Hydrostatic Pressure Gene Expression versus LSJL gene expression

Gene expression profiles in chondrosarcoma cells subjected to cyclic stretching and hydrostatic pressure. A cDNA array study.

"We investigate mRNA expression profiles in human chondrosarcoma cells stretched 8% for 6 hours at a frequency of 0.5 Hz. In addition, cultures were exposed to continuous and cyclic (0.5 Hz) 5 MPa hydrostatic pressure. Cyclic stretch had a more profound effect on the gene expression profiles than 5 MPa hydrostatic pressure. Several genes involved with the regulation of cell cycle were increased in stretched cells, as well as mRNAs for PDGF-B, glucose-1-phosphate uridylyltransferase, Tiam1, cdc37 homolog, Ptn{up in LSJL}Gem{up in LSJL}, integrin alpha6, and matrix metalloproteinase-3{up in LSJL}. Among down-regulated genes were plakoglobin, TGF-alpha, retinoic acid receptor-alpha and Wnt8b. A smaller number of changes was detected after pressure treatments. Plakoglobin was increased under cyclic and continuous 5 MPa hydrostatic pressure, while mitogen-activated protein kinase-9{down in LSJL}, proliferating cell nuclear antigen, Rad6, CD9 antigen{down in LSJL}, integrins alphaE and beta8, and vimentin{up in LSJL} were decreased."

Other genes upregulated by cyclic stretch alter altered by LSJL(up unless otherwise noted):

Col6a3

Cks2(down)

GAS1

Down:

Dvl1

L1CAM(Chl1 is upregulated in LSJL and CHL1 is proported to be homologous to L1CAM)

The pericellular environment regulates cytoskeletal development and the differentiation of mesenchymal stem cells and determines their response to hydrostatic pressure.

"[We] examine the interplay between matrix stiffness and hydrostatic pressure (HP) in regulating chondrogenesis of mesenchymal stem cells (MSCs) and the mechanotransductive roles of integrins and the cytoskeleton. MSCs were seeded into 1 %, 2 % or 4 % agarose hydrogels and exposed to cyclic hydrostatic pressure. In a permissive media, the stiffer hydrogels supported an osteogenic phenotype, with little evidence of chondrogenesis observed regardless of the matrix stiffness. In a chondrogenic media, the stiffer gels suppressed cartilage matrix production and gene expression, with the addition of RGDS (an integrin blocker) found to return matrix synthesis to similar levels as in the softer gels. Vinculin, actin and vimentin organisation all adapted within stiffer hydrogels, with the addition of RGDS again preventing these changes. While the stiffer gels inhibited chondrogenesis, they enhanced mechanotransduction of HP. RGDS suppressed the mechanotransduction of HP, suggesting a role for integrin binding as a regulator of both matrix stiffness and HP. Intermediate filaments also appear to play a role in the mechanotransduction of HP, as only vimentin organisation adapted in response to this mechanical stimulus. Matrix density and/or stiffness modulates the development of the pericellular matrix and consequently integrin binding and cytoskeletal structure. Physiological cues such as HP enhance chondrogenesis of MSCs as the pericellular environment matures and the cytoskeleton adapts, and points to a novel role for vimentin in the transduction of HP."

25 kPa of hydrostatic pressure had higher Sox9, Acan, and Col2a1 levels.

"The addition of RGDS in stiffer hydrogels led to the development of a cytoskeleton similar to that in the softer 1 % hydrogels, where HP had no beneficial effect on chondrogenesis."