膝軟骨損傷是膝蓋常見疾病，病發原因可能為受到巨大撞擊、關節炎、骨軟骨炎、骨壞死或其他有關於韌帶受傷所產生的併發症。臨床上治療軟骨受傷的方式以保守治療為主，若患病部位持續惡化，則最終仍需走向全關節置換一途。組織工程的概念結合近幾年微創手術已證實有較好的癒後和縮短恢復期等優點，使得開發可注射型支架成為必要發展方向。
本研究開發一種含有「聚N-異丙基丙烯醯胺」、「聚乙二醇」結合「硫化軟骨素」的溫感型水膠探討此共聚物混合臏下脂肪墊間質幹細胞所形成的三維支架對軟骨組織工程的影響。由結果顯示加入硫化軟骨素和聚乙二醇並不會使聚N-異丙基丙烯醯胺本身所具有的相轉變溫度特性消失。甚至此「聚乙二醇與聚N-異丙基丙烯醯胺接枝硫化軟骨素」水凝膠的生物可相容性與機械強度皆因共聚硫化軟骨素和聚乙二醇而結合此二材料本身的優點而提高。
此外，許多文獻指出硫化軟骨素擁有促進和誘發間質幹細胞走向軟骨再生的能力，然而以本篇所設定的條件觀察軟骨化重要胞外基質glycosaminoglycans之定量分析，即使在培養21天後仍沒有顯著提升，顯示若無常見生長因子例如TGF-β之輔助，單獨存在硫化軟骨素無法啟動幹細胞分化之程序。
以紐西蘭大白兔骨軟骨缺損模型測試「聚乙二醇與聚N-異丙基丙烯醯胺接枝硫化軟骨素」水凝膠，術後4周與12周分別以外觀、組織染色及微計算機斷層掃描技術定性定量修復組織，相對於純聚N-異丙基丙烯醯胺水凝膠，本篇發展之共聚物水凝膠效果良好，尤以植入聚N-異丙基丙烯醯胺接枝硫化軟骨素組別於術後四周效果最佳。然而，我們推測應是硫化軟骨素之劑量不足，使術後12周的結果未臻理想。我們亦發現於植入物和原生組織之邊界產生glycosaminoglycans逐漸流失的現象，歸因於此溫感型水膠係以物理性方式成膠，即使加入硫化軟骨素和聚乙二醇提升該水膠之強度仍不足以達到機械穩定的狀態。未來仍可以藉由修改硫化軟骨素或聚乙二醇之濃度、分子量更進一步修改水凝膠的各項特性，以期作為軟骨組織工程中理想支架材料。

Articular cartilage defects are common conditions affecting the knee joint. It is often caused by trauma, osteonecrosis, osteochondritis, and other conditions in associated with ligament injuries, such as ACL tears. Early cartilage defects are frequently treated with conservative therapies. When the defect continued to deteriorate, eventually, joint replacement operations are needed. However, tissue engineering approach may provide the alternative choice to repair the articular cartilage defect. Recently, minimal invasive surgery become the trend due to faster recovery time and good outcome, so development of injectable cartilage defect repair scaffold is needed.
In this study, the PEG-PNIPAAm-g-Chondroitin sulfate (CS) thermosensitive hydrogel was synthesized to investigate its potential as a three-dimensional (3D) culture matrix with infrapatellar fat pad derived mesenchymal stem cells (IFPMSCs). The results revealed that hydrogel composites preserved their sol–gel transition properties in the presence of CS and PEG. Particularly, inclusion of CS and PEG into the hydrogels would provide both enhanced mechanical properties and bioactivity to the composites. Mechanical testing results show that this polymeric hydrogel has significant stiffness than pure PNIPAAm and natural network. Furthermore, numerous studies have shown the ability of CS to induce or enhance chondrogenesis, while the cartilage extracellular matrix wasn’t significantly increase in this study after twenty-one days. It reveals that mesenchymal stem cells couldn’t be induced chondrogenesis by CS alone without chondrogenic supplements.
Using New Zealand White Rabbit osteochondral defect as model showed that repairs of PNCS and NCS groups are much better than pure PNIPAAm hydrogel after 4 weeks and 12 weeks, especially NCS group after 4 weeks. Whereas such a positive result in NCS group didn’t maintain after 12 weeks, which may imply the shortage of chondroitin sulfate. Moreover, there was a synergistic increased loss of glycosaminoglycan around the edge of defect due to the poor mechanical integrity, the limitation of physical gels which could be solved by the tailoring of the material composition. This new material composed of PEG, PNIPAAm, and CS with more modifications (e.g. dose-dependent of CS or ratio of composition) and evaluations could be a promising candidate for cartilage tissue engineering.

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