胎盘组织——间充质干细胞的新来源

间充质干细胞（mesenchymal stemcells,MSC）是最早分离自人骨髓组织的一类具有多向分化潜能的干细胞,随后陆续在人脂肪组织、外周血、肌肉和结缔组织中也发现了MSC。目前MSC是临床研究最普遍的细胞来源,在组织工程研究、创伤修复和肿瘤治疗等领域应用广泛,但MSC在骨髓、外周血等组织中的含量极低,并且有研究表明MSC含量会随着人年龄的增长而逐渐降低,同时细胞的增殖分化能力也大大下降因此国内外学者们开始探索在更为幼稚的组织如胚胎、胎盘组织中是否含有MSC。     

The derivation of mesenchymal stem cells from human embryonic stem cells

Human embryonic stem cells (hESCs) hold promise for tissue regeneration therapies by providing a potentially unlimited source of cells capable of undergoing differentiation into specified cell types. Several preclinical studies and a few clinical studies use human bone marrow stromal cells (hBMSCs) to treat skeletal diseases and repair damaged tissue. However, hBMSCs have limited proliferation and differentiation capacity, suggesting that an alternate cell source is desirable, and hESCs may serve this purpose. Here we describe a protocol for the reproducible derivation of mesenchymal stem cells from hESCs (hES-MSCs). The hES-MSCs have a similar immunophenotype to hBMSCs, specifically they are CD73+, STRO-1+ and CD45-, and are karyotypically stable. The derived hES-MSCs are also capable of differentiating into osteoblasts and adipocytes. When the hES-MSCs were genetically modified with the lineage-specific Col2.3-GFP lentivirus and cultured in osteogenic medium, increased GFP expression was detected over time, indicating the hES-MSCs have the capacity to differentiate down the osteogenic lineage and had progressed toward a mature osteoblast phenotype.     

Comparison of different cryopreservation protocols for human umbilical cord tissue as source of mesenchymal stem cells

The main purpose of this study is to establish an effective cryopreservation protocol for the umbilical cord tissue as a source of mesenchymal stem cells (MSCs). In this context, it was aimed to use a cryoprotectant that could be an alternative to dimethyl sulfoxide (DMSO) which is commonly used despite the toxic side effects. Therefore, two different cryopreservation solutions were prepared using 10% DMSO and 10% 1,2 propanediol (PrOH). The fresh tissue group that was not performed cryopreservation was used as the control group. Following the cryopreservation step, MSCs were isolated from all groups and compared with each other to assess the efficiency of the cryopreservation solutions. The comparison was performed in terms of followings: morphology, immunophenotypes, growth kinetics, differentiation, and ultrastructural features. Based on the results, there were no significant morphological and immunophenotypic differences between the MSCs isolated from cryopreserved tissue groups and the MSCs isolated from the fresh tissue group. According to the growth kinetic analysis, the cells isolated from the PrOH group had a lower proliferation rate than the cells isolated from the fresh tissue. However, there was no significant difference between the cryopreserved groups in this respect. Osteogenic and adipogenic differentiation was observed in all groups. Upon comparison of the cryopreserved groups, PrOH group was discovered to hold a minor superiority in terms of these modes of differentiation. These results suggest that PrOH, which is considered as a cryoprotectant with low toxicity, could be used as a preferred cryoprotectant instead of DMSO concerning the process of cryopreservation of the umbilical cord.     

High-potential human mesenchymal stem cells

Bone marrow-derived stromal mesenchymal stem cells (MSCs) have been characterized in vitro by their growth characteristics, the expression of a panel of surface antigens, and their potential to differentiate into mesenchymal lineages. They can be separated by physical methods as well as by immunological or chemical separation or cultivation. Different protocols are used in different laboratories, making the comparison of various reported MSC populations difficult. Here we describe a population of bone marrow-derived adult stem cells that has been separated on a Percoll gradient with low density. It is characterized by an extraordinary high proliferative potential and a conserved phenotype characteristic of MSCs that retain their plutipotentiality in culture, as evidenced by their ability to differentiate into osteo-, chondro-, and adipogenic lineages. Separation of these cells provide an effective and convenient method for rapid expansion of pluripotential human MSCs for clinical use where large amounts of stem cells are needed.     

