Engineering cartilaginous grafts using chondrocyte‐laden hydrogels supported by a superficial layer of stem cells

During postnatal joint development, progenitor cells that reside in the superficial region of articular cartilage first drive the rapid growth of the tissue and later help direct the formation of mature hyaline cartilage. These developmental processes may provide directions for the optimal structuring of co‐cultured chondrocytes (CCs) and multipotent stromal/stem cells (MSCs) required for engineering cartilaginous tissues. The objective of this study was to engineer cartilage grafts by recapitulating aspects of joint development where a population of superficial progenitor cells drives the development of the tissue. To this end, MSCs were either self‐assembled on top of CC‐laden agarose gels (structured co‐culture) or were mixed with CCs before being embedded in an agarose hydrogel (mixed co‐culture). Porcine infrapatellar fat pad‐derived stem cells (FPSCs) and bone marrow‐derived MSCs (BMSCs) were used as sources of progenitor cells. The DNA, sGAG and collagen content of a mixed co‐culture of FPSCs and CCs was found to be lower than the combined content of two control hydrogels seeded with CCs and FPSCs only. In contrast, a mixed co‐culture of BMSCs and CCs led to increased proliferation and sGAG and collagen accumulation. Of note was the finding that a structured co‐culture, at the appropriate cell density, led to greater sGAG accumulation than a mixed co‐culture for both MSC sources. In conclusion, assembling MSCs onto CC‐laden hydrogels dramatically enhances the development of the engineered tissue, with the superficial layer of progenitor cells driving CC proliferation and cartilage ECM production, mimicking certain aspects of developing cartilage. Copyright © 2015 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.     

CD271及CD133用于阳性分选富集骨髓间充质干细胞的比较

本研究旨在通过对CD271（低亲和性神经生长因子受体，low affinity nerve growth factor receptor，LNG—FR）及CD133免疫磁珠阳性分选富集骨髓间充质干细胞（mesenchymal stem cells，MSCs）的比较，选出一种相对理想的从骨髓中富集间充质干细胞的免疫磁珠分选方法。采用免疫磁珠的方法得到骨髓单个核细胞中的CD271^＋细胞及CD133^＋细胞；将得到的细胞分别进行培养，14天后计数成纤维细胞集落形成单位（colony forming unit—fibro—blast，CFU—F）；对每个传代细胞进行计数，绘制细胞增殖曲线；取两种方法得到的细胞培养至3代以后，流式细胞术检测细胞表面抗原，通过细胞形态及免疫化学染色鉴定比较成骨及成脂肪定向诱导分化。结果表明：CD271阳性分选纯度为（89．50±0．98）％，CD133阳性分选纯度为（88．03±3．06）％；1×10^4个CD271^＋细胞培养后产生的CFU—F数目是1×10^4个CD133^＋细胞培养后形成CFU—F数目的2倍，CD271^-细胞培养后无CFU—F形成，而CD133^-细胞培养后可形成少量的CFU—F；两种方法得到的细胞培养至第3代后表型基本一致，即CD34^-、CD14^-、CD45^-、CD90^＋、CD29^＋、CD44^＋、CD105^＋、CD73^＋；CD271^＋细胞的增殖能力比CD133^＋细胞的高出3倍，而且具有更强的成骨、成脂肪分化潜能。结论：虽然CD271及CD133阳性分选都可以得到间充质干细胞，但相比之下，CD271阳性分选得到的间充质干细胞有更强的增殖和分化能力，因而CD271阳性分选是一种相对理想的从骨髓中富集阃充质干细胞的免疫磁珠分选方法。     

In vitro simulation of the early proinflammatory phase in fracture healing reveals strong immunomodulatory effects of CD146‐positive mesenchymal stromal cells

