An in vitro expansion score for tissue‐engineering applications with human bone marrow‐derived mesenchymal stem cells

Human bone marrow‐derived mesenchymal stem cells (MSCs) have limited growth potential in vitro and cease to divide due to replicative senescence, which from a tissue‐engineering perspective has practical implications, such as defining the correct starting points for differentiation and transplantation. Time spent in culture before the loss of required differentiation potential is different and reflects patient variability, which is a problem for cell expansion. This study aimed to develop a score set which can be used to quantify the senescent state of MSCs and predict whether cells preserve their ability to differentiate to osteogenic, adipogenic and chondrogenic phenotypes, based on colony‐forming unit (CFU) assay, population doubling time (PDT), senescence‐associated β‐galactosidase (SA‐β‐Gal) activity, cell size, telomere length and gene expression of MSCs cultured in vitro over 11 passages. This set of morphological, physiological and genetic senescence markers was correlated to the ability of MSCs to differentiate. Differentiation efficiency was assessed by marker genes and protein expression. CFUs decreased with increasing passage number, whereas SA‐β‐Gal activity and PDT increased; however, the correlation with MSCs' differentiation potential was sometimes unexpected. The expression of genes related to senescence was higher in late‐passage cells than in early‐passage cells. Early‐passage cells underwent efficient osteogenic differentiation, with mid‐passage cells performing best in chondrogenic differentiation. Late‐passage cells preserve only adipogenic differentiation potential. Based on this marker set, we propose a senescence score in which combined markers give a reliable quality control of MSCs, not depending only on mechanistic passage number. Copyright © 2013 John Wiley & Sons, Ltd.     

Large‐scale expansion of pre‐isolated bone marrow mesenchymal stromal cells in serum‐free conditions

The regenerative potential of mesenchymal stromal or stem cells (MSCs) has generated tremendous interest for treating various degenerative diseases. Regulatory preference is to use a culture medium that is devoid of bovine components for stem cell expansion intended for therapeutic applications. However, a clear choice an alternative to fetal bovine serum (FBS) has not yet emerged. We have screened five different commercially available serum‐free media (SFM) for their ability to support the growth and expansion of pre‐isolated undifferentiated bone marrow‐derived MSCs (BM‐MSCs) and compared the results with cells grown in standard FBS‐containing medium as control. In addition, based on initial screening results, BD Mosaic? Mesenchymal Stem Cell Serum‐free (BD‐SFM) medium was evaluated in large‐scale cultures for the performance and culture characteristics of BM‐MSCs. Of the five different serum‐free media, BD‐SFM enhanced BM‐MSCs growth and expansion in Cell STACK (CS), but the cell yield per CS‐10 was less when compared to the control medium. The characteristics of MSCs were measured in terms of population doubling time (PDT), cell yield and expression of MSC‐specific markers. Significant differences were observed between BD‐SFM and control medium in terms of population doublings (PDs), cell yield, CFU‐F and morphological features, whereas surface phenotype and differentiation potentials were comparable. The BD‐SFM‐cultured MSCs were also found to retain the differentiation potential, immune‐privileged status and immunosuppressive properties inherent to MSCs. Our results suggest that BD‐SFM supports large‐scale expansion of BM‐MSCs for therapeutic use. Copyright © 2014 John Wiley & Sons, Ltd.     

Optimization of the use of a pharmaceutical grade xeno‐free medium for in vitro expansion of human mesenchymal stem/stromal cells

Human bone marrow‐derived mesenchymal stem/stromal cells (hMSCs) are considered promising therapeutic agents in the field of cell therapy and regenerative medicine, mainly due to their relative facility to be isolated, multi‐differentiation potential, and immunomodulatory role. However, their application in clinics requires a crucial step of in vitro expansion. Most of the protocols for hMSCs in vitro culture use foetal bovine serum as medium supplement that, being from animal origin, presents several safety concerns and may initiate xenogeneic immune responses after cells transplantation. This work reports the optimization of a pharmaceutical‐grade xeno‐free strategy for hMSCs in vitro expansion based on the supplementation of basal medium with a pharmaceutical‐grade human plasma‐derived supplement for cell culture (SCC) and 2 human growth factors (bFGF and TGFβ1), plus a coating of human plasma fibronectin (Fn). After 4 weeks in culture, this strategy improves hMSCs expansion yield about 4.3‐fold in comparison with foetal bovine serum supplementation and 4.5‐fold compared with a commercially available xeno‐free medium. hMSCs expanded in SCC‐based formulation maintained their phenotype and differentiation capacity into osteogenic, adipogenic, and chondrogenic lineages, without alterations in cell karyotype. Overall, the SCC‐based medium appears to be an excellent alternative for the xeno‐free expansion of hMSCs as therapeutic agents for clinical applications.     

