Whatever their differentiation status,human progenitor derived – or mature – endothelial cells induce osteoblastic differentiation of bone marrow stromal cells

Association of the bone‐forming osteoblasts (OBs) and vascular endothelial cells (ECs) into a biomaterial composite provides a live bone graft substitute that can repair the bone defect when implanted. An intimate functional relationship exists between these cell types. This communication is crucial to the coordinated cell behaviour necessary for bone development and remodelling. Previous studies have shown that direct co‐culture of primary human osteoprogenitors (HOPs) with primary human umbilical vein endothelial cells (HUVECs) stimulates HOPs differentiation and induces tubular‐like networks. The present work aims to test the use of human bone marrow stromal cells (HBMSCs) co‐cultured with human endothelial progenitor cells in order to assess whether progenitor‐derived ECs (PDECs) could support osteoblastic differentiation as mature ECs do. Indeed, data generated from the literature by different laboratories considering these co‐culture systems appear difficult to compare. Monocultures of HUVECs, HOPs, HBMSCs (in a non‐orientated lineage), PDECs (from cord blood) were used as controls and four combinations of co‐cultures were undertaken: HBMSCs–PDECs, HBMSCs–HUVECs, HOPs–PDECs, HOPs–HUVECs with ECs (mature or progenitor) for 6 h to 7 days. At the end of the chosen co‐culture time, intracellular alkaline phosphatase (ALP) activity was detected in HOPs and HBMSCs and quantified in cell extracts. Quantitative real‐time polymerase chain reaction (qPCR) of ALP was performed over time and vascular endothelial growth factor (VEGF) was measured. After 21 days, calcium deposition was observed, comparing mono‐ and co‐cultures. We confirm that ECs induce osteoblastic differentiation of mesenchymal stem cells in vitro. Moreover, HUVECs can be replaced by PDECs, the latter being of great interest in tissue engineering. Copyright © 2012 John Wiley & Sons, Ltd.     

Co‐culture of adipose‐derived stem cells and endothelial cells in fibrin induces angiogenesis and vasculogenesis in a chorioallantoic membrane model

Neovascularization of adipose tissue equivalents is a crucial step in successful adipose tissue engineering, since insufficient vascularization results in graft resorption in an in vivo situation. A possible cellular approach to overcome this limitation is the co‐implantation of adipose‐derived stem cells (ASCs) with endothelial cells to stimulate the formation of a vascular network. We investigated the potential of ASCs derived from human abdominal fat tissue co‐cultured with endothelial progenitor cells (EPCs) from human peripheral blood to stimulate neovascularization of fibrin constructs on the chorioallantoic membrane (CAM) of fertilized chicken eggs, in direct comparison to human umbilical vein endothelial cells (HUVECs). After 9 days of incubation, cell–fibrin constructs were explanted and histologically evaluated with respect to ingrowth of avian blood vessels into the construct and formation of human blood vessels by co‐implanted endothelial cells. When administered on the CAM, ASCs successfully guided host vasculature into the construct (angiogenesis) and guided formation of capillary‐like structures by co‐implanted human endothelial cells (vasculogenesis), with HUVECs being superior to EPCs, leading to a perfused avian and human capillary network within the fibrin construct. However, the results also showed that perfused human blood vessels were only observed near the CAM compared to unperfused capillary‐like structures near the top of the construct, indicating that perfusion of the cell–fibrin construct takes longer than 9 days. In conclusion, as blood vessel formation is an essential step during adipogenic differentiation, the data support our hypothesis that cellular communication between transplanted ASCs and endothelial cells is beneficial for vasculogenesis. Copyright © 2013 John Wiley & Sons, Ltd.     