The impact of microenvironmental cues and changes due to injury on the phenotype and fate of mesenchymal stromal cells (MSCs) is poorly understood. Here, we aimed to simulate the microenvironment associated with the early stage of bone healing in vitro and to study the regenerative response of MSCs. We enriched CD146+ MSCs from the human bone marrow. Different physiological and pathological microenvironments were simulated by using conditioned medium (CM) from human endothelial cells and osteoblasts (healthy bone), femoral head‐derived bone fragments (injured bone), and activated platelets (platelet‐rich plasma [PRP], injury). Cells were incubated in CM and analyzed with respect to proliferation, gene expression, migration, osteogenic differentiation, and their effect on polyclonally induced proliferation of peripheral blood mononuclear cells. CD146+ MSCs showed a specific response to different microenvironments. Cell proliferation was observed in all media with the highest values in PRP‐CM and injured bone‐CM. Gene expression analysis revealed the upregulation of chemokines, proinflammatory, proangiogenic, and genes involved in immunomodulation in cells stimulated with PRP‐ and injured bone‐CM, suggesting strong paracrine activity. PRP‐CM led to pronounced inhibition of lymphocyte proliferation by CD146+MSCs. Our results indicate that a microenvironment simulating bone injury elicits strong immunomodulatory and proangiogenic activity of CD146+ MSCs. This suggests that in the early stage of bone healing, the prime function of MSCs and their CD146+ subpopulation is in regulating the immune response and inducing neovascularization. Future studies will investigate the key components in CM driving this function, which might be potential targets to therapeutically stimulate the regenerative potential of MSCs.     

人脐带和骨髓源间充质干细胞对脐血单个核细胞增殖能力的影响

目的：探讨人脐带间充质干细胞（UCMSCs）与骨髓间充质干细胞（BMMSCs）在体外对造血干细胞的支持作用。方法分别从人脐带和骨髓中分离、培养间充质干细胞,通过免疫细胞化学染色等方法对其进行表型鉴定;采用流式细胞仪测定脐血单个核细胞的周期分布,采用甲基纤维素法测定脐血单个核细胞混合集落形成单位（CFU-Mix）,比较 UCMSCs和BMMSCs对脐血单个核细胞细胞周期、CFU-Mix形成能力的影响。结果成功培养获得 UCMSCs和BMMSCs,鉴定结果符合预期;与非共培养组细胞相比,UCMSCs和 BMMSCs共培养均能促进脐血单个核细胞进入增殖周期,并增加其形成CFU-Mix的能力（P＜0．05）,但UCMSCs和BMMSCs共培养组之间比较差异无统计学意义（P＞0．05）。结论成功从人脐带和骨髓组织中培养获得间充质干细胞,两种来源的间充质干细胞均能提高脐血单个核细胞的体外增殖能力及 CFU-Mix形成能力,均具有造血支持作用。     

骨髓增生异常综合征患者间充质干细胞的生物学特性及其支持造血的体外研究

为了解骨髓增生异常综合征（MDS）患者间充质干细胞（MSC）的生物学特性,探讨其对体外造血的支持能力,采集MDS的骨髓标本,分离、培养和扩增MSC,进行细胞形态观察和免疫表型、成骨分化及增殖能力检测,并对骨髓细胞进行成纤维细胞集落（CFU-F）形成分析.对MDS患者的MSC进行贴壁培养,接种脐血单个核细胞（MNC）,以观察细胞数和CFU-GM的变化,作为MDS患者MSC支持造血体外实验.结果表明：来自MDS患者的MSC呈典型的成纤维样细胞形态,表型鉴定CD34,CD45阴性,SH2（CD105）,SH3（CD73）,Thy-1（CD90）阳性,体外诱导可向成骨细胞分化,其增殖能力和CFU-F形成能力与源于正常供者的MSC相当.支持造血的体外实验显示,实验组培养上清中的细胞总数和CFU-GM计数在第2周后均显著低于对照组（P＜0.05）.结论：来源于MDS患者骨髓的间充质干细胞的生物学特性与正常供者的MSCs无差异,但其体外支持造血的功能较后者显著减弱.     