Transient serum exposure regimes to support dual differentiation of human mesenchymal stem cells

Human mesenchymal stem cells (MSCs), which can generate both osteoblasts and chondrocytes, represent an ideal resource for orthopaedic repair using tissue‐engineering approaches. One major difficulty for the development of osteochondral constructs using undifferentiated MSCs is that serum is typically used in culture protocols to promote differentiation of the osteogenic component, whereas existing chondrogenic differentiation protocols rely on the use of serum‐free conditions. In order to define conditions which could be compatible with both chondrogenic and osteogenic differentiation in a single bioreactor, we have analysed the efficiency of new biphasic differentiation regimes based on transient serum exposure followed by serum‐free treatment. MSC differentiation was assessed either in serum‐free medium or with a range of transient exposure to serum, and compared to continuous serum‐containing treatment. Although osteogenic differentation was not supported in the complete absence of serum, marker expression and extensive mineralization analyses established that 5 days of transient exposure triggered a level of differentiation comparable to that observed when serum was present throughout. This initial phase of serum exposure was further shown to support the successful chondrogenic differentiation of MSCs, comparable to controls maintained in serum‐free conditions throughout. This study indicates that a culture based on temporal serum exposure followed by serum‐free treatment is compatible with both osteogenic and chondrogenic differentiation of MSCs. These results will allow the development of novel strategies for osteochondral tissue engineering approaches using MSCs for regenerative medicine. Copyright © 2012 John Wiley & Sons, Ltd.     

Mesenchymal stem cells from CD34− human umbilical cord blood

Umbilical cord blood (UCB) is well known to be a rich source of stem cells especially for haematopoietic stem cells (HSCs). Recently, mesenchymal stem cells (MSCs) have also been shown to exist in cord blood. Although MSCs have been described by a subset of surface antigens after expansion, little is known about the cell surface phenotype of undifferentiated MSCs. The aim of this study therefore was to clarify whether undifferentiated MSCs are resident among CD34^? UCB cells. CD34⁺ cells were separated from UCB mononuclear cells (MNCs) by magnetic sorting and the CD34^? cell fractions were cultured in Dulbecco's modified Eagle's medium (DMEM) with 10% foetal calf serum (FCS) and basic‐fibroblast growth factor. Isolated CD34⁺ cells were also cultured in the same medium. Adherent fibroblast‐like cells at passage 3–4 were analyzed by fluorescence‐activated cell sorting (FACS) for MSC marker expression , and standard adipogenic, osteogenic and chondrogenic assays were used to investigate their differentiation potentials. After 4–5 weeks in culture, the cells from the CD34^? fraction became confluent with flat and fibroblast‐like morphology. These cells were positively stained for the mesenchymal cell markers CD29, CD73 and CD105. In adipogenic differentiation, the cells showed oil red O positive and expressed FABP4, adipsin and proliferation‐activated receptor γ‐2 (PPARγ2 genes) associated with adipogenesis. In osteogenic differentiation, calcium accumulation and osteocalcin were detected. The cells grown in chondrogenic conditions were positively stained for human aggrecan and expressed collagen type II and Sox‐9 genes. In contrast, cells from the CD34⁺ fraction failed to generate any cells with MSC morphology under the same culture conditions. Our results showed that UCB contained MSCs which are only resident in the CD34^? fraction. The MSCs could be induced to differentiate into at least three lineage cell types, adipocytes, osteoblasts and chondrocytes.     

A composite Gelatin/hyaluronic acid hydrogel as an ECM mimic for developing mesenchymal stem cell‐derived epithelial tissue patches