Internalization of microparticles by endothelial cells promotes platelet/endothelial cell interaction under flow

Summary. Background: Microparticles (MPs) released by activated or apoptotic cells increase in number in the blood of subjects with vascular or metabolic diseases and may contribute to thrombotic complications. Objectives: In this study, we investigated whether MPs promoted platelet recruitment to endothelial cells in flow conditions, and by which mechanism. Methods: Human umbilical vein endothelial cells (HUVECs) grown in microslide perfusion chambers were exposed to MPs prepared in vitro from HUVECs, monocytes or platelets. Results: Videomicroscopy of DIOC‐labelled blood perfused at arterial rate on human umbilical vein ECs demonstrated that, irrespective of their cell origin, MPs promoted the formation of platelet strings at the surface of HUVECs. This platelet/endothelial cell interaction was dependent on von Willebrand factor (VWF) expression at the HUVEC surface and involved Glycoprotein Ib and P‐selectin. Interestingly, HUVECs internalized MPs within a few hours through a process involving anionic phospholipids, lactadherin and αvβ3 integrin. This uptake generated the production of reactive oxygen species via the xanthine/xanthine oxidase system (inhibited by allopurinol and the ROCK inhibitor Y‐27632) and the NADPH oxidase (inhibited by SOD). Reactive oxygen species appeared essential for VWF expression at the endothelial cell surface and subsequent platelet/endothelial cell interaction under flow. The pathophysiological relevance of this process is underlined by the fact that circulating MPs from Type I diabetic patients induced platelet/endothelial cell interaction under flow, with an intensity correlated with the severity of the vasculopathy.     

Adipose‐derived stem cells induce vascular tube formation of outgrowth endothelial cells in a fibrin matrix

Vascularization of engineered tissues is one of the current challenges in tissue engineering. Several strategies aim to generate a prevascularized scaffold which can be implanted at sites of injury or trauma. Endothelial cells derived from peripheral blood (outgrowth endothelial cells, OECs) display promising features for vascular tissue engineering, including their autologous nature, capacity for proliferation and ability to form mature vessels. In this study we investigated the ability of OECs to form vascular structures in co‐culture with adipose‐derived stem cells (ASCs) in a fibrin matrix. Using microcarrier beads coated with OECs, we showed ingrowth of endothelial cells in the fibrin scaffold. Furthermore, co‐cultures with ASCs induced vessel formation, as evidenced by immunostaining for CD31. The degradation of fibrin is at least in part mediated by expression of matrix metalloproteinase‐14. Moreover, we showed OEC/ASC‐induced vessel‐like structure formation even in the absence of microcarrier beads, where increasing amounts of ASCs resulted in a denser tubular network. Our data add new insights into co‐culture‐induced vessel formation of outgrowth endothelial cells within a fibrin matrix in an autologous system. Copyright © 2012 John Wiley & Sons, Ltd.     

内皮祖细胞在膀胱细胞外基质上的生长及分化

背景：传统的组织工程膀胱支架材料本身无血管结构,植入体内后面临血管化不足的问题。目的：观察内皮祖细胞与膀胱细胞外基质的生物相容性。方法：分离培养兔内皮祖细胞,种植于兔膀胱细胞外基质上与其复合培养。将复合生长材料植入兔背部皮下检测其组织相容性。结果与结论：兔内皮祖细胞能够在膀胱细胞外基质表面正常黏附、生长、增殖,细胞形态良好。内皮祖细胞-膀胱细胞外基质植入兔体内后1周时,可见材料周围炎症反应明显,粘连严重,出血较多;苏木精-伊红染色可见组织中较多炎性细胞浸润,胶原及弹性纤维排列松散。植入后8周时可见材料已降解成碎细丝状,与周围组织融合生长在一起,但质地略脆,易出血;苏木精-伊红染色可见组织中已无明显炎症细胞浸润反应,胶原及弹性纤维排列紧密并且有新生血管长入其中。结果表明内皮祖细胞与膀胱细胞外基质具有良好的相容性,复合培养物与体内组织具有良好的相容性。     

内皮祖细胞在膀胱细胞外基质上的生长及分化

背景:传统的组织工程膀胱支架材料本身无血管结构,植入体内后面临血管化不足的问题。目的:观察内皮祖细胞与膀胱细胞外基质的生物相容性。方法:分离培养兔内皮祖细胞,种植于兔膀胱细胞外基质上与其复合培养。将复合生长材料植入兔背部皮下检测其组织相容性。结果与结论:兔内皮祖细胞能够在膀胱细胞外基质表面正常黏附、生长、增殖,细胞形态良好。内皮祖细胞-膀胱细胞外基质植入兔体内后1周时,可见材料周围炎症反应明显,粘连严重,出血较多;苏木精-伊红染色可见组织中较多炎性细胞浸润,胶原及弹性纤维排列松散。植入后8周时可见材料已降解成碎细丝状,与周围组织融合生长在一起,但质地略脆,易出血;苏木精-伊红染色可见组织中已无明显炎症细胞浸润反应,胶原及弹性纤维排列紧密并且有新生血管长入其中。结果表明内皮祖细胞与膀胱细胞外基质具有良好的相容性,复合培养物与体内组织具有良好的相容性。     