Cultured cell‐derived extracellular matrices to enhance the osteogenic differentiation and angiogenic properties of human mesenchymal stem/stromal cells

Cell‐derived extracellular matrix (ECM) consists of a complex assembly of fibrillary proteins, matrix macromolecules, and associated growth factors that mimic the composition and organization of native ECM micro‐environment. Therefore, cultured cell‐derived ECM has been used as a scaffold for tissue engineering settings to create a biomimetic micro‐environment, providing physical, chemical, and mechanical cues to cells, and support cell adhesion, proliferation, migration, and differentiation. Here, we present a new strategy to produce different combinations of decellularized cultured cell‐derived ECM (dECM) obtained from different cultured cell types, namely, mesenchymal stem/stromal cells (MSCs) and human umbilical vein endothelial cells (HUVECs), as well as the coculture of MSC:HUVEC and investigate the effects of its various compositions on cell metabolic activity, osteogenic differentiation, and angiogenic properties of human bone marrow (BM)‐derived MSCs, vital features for adult bone tissue regeneration and repair. Our findings demonstrate that dECM presented higher cell metabolic activity compared with tissue culture polystyrene. More importantly, we show that MSC:HUVEC ECM enhanced the osteogenic and angiogenic potential of BM MSCs, as assessed by in vitro assays. Interestingly, MSC:HUVEC (1:3) ECM demonstrated the best angiogenic response of MSCs in the conditions tested. To the best of our knowledge, this is the first study that demonstrates that dECM derived from a coculture of MSC:HUVEC impacts the osteogenic and angiogenic capabilities of BM MSCs, suggesting the potential use of MSC:HUVEC ECM as a therapeutic product to improve clinical outcomes in bone regeneration.     

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.     

成人骨髓间充质干细胞中各亚群的比较研究

为了观察成人骨髓间充质干细胞在体外培养中的形态，比较不同亚群细胞的免疫表型和细胞周期等生物学性状的差异，取正常人骨髓单个核细胞，进行间充质干细胞(mesenchymal stem cell，MSC)培养，倒置相差显微镜观察MSC不同亚群细胞的形态；流式细胞术检测MSC不同亚群细胞的表型并进行细胞周期分析；用10μm滤膜将不同群体细胞分离，分别接种半固体培养体系。结果表明：①MSC在体外培养中明显分为两群，成纤维样梭形细胞为成熟的MSC，即mMSC；体积很小的圆形细胞为RS细胞(rapidly MSC self-renewing cells)；②99％的RS细胞处于G0／G1期，mMSC中处于G0／G1期的细胞占90％。③两群细胞的系定向抗原均为阴性(CD34、CD45、CD3、CD19、CD33、HLA-DR、CD38等)，而CD90、CD105、C166、CD29、CD44、CD49e、CD54、CD13呈阳性表达，但RS细胞表面这些抗原表达的阳性率和平均荧光强度都明显低于mMSC。而CD117和KDR的表达则显著高于mMSC。④半固体培养4—5周后两种细胞群体均未见造血细胞集落形成。结论：MSC是一个异质性的细胞群体，其中包含的RS细胞可能是一种更原始的中胚层前体细胞，具有更强的自我更新和多向分化潜能。     

人骨髓间充质干细胞对T淋巴细胞的免疫调节作用

为了探讨人骨髓间充质干细胞（mesenchymal stem cell，MSC）体外对T淋巴细胞的免疫调节作用，从人骨髓液中分离培养MSC，通过细胞形态、免疫组织化学及流式细胞术检测其表面标记进行鉴定；将植物血凝素（PHA）及从人脐血中分离培养的树突状细胞（dendritic cell，DC）作为刺激因素，经磁珠分选的人CD2^＋ T淋巴细胞作为反应细胞．用^3H—TdR标记β液体闪烁计数仪检测与MSC共培养前后T淋巴细胞增殖能力的变化；用流式细胞术检测与MSC共培养10天后的CD2^＋ T细胞内各亚群Th1、Th2、Tc1、Tc2比例的变化。结果表明：MSC能明显抑制由DC诱导的T淋巴细胞增殖（P=0．004），同时MSC抑制由PHA引起的T细胞增殖，但不具有显著性差异（P=0．26），MSC培养上清液单独并不具备抑制T细胞增殖的作用，与MSC共培养后的T细胞亚群中，Th2及Tc2亚群含量较共培养前明显增加（P〈0．05）。结论：MSC对由DC和PHA诱导的淋巴细胞增殖反应均具有抑制作用，并且这种作用可能与细胞间相互作用及诱导T细胞亚群的改变有关。     

