Indiana University-Purdue University Indianapolis (IUPUI) / Human cord blood (CB) derived circulating endothelial colony forming cells (ECFCs) display a hierarchy of clonogenic proliferative potential and possess de novo vessel forming ability upon implantation in immunodeficient mice. Since survival of ECFC post-implantation is a critical variable that limits in vivo vasculogenesis, we tested the hypothesis that activation of Notch signaling or co-implantation of ECFC with human platelet lysate (HPL) would enhance cultured ECFC vasculogenic abilities in vitro and in vivo. Co-implantation of ECFCs with Notch ligand Delta-like 1 (DL1) expressing OP9 stromal cells (OP9-DL1) decreased apoptosis of ECFC in vitro and increased vasculogenesis of ECFC in vivo. The co-culture of ECFC with HPL diminished apoptosis of ECFC by altering the expression of pro-survival molecules (pAkt, pBad and Bcl-xL) in vitro and increased vasculogenesis of human EC-derived vessels both in vitro and in vivo. Thus, activation of the Notch pathway by OP9-DL1 stromal cells or co-implantation of ECFC with HPL enhances vasculogenesis and augments blood vessel formation by diminishing apoptosis of the implanted ECFC. The results from this study will provide critical information for the development of a cell therapy for limb and organ re-vascularization that can be applied to recovery of ischemic tissues in human subjects.

幹細胞療法是近年的研究熱點之一，然而幹細胞在組織修復中的實際應用受到移植後幹細胞存活率低的制約，約80% 的幹細胞在移植至組織後不能存活。 人類臍帶血管周皮 (HUCPV) 幹細胞為多功能間充質幹細胞移植提供豐富的細胞來源。 在合適的誘導環境下，它們具有向多種間充質細胞系分化的能力。 與從骨髓或臍帶血中提取的間充質幹細胞比較，人類臍帶血管周皮幹細胞的體外增殖更為容易。 在本研究中，我們從人類臍帶血管周圍組織中分離人類臍帶血管周皮幹細胞，並採用流式細胞技術分選細胞表面標記物CD34、CD45呈陰性同時CD44 、CD90、 CD105、 CD146呈陽性的HUCPV細胞。HUCPV細胞在體外培養以及三維支架的環境下具有分化為骨和軟骨的能力。 / 在本研究中，我們主要研究腦和生殖器官表達基因（BRE）在HUCPV細胞中的功能。 BRE蛋白與其他已知蛋白的同源性均不高，目前尚未鑑定出任何功能性的結構域。 至今為止，BRE基因的已知功能大多數是通過對腫瘤模型的研究發現的。 據報導，BRE能夠提高DNA損傷的腫瘤細胞的存活率，但BRE在幹細胞中的作用仍不清楚。 我們發現，當HUCPV細胞分化後，其BRE的表達水平降低。 此外，利用BRE-siRNA降低HUCPV細胞中BRE基因的表達，能夠促進HUCPV細胞向骨和軟骨分化的進程。 因此，我們假設BRE對維持HUCPV細胞的幹細胞功能具有重要的作用。 由於經過BRE基因沉默處理的HUCPV細胞與對照組相比並無顯著的表型差別，我們採用微陣列（microarray）以及比較蛋白組學的方法研究兩者間的區別，從而找出BRE基因的功能以及可能涉及BRE的信號通路。 / 通過微陣列技術，我們深入地分析了BRE基因表達沉默後HUCPV細胞的轉錄組。 在經過BRE基因沉默處理的HUCPV細胞中，我們發現與維持幹細胞多向分化潛能有關的OCT4、 FGF5和FOXO1A等基因的表達顯著下調。 另外，BRE基因的沉默能夠影響表觀遺傳調控基因以及TGF-β 信號通路組成部件的表達，而TGF -β 信號通路是維持幹細胞自我更新的重要通路。 這些結果提示，BRE作為一個重要的調控因子，在維持HUCPV細胞的多向分化潛能的同時能夠防止細胞分化。 / 在比較蛋白組學的研究中，我們發現BRE基因的沉默能夠降低細胞骨架結合蛋白的表達，例如actin, annexin II 及 tropomyosin。 此外，我們利用免疫共沉澱的方法證明了BRE蛋白與actin及 annexin II蛋白直接結合。 細胞骨架的改變可能為HUCPV細胞的分化提供了一個有利的環境，因而BRE基因的沉默能夠促進HUCPV細胞向骨和軟骨分化。 支持這一推論的其中一個依據是Lim et al., 2000; Solursh, 1989; Zhang et al., 2006，文獻報導肌動蛋白多聚化抑製劑能夠促進軟骨形成的過程。 綜上所述，本研究為進一步研究BRE基因在HUCPV細胞中的功能以及與BRE直接作用的蛋白打下了基礎。 / Stem cells therapy has gained considerable attention in recent years. However, the practical use of stem cells for tissue repair has been hindered due to their low survival rate after grafting into tissues, for approximately 80% of the stem cells died after implantation. Human umbilical cord perivascular (HUCPV) stem cells offer a new and rich resource of multipotent mesenchymal stem cells. These cells possess the ability to differentiate into various mesenchymal cell lineages when induced. HUCPV cells can be more easily amplified in culture than mesenchymal stem cells extracted from bone marrow or umbilical cord blood. In this study, HUCPV cells were isolated from the perivascular regions of human umbilical cords. The HUCPV cells were sorted using flow cytometer for CD34⁻, CD44⁺, CD45⁻, CD90⁺, CD105⁺ and CD146⁺ surface markers. These HUCPV cells were found to be capable of differentiating into osteogenic lineage in monolayer culture and chondrogenic lineage in pellet culture. These cells were also found to be capable of differentiating into osteogenic and chondrogenic lineage in silk fibroin which acted as three-dimensional scaffolds for the cells to grow on. / The function of the Brain and Reproductive Organ-Expressed (BRE) gene in the context of HUCPV cells was investigated. The BRE protein shares