Shear stress with appropriate time‐step and amplification enhances endothelial cell retention on vascular grafts

Endothelial cells (ECs) are sensitive to changes in shear stress. The application of shear stress to ECs has been well documented to improve cell retention when placed into a haemodynamically active environment. However, the relationship between the time‐step and amplification of shear stress on EC functions remains elusive. In the present study, human umbilical cord veins endothelial cells (HUVECs) were seeded on silk fibroin nanofibrous scaffolds and were preconditioned by shear stress at different time‐steps and amplifications. It is shown that gradually increasing shear stress with appropriate time‐steps and amplification could improve EC retention, yielding a complete endothelial‐like monolayer both in vitro and in vivo. The mechanism of this improvement is mediated, at least in part, by an upregulation of integrin β1 and focal adhesion kinase (FAK) expression, which contributed to fibronectin (FN) assembly enhancement in ECs in response to the shear stress. A modest gradual increase in shear stress was essential to allow additional time for ECs to gradually acclimatize to the changing environment, with the goal of withstanding the physiological levels of shear stress. This study recognized that the time‐steps and amplifications of shear stress could regulate EC tolerance to shear stress and the anti‐thrombogenicity function of engineered vascular grafts via an extracellular cell matrix‐specific, mechanosensitive signalling pathway and might prevent thrombus formation in vivo. Copyright © 2016 John Wiley & Sons, Ltd.     

Micropatterned three‐dimensional hydrogel system to study human endothelial–mesenchymal stem cell interactions

The creation of vascularized engineered tissues of clinically relevant size is a major challenge of tissue engineering. While it is known that endothelial and mural vascular cells are integral to the formation of stable blood vessels, the specific cell types and optimal conditions for engineered vascular networks are poorly understood. To this end, we investigated the vasculogenic potential of human mesenchymal stem cell (MSC) populations derived from three different sources: (a) bone marrow aspirates; (b) perivascular cells from the umbilical cord vein; and (c) perivascular cells from the umbilical cord artery. Cell populations were isolated and identified as MSCs according to their phenotypes and differentiation potential. Human umbilical vein endothelial cells (HUVECs) were used as a standard for endothelial cells. A novel co‐culture system was developed to study cell–cell interactions in a spatially controlled three‐dimensional (3D) fibrin hydrogel model. Using microfluidic patterning, it was possible to localize hydrogel‐encapsulated HUVECs and MSCs within separate channels spaced at 500, 1000 or 2000 µm. All three MSC populations had similar expression profiles of mesenchymal cell markers and similar capacity for osteogenic and adipogenic differentiation. However, bone marrow‐derived MSCs (but not umbilical vein or artery derived MSCs) showed strong distance‐dependent migration toward HUVECs and supported the formation of stable vascular networks resembling capillary‐like vasculature. The presented approach provides a simple and robust model to study the cell–cell communication of relevance to engineering vascularized tissues. Copyright © 2009 John Wiley & Sons, Ltd.     

In vitro analysis of the interactions between preadipocytes and endothelial cells in a 3D fibrin matrix

The volume‐persistent survival of transplanted adipose tissue in vivo relies on early vascularization, due to an otherwise early induction of apoptosis of the centrally located cells. Thus, one way to enable the early formation of a capillary network resulting in a sufficient perfusion of the transplanted construct might be the co‐transplantation of autologous preadipocytes with endothelial cells. To investigate preadipocyte–endothelial cell interaction, three‐dimensional proliferation‐ and angiogenesis assays were performed in vitro. Proliferation rates of co‐cultured endothelial cells and preadipocytes suspended in a fibrin matrix were elucidated by Alamarblue assays. The spheroid angiogenesis model was applied for analyzing the effects of vascular endothelial cell growth factor (VEGF) and basic fibroblast growth factor (bFGF) (produced by preadipocytes) as well as the impact of cell‐cell interaction between preadipocytes and endothelial cells and fibrin matrix on endothelial cell migration. Preadipocytes proliferated in fibrin glue, whereas endothelial cells underwent apoptosis. By co‐culturing, both cell types demonstrated an increased proliferation rate. Preadipocytes provoked migration of endothelial cells. Blocking bFGF and/or VEGF led to a significant decrease of migration. Changes in fibrin structure were followed by migration of single cells instead of sprouting. An appropriate fibrin matrix as well as already differentiated endothelial cells are necessary for preadipocytes to develop their angiogenic activity via bFGF and VEGF.     

