循環壓縮頻率對軟骨細胞於多孔隙基材上之生長及基質合成的影響

Abstract

由於關節軟骨缺乏自我修復的能力，而目前的治療方式皆無法有效的治療軟骨損傷。因此，近年來研究者利用組織工程的方式，嘗試在體外建構一個可以移植至關節來取代受損的組織，然而由於在體外培養與體內的環境不同，造成培養出的組織不具有原生軟骨的功能性。關節軟骨在體內是不斷承受循環負載的環境，因而許多研究者在培養過程中，利用機械刺激的方式，去模擬細胞在體內的受力情形。 先前的研究已經建立一套結合灌流與壓縮的系統，並證實動態壓縮於0.1 Hz, 10 % 時對基質合成有幫助。而本研究更進一步系統化的測定連續壓縮在大範圍的頻率下(0.01 Hz, 0.1 Hz, 1 Hz)其GAG、 Type II collagen與基因表現，以估定軟骨細胞在多孔隙支架上接受不同負載模式時細胞發育的能力。經過十四天的培養，結果顯示靜態壓縮減少22 % GAG 與31 % collagen II的合成，而動態壓縮頻率於0.1 Hz下明顯增加49 % GAG合成，於1 Hz下增加56 % GAG 和46 % collagen II 合成，另外由基因表現與染色結果得知，軟骨細胞可維持原來的型態，不會朝去分化的路徑發展。 由此可知靜態壓縮抑制細胞外間質的合成量，反觀動態壓縮於中、高頻時，能刺激細胞外間質合成能力，始其形成類似天然的軟骨組織。故結果證實這個假設，長期動態壓縮頻率是重要的機械因子，可調控軟骨細胞在多孔隙支架上的新陳代謝作用。

Articular cartilage has a limited capacity for self-regeneration and none of the current treatments or therapies that are used to rectify damaged cartilage are ideal or permanent. As a result, researchers are looking to tissue engineering to grow constructs in vitro with the view of implanting them into joints to replace damaged tissue. However, in vitro cultures cause the original characteristics to be lost due to the difference between in vivo and in vitro. Actually, cartilage is running a cycle between compression and restoring continuously. For this reason Approaches used in cartilage tissue engineering involve the application of mechanical stimuli to cells to emulate the forces experienced by cells in vivo. Previous study has designed a bioreactor which can apply compressive stress to cartilage and confirm that dynamic loading stimulate ECM synthesis at frequency 0.1 Hz, 10 % strain. Further, present study was designed to systematically determine whether and to what extent the frequency of long-term continuous loading (0.01 Hz, 0.1 Hz, 1 Hz, 10 % , 14 days) modulates The GAG and collagen II biosynthesis, and to assess chondrocyte viability in PLGA porous scaffold exposed to different loading patterns. After 14 days culture, static compression reduce 22 % GAG and 31 % collagen II synthesis, A significant increase in ECM was associated with loading at 0.1 Hz(49 % GAG), and an even greater increase with loading at 1 Hz produced 56 % GAG and 46 % collagen II increase. In addition, gene expression and stain shows the maintenance of chondrocyte phenotype and formation of cartilage-like constructs in the compressive cultures. Our results confirm the hypothesis that the frequency of long-term loading is an important mechanical factor controlling the metabolic activities of chondrocytes.