Hydrostatic Pressure Influences HIF-2 Alpha Expression in Chondrocytes

Abstract

Hypoxia-inducible factor (HIF)-2α is considered to play a major role in the progression of osteoarthritis. Recently, it was reported that pressure amplitude influences HIF-2α expression in murine endothelial cells. We examined whether hydrostatic pressure is involved in expression of HIF-2α in articular chondrocytes. Chondrocytes were cultured and stimulated by inflammation or hydrostatic pressure of 0, 5, 10, or 50 MPa. After stimulation, heat shock protein (HSP) 70, HIF-2α, nuclear factor kappa B (NF-κB), matrix metalloproteinase (MMP)-13, MMP-3, and vascular endothelial growth factor (VEGF) gene expression were evaluated. The levels of all gene expression were increased by inflammatory stress. When chondrocytes were exposed to a hydrostatic pressure of 5 MPa, HIF-2α, MMP-13, and MMP-3 gene expression increased significantly although those of HSP70 and NF-κB were not significantly different from the control group. In contrast, HIF-2α gene expression did not increase under a hydrostatic pressure of 50 MPa although HSP70 and NF-κB expression increased significantly compared to control. We considered that hydrostatic pressure of 5 MPa could regulate HIF-2α independent of NF-κB, because the level of HIF-2α gene expression increased significantly without upregulation of NF-κB expression at 5 MPa. Hydrostatic pressure may influence cartilage degeneration, inducing MMP-13 and MMP-3 expression through HIF-2α.

Bioreactor mechanically guided 3D mesenchymal stem cell chondrogenesis using a biocompatible novel thermo-reversible methylcellulose-based hydrogel

“…Finally, COL 10 was detected in loaded specimens (C, lower panel, in green) but in a lower amount in comparison with COL 2, thus confirming that cells were not adopting a hypertrophic phenotype due to the continuous mechanical stimulation provided by daily bioreactor operating. These data are in accordance to literature as compressive stress combined with shear flow allows a higher MSC commitment11333442. Hence, IF staining confirmed the PCR data, providing further important indication of the successful bioreactor-guided chondrogenesis.…”

“…Thus, although cells are metabolically active (as confirmed by PCR findings and increased GAG synthesis), they seem to lack the appropriate environment or proper stimuli to produce a structured extracellular matrix within the timeframe of this experiment9. Moreover, by using fibrin glue as cells matrix in a newly developing construct, the bulk of the newly synthesized GAG was released into the culture medium as the pericellular matrix was not sufficiently developed to retain the newly produced GAG323334. Therefore, the MC hydrogel seems to act similarly to fibrin according to obtained and previous results.…”

Treadmill Running Ameliorates Destruction of Articular Cartilage and Subchondral Bone, Not Only Synovitis, in a Rheumatoid Arthritis Rat Model

“…Mechanical stress is also directly applied to articular cartilage and bone during treadmill running [ 27 ]. We previously reported that moderate hydrostatic pressure on chondrocytes enhances production of the cartilage matrix, and excessive hydrostatic pressure promotes the expression of proinflammatory cytokines such as IL-6, TNF-α, and a cartilage matrix-degrading enzyme [ 28 , 29 ]. Therefore, we suspected that treadmill running may act as not only a suppressor of pro-inflammatory cytokine production from the synovial membrane, but also a joint protector through mechanical stress applied to the articular cartilage per se, resulting in suppression of joint destruction.…”

Targeting VEGF and Its Receptors for the Treatment of Osteoarthritis and Associated Pain

“…Mechanical overload in bovine cartilage disks increases MMP and decreases TIMP expression, and this can be reversed with a VEGFR-2 inhibitor. (49) Mechanical loads are thought to stimulate both hypoxia inducible factor-1a-and -2a (HIF-1 a and HIF-2a)mediated upregulation of VEGF in chondrocytes, (49,109,110) and hypoxia itself is a prime regulator of increased HIFs. (103,108,111,112) Mechanical loading at osteocytes also increases VEGF expression.…”