Proliferation as a requirement for in vitro chondrogenesis of human mesenchymal stem cells

During embryonic cartilage development, proliferation and differentiation are tightly linked with a transient cell cycle arrest observed during determination and before main extracellular matrix production. Aim of this study was to address whether these steps are imitated during in vitro differentiation of mesenchymal stem cells (MSCs) and are crucial for a proper chondrogenesis. Human MSCs were expanded in distinct media and subjected to pellet culture in chondrogenic medium. Cells were labeled with 5-iodo-2'-deoxyuridin (IdU) or treated with mitomycin C at various time points during culture. Apoptosis was detected by cleaved caspase 3. Proliferation rate of expanded MSCs at start of pellet culture showed a positive correlation with chondrogenesis according to DNA content, proteoglycan deposition, collagen type II content, and final pellet size. Evenly distributed IdU signals at day 1 diminished and became restricted primarily to the periphery by day 3. Between days 10 and 21, IdU-positive cells were detected throughout coinciding with collagen type II positivity. Little IdU incorporation occurred after day 21 and in areas of strong matrix deposition. DNA content decreased and apoptosis was detected up to day 14. Irreversible growth arrest by mitomycin C fully blocked chondrogenic differentiation and seemed to arrest differentiation at the stage reached at treatment. In conclusion, chondrogenesis involved a transient proliferation phase appearing simultaneously with start of collagen type II deposition and growth was crucial for proper chondrogenesis. Growth and differentiation steps, thus, seemed closely coordinated and resembled, with respect to proliferation, stages known from embryonic cartilage development. Stimulation of proliferation and prevention of early apoptosis are attractive goals to further improve MSC chondrogenesis.     

Fetal membranes as a source of stem cells

In recent years, a constant growth of knowledge and clinical applications of stem cells have been observed. Mesenchymal stromal cells, also described as mesenchymal stem cells (MSCs) represent a particular cell type for research and therapy because of their ability to differentiate into mesodermal lineage cells. The most investigated source of MSCs is bone marrow (BM). Yet, collection of BM is an invasive procedure associated with significant discomfort to the patient. The procedure results in a relatively low number of these cells, which can decrease with donor's age. Therefore, it seems to be very important to find other sources of mesenchymal stem cells nowadays. A human placenta, which is routinely discarded postpartum, in spite of its natural aging process, is still a rich source of stem cells capable to proliferate and in vitro differentiate in many directions. Besides homing and differentiation in the area of injury, MSCs there elicit strong paracrine effects stimulating the processes of repair. In this review, we focus on the biology, characteristics and potential clinical applications of cells derived from human fetal membranes: amnion and chorion.     

Differentiation of human embryonic stem cells into bipotent mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent progenitors that can be found in many connective tissues, including fat, bone, cartilage, and muscle. We report here a method to reproducibly differentiate human embryonic stem cells (hESCs) into MSCs that does not require the use of any feeder layer. The cells obtained with this procedure are morphologically similar to bone marrow MSCs, are contact-inhibited, can be grown in culture for about 20 to 25 passages, have an immunophenotype similar to bone marrow MSCs (negative for CD34 and CD45 and positive for CD13, CD44, CD71, CD73, CD105, CD166, human leukocyte antigen [HLA]-ABC, and stage-specific embryonic antigen [SSEA]-4), can differentiate into osteocytes and adipocytes, and can be used as feeder cells to support the growth of undifferentiated hESCs. The ability to produce MSCs from hESCs should prove useful to produce large amounts of genetically identical and genetically modifiable MSCs that can be used to study the biology of MSCs and for therapeutic applications.     