Here we report fabrication of Gelatin‐based biocomposite films and their application in developing epithelial patches. The films were loaded with an epithelial cell growth factor cocktail and used as an extracellular matrix mimic for in vitro regeneration of organized respiratory epithelium using Calu‐3 cell line and mesenchymal stem cells (MSCs). Our data show differentiation of Calu‐3 cells on composite films as evidenced by tight junction protein expression and barrier formation. The films also supported attachment, migration, and proliferation of alveolar basal epithelial cell line A549. We also show the suitability of the composite films as a biomimetic scaffold and growth factor delivery platform for differentiation of human MSCs to epithelial cells. MSCs differentiation to the epithelial lineage was confirmed by staining for epithelial and stem cell specific markers. Our data show that the MSCs acquire the epithelial characteristics after 2 weeks with significant reduction in vimentin, increase in pan cytokeratin expression, and morphological changes. However, despite the expression of epithelial lineage markers, these cells did not form fully functional tight junctions as evidenced by low expression of junctional protein ZO1. Further optimisation of culture conditions and growth factor cocktail is required to enhance tight junction formation in MSCs‐derived epithelial cells on the composite hydrogels. Nevertheless, our data clearly highlight the possibility of using MSCs in epithelial tissue engineering and the applicability of the composite hydrogels as transferrable extracellular matrix mimics and delivery platforms with potential applications in regenerative medicine and in vitro modelling of barrier tissues.     

Integrated culture platform based on a human platelet lysate supplement for the isolation and scalable manufacturing of umbilical cord matrix‐derived mesenchymal stem/stromal cells

Umbilical cord matrix (UCM)‐derived mesenchymal stem/stromal cells (MSCs) are promising therapeutic candidates for regenerative medicine settings. UCM MSCs have advantages over adult cells as these can be obtained through a non‐invasive harvesting procedure and display a higher proliferative capacity. However, the high cell doses required in the clinical setting make large‐scale manufacturing of UCM MSCs mandatory. A commercially available human platelet lysate‐based culture supplement (UltraGRO^TM, AventaCell BioMedical) (5%(v/v)) was tested to effectively isolate UCM MSCs and to expand these cells under (1) static conditions, using planar culture systems and (2) stirred culture using plastic microcarriers in a spinner flask. The MSC‐like cells were isolated from UCM explant cultures after 11 ± 2 days. After five passages in static culture, UCM MSCs retained their immunophenotype and multilineage differentiation potential. The UCM MSCs cultured under static conditions using UltraGRO^TM‐supplemented medium expanded more rapidly compared with UCM MSCs expanded using a previously established protocol. Importantly, UCM MSCs were successfully expanded under dynamic conditions on plastic microcarriers using UltraGRO^TM‐supplemented medium in spinner flasks. Upon an initial 54% cell adhesion to the beads, UCM MSCs expanded by >13‐fold after 5–6 days, maintaining their immunophenotype and multilineage differentiation ability. The present paper reports the establishment of an easily scalable integrated culture platform based on a human platelet lysate supplement for the effective isolation and expansion of UCM MSCs in a xenogeneic‐free microcarrier‐based system. This platform represents an important advance in obtaining safer and clinically meaningful MSC numbers for clinical translation. Copyright © 2016 John Wiley & Sons, Ltd.     

用于造血干细胞移植的人骨髓间充质干细胞体外扩增研究

本研究旨在检查4种不同培养液体外培养人骨髓间充质干细胞（bone marrow mesenchymal stem cells，BM-MSCs）的效果，建立一种基于临床移植需要的分离、培养人BM-MSC的方法，为BM-MSC联合造血干细胞移植的临床应用提供实验基础。采用Ficoll Paque细胞分离液从16例新鲜成人骨髓穿刺液中分离BM—MSC，分别用含10％脐带血血清、胎牛血清、成人血清的DMEM／F12培养液和MesenCuh培养液培养，用流式细胞术检测细胞表面抗原，以成骨诱导体系及脂肪诱导体系分别诱导各组BM-MSC定向分化，通过细胞形态观察、免疫表型及免疫化学染色进行鉴定。结果表明：4种培养液都能从成人骨髓液中分离培养出BM—MSC，脐带血血清组和Mesen Cuh组培养的BM—MSC在增殖数量和速度上相似，但均优于FCS组和AB型血清组。脐带血血清组和Mesen Cuh组培养的BM-MSC表达CD29、CD73、CD105的阳性率比FCS组和AB型血清组高（P〈0．05），而CD31阳性率低于FCS组和AB型血清组（P〈0．05），脐带血血清组和MesenCuh组培养的BM—MSC诱导为成骨细胞和脂肪细胞阳性率高于FCS组和AB型血清组（P〈0．05）。结论：4种不同培养液能够从成人骨髓液中分离出BM—MSC，脐带血血清组和MesenCuh组培养的BM-MSC的纯度和体外诱导分化能力比FCS组和AB型血清组高，含有脐带血血清的培养体系具有临床应用价值。     

