of TGF-β 1 was clearly enhanced during RPM culture for 24 h. Taken these results together we suggest that chondrocytes exposed to the RPM seem to change their extracellular matrix production behavior, while they rearrange their cytoskeletal proteins prior to forming 3D aggregates.