Umbilical cord blood as a source of stem cells

Umbilical cord blood (UCB) is a source of the rare but precious primitive hematopoietic stem cells (HSC) and progenitor cells that can reconstitute the hematopoietic system in patients with malignant and nonmalignant disorders treated with myeloablative therapy. UCB cells possess an enhanced capacity for progenitor cell proliferation and self-renewal in vitro. UCB is usually discarded, and it exists in almost limitless supply. The blood remaining in the delivered placenta is safely and easily collected and stored. The predominant collection procedure currently practiced involves a relatively simple venipuncture, followed by gravity drainage into a standard sterile anti-coagulant-filled blood bag, using a closed system, similar to the one utilized on whole blood collection. After aliquots have been removed for routine testing, the units are cryopreserved and stored in liquid nitrogen. UCB banks are being established throughout the world and UCB units are collected for allogeneic unrelated and related HSC transplantation. In unrelated cord blood banks donated UCB units are collected and stored for allogeneic use in patients who do not have an identified HLA matched relative. UCB banks report available units to national and international donor registries. The second model of UCB banking is referred to as family banking, where UCB is stored for the benefit of the donor or their family members. After more than one decade of clinical experience, it is currently accepted that UCB transplants, related and unrelated, are equivalent to or might compare favorably with bone marrow (BM) transplants, especially in children. Initial studies of long-term survival in children with both malignant and non-malignant hematologic disorders, who were transplanted with UCB from a sibling donor, demonstrated comparable or superior survival to children who received BM transplantation. One factor that limits the use of UCB transplantation in adult patients is the relatively limited number of HSC that may be harvested from umbilical cord, resulting in a slower time to engraftment and higher transplant related mortality, mainly due to the long aplasia period after transplantation and susceptibility to viral and fungal infections. Despite prolonged periods of aplasia, the apparent reduction in the incidence and severity of graft versus host disease (GVHD) may in turn underline comparable rates of survival in some series comparing UCB to adult-donor sources. The "naive" nature of UCB lymphocytes may explain the lower incidence and severity of GVHD encountered in UCB transplantation compared to the allogeneic BM transplant setting. UCB transplantation does not seem to be associated with increased rates of disease relapse. The available data suggest that nucleated cell dose in UK unit should be the primary criterion for donor selection. In 1991, the UCB transplantation program was established at the Zagreb University Hospital Center for related transplants, and until now 4 UCB transplantations have been performed successfully. In order to speed up the engraftment rate, several strategies such as multiple UCB transplants and ex vivo expansion of HSC have been assayed. The current strategies are focused on the development of much more efficient technologies for ex vivo production of progenitor cells, but whether expansion will speed engraftment and improve outcome after UCB remains to be determined. UCB is known to contain extremely immature stem cells. Consequently, such pluripotent or, perhaps, multipotent stem cells have been proposed as elements suitable for cellular therapy and regenerative medicine. Up to date there are no conclusive data regarding these possibilities but preliminary in vitro and animal studies in the field of tissue regeneration suggest some degree of plasticity and/or transdifferentiation. UCB cells are showing their unique qualities and potential, and consequently UCB banks might dramatically increase the scope of their clinical application.     

人骨髓间充质干细胞向心肌样细胞分化

目的讨论小型猪心肌细胞(CMs)裂解液对人骨髓间充质干细胞(MSCs)的体外诱导分化作用。方法用5-aza、小型猪CMs裂解液二种方法体外诱导人MSCs的分化,单纯培养基(DMEM)培养为对照组,观察细胞形态改变。用细胞免疫化学、免疫荧光法检测MSCs的α-actin、cTnT、Cx43和CD31的表达,MTT法测定细胞增殖。结果小型猪CMs裂解液诱导人MSCs所得心肌样细胞(CLCs)表达cTnT、Cx43和CD31;5-aza诱导组MSCs表达cTnT和Cx43,不表达CD31;5-aza培养初期对MSCs的增殖具有明显的抑制作用,CMs裂解液促进MSCs的增殖。结论小型猪CMs裂解液培养基可以诱导人MSCs分化为心肌样细胞及内皮样细胞,并且具有很强的促细胞增殖作用,优于目前广泛研究的肌细胞诱导分化剂5-aza。本研究为大规模诱导人MSCs向CMs分化创造了条件。     