肝细胞生长因子与成纤维生长因子联合诱导入脐带间充质干细胞向肝样细胞的分化

背景:成纤维生长因子可促进间充质干细胞增殖、贴壁生长,但对其诱导间充质干细胞向肝细胞分化的实验报道为数不多.当肝细胞生长因子质量浓度达1 μg/L时,可促进肝细胞有丝分裂,它是正常肝细胞最强的促有丝分裂剂.目的:体外分离培养人脐带间充质干细胞,拟揭示其生物学特性及在细胞因子联合诱导下向肝样细胞分化的能力.设计、时间及地点:细胞学体外观察,于2008-08/2009-04在暨南大学血研所完成.材料:脐带取自健康足月胎儿,产妇对实验知情同意,由广州华侨医院提供.肝细胞生长因子、成纤维生长因子为美国Peprotech产品.方法:Ⅳ型胶原酶消化+差速贴壁法分离培养人脐带间充质干细胞,取传至第3代细胞,进行细胞表面抗原分析、细胞周期测定,检测其成脂、成骨能力.取第5代细胞.调整细胞密度为5×10~9 L~(-1),分为2组:对照组用含体积分数为5%胎牛血清的DMEM/F12培养液培养;诱导组在其基础上,添加20 μg/L肝细胞生长因子、10 μg/L成纤维生长因子联合诱导其向肝样细胞分化.主要观察指标:人脐带间充质干细胞的生物学特性,人脐带间充质干细胞体外向肝样细胞的分化情况.结果:成功从人脐带中分离并纯化得到间充质干细胞,第3代细胞92.2%处在G_0/G_1期;表达CD29,CD44,CD105,不表达造血细胞标志CD34,CD45;油红O染色后胞浆中呈现红色颗粒,碱性磷酸酶染色后细胞质呈黑色,具有成脂、成骨能力.经肝细胞生长因子、成纤维生长因子联合诱导10 d后,RT-PCR及Western blot检测结果显示细胞表达肝细胞特异性抗原甲胎蛋白、白蛋白,对照组均呈阴性表达.结论:人脐带中含有丰富的间充质干细胞,其具有较强的多向分化潜能,经肝细胞生长因子与成纤维生长因子联合诱导后,易向肝样细胞分化.     

Angiogenic potential of human mesenchymal stromal cell and circulating mononuclear cell cocultures is reflected in the expression profiles of proangiogenic factors leading to endothelial cell and pericyte differentiation

Endothelial progenitors found among the peripheral blood (PB) mononuclear cells (MNCs) are interesting cells for their angiogenic properties. Mesenchymal stromal cells (MSCs) in turn can produce proangiogenic factors as well as differentiate into mural pericytes, making MSCs and MNCs an attractive coculture setup for regenerative medicine. In this study, human bone marrow‐derived MSCs and PB‐derived MNCs were cocultured in basal or osteoblastic medium without exogenously supplied growth factors to demonstrate endothelial cell, pericyte and osteoblastic differentiation. The expression levels of various proangiogenic factors, as well as endothelial cell, pericyte and osteoblast markers in cocultures were determined by quantitative polymerase chain reaction. Immunocytochemistry for vascular endothelial growth factor receptor‐1 and α‐smooth muscle actin as well as staining for alkaline phosphatase were performed after 10 and 14 days. Messenger ribonucleic acid expression of endothelial cell markers was highly upregulated in both basal and osteoblastic conditions after 5 days of coculture, indicating an endothelial cell differentiation, which was supported by immunocytochemistry for vascular endothelial growth factor receptor‐1. Stromal derived factor‐1 and vascular endothelial growth factor were highly expressed in MSC‐MNC coculture in basal medium but not in osteoblastic medium. On the contrary, the expression levels of bone morphogenetic protein‐2 and angiopoietin‐1 were significantly higher in osteoblastic medium. Pericyte markers were highly expressed in both cocultures after 5 days. In conclusion, it was demonstrated endothelial cell and pericyte differentiation in MSC‐MNC cocultures both in basal and osteoblastic medium indicating a potential for neovascularization for tissue engineering applications.     