Electrical stimulation of adipose‐derived mesenchymal stem cells and endothelial cells co‐cultured in a conductive scaffold for potential orthopaedic applications

Electrical stimulation (ES) has emerged as a useful tool to regulate cell behaviour, but the effect of ES on mesenchymal stem cell (MSC)/vasculogenic cell co‐culture has not been investigated. Herein, human adipose‐derived MSCs (AD‐MSCs) and umbilical vein endothelial cells (HUVECs) were co‐cultured in an electrically conductive polypyrrole/chitosan scaffold. Compared with AD‐MSC monoculture, calcium deposition in the co‐culture without and with ES (200 μA for 4 h/day) was 139% and 346% higher, respectively, after 7 days. As the application of ES to AD‐MSC monoculture only increased calcium deposition by 56% compared with that without ES after 7 days, these results indicate that ES and co‐culture with HUVECs have synergistic effects on AD‐MSCs' osteogenic differentiation. ES application also significantly enhanced CD31 expression of HUVECs. In HUVEC monoculture, application of ES increased CD31 expression by 224%, whereas the corresponding increase in AD‐MSC/HUVEC co‐culture with ES application was 62%. The gene expression results indicate that ES enhanced the cellular functions in AD‐MSC and HUVEC monoculture via autocrine bone morphogenetic protein‐2 (BMP‐2) and vascular endothelial growth factor (VEGF), respectively. In co‐culture, crosstalk between AD‐MSCs and HUVECs due to paracrine BMP‐2 and VEGF enhanced the cellular functions compared with the respective monoculture. With application of ES to the AD‐MSC/HUVEC co‐culture, autocrine signalling was enhanced, resulting in further promotion of cellular functions. These findings illustrate that co‐culturing AD‐MSC/HUVEC in a conductive scaffold with ES offers potential benefits for bone defect therapy.     

Bone marrow‐on‐a‐chip: Long‐term culture of human haematopoietic stem cells in a three‐dimensional microfluidic environment

Multipotent haematopoietic stem and progenitor cells (HSPCs) are the source for all blood cell types. The bone marrow stem cell niche in which the HSPCs are maintained is known to be vital for their maintenance. Unfortunately, to date, no in vitro model exists that accurately mimics the aspects of the bone marrow niche and simultaneously allows the long‐term culture of HSPCs. In this study, a novel three‐dimensional coculture model is presented, based on a hydroxyapatite coated zirconium oxide scaffold, comprising of human mesenchymal stromal cells (MSCs) and cord blood derived HSPCs, enabling successful HSPC culture for a time span of 28 days within the microfluidic multiorgan chip. The HSPCs were found to stay in their primitive state (CD34⁺CD38^?) and capable of granulocyte, erythrocyte, macrophage, megakaryocyte colony formation. Furthermore, a microenvironment was formed bearing molecular and structural similarity to the in vivo bone marrow niche containing extracellular matrix and signalling molecules known to play an important role in HSPC homeostasis. Here, a novel human in vitro bone marrow model is presented for the first time, capable of long‐term culture of primitive HSPCs in a microfluidic environment.     

Ectopic bone formation by aggregated mesenchymal stem cells from bone marrow and adipose tissue: A comparative study