人外周血内皮祖细胞培养方法的建立

背景：成人外周血来源丰富,但内皮祖细胞含量较少,为使其能够更好的应用于组织工程及细胞治疗,有必要建立外周血内皮祖细胞成熟、稳定的体外扩增体系。目的：建立稳定的人外周血分离、培养和体外扩增血管内皮祖细胞的方法。方法：应用密度梯度离心法,获取外周血单个核细胞,将分选后细胞接种于预先包埋了人纤维连接蛋白的培养板上,加入内皮祖细胞专用培养基中培养3d后,洗掉非贴壁细胞,培养至第6天,收集贴壁细胞,应用倒置显微镜和苏木精-伊红染色进行细胞形态学观察;采用MTT法和细胞计数测定第1,3代细胞生长曲线;应用流式细胞仪测定祖细胞和内皮细胞系标志,对培养的细胞进行鉴定。结果与结论：细胞生长曲线测定表明接种后第3天细胞进入指数增生期,至第6天进入平台期,随着传代次数的增加,细胞增殖速度变慢,同时表达干细胞表面标志CD34、CD133和内皮细胞表面标志血管性血友病因子、血管内皮生长因子受体2。证明人外周血可以分离培养内皮祖细胞。     

人外周血内皮祖细胞培养方法的建立

背景:成人外周血来源丰富,但内皮祖细胞含量较少,为使其能够更好的应用于组织工程及细胞治疗,有必要建立外周血内皮祖细胞成熟、稳定的体外扩增体系.目的:建立稳定的人外周血分离、培养和体外扩增血管内皮祖细胞的方法.方法:应用密度梯度离心法,获取外周血单个核细胞,将分选后细胞接种于预先包埋了人纤维连接蛋白的培养板上,加入内皮祖细胞专用培养基中培养3d 后,洗掉非贴壁细胞,培养至第6 天,收集贴壁细胞,应用倒置显微镜和苏木精-伊红染色进行细胞形态学观察;采用MTT 法和细胞计数测定第1,3 代细胞生长曲线;应用流式细胞仪测定祖细胞和内皮细胞系标志,对培养的细胞进行鉴定.结果与结论:细胞生长曲线测定表明接种后第3 天细胞进入指数增生期,至第6 天进入平台期,随着传代次数的增加,细胞增殖速度变慢,同时表达干细胞表面标志CD34、CD133 和内皮细胞表面标志血管性血友病因子、血管内皮生长因子受体2.证明人外周血可以分离培养内皮祖细胞.     

Endothelial colony‐forming cells for preparing prevascular three‐dimensional cell‐dense tissues using cell‐sheet engineering

Vascular‐derived endothelial cell (EC) network prefabrication in three‐dimensional (3D) tissue constructs before transplantation is useful for inducing functional anastomosis with the host vasculature. However, the clinical application of ECs is limited by cell isolation from the existing vasculature, because of the requirement for invasive biopsies and difficulty in obtaining a sufficient number of cells. Endothelial colony‐forming cells (ECFCs), which are a subtype of endothelial progenitor cells in the blood, have a strong proliferative and vasculogenic potential. This study attempted to fabricate prevascular 3D cell‐dense tissue constructs using cord blood‐derived ECFCs and evaluate the in vivo angiogenic potential of these constructs. Human umbilical vascular endothelial cells (HUVECs) were also used in comparison with ECFCs, which were sandwiched between two human dermal‐derived fibroblast (FB) sheets using a fibrin‐coated cell‐sheet manipulator. The inserted ECFCs in double‐layered FB sheets were cultured for 3 days, resulting in the formation of network structures similar to those of HUVECs. Additionally, when ECFCs were sandwiched with three FB sheets, a lumen structure was found in the triple‐layered cell‐sheet constructs at 3 days after co‐culture. These constructs containing ECFCs were transplanted into the subcutaneous tissue of immune‐deficient rats. One week after transplantation, ECFC‐lined functional microvessels containing rat erythrocytes were observed in the same manner as transplanted HUVEC‐positive grafts. These results suggest that ECFCs might become an alternative cell source for fabricating a prevascular structure in 3D cell‐dense tissue constructs for clinical application. Copyright © 2013 John Wiley & Sons, Ltd.     