Endothelial cells stimulate osteogenic differentiation of mesenchymal stem cells on calcium phosphate scaffolds

The interaction of mesenchymal stem cells (MSCs) with endothelium in vivo is significant for regenerative processes in organisms. To design concepts for tissue engineering for bone regeneration based on this interaction, the osteogenic differentiation of human bone marrow‐derived MSCs in a co‐culture with human dermal microvascular endothelial cells (HDMECs) was studied. The experiments were focussed on the regulation of MSCs in a co‐culture with HDMECs on different calcium phosphate scaffolds. Alkaline phosphatase (ALP) activity and mRNA expression of various osteogenic markers increased significantly when cells were co‐cultured on materials with calcium phosphate scaffolds compared to tissue culture polystyrene or when MSCs were cultured alone. In addition, it was observed that the expression of osteopontin and osteocalcin was highly sensitive to the substrate for cell adhesion. Whereas these late osteogenic markers were down‐regulated in co‐cultures on polystyrene, they were up‐regulated on calcium phosphate and moreover, were differentially expressed on the three calcium phosphate scaffolds tested. To enhance the osteogenic differentiation of MSCs in a co‐culture, direct cell‐cell interactions were required. Concerning molecular mechanisms in the interactions between both cell types, it was found that connexin 43 was expressed in contact sites and more apparently, endothelial cells grew over the MSCs, which facilitated direct cellular interactions mediated by various adhesion receptors. This study revealed significant findings for the design of implant materials suitable for regeneration of bone by stimulating the functional interaction of MSCs with endothelial cells. Copyright © 2012 John Wiley & Sons, Ltd.     

肝细胞生长因子与成纤维生长因子联合诱导人脐带间充质干细胞向肝样细胞的分化

背景：成纤维生长因子可促进间充质干细胞增殖、贴壁生长,但对其诱导间充质干细胞向肝细胞分化的实验报道为数不多。当肝细胞生长因子质量浓度达1μg／L时,可促进肝细胞有丝分裂,它是正常肝细胞最强的促有丝分裂剂。 目的：体外分离培养人脐带间充质干细胞,拟揭示其生物学特性及在细胞因子联合诱导下向肝样细胞分化的能力。 设计、时间及地点：细胞学体外观察,于2008—08／2009-04在暨南大学血研所完成。 材料：脐带取自健康足月胎儿,产妇对实验知情同意,由广州华侨医院提供。肝细胞生长因子、成纤维生长因子为美国Peprotech产品。 方法：Ⅳ型胶原酶消化＋差速贴壁法分离培养人脐带间充质干细胞,取传至第3代细胞,进行细胞表面抗原分析、细胞周期测定,检测其成脂、成骨能力。取第5代细胞,调整细胞密度为5×10^9L^-1,分为2组：对照组用含体积分数为5％胎牛血清的DMEM／F12培养液培养：诱导组在其基础上,添加20μg／L肝细胞生长因子、10μg／L成纤维生长因子联合诱导其向肝样细胞分化。 主要观察指标：人脐带间充质干细胞的生物学特性,人脐带间充质干细胞体外向肝样细胞的分化情况。 结果：成功从人脐带中分离并纯化得到间充质干细胞,第3代细胞92．2％处在G0/G1期：表达CD29,CD44,CD105,不表达造血细胞标志CD34,CD45．油红O染色后胞浆中呈现红色颗粒,碱性磷酸酶染色后细胞质呈黑色,具有成脂、成骨能力。经肝细胞生长因子、成纤维生长因子联合诱导10d后,RT-PCR及Western blot检测结果显示细胞表达肝细胞特异性抗原甲胎蛋白、白蛋白,对照组均呈阴性表达。 结论：人脐带中含有丰富的间充质干细胞,其具有较强的多向分化潜能,经肝细胞生长因子与成纤维生长因子联合诱导后,易向肝样细胞分化。     

人骨髓间充质干细胞体外扩增的生物学评估

本研究旨在对骨髓间充质干细胞（mesenchymal stem cells，MSC）进行移植前增殖分化能力测定，病毒学检查，核型分析，PCR-STR和甩A的检测，以便为临床应用提供安全、可靠的移植细胞。采用贴壁法分离骨髓MSC，在相同条件下分别考察各代细胞形态、生长、表面标记、成骨、成脂分化能力的变化情况，并进行不同生长时期的核型分析，利用札A—SBT技术检测4个不同供者来源的MSC的HLA-I和HLA—II位点的高分辨分型；应用PCR—STR技术检测4个不同供者来源的MSC基因遗传标记。并且利用ELISA方法检测HIV，HBV，HCV和TP，使用PCR方法检测支原体污染。结果表明：随着传代次数增加，MSC的增殖能力、成骨能力均有所下降。在扩增过程中，MSC始终保持较高的纯度，CD29、CD44、CD105、CD166、CD73均表达阳性，CD14、CD34、CD45、CD80和CD86均表达阴性。在8代以前未发现核型变异。4个不同供者来源的MSC的札A高分辨分型和STR基因分型结果为MSC3的TP表达阳性，MSC2在5代出现支原体污染。结论：在体外培养过程中MSC干细胞特性逐渐丢失，其中向成骨方向的分化潜能降低。MSC在8代以前可作为实验研究及临床应用的良好对象。     

