Effects of Medium and Temperature on Cellular Responses in the Superficial Zone of Hypo-Osmotically Challenged Articular Cartilage

Abstract

Osmotic loading of articular cartilage has been used to study cell-tissue interactions and mechanisms in chondrocyte volume regulation in situ. Since cell volume changes are likely to affect cell’s mechanotransduction, it is important to understand how environmental factors, such as composition of the immersion medium and temperature affect cell volume changes in situ in osmotically challenged articular cartilage. In this study, chondrocytes were imaged in situ with a confocal laser scanning microscope (CLSM) through cartilage surface before and 3 min and 120 min after a hypo-osmotic challenge. Samples were measured either in phosphate buffered saline (PBS, without glucose and Ca2+) or in Dulbecco’s modified Eagle’s medium (DMEM, with glucose and Ca2+), and at 21 °C or at 37 °C. In all groups, cell volumes increased shortly after the hypotonic challenge and then recovered back to the original volumes. At both observation time points, cell volume changes as a result of the osmotic challenge were similar in PBS and DMEM in both temperatures. Our results indicate that the initial chondrocyte swelling and volume recovery as a result of the hypo-osmotic challenge of cartilage are not dependent on commonly used immersion media or temperature.

The rate of hypo-osmotic challenge influences regulatory volume decrease (RVD) and mechanical properties of articular chondrocytes

“…In previous studies the speed of RVD in isolated chondrocytes reduces at temperatures below 37 C 11,12,15,42 . However, a recent study by Huttu et al showed temperature doesn't affect chondrocyte volume regulation in situ 43 . In our study, conducted at room temperature, 65.6% of chondrocytes exhibited RVD in response to sudden hypoosmotic challenge.…”

Osmotically Rupturing Phagosomes in Macrophages Using PNIPAM Microparticles

“…We believe that this is acceptable because the weight fraction of the nanoparticles in the dry microparticles is very low (∼0.67%). The molarity of DMEM has been reported as 0.29 M . We assume that the complete medium, which was DMEM supplemented with 10% FBS and antibiotics and l -glutamine, had the same molarity, that is, M medium = 0.29 M. Kawasaki et al found that the partition coefficient, K , for Na + and Cl – ions and collapsed PNIPAM gel is ∼0.15 in 0.3 M NaCl at 40 °C .…”