Endothelial cell seeding of (heparinized) collagen matrices: effects of bFGF pre-loading on proliferation (after low density seeding) and pro-coagulant factors.

Endothelial cell seeding to improve the performance of small-diameter vascular grafts requires a suitable substrate, such as crosslinked collagen. In addition to providing a suitable substrate for adhesion and growth of endothelial cells, proliferation of seeded endothelial cells can be enhanced by local, sustained release of basic fibroblast growth factor (bFGF, a heparin-binding growth factor for endothelial cells). We have previously shown that collagen crosslinked using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS) supports adhesion and proliferation of human umbilical vein endothelial cells (HUVECs). In the present study, HUVECs were seeded on (heparinized) EDC/NHS-crosslinked collagen, pre-loaded with bFGF. Proliferation of HUVECs on (heparinized) crosslinked collagen increased with increasing amounts of pre-loaded bFGF. The minimal cell-seeding density required for proliferation proved to be very low after pre-loading the substrates with bFGF, and was 4-fold lower for heparinized crosslinked collagen compared to crosslinked collagen (250 versus 1000 cells/cm(2)). Pro-coagulant properties (von Willebrand factor secretion and tissue factor expression) of HUVECs seeded on (heparinized) crosslinked collagen, with or without pre-loading of bFGF, were comparable to those of HUVECs on TCPS. It is concluded that heparinized, EDC/NHS-crosslinked collagen pre-loaded with bFGF is a candidate matrix for in vivo endothelial cell seeding of synthetic vascular graft materials.     

血管内皮祖细胞在组织工程皮肤构建中的意义

背景:血管内皮祖细胞可加速缺血部位的血管化.目的:综合分析血管内皮祖细胞加速组织工程皮肤血管化的方法和途径.方法:计算机检索中国期刊全文数据及PubMed数据库1999-09/2009-09相关文章,检索词为"血管内皮祖细胞,组织工程皮肤,血管新生,endothelial progenitor cell(EPC),tissue engineered skin,vascularization".纳入与血管内皮祖细胞与组织工程皮肤研究现状与发展密切相关文章,包括:①血管内皮祖细胞的生物学特性、动员方法及促进血管新生的可能机制.②组织工程皮肤的应用现状.③组织工程皮肤中血管内皮祖细胞的研究现状.结果与结论:血管内皮祖细胞是指特异性归巢于血管新生组织,并能分化增生为成熟内皮细胞的一群祖细胞.近年来大量的动物实验证实,通过移植体外培养的血管内皮祖细胞到肢体缺血部位,可以加速缺血部位的血管化.在心肌梗死方面已经进行了自体血管内皮祖细胞治疗心肌梗死的临床试验,使其临床应用逐渐成为可能.而目前构建的组织工程皮肤中缺少血管成分,严重影响人工皮肤中活细胞的存活及其功能实现,如何构建出含有血管的人工皮肤及加速人工真皮替代物血管化引起了广大的关注.应用血管内皮祖细胞促进组织工程皮肤血管化进而提高其成活率有重要的临床意义.     

Type I collagen, fibrin and PuraMatrix matrices provide permissive environments for human endothelial and mesenchymal progenitor cells to form neovascular networks