Influence of in vitro biomimicked stem cell ‘niche’ for regulation of proliferation and differentiation of human bone marrow‐derived mesenchymal stem cells to myocardial phenotypes: serum starvation without aid of chemical agents and prevention of spontaneous stem cell transformation enhanced by the matrix environment

Niche appears important for preventing the spontaneous differentiation or senescence that cells undergo during in vitro expansion. In the present study, it was revealed that human bone marrow‐derived mesenchymal stem cells (hBM‐MSCs) undergo senescence‐related differentiation into the myocardial lineage in vitro without any induction treatment. This phenomenon occurred over the whole population of MCSs, much different from conventional differentiation with limited frequency of occurrence, and was accompanied by a change of morphology into large, flat cells with impeded proliferation, which are the representative indications of MSC senescence. By culturing MSCs under several culture conditions, it was determined that induction treatment with 5‐azacytidine was not associated with the phenomenon, but the serum‐starvation condition, under which proliferation is severely hampered, caused senescence progression and upregulation of cardiac markers. Nevertheless, MSCs gradually developed a myocardial phenotype under normal culture conditions over a prolonged culture period and heterogeneous populations were formed. In perspectives of clinical applications, this must be prevented for fair and consistent outcomes. Hence, the biomimetic 'niche' was constituted for hBM‐MSCs by cultivating on a conventionally available extracellular matrix (ECM). Consequently, cells on ECM regained a spindle‐shape morphology, increased in proliferation rate by two‐fold and showed decreased expression of cardiac markers at both the mRNA and protein levels. In conclusion, the outcome indicates that progression of MSC senescence may occur via myocardial differentiation during in vitro polystyrene culture, and this can be overcome by employing appropriate ECM culture techniques. Copyright © 2013 John Wiley & Sons, Ltd.     

兔骨髓间充质干细胞在肿瘤微环境诱导下向肌纤维母细胞的分化

背景:骨髓间充质干细胞可以促进肿瘤间质重构,但具体机制尚不明确,而肌纤维母细胞则是肿瘤间质重构过程中发挥重要作用的一类细胞.目的:观察骨髓间充质干细胞在肿瘤微环境诱导下能否分化为肌纤维母细胞.设计、时间及地点:细胞学体外观察及体内移植实验,于2006-06/2007-12在山东大学齐鲁医院低温医学实验室完成.材料:3月龄雄性新西兰大白兔12只,购自山东省农业科学院.方法:穿刺抽取兔骨髓,密度梯度法分离培养骨舒间充质于细胞,传至第2代行DAPI标记,调整细胞密度为5×10~(10) L~(-1),分为2组:实验组加入含体积分数为10%胎牛血清、30% VX2瘤细胞株培养上清的低糖DMEM,对照组加入含体积分数为10%胎牛血清的低糖DMEM,培养14 d.向兔大腿肌肉内注入VX2细胞悬液,2周后触摸到生成肿瘤后,抽取DAPI标记的第2代骨髓间充质干细胞悬液100 μL,从前后左右4个方向均匀回输入肿瘤组织内,3周后取材.主要观察指标:采用免疫荧光法和RT-PCR检测骨髓间充质干细胞中α-SMA和Vimentin的表达,免疫荧光法鉴定骨髓间充质干细胞回输后在肿瘤组织中的分布及分化.结果:第2代骨髓间充质干细胞经VX2培养上清诱导2周后,Cy3免疫荧光结果显示α-SMA和Vimentin呈强阳性表达,对照组呈弱阳性表达.与对照组比较,实验组α-SMA及Vimentin mRNA的表达水平均明显升高(P＜0.01,P＜0.05).回输入 VX2肿瘤组织3周后,骨髓间充质干细胞主要分布于肿瘤间质,其细胞核周围胞浆中α-SMA和Vimentin均呈强阳性表达,表明骨髓间充质干细胞在肿瘤组织中已分化为肌纤维母细胞.结论:在肿瘤微环境的诱导下,骨髓间充质干细胞可以分化为肌纤维母细胞,从而促进肿瘤的生长与发展.     