Tissue engineered constructs (TECs) based on spheroids of bone marrow mesenchymal stromal cells (BM‐MSCs) combined with calcium phosphate microparticles and enveloped in a platelet‐rich plasma hydrogel showed that aggregation of MSCs improves their ectopic bone formation potential. The stromal vascular fraction (SVF) and adipose‐derived MSCs (ASCs) have been recognized as an interesting MSC source for bone tissue engineering, but their ectopic bone formation is limited. We investigated whether aggregation of ASCs could similarly improve ectopic bone formation by ASCs and SVF cells. The formation of aggregates with BM‐MSCs, ASCs and SVF cells was carried out and gene expression was analysed for osteogenic, chondrogenic and vasculogenic genes in vitro. Ectopic bone formation was evaluated after implantation of TECs in immunodeficient mice with six conditions: TECs with ASCs, TECs with BM‐MSC, TECs with SVF cells (with and without rhBMP2), no cells and no cells with rhBMP2. BM‐MSCs showed consistent compact spheroid formation, ASCs to a lesser extent and SVF showed poor spheroid formation. Aggregation of ASCs induced a significant upregulation of the expression of osteogenic markers like alkaline phosphatase and collagen type I, as compared with un‐aggregated ASCs. In vivo, ASC and SVF cells both generated ectopic bone in the absence of added morphogenetic proteins. The highest incidence of bone formation was seen with BM‐MSCs (7/9) followed by SVF + rhBMP2 (4/9) and no cells + rhBMP2 (2/9). Aggregation can improve ectopic bone tissue formation by adipose‐derived cells, but is less efficient than rhBMP2. A combination of both factors should now be tested to investigate an additive effect.     

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.     

间充质干细胞和内皮祖细胞对脐血造血干/祖细胞体外扩增效力的影响

目的比较脐带来源的间充质干细胞(Mesenchymal stem cells,MSCs)和内皮祖细胞(Endothelial progeni-tor cells,EPCs)对脐血造血干/祖细胞(Hematopoietic stem/progenitor cells,HSCs/HPCs)的体外扩增效力。方法正常人脐血中分离单个核细胞(Mononuclear cells,MNCs),流式细胞术检测其中HSCs/HPCs所占比例,将MNCs分别接种于处理后的MSCs或EPCs或仅接种于培养液中,比较不同培养条件对HSCs/HPCs扩增能力、表面抗原CD34的表达以及集落形成能力的影响。结果共培养过程中,MSC组和EPC组的MNCs扩增倍数均明显高于对照组,且EPC组更为显著。扩增7天后,对照组、MSC组和EPC组的HSCs/HPCs CD34的表达均较扩增前下降,其中EPC组下降的最为显著,MSC组最不显著。共培养4天后,MSC组的HSCs/HPCs集落形成总数为EPC组的2.47倍(**,P<0.01),共培养7天后,MSC组的HSCs/HPCs集落形成总数为EPC组的3.45倍(**,P<0.01);EPC组与对照组的HSCs/HPCs集落形成总数无显著性差异。结论 MSC和EPC均可为HSCs/HPCs的体外扩增提供适宜的微环境,MSC可抑制HSCs/HPCs的分化,有助于维持其表面抗原CD34的表达,并保持其造血重建潜能和归巢能力;而EPC则可有效促进HSCs/HPCs的分化。     

人骨髓间充质干细胞体外对异基因T淋巴细胞表型的影响

为了研究间充质干细胞 (mesenchymalstemcell,MSC)的免疫调节作用 ,探讨防治异基因骨髓移植中移植物抗宿主病 (GVHD)和移植排斥反应 (HVGR)的可能途径 ,从人骨髓中分离培养间充质干细胞 ,并通过其形态的均一性及流式细胞术检测表面标志以鉴定其纯度 ,将MSC分别以 8× 10 4 (A组 )、4× 10 4 (B组 )和 2× 10 4 (C组 )个细胞 孔分别接种于 6孔板 ,并与经分离的外周血T淋巴细胞共培养 7天 ,以单独培养的外周血T淋巴细胞为对照组 ,用流式细胞仪分别在培养 0、2 4、72小时和 7天测定各组T细胞上CD3、CD4、CD8、CD2 5表达的变化。结果表明 :T细胞和MSC共培养组与T细胞单独培养组相比 ,A组和B组CD4 CD2 5 免疫调节性T细胞和CD8 T细胞明显增多 ,A组和B组之间无明显差别。实验组和对照组相比CD3、CD4、CD2 5表达无明显差别。结论 :骨髓MSCs在体外可使外周血T细胞表型发生改变 ,CD4 CD2 5 免疫调节性T细胞和CD8 T细胞明显增多 ,本研究结果为临床异基因造血干细胞移植预防GVHD时MSCs的输注数量提供了参考。     