no homology with any other known gene products and contains no known functional domain. To date, most of what we know about the function of this gene has been conducted in the tumor model. It has been reported that BRE can enhance the cellular survival of cancer cells following DNA damage. The role of BRE in stem cells has never been examined. We have established that BRE expression was down-regulated when HUCPV cells started to differentiate. In addition, silencing BRE expression, using BRE-siRNA, in HUCPV cells could accelerate osteogenic and chondrogenic differentiation. Hence, we hypothesized that BRE played an important role in maintaining the stemness of HUCPV cells. Because there was a lack of phenotypic difference between the BRE-silenced HUCPV cells and cells transfected with the control-siRNA, we decided to profile these cells using microarray and proteomic analyses. The aim was to elucidate the function of the BRE gene and establish whether BRE was involved in any signaling pathways. / In the microarray analysis, we examined the transcriptome of HUCPV cells in response to BRE-silencing in depth. Amongst the genes that we identified were significantly down-regulated by BRE-silencing and involved in the maintenance of pluripotency in ES cells were OCT4, FGF5 and FOXO1A. BRE-silencing also altered the expression of epigenetic genes and also components of the TGF-β signaling pathway. This pathway is crucially involved in maintaining stem cell self-renewal. Therefore, we propose that BRE acts like a modulator that promotes stemness and at the same time inhibits the differentiation of HUCPV cells. / In the comparative proteomic study, BRE-silencing resulted in decreased expression patterns of cytoskeletal binding proteins such as actin, annexin II and tropomyosin. In addition, co-immunoprecipitation experiments revealed that the BRE protein can bind directly with actin and annexin II. It is possible that altering the cytoskeleton may provide a favorable environment for HUCPV cells to differentiate. This may explain why we were able to accelerate osteogenic and chondrogenic differentiation following BRE-silencing. In support of the view, it has been reported that chondrogenesis could be enhanced after cells have been treated with actin polymerization inhibitors (Lim et al., 2000; Solursh, 1989; Zhang et al., 2006). In sum, our studies provide an insight into the function of the BRE gene in HUCPV cells and the proteins that BRE can directly act on. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chen, Elve. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 135-159). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Thesis/Assessment Committee --- p.i / Abstract --- p.ii / 摘要 --- p.v / Acknowledgements --- p.viii / List of Figures --- p.ix / List of Tables --- p.xiii / Table of Abbreviations --- p.xiv / Contents --- p.xviii / Chapter 1 --- p.1 / Literature Review --- p.1 / Chapter 1.1 --- Stem cells --- p.1 / Chapter 1.2 --- Embryonic stem cells (ESCs) --- p.2 / Chapter 1.3 --- Epiblast-derived stem (EpiS) cells --- p.2 / Chapter 1.4 --- Somatic stem cells (SSCs) --- p.3 / Chapter 1.5 --- Induced pluripotent stem (iPS) cells --- p.5 / Chapter 1.6 --- Human umbilical cord perivascular (HUCPV) cells --- p.7 / Chapter 1.7 --- CD146 --- p.8 / Chapter 1.8 --- Stem cell senescence --- p.9 / Chapter 1.9 --- Brain and reproductive organ-expressed (BRE) protein --- p.12 / Chapter 1.10 --- Stem cell self-renewal --- p.14 / Chapter 1.11 --- Apoptosis --- p.16 / Chapter 1.12 --- Stem cell niche --- p.21 / Chapter 1.13 --- Stem cell homing --- p.22 / Chapter 1.14 --- Objective --- p.22 / Chapter 2 --- p.24 / Accelerated osteogenic and chondrogenic differentiation of HUCPV cells by modulating the expression of BRE --- p.24 / Chapter 2.1 --- Introduction --- p.24 / Chapter 2.2 --- Rationale --- p.27 / Chapter 2.3 --- Materials and Methods --- p.27 / Chapter 2.3.1 --- Extraction of HUCPV cells from umbilical cord --- p.27 / Chapter 2.3.2 --- Cell culture condition --- p.28 / Chapter 2.3.3 --- Flow cytometry analysis and cell sorting --- p.28 / Chapter 2.3.4 --- In vitro osteogenic differentiation --- p.29 / Chapter 2.3.5 --- In vitro chondrogenic differentiation --- p.29 / Chapter 2.3.6 --- Alcian blue staining --- p.29 / Chapter 2.3.7 --- Alizarin red S staining --- p.30 / Chapter 2.3.8 --- Immunofluorescence analysis --- p.30 / Chapter 2.3.9 --- Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) --- p.31 / Chapter 2.3.10 --- Transfection with siRNA --- p.35 / Chapter 2.3.11 --- Microarray --- p.35 / Chapter 2.3.12 --- Cell lysis and immunoprecipitation --- p.36 / Chapter 2.3.13 --- SDS-PAGE and Western blot --- p.36 / Chapter 2.3.14 --- Isoelectric focusing and 2-dimensional gel electrophoresis --- p.37 / Chapter 2.3.15 --- Migration (wound healing) assay --- p.38 / Chapter 2.4 --- Results --- p.38 / Chapter 2.4.1 --- HUCPV cells were capable to differentiate into osteoblasts and chondrocytes --- p.38 / Chapter 2.4.2 --- BRE expression is down-regulated when HUCPV cells begins to differentiate --- p.40 / Chapter 2.4.3 --- Silencing of BRE expression accelerates induction of osteogenesis and chondrogenesis --- p.40 / Chapter 2.4.4 --- Microarray analysis of BRE-silenced HUCPV cells --- p.42 / Chapter 2.4.4.1 --- Stemness factors --- p.43 / Chapter 2.4.4.2 --- Epigenetic regulation --- p.43 / Chapter 2.4.4.3 --- Signaling pathways crucial for stemness maintenance --- p.44 / Chapter 2.4.4.4 --- TGF-β signaling --- p.44 / Chapter 2.4.4.5 --- FGF signaling --- p.44 / Chapter 2.4.4.6 --- NOTCH signaling --- p.45 / Chapter 2.4.4.7 --- WNT signaling --- p.46 / Chapter 2.4.4.8 --- Homeobox transcription factors (HOX) --- p.46 / Chapter 2.4.4.9 --- Cell cycle regulation --- p.47 / Chapter 2.4.4.10 --- Chemokines and cytokines regulation --- p.48 / Chapter 2.4.4.11 --- Apoptosis --- p.49 / Chapter 2.4.5 --- BRE-silencing alters the cellular proteome of HUCPV cells --- p.50 / Chapter 2.4.5.1 --- BRE-silencing alters the cytoskeletal binding proteins of HUCPV cells --- p.51 / Chapter 2.4.5.2 --- BRE-silencing alters the expressions of stemness-related proteins in HUCPV cells --- p.52 / Chapter 2.4.5.3 --- BRE-silencing alters the expressions of apoptosis-related proteins in HUCPV cells --- p.53 / Chapter 2.5 --- Discussion --- p.86 / Chapter 2.5.1 --- Microarray study discussion --- p.87 / Chapter 2.5.2 --- Proteomic study discussion --- p.89 / Chapter 3 --- p.93 / Replicative senescence alters the transcriptome and proteome of HUCPV cells --- p.93 / Chapter 3.1 --- Introduction --- p.93 / Chapter 3.2 --- Materials and methods --- p.93 / Chapter 3.3 --- Results --- p.93 / Chapter 3.3.1 --- Microarray analysis of aged HUCPV cells --- p.94 / Chapter 3.3.1.1 --- Stemness factors --- p.95 / Chapter 3.3.1.2 --- Epigenetic regulation --- p.96 / Chapter 3.3.1.3 --- Senescence associated markers --- p.96 / Chapter 3.3.1.4 --- Chemokines and cytokines regulation --- p.97 / Chapter 3.3.1.5 --- Matrix metalloproteinases regulation --- p.97 / Chapter 3.3.1.6 --- WNT signaling --- p.98 / Chapter 3.3.1.7 --- Toll-like receptor signaling pathway --- p.98 / Chapter 3.3.2 --- Proteomic profiling of aged HUCPV cells --- p.98 / Chapter 3.4 --- Discussion --- p.117 / Chapter 3.4.1 --- Aging alters the transcriptome of HUCPV cells --- p.117 / Chapter 3.4.2 --- Aging alters the proteome of HUCPV cells --- p.118 / Chapter 4 --- p.121 / Osteogenic and chondrogenic differentiation capacities of HUCPV cells in silk fibroin scaffold --- p.121 / Chapter 4.1 --- Introduction --- p.121 / Chapter 4.2 --- Materials and methods --- p.121 / Chapter 4.2.1 --- Extraction of silk fibroin --- p.121 / Chapter 4.2.2 --- Fabrication of porous silk fibroin scaffold --- p.122 / Chapter 4.2.3 --- Scanning electron microscopy --- p.123 / Chapter 4.2.4 --- Cell culture --- p.123 / Chapter 4.3 --- Results --- p.124 / Chapter 4.4 --- Discussion --- p.132 / Chapter 5 --- p.133 / Conclusions --- p.133 / References --- p.135