诱导人骨髓间充质干细胞向肝系细胞分化过程中肝细胞生长因子和碱性成纤维细胞生长因子的作用

背景:骨髓间充质干细胞是一种存在于骨髓内的非造血干细胞,因其具有自我更新能力及多向分化潜能,且分离培养方法成熟,在组织器官修复及再生方面显示出良好的应用前景,将为终末期肝病的治疗如生物人工肝及肝细胞移植提供新的细胞来源,但目前人骨髓间充质干细胞向肝系细胞诱导分化培养体系尚不成熟。目的:观察肝细胞生长因子和碱性成纤维细胞生长因子联合应用诱导人骨髓间充质干细胞在体外向肝系细胞分化的可能性。设计:开放性实验。单位:南昌大学第一附属医院传染科与泌尿外科研究所。材料:实验于2004-07/2005-03在南昌大学第一附属医院泌尿外科研究所完成。所用骨髓由成年健康志愿者提供(均对本实验知情同意)。DMEM/F12培养基(Gibco公司);表皮细胞生长因子,肝细胞生长因子,胰岛素,转铁蛋白,鼠抗人甲胎蛋白单克隆抗体,FITC-兔抗鼠IgG(Sig-ma公司);碱性成纤维细胞生长因子(Invitrogen公司);鼠抗人角蛋白18,19单克隆抗体(Chemicon公司);胎牛血清(杭州四季青)。方法:以骨髓腔穿刺方式抽取成年健康志愿者髂后上棘处骨髓10mL,采用密度梯度离心法分离和反复贴壁法纯化骨髓间充质干细胞。取培养至4～8代细胞,消化后以107L-1接种到放置20mm×20mm爬片的预先铺被有0.1%明胶的24孔板中,次日换液,改用无血清DMEM/F12培养基(含20μg/L的表皮细胞生长因子和10μg/L的碱性成纤维细胞生长因子)培养2d后,换成无血清DMEM/F12培养基(含20μg/L的肝细胞生长因子,10μg/L的碱性成纤维细胞生长因子,5mg/L的胰岛素,5mg/L的转铁蛋白)进行诱导分化,每3d换液1次,以未加入肝细胞生长因子和碱性成纤维细胞生长因子的骨髓间充质干细胞作为对照组。骨髓间充质干细胞诱导培养过程中,放射免疫荧光法测甲胎蛋白浓度。诱导当天及第7,14,21,28天,取诱导细胞爬片,细胞免疫荧光法检测肝细胞表面标志物甲胎蛋白、角蛋白18和角蛋白19的表达,并进行糖原染色检测诱导细胞的糖原合成情况。主要观察指标:①细胞形态学观察。②培养上清液中甲胎蛋白表达量的测定。③肝细胞表面标志检测结果。④诱导细胞的糖原合成情况。结果:①诱导第14天可观察到细胞变成短梭形和多角形,随培养时间的延长多角形细胞增多,并可形成肝细胞样的细胞集落。②诱导第14天培养上清液内可检测到甲胎蛋白的分泌,每孔浓度为0.1μg/L;第17天达高峰0.4μg/L;第21天下降至0.3μg/L。③诱导第14天甲胎蛋白、角蛋白18表达呈阳性,第28天角蛋白19表达呈阳性。④诱导第21天糖原染色呈阳性反应。结论:肝细胞生长因子和碱性成纤维细胞生长因子能够诱导人骨髓间充质干细胞在体外向肝细胞分化,表达肝细胞特异性表面标志,并具有合成糖原、分泌甲胎蛋白的功能。     

Agonism of Wnt–β‐catenin signalling promotes mesenchymal stem cell (MSC) expansion

Promoting mesenchymal stem cell (MSC) proliferation has numerous applications in stem cell therapies, particularly in the area of regenerative medicine. In order for cell‐based regenerative approaches to be realized, MSC proliferation must be achieved in a controlled manner without compromising stem cell differentiation capacities. Here we demonstrate that 6‐bromoindirubin‐3′‐oxime (BIO) increases MSC β‐catenin activity 106‐fold and stem cell‐associated gene expression ~33‐fold, respectively, over untreated controls. Subsequently, BIO treatment increases MSC populations 1.8‐fold in typical 2D culture conditions, as well as 1.3‐fold when encapsulated within hydrogels compared to untreated cells. Furthermore, we demonstrate that BIO treatment does not reduce MSC multipotency where MSCs maintain their ability to differentiate into osteoblasts, chondrocytes and adipocytes using standard conditions. Taken together, our results demonstrate BIO's potential utility as a proliferative agent for cell transplantation and tissue regeneration. Copyright © 2013 John Wiley & Sons, Ltd.     

