以基質金屬蛋白酶建立具細胞專一生物可降解性之超分子水膠應用於三維人類骨髓間葉幹細胞培養

Abstract

Naphthalene -Phe-Phe (NapFF)為生物化學中常用的超分子序列，常被作為藥物釋放、細胞內調控和酵素活性分析的工具。許多文獻指出，NapFF不僅可以作為自組裝過程中，有效的成膠組件，也具有高度生物相容性和酵素調控成膠之特性，可應用在組織工程、再生醫學和注射治療等領域。然而，目前生物相容性試驗中，只利用低濃度之NapFF進行平面液態培養，尚未達到成膠濃度，以應用在三維組織工程研究上。因此，我們分別以海拉細胞和人類骨髓間葉幹細胞(Human bone marrow mesenchymal stem cells; hMSCs)為模型，進行NapFF水膠的三維細胞培養，利用DNA含量和明膠蛋白酵素電泳法，測定細胞增殖率、細胞存活度及進行特定蛋白質分析。 目前，我們加入含有氯化鈣之細胞懸浮液，已成功的建立NapFF三維之含細胞的超分子水膠。利用FTIR、CD spectra和SEM images，釐清鈣離子和NapFF上之羧基和酰胺的交互作用，並如何誘發NapFF進行自組裝並成膠的分子機轉，並影響到NapFF之奈米纖維尺度大小。此外，在細胞培養的實驗中，發現hMSCs在NapFF超分子水膠中，相對海拉細胞有較好的細胞增殖率和細胞存活度，且會降解NapFF水膠。在明膠蛋白酵素電泳法分析中，hMSCs的基質金屬蛋白酶(Matrix metalloproteinase-2; MMP-2)活性相對海拉細胞具有顯著性的差異。因此我們認為不同細胞之MMPs的活性差異，會導致細胞增殖與否和水膠的降解，而實驗顯示NapFF對於hMSCs具有細胞培養專一性。 為了進一步證明NapFF超分子水膠可應用在三維列印技術的可能性，我們包埋螢光分子代替生長因子在鈣離子誘發之NapFF自組裝水膠，測量螢光分子之擴散速率。研究結果顯示，含有氯化鈣的培養液，可以有效的抑制螢光分子的擴散，表示鈣離子誘發之NapFF自組裝水膠可以包埋生長因子，建立良好的細胞微環境提供幹細胞增殖並分化。

NapFF is a small unique unnatural amino acid. It has a potential to act as a small molecule hydrogelator. This may leads to the formation of NapFF supramolecular hydrogels, a unique type of soft material that consist of water. Apart, from NapFF’s ability to form building blocks for supramolecular self-assembly it has also excellent biocompatibility. Owing, to these properties NapFF have attracted much attention in biochemistry for its application in drug release, inner cellular regulation and enzyme activity analysis. The above mentioned properties of NapFF can further be exploited for its application in tissue engineering, regenerative medicine and minimal invasive threapy. However, before its practical application in these fields there are number of challenges need to be met such as low concentration of cultivated cells with NapFF and liquid form in biocompatibility test, less than the gelation concentrations for three-dimensional (3D) tissue engineering. In this study, we have successfully encapsulated HeLa cells and human bone marrow mesenchymal stem cells (hBMSCs) in 3D supramolecular hydrogel of NapFF in vitro. Quantifying DNA contents and enzyme activities were evaluated by studying the cells proliferation rates, viability and protein expressions. In this study, 3D cells-encapsulating supramolecular hydrogel of NapFF has been fabricated successfully via cell suspensions containing CaCl2 supplement. The FTIR, CD spectra and SEM study, is applied successfully to study the interactions of Ca2+ with the carboxylic acid and amide groups of NapFF. This type of metal ion interaction, also contributes to the self-assembly of hydrogels which further affected the diameter of NapFF nanofibers. In the cell encapsulation experiments, hBMSCs showed better proliferation rate, viability and biodegradability in NapFF supramolecular hydrogel, as compared with HeLa cells. According to gelatin zymography, the matrix metalloproteinase-2 (MMP-2) activity of hBMSCs was approximately 10-fold higher than HeLa cells. We proposed that the difference between enzyme activities in cells have permitted the cell proliferation and NapFF degradation. All of these results indicate that NapFF equipped with the characteristic of cell-type specific 3D cultivation for hBMSCs. Further, to apply this study in 3D printing technique a NapFF supramolecular hydrogel, with a fluorescence molecule embedded on it was prepared. This was done to substitute growth factor in Ca2+-induced NapFF hydrogels, and the diffusion ability is studied. On the basis of these experiments, it is concluded that the diffusion of fluorescence molecule can be suppressed by medium containing CaCl2. The study can also be applied to establish cellular microenvironment, which will be suitable for stem cells proliferation and differentiation.