探討間葉幹細胞分化過程中脂小體增生活化受體在免疫調控所扮演的角色

Study on the role of Peroxisome Proliferator-Activated Receptors (PPARs) in the immune regulatory activities during mesenchymal stem cell differentiation

郭卉玲(Huei-Ling Kuo)

指導教授 ： 江伯倫

國立臺灣大學/醫學院/免疫學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602124

摘要

間葉幹細胞(Mesenchymal stem cells, MSCs)是一種具有自我更新能力及高度分化潛能的成體幹細胞，間葉幹細胞能夠進一步分化成脂肪細胞、硬骨細胞和軟骨細胞等，更有研究指出間葉幹細胞具備免疫抑制之調控能力。但是許多肥胖相關的代謝疾病，例如:第二型糖尿病、心血管疾病則是由脂肪細胞所造成的發炎反應，同時有巨噬細胞受到脂肪組織所分泌的賀爾蒙或是趨化因子所吸引而聚集，並在發炎反應中扮演重要的角色。我們假設在間葉幹細胞的脂肪分化過程中有些調控因子產生了變化，其中像是脂小體增生活化受體γ (peroxisome proliferator-activated receptor-γ, PPAR-γ)在發炎及抗發炎的角色也尚未釐清，因此我們的研究希望探討間葉幹細胞在脂肪分化過程中基因及細胞激素的改變。
在間葉幹細胞脂肪分化過程中，會有許多發炎激素的分泌和相關基因表現，包括了介白素-6 (IL-6)、腫瘤壞死因子-α (TNF-α)和單核球趨化蛋白-1 (mcp1)，但間葉幹細胞表面抗原的表現與免疫調控能力皆會隨著分化而降低，抗發炎的介白素1受體拮抗劑 (IL-1Ra)亦會與分化呈現負相關趨勢，此外，脂小體增生活化受體γ更能透過抑制介白素1受體拮抗劑來促進脂肪分化的情形。
目前我們發現在間葉幹細胞脂肪分化過程中，加入脂小體增生活化受體γ促進劑能夠增加脂聯素 (adiponectin)的表現，並且使細胞大量表現發炎相關基因；反之，加入脂小體增生活化受體γ抑制劑則造成相反的效果，不過無論促進劑或是抑制劑在細胞的型態以及分化速度上都會造成抑制效果。除此之外，這兩個組別的細胞皆無法有效的抑制T淋巴球增生，代表細胞免疫調控能力皆受到抑制。未來我們將繼續探討是否有其他更重要的免疫調控因子影響間葉幹細胞脂肪分化及免疫抑制能力。

關鍵字

間葉幹細胞 ； 脂肪分化 ； 發炎反應 ； 脂小體增生活化受體γ ； 介白素1受體拮抗劑

並列摘要

Mesenchymal stem cells (MSCs) are self-renewable multipotent progenitor cells that can differentiate into a variety of cell types including adipocytes, osteocytes and chondrocytes. Recent studies have demonstrated that MSCs could exert an immunosuppressive activity. However, many obesity-related metabolic diseases such as type II diabetes are attributed to adipocyte-induced inflammation. Macrophages recruited by adipose tissue-derived hormones or chemokines, play the key roles in the chronic inflammation. We hypothesized that some mediators might be changed during the MSCs adipogenesis. Especially, the role of PPAR-γ in inflammation and anti-inflammation are still unclear. Hence, this study was performed to examine the gene and cytokine profiles of MSCs in different differential process.
Alone with MSCs adipogenesis, more inflammatory cytokines, including IL-6, TNF-α, and mcp1 were secreted and expressed. But the expression of MSCs surface markers and immune-modulatory function were decreased. Also, the expression of IL-1Ra was negatively correlated with adipogeneic process of MSCs. Furthermore, peroxisome proliferator-activated receptors (PPARs) can promote adipogenesis by inhibiting IL-1Ra expression.
So far, we discovered that adding PPAR-γ agonist could enhance adiponectin and inflammatory genes expression. On the other hand, adding PPAR-γ antagonist resulted in the opposite effects. Further, the cells of PPAR-γ agonist and antagonist group inhibited phenotypic change or adipogenic progressing. Also, agonist and antagonist decreased MSCs immunosuppressive function during adipogenic process. We would like to find out if there is any factor that can directly influence MSCs adipogenesis and their immune-suppressive function.

並列關鍵字

mesenchymal stem cells ； adipogenesis ； inflammation ； PPAR-γ ； IL-1Ra

參考文獻

1. Birbrair, A., et al., Nestin-GFP transgene reveals neural precursor cells in adult skeletal muscle. PLoS ONE, 2011. 6(2): p. e16816.

2. da Silva Meirelles, L., P.C. Chagastelles, and N.B. Nardi, Mesenchymal stem cells reside in virtually all post-natal organs and tissues. J Cell Sci, 2006. 119(Pt 11): p. 2204-13.

3. Dominici, M., et al., Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy position statement. Cytotherapy, 2006. 8(4): p. 315-7.

4. Klingemann, H., D. Matzilevich, and J. Marchand, Mesenchymal stem cells – sources and clinical applications. Transfusion Medicine and Hemotherapy, 2008. 35(4): p. 272-277.

5. Bartholomew, A., et al., Mesenchymal stem cells suppress lymphocyte proliferation in vitro and prolong skin graft survival in vivo. Exp Hematol, 2002. 30(1): p. 42-8.