Effects of different sera on adipose tissue-derived mesenchymal stromal cells

Current cell therapy protocols require considerable numbers of mesenchymal stromal cells (MSCs), which can be obtained only by in vitro expansion. The most important issue is a choice of optimal growth supplements for cell culture. Ideally, these should be of known composition, free of animal components and allow production of large homogenic populations of MSCs in a considerably short period of time. Since this standard has not been achieved to date, we aimed to assess the molecular responses of MSCs to different growth supplements commonly in use. MSCs were isolated from breast or abdominal adipose tissue and plated into DMEM supplemented with one of four different sera: fetal calf serum (FCS), pretested fetal calf serum (FCS-Sp), human allogeneic serum (HS) or artificial serum substitute (AS). MSCs cultivated with different serum supplements demonstrated distinct morphologies, high adipogenic and osteogenic differentiation potential and expressed characteristic antigens. Using real-time PCR, we found a large increase in PPARγ and Msx2 gene expression in both lines of proliferating MSCs cultivated with AS. We found that MSCs cultivated in the presence of different sera had similar global proteomic expression patterns, but comparisons of identified proteins revealed most differences in the MSCs cultivated with AS. Our results indicate that MSCs cultivated in the presence of FCS and HS display similar growth, differentiation, immunophenotypic and proteomic properties, while AS induces more profound changes in the physiology of MSCs, suggesting that further fundamental studies should be done before its introduction into clinical practice.     

Production of human tissue‐engineered skin trilayer on a plasma‐based hypodermis

Full thickness wounds require a dermal component to achieve functional permanent skin restoration. Currently available tissue‐engineered skin substitutes lack a subcutaneous fat layer that would functionally contribute some of the mechanical and thermoregulatory properties of normal skin. To generate a trilayer engineered skin equivalent, we included bone marrow mesenchymal (BM‐MSC) or adipose tissue‐derived (ASC) stromal cells in a human plasma hydrogel exposed to adipogenic clues for three weeks. Approximately half of the cells differentiated under these conditions into mature adipocytes that survived for two years in culture with minimal medium change. In vitro generation of bona fide fully differentiated adipocytes was assessed by leptin secretion and ultrastructurally demonstrated through semithin to ultrathin sectioning and lipid staining with osmium tetroxide. Furthermore, presence of BM‐MSCs or ASCs within the subcutaneous layer contributed to the epidermal differentiation program, with more proliferating basal cells depositing basal membrane proteins and differentiating into mature keratinocytes that were able to generate a pluristratified epithelium. In conclusion, we engineered a fully differentiated human skin trilayer that could present multiple applications such as use for in vitro drug absorption tests and regenerative therapies. Copyright © 2012 John Wiley & Sons, Ltd.     

SIRT1‐dependent anti‐senescence effects of cell‐deposited matrix on human umbilical cord mesenchymal stem cells

Human umbilical cord‐derived mesenchymal stem cells (UC‐MSCs) are considered an attractive cell source for tissue regeneration. However, environmental oxidative stress can trigger premature senescence in MSCs and thus compromises their regenerative potential. Extracellular matrix (ECM) derived from MSCs has been shown to facilitate cell proliferation and multi‐lineage differentiation. This investigation evaluated the effect of cell‐deposited decellularized ECM (DECM) on oxidative stress‐induced premature senescence in UC‐MSCs. Sublethal dosages of H₂O₂, ranging from 50 μm to 200 μm , were used to induce senescence in MSCs. We found that DECM protected UC‐MSCs from oxidative stress‐induced premature senescence. When treated with H₂O₂ at the same concentration, cell proliferation of DECM‐cultured UC‐MSCs was twofold higher than those on standard tissue culture polystyrene (TCPS). After exposure to 100 μm H₂O₂, fewer senescence‐associated β‐galactosidase‐positive cells were observed on DECM than those on TCPS (17.6  ±  4.0% vs. 60.4  ±  6.2%). UC‐MSCs cultured on DECM also showed significantly lower levels of senescence‐related regulators, such as p16^INK4α and p21. Most importantly, DECM preserved the osteogenic differentiation potential of UC‐MSCs with premature senescence. The underlying molecular mechanisms involved the silent information regulator type 1 (SIRT1)‐dependent signalling pathway, confirmed by the fact that the SIRT1 inhibitor nicotinamide counteracted the DECM‐mediated anti‐senescent effect. Collagen type I, rather than fibronectin, partially contributed to the protective effect of decellularized matrix. These findings provide a new strategy of using stem cell‐deposited matrix to overcome the challenge of cellular senescence and to facilitate the clinical application of MSCs in regenerative medicine. Copyright © 2017 John Wiley & Sons, Ltd.