Table 3 Experimental conditions for in vitro mechanical loading models
Cell type | Shear stress/Pa | Flow type | Flow duration | mRNA changes | Other responses | Ref. |
|---|---|---|---|---|---|---|
Primary osteocytes | ||||||
Chicken primary osteocytes | 0.5 | p | 1 h | PGE2↑ | All three cell populations rapidly (osteocytes: within 5 min, osteoblast and osteocyte containing population, periosteal fibroblasts: within 10 min) increased their release of prostaglandins E2 and I2 in response to PFF, but the response by osteocytes was 2–4 times higher than that by osteoblast and osteocyte containing population or periosteal fibroblasts. | |
Chicken primary osteocytes | 0.7 | p | 10 min | PGE2↑ | PFF raises intracellular Ca2+ by an enhanced entry through mechanosensitive ion channels in combination with Ca2+ and inositol trisphosphate-induced Ca2+ release from intracellular stores. | |
Mouse primary calvarial bone cell | 0.70 ± 0.03 | p | 1 h | PGHS-2↑ | Northern blot analysis detected after 1 h of PFF treatment increased PGHS-2 mRNA expression about twofold; more PGE2 was released under PFF condition. | |
Human primary trabecular bone cell | 0.7 | p | 1 h | PGE2↑ | Cultured cells responded to mechanical stress with enhanced release of prostaglandin E2 (PGE2) and I2 (PGI2) by western blot. | |
Human primary bone cells | 0.7 | p | 1 h | Cox-2↑PGE2↑ | One-hour PFF treatment stimulated the release of PGE2 by 3.5 folds and PGI2 by 2.2-fold. PFF also increased the expression of Cox-2 mRNA by 2.9 folds, but did not change Cox-1 mRNA by QPCR. | |
Human primary bone biopsies cells | 0.7 | p | 1 h | NO↑PGE2↑ | The PFF-mediated upregulation of PGE2 release during 24 h of postincubation after 1 h of PFF was significantly reduced in osteoporotic patients compared with six age-matched controls as well as with the whole nonosteoporotic group. | |
Osteocyte-like cell lines | ||||||
Ocy454 | 0.5–2.0 | Un-L | 2 h or 3 days | Rankl↓Sost↑ | Ocy454 cells recapitulated the in vivo response to mechanical unloading with increased expression of Sost (3.4 ± 1.9-fold), Sclerostin (4.7 ± 0.1-fold), and the receptor activator of Rankl/Opg (2.5 ± 0.7-fold) ratio. | |
MLO-Y4 | 0.5–5.0 | o | 1–4 h | Rankl↓Opg↓Cox-2↑ | OFF stimulation simultaneously upregulated the Cox-2 mRNA expression and downregulated the Rankl/Opg mRNA levels. | |
MLO-Y4 | 0.7 | p | 1 h | Rankl/Opg↓Opg↑ MEPE↑ | PFF upregulated MEPE gene expression by 2.5-fold, but not PHEX expression. PFF decreased the Rankl/Opg ratio at 1-h PFF treatment. | |
MLO-Y4 | 16.0 | s | 0.5–2 h | Opg↑ | MLO-Y4 cells plated at lower densities release more PGE2 than cells plated at higher densities. Cell surface biotinylation analysis showed that surface expression of Cx43 was increased by shear stress. | |
MLO-Y4 | 16.0 | s | 0.5–2 h | Cx43↑ | SFF has stimulatory effects on MLO-Y4 cells with early effects on cellular morphology, opening of gap junctions, and redistribution of Cx43 protein and delayed effects on Cx43 protein expression. | |