The field of tissue engineering seeks to create metabolically demanding, functional tissues, which will require blood vessel networks capable of forming rapidly in a variety of extracellular matrix (ECM) environments. We tested whether human endothelial progenitor cells (EPCs) and mesenchymal progenitor cells (MPCs) could form microvascular networks in type I collagen, fibrin and an engineered peptide hydrogel, PuraMatrix, in 7 days in vivo in immune-deficient mice. These results are compared to those previously published, based on the Matrigel ECM. Perfused blood vessels formed in all three types of ECM within 7 days. Collagen at 5 and 6 mg/ml and 10 mg/ml fibrin supported vessel formation at 30-60 vessels/mm(2), and PuraMatrix enabled vessel formation to 160 vessels/mm(2), significantly greater than collagen or fibrin. Vessels were composed of EPCs with perivascular cells on their abluminal surfaces. EPCs injected alone formed a low density of blood vessels in collagen and PuraMatrix, while MPCs injected alone resulted in sparse vessel networks in all ECMs tested. A rheometer was used to determine whether the ECMs which supported vascularization had bulk physical properties similar to or distinct from Matrigel. Collagen and fibrin were the stiffest matrices to support extensive vascularization, with storage moduli in the range 385-510 Pa, while Matrigel, at 80 Pa, and PuraMatrix, at 5 Pa, were far more compliant. Thus, EPCs and MPCs were capable of vasculogenesis in environments having disparate physical properties, although vascular density was greater in more compliant ECMs. We propose that EPC/MPC-mediated vascularization is a versatile technology which may enable the development of engineered organs.     

Hydrogel surfaces to promote attachment and spreading of endothelial progenitor cells

Endothelialization of artificial vascular grafts is a challenging process in cardiovascular tissue engineering. Functionalized biomaterials could be promising candidates to promote endothelialization in repair of cardiovascular injuries. The purpose of this study was to synthesize hyaluronic acid (HA) and heparin‐based hydrogels that could promote adhesion and spreading of endothelial progenitor cells (EPCs). We report that the addition of heparin into HA‐based hydrogels provides an attractive surface for EPCs promoting spreading and the formation of an endothelial monolayer on the hydrogel surface. To increase EPC adhesion and spreading, we covalently immobilized CD34 antibody (Ab) on HA–heparin hydrogels, using standard EDC/NHS amine‐coupling strategies. We found that EPC adhesion and spreading on CD34 Ab‐immobilized HA–heparin hydrogels was significantly higher than their non‐modified analogues. Once adhered, EPCs spread and formed an endothelial layer on both non‐modified and CD34 Ab‐modified HA–heparin hydrogels after 3 days of culture. We did not observe significant adhesion and spreading when heparin was not included in the control hydrogels. In addition to EPCs, we also used human umbilical cord vein endothelial cells (HUVECs), which adhered and spread on HA–heparin hydrogels. Macrophages exhibited significantly less adhesion compared to EPCs on the same hydrogels. This composite material could possibly be used to develop surface coatings for artificial cardiovascular implants, due to its specificity for EPC and endothelial cells on an otherwise non‐thrombogenic surface. Copyright © 2012 John Wiley & Sons, Ltd.     

Glycosaminoglycans restrained in a fibrin matrix improve ECM remodelling by endothelial cells grown for vascular tissue engineering

The success of a biocompatible vascular graft depends upon its mechanical attributes and post‐implantation healing responses. Mechanical strength is a paramount issue because grafts placed in the arterial circulation must be capable of withstanding long‐term haemodynamic stress without graft failure. Extracellular matrix (ECM) proteins that are deposited by the cells to remodel the environment play a major role in determining the construct stability and strength. A suitable scaffold that stimulates ECM deposition and remodelling by cells grown in vitro may generate tissues with normal function. The objective of this study was to prove that fibrin matrix composition can be modified with growth factors (GFs) and glycosaminoglycans (GAGs) to promote ECM remodelling coupled with endothelial cell (EC) growth. Effect of GFs and GAGs on ECM production and remodelling was studied separately and in combination. Matrices recovered after EC cultures were analysed after immunochemical staining and it was observed that GFs and GAGs influence collagen IV and elastin deposition. Quantitative PCR analysis of mRNA after specific periods of culture demonstrated significant upregulation of elastin and collagen expression in EC by combination of GFs and GAGS when compared to their individual effects. The results of experiments conducted with various combinations of GFs and GAGs show that a biomimetic approach of immobilization of signalling molecules in fibrin can upregulate ECM remodelling with simultaneous degradation of the fibrin matrix and deposition of collagen IV and elastin. Hence, this combination may be suitable for cardiovascular tissue generation in vitro. Copyright © 2009 John Wiley & Sons, Ltd.     

