Neocartilage Formation in 1 g, Simulated, and Microgravity Environments: Implications for Tissue Engineering

Abstract

The aim of this study was to analyze and compare the deposition of cartilage-specific extracellular matrix components and cellular organization in scaffold-free neocartilage produced in microgravity and simulated microgravity. Porcine chondrocytes were seeded (100 x 10(6)/mL) into cylindrical culture chambers (n = 8) and cultured in the following environments: (i) microgravity during the Flight 7S (Cervantes mission) on the International Space Station (ISS), (ii) simulated microgravity in a random positioning machine (RPM), and (iii) normal gravity (1 g, control). After 16 days, each neocartilage tissue was processed for histology, immunohistochemistry, quantitative real-time reverse transcriptase-polymerase chain reaction, and histomorphometric analysis. Weaker extracellular matrix staining of ISS neocartilage tissue was noted compared with both Earth-cultivated tissues. Higher collagen II/I expression ratios were observed in ISS samples compared with control tissue. Conversely, higher aggrecan/versican gene expression profiles were seen in control 1 g samples compared with microgravity samples. Cell density produced in microgravity was significantly reduced compared with the normal gravity neocartilage tissues. Tissue cultivated on the RPM showed intermediate characteristics compared with ISS and 1 g conditions. These data indicate that the RPM system does not sustain microgravity. Although microgravity impacts the development of in vitro generated cartilage, simulated microgravity using the RPM may be a useful tool to produce cartilaginous tissue grafts with fewer cells.