2011-08-012024-05-14https://scholars.lib.ntu.edu.tw/handle/123456789/658581摘要：生物體的老化是因為組織器官功能的退化，這現象已被證實和細胞層面的老化有關。影響停經後婦女生活非常嚴重的骨質疏鬆症(osteoporosis)，主因其骨頭中的成骨細胞(Osteoblast)與去骨細胞(Osteoclast)不平衡所造成。醫學上已知隨著年齡的老化，骨髓中的間質幹細胞（Mesenchymal Stem Cell，是成骨細胞與脂肪細胞的前驅細胞）的數目會下降，但此同時骨髓中的脂肪細胞則會明顯的增加。是否間質幹細胞會因為老化而影響其分化方向的選擇與分化的能力，這其中的作用機制目前仍不清楚。目前已知間質幹細胞分化為成骨細胞和脂肪細胞主要分別是透過PPARγ2 以及RUNX2 來達到基因轉錄的調控。我們實驗室之前發現植物性荷爾蒙白棃蘆醇(resveratrol)可以同時增加骨密度及抑制乳癌細胞，且其機轉分別是透過forkheadprotein FOXA1 及FOXO3a（發表在J Biol Chem 2007）。而FOXO 在幹細胞的分化及凋亡已被學者報告占有極重要的角色（Cell 2007）。值得注意的是，白藜蘆醇也是抗老化基因SIRT1 的興奮劑(agonist)，而SIRT1 已知可抑制脂肪細胞中PPARγ 的活性。我們研究團隊之前發表胚胎幹細胞衍生來的間質幹細胞可抑制免疫反應（Stem Cells2009），最近更進一步發現在此間質幹細胞中，SIRT1 可透過和FOXO3A 結合來活化RUNX2 基因的轉錄和表現 ( J Bone Miner Res, in revision )。因此我們想要進一步來探討：老化對間質幹細胞分化方向的影響及其作用機轉。吾人計劃朝如下的目標去進行：目標一：在活性氧化物誘發間質幹細胞老化的模式中，評估老化對間質幹細胞分化方向與潛能的影響（第1-12 個月），目標二：探討間質幹細胞老化時PPARγ2、RUNX2 以及SIRT1 之間的交互調控，及探究傾向往脂肪分化的原因（第13-24 個月）目標三：在活體動物實驗中，驗證老化對間質幹細胞分化方向與潛能的影響（第25-36 個月）。本計劃的研究成果，預計將能帶來以下的價值：（1） 釐清老化對間質幹細胞分化方向的影響。（2） 進ㄧ步瞭解相關轉錄因子在間質幹細胞老化時的作用機轉。（3） 在活體動物實驗中驗證老化對間質幹細胞分化方向的影響，奠定骨質疏鬆症等重要老化疾病治療研究的基礎。<br> Abstract: In complex organisms, aging is associated with loss of function and degeneration in mostorgan systems; this is manifested at the cellular level as senescence. In the bone marrow (BM),aging is associated with an overwhelming increase of adipocytes at the expense of other celltypes, and it is known that the numbers of BM mesenchymal stem cells (MSCs)—theprogenitors of osteoblasts and adipocytes—are decreased with age. This phenomenon mayplay a role in osteoporosis, a disease of epidemic proportions in which bone formation is out ofbalance with resorption. Research has also shown that the osteoblastic differentiation capacityof BMMSCs may be decreased, but the mechanism remains largely unclear.Lineage commitment of MSCs to adipocytes and osteoblasts is competitively balancedand controlled by the transcription factors PPARγ2 and RUNX2, respectively. Our lab has beeninterested in the therapeutic osteogenic effects of natural compounds including resveratrol, aphytoestrogen, on osteoblasts and MSCs, We previously found that resveratrol cansimultaneously increase bone mineral density without increasing breast cancer formation viathe forkhead proteins FOXA1 and FOXO3A, respectively (published in J Biol Chem 2007).Interestingly, FOXO3A appears to be important in stem cell differentiation, and its functioncan be modified by SIRT1, an anti-aging gene for which resveratrol is an agonist. While SIRT1was reported to suppress PPARγ2 and adipogenesis and in vivo studies show osteogenesisincreased, it is still unclear how this is mediated at the molecular level.We have published that embryonic stem cell-derived multipotent progenitors (EMPs) ,which is a novel source of MSCs,. possess strong immunosuppressive effect ( Stem Cells 2009).Recently we further found that resveratrol via SIRT1 can act as an activator on RUNX2transcription of EMPs. This previously unreported action of SIRT1 on RUNX2 is mediatedthrough binding with FOXO3A via a novel FOXO-response element which we uncovered (inrevision for J Bone Miner Res).Thus, in this proposal, we are interested in elucidating the molecular mechanismsby which senescence can influence the lineage commitment of MSCs. Our Aims are: (1) toevaluate the influence of senescence on lineage commitment of MSCs using aROS-mediated model, (2) to investigate how the crosstalk of PPARγ2, RUNX2, andSIRT1 in senescent MSCs alters lineage commitment toward adipogenesis thanosteogenesis, and (3) to examine the in vivo effects of senescence on MSC lineagecommitment. We hope our study can yield mechanistic insight and provide therapeuticsolutions in light of the rapid graying of the world and the epidemic rise of age-related diseasesincluding osteoporosis.老化骨質疏鬆症活性氧化物間質幹細胞分化方向senescenceosteoporosisROSmesenchymal stem cellslineage commitment