Isolation and characterization of mesenchymal cells from human fetal membranes

Bone marrow (BM) multipotent mesenchymal stromal cells (MSCs) present with multipotent differentiation potential and immunomodulatory properties. As an alternative to bone marrow, we have examined fetal membranes, amnion and chorion, of term human placenta as a potential source of multipotent MSCs. Here we show that amnion mesenchymal cells (AMCs) and chorion mesenchymal cells (CMCs), isolated by mechanical separation and subsequent enzymatic digestion, demonstrate plastic adherence and fibroblast-like morphology and are able to form colonies that could be expanded for at least 15 passages. By FACS analysis, AMCs and CMCs were shown to be phenotypically similar to BM-MSCs and, when cultured in differentiation media, they demonstrated high morphogenetic plasticity by differentiating into osteocytes, chondrocytes and adipocytes. In an attempt to isolate cells with MSC characteristics from human fetal membranes, AMCs and CMCs expressing CD271 were enriched by immunomagnetic isolation and were demonstrated to possess higher clonogenic and osteogenic differentiation potential than CD271-depleted fractions. Based on these findings, amnion and chorion can be considered as a novel and convenient source of adult MSCs.     

Collagen modules for in situ delivery of mesenchymal stromal cell‐derived endothelial cells for improved angiogenesis

Modular tissue engineering is a strategy to create scalable, self‐assembling, three‐dimensional (3D) tissue constructs. This strategy was used to deliver endothelial‐like cells derived from bone marrow mesenchymal stromal cells (EL‐MSCs) to locally induce vascularization. First, tissue engineered modules were formed, comprising EL‐MSCs and collagen‐based cylinders. Seven days of module culture in a microfluidic chamber under continuous flow resulted in the formation of interstices, formed by random packing of the modules, which served as channels and were lined by the EL‐MSCs. We observed maintenance of the endothelial phenotype of the EL‐MSCs, as demonstrated by CD31 staining, and the cells proliferated well. Next, collagen modules covered with EL‐MSCs, with or without embedded MSCs, were implanted subcutaneously in immune‐compromised SCID/Bg mice. After 7 days, CD31‐positive vessels were observed in the samples. These data demonstrate the feasibility of EL‐MSCs coated collagen module as a strategy to locally stimulate angiogenesis and vasculogenesis. Copyright © 2013 John Wiley & Sons, Ltd.     

Cartilage graft engineering by co‐culturing primary human articular chondrocytes with human bone marrow stromal cells

Co‐culture of mesenchymal stromal cells (MSCs) with articular chondrocytes (ACs) has been reported to improve the efficiency of utilization of a small number of ACs for the engineering of implantable cartilaginous tissues. However, the use of cells of animal origin and the generation of small‐scale micromass tissues limit the clinical relevance of previous studies. Here we investigated the in vitro and in vivo chondrogenic capacities of scaffold‐based constructs generated by combining primary human ACs with human bone marrow MSCs (BM‐MSCs). The two cell types were cultured in collagen sponges (2 × 6 mm disks) at the BM‐MSCs:ACs ratios: 100:0, 95:5, 75:25 and 0:100 for 3 weeks. Scaffolds freshly seeded or further precultured in vitro for 2 weeks were also implanted subcutaneously in nude mice and harvested after 8 or 6 weeks, respectively. Static co‐culture of ACs (25%) with BM‐MSCs (75%) in scaffolds resulted in up to 1.4‐fold higher glycosaminoglycan (GAG) content than what would be expected based on the relative percentages of the different cell types. In vivo GAG induction was drastically enhanced by the in vitro preculture and maximal at the ratio 95:5 (3.8‐fold higher). Immunostaining analyses revealed enhanced accumulation of type II collagen and reduced accumulation of type X collagen with increasing ACs percentage. Constructs generated in the perfusion bioreactor system were homogeneously cellularized. In summary, human cartilage grafts were successfully generated, culturing BM‐MSCs with a relatively low fraction of non‐expanded ACs in porous scaffolds. The proposed co‐culture strategy is directly relevant towards a single‐stage surgical procedure for cartilage repair. Copyright © 2012 John Wiley & Sons, Ltd.