Spontaneous hepatocyte migration towards an endothelial cell tube network

A crucial part of the engineering liver tissue is contribution of nonparenchymal cells and maintenance of a complex three‐dimensional (3D) structure in vitro for their normal physiology and function. We generated 3D hepatic tissue using primary isolated rat hepatocytes and an endothelial cell tube network from human endothelial vein epithelial cells (HUVECs). To create the 3D hepatic tissue, coculture of primary hepatocytes and tube‐structured HUVECs was performed on a Matrigel®. After the HUVECs formed the tube structures, primary isolated rat hepatocytes were inoculated onto the HUVEC tube‐structured layer and cultured for 24 hr. We investigated the cell migration, cellular interaction, and distributions of HUVEC tube structures and hepatocytes using multi cell‐imaging incubator, confocal microscopy, and electron microscopy analyses. During the culture time, time‐lapse imaging showed spontaneous migration of the hepatocytes in the gel, and after the 24‐hr culture period, the vast majority of the hepatocytes had moved and adhered to the surface of the HUVEC tube structures. A confocal microscopy assay confirmed this unique 3D cellular interaction between hepatocytes and HUVEC tube structures. The hepatocytes were able to maintain their spherical shape, as well as HUVECs (tube‐like form with tubular cavity). We speculate that coculturing of hepatocytes and endothelial cells replicates part of their normal physiology and may help induce migration in vitro and the growth of complex biological tissue structures.     

血管内皮生长因子在鼠尾胶原凝胶诱导三维血管新生中的作用研究

背景:血管新生在组织工程研究中已引起了高度重视.血管内皮生长因子在二维平面培养中已证实能促进血管新生.目的:观察血管内皮生长因子在三维血管新生中的作用.方法:取SD大鼠骨髓,分离出内皮祖细胞.待细胞融合至70%～80%时添加鼠尾另一层胶原凝胶建立三维立体模型.实验组采用完全培养液含M199培养液、胎生血清加血管内皮生长因子及双抗;对照组培养液中不含血管内皮生长因子.培养第1,4,7,20天观察骨髓来源内皮祖细胞的体外培养和扩增情况并进行细胞鉴定.三维立体模型建立后第3,6,9,12天进行形态观察及定性定量分析.结果与结论:实验组内皮祖细胞在三维基质内向胶原基质内生长,24 h内即可出现向胶原内的出芽及浸润并逐渐形成分支样结构,对照组细胞生长慢,出芽慢,管状结构细小,向胶原内浸润的深度浅,网状结构稀疏,不完整.实验组新生血管数目显著高于对照组(P<0.01).取第3,6,9,12天的凝胶块检测,可见内皮素1、内皮型一氧化氮合成酶3表达阳性.结果表明,血管内皮生长因子能动员和诱导内皮祖细胞促进血管新生.鼠尾胶原凝胶可以诱导内皮祖细胞表现出血管新生中的迁移、增殖和发芽等步骤.     

人脐静脉内皮细胞单层通透性改变的效应因子

背景：外源性刺激引起血管屏障功能损伤的分子机制是血管病理生理学尚未阐明的热点问题之一。目的：探讨炎症递质脂多糖诱导的人脐静脉内皮细胞单层通透性改变的效应分子,寻找有效治疗靶点。方法：应用脂多糖刺激并观察人脐静脉内皮细胞骨架蛋白F-actin和细胞单层通透性的改变。应用荧光免疫组化和Westernblot方法检测脂多糖刺激前后细胞中RhoA和SRF等信号分子的改变。并通过阻断实验证实RhoA-SRF信号通路的作用。结果与结论：100μg/L脂多糖刺激6h可引起人脐静脉内皮细胞中F-actin快速重构并形成大量应力纤维,细胞单层通透性明显增强。细胞中活化RhoA的表达明显增加,SRF发生明显的入核转位现象。应用特异性分子抑制剂Y27632抑制RhoA的活化后,细胞中F-actin重构现象消失,细胞单层通透性增加也受到明显抑制,SRF蛋白发生明显的出现转位。而应用LatrunculinB抑制脂多糖刺激的人脐静脉内皮细胞中F-actin应力纤维形成,对抗通透性增加,但RhoA活化未受到干扰,SRF入核现象则受到抑制。提示RhoA-SRF通路的活化介导了脂多糖诱导的人脐静脉内皮细胞中F-actin重构和内皮单层通透性增加,特异性抑制F-actin也可以阻断脂多糖引起的血管内皮单层通透性增加,同时反馈抑制SRF的入核活化现象。