不同種類的細胞對於承受不同的作用力，也會呈現不同型態的表現，如位於膝關節中軟骨細胞，受到壓縮應力、張應力、剪應力和靜水壓等力量的作用，誘使軟骨細胞產生一連串的生理化學反應，如蛋白醣(proteoglycan)、第二型膠原蛋白(collagen type II)、葡萄糖胺聚糖(glycosaminoglycans)、蛋白聚醣(aggrecan)等胞外基質(Extracellular matrix)的增加，有助於細胞的生長與存活。之前的研究結果顯示靜水壓的結果最為顯著。
此研究使用豬的膝關節面軟骨組織所萃取出的軟骨細胞，進行力學性的刺激研究，因此設計出一套動態靜水壓生物反應器(Hydordynamic pressure bioreactor)，以接近人體內真實環境的受力作用狀態的壓力值2.24 MPa，頻率為0.1 Hz作為力學刺激的大小，軟骨細胞分別種植在3 cm培養皿和洋菜凝膠(agarose gel)裡面，再放入無菌採樣袋之中，抽出空氣注入F12 培養液，再拿到生物反應器之中進行每天一小時，連續七天的力學刺激。以觀察軟骨細胞在受到力學刺激時所產生的影響，期望軟骨細胞在動態靜水壓作用之下，使得軟骨細胞能夠加速分泌胞外基質。
軟骨細胞經過生物反應器的刺激後的效果，採用軟骨細胞指標性染色技術(alcian blue & masson’s trichrome stain)來確認軟骨細胞所分泌出來的胞外基質:蛋白醣(proteoglycan)和第二型膠原蛋白(collagen type II)的量，最後再使用動態力學量測儀(Dynamic Mechanical Analyzer )進行壓縮彈性系數(compressive modulus)量測，比較動態靜水壓是否有助於提升軟骨細胞的力學性質。
實驗結果顯示，有經過力學刺激的群組，比未經力學刺激的群組，不論在蛋白醣、葡萄糖胺聚糖、第二型膠原蛋白的分泌量上都有明顯增加，而在壓縮彈性系數量測下，受刺激組也是未受力學刺激的控制組來的六倍，結果顯示軟骨細胞在此實驗所設計之動態靜水壓反應器的刺激下可明顯增加胞外基質的分泌。

Different cells will react differently when they are under different loading conditions. For example, when the chondrocytes on the knee joint are under compressiive stress, tensile stress, shearing stress, or hydrostatic pressure, they will cause a series of chemical reactions on cells, which increase extracellular matrix (ECM) like proteoglycans, glycoprotein, collagen type II, glycosaminoglycans, aggrecan etc. This mechanism helps cells grow up and survive. From previous studies, dynamic hydrostatic pressure has the most significant effect on chondrocytes.
This study, chondrocytes harvested from swine’s knee joint tissue were used to evaluate the effect from mechanical stimulation. A hydrodynamic pressure bioreactor similar to joint mechanical environment was built for this study. The pressure level is 2.24 MPa and frequency is 0.1 Hz. Chondrocytes were cultured in culture dish and agarose gel respectively, and then sealed into sterilized bags. After suck out extra air and inject F12 culture medium into the bag, chondrocytes inside the bag were stimulated one hour per day and 7 consecutive days. We hope chondrocytes can synthesize ECM faster under the mechanical stimulation from this bioreactor.
The influence of chondrocytes after stimulation from bioreactor was evaluated by cytostain for ECM synthesized by chondrocytes. Alcian blue and Masson’s Trichorme stains were used to check the outcome of proteoglycan and type II collagen respectively. The mechanical properties of chondrocytes with synthesized matrix were tested by Dynamic Mechanical Analyzer. The compressive modulus was measured to evaluate the mechanical enhancement by stimulation from bioreactor.
The staining results show the chondrocytes under bioreactor’s stimulation, their proteoglycan, glycosamnioglycan, type II collagen syntheses have significant increase comparing to unloading group. The compressive modulus for loading group is 6 times of unloading group. From this result, we conclude that the chondrocytes dramatically increase ECM syntheses under the hydrodynamic bioreactor stimulation.

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