Nonviable human pre-implantation embryos as a source of stem cells for research and potential therapy

Human embryonic stem cells are derived from the inner cell mass of the human blastocyst. Presumably normal (frozen/thawed) human preimplantation embryos that remain unused following assisted reproduction procedures have provided the main source of blastocysts for stem cell derivation. Alternatively, embryos have been generated from gametes donated for the unique purpose of in vitro fertilization, blastocyst culture, and stem cell isolation. This article describes two previously published methods—and the background to those methods—that allow the use of nonviable embryos excluded from transfer and cryopreservation as a source of stem cells. The first method is based on the observation that some blastomeres from embryos with abnormal division during the first 3–5 d in culture can continue very limited development in isolation. When aggregated in a chimaeric form, some of these blastomeres can contribute to the formation of normally organized blastocysts. Blastocysts so obtained provide a route to embryonic stem cells from otherwise nonviable embryos. Thus the inner cell masses of blastocysts obtained from trisomic embryos were placed on feeder cells and cultured for seven additional days, following which the resulting cell colonies were examined for chromosome content. The second method concerns embryos diagnosed with specific chromosome abnormalities many of which are incompatible with life. Some of these aneuploidies do not preclude development to the blastocyst stage in culture. A proportion of these cells were found to be disomic and the cultures were shown to express OCT-4, a molecular marker for pluripotent cells. This apparent correction of the trisomic state in some cells within the colonies suggests that embryos with cromosomal abnormalities incompatible with life may be another source of human embryonic stem cells.     

人骨髓源和胎盘源间充质干细胞对T细胞增殖抑制作用的比较

目的:比较研究人骨髓源和胎盘源间充质干细胞介导的T细胞增殖抑制作用机制。方法:应用流式细胞术(FCM)分别检测B7H4和PDL1在人骨髓源间充质干细胞(HBMSCs)和胎盘源间充质干细胞(HPMSCs)上的表达;应用抗体阻断试验分析B7H4、PDL1分别在HBMSCs和HPMSCs对T细胞增殖及周期影响中的作用。结果:HBMSCs上高表达免疫负性调控分子B7H4,而HPMSCs上高表达免疫负性调控分子PDL1。分别应用B7H4mAb和PDL1mAb阻断,可使HBMSCs和HPMSCs对PHA激发的T细胞增殖抑制作用明显减弱;下调T细胞周期中G0/G1期细胞数量,上调S期细胞数量,明显减弱HBMSCs和HPMSCs对T细胞周期的影响。结论:HBMSCs和HPMSCs可通过表达不同的免疫负性调控分子介导T细胞的增殖抑制作用。     

Interactions between human mesenchymal stem cells and natural killer cells

Mesenchymal stem cells (MSCs) are multipotent progenitor cells representing an attractive therapeutic tool for regenerative medicine. They possess unique immunomodulatory properties, being capable of suppressing T-cell responses and modifying dendritic cell differentiation, maturation, and function, whereas they are not inherently immunogenic, failing to induce alloreactivity to T cells and freshly isolated natural killer (NK) cells. To clarify the generation of host immune responses to implanted MSCs in tissue engineering and their potential use as immunosuppressive elements, the effect of MSCs on NK cells was investigated. We demonstrate that at low NK-to-MSC ratios, MSCs alter the phenotype of NK cells and suppress proliferation, cytokine secretion, and cyto-toxicity against HLA-class I- expressing targets. Some of these effects require cell-to-cell contact, whereas others are mediated by soluble factors, including transforming growth factor-beta1 and prostaglandin E2, suggesting the existence of diverse mechanisms for MSC-mediated NK-cell suppression. On the other hand, MSCs are susceptible to lysis by activated NK cells. Overall, these data improve our knowledge of interactions between MSCs and NK cells and consequently of their effect on innate immune responses and their contribution to the regulation of adaptive immunity, graft rejection, and cancer immunotherapy.     

Expansion and chondrogenic differentiation of human mesenchymal stem cells

The potential of human mesenchymal stem cells (hMSC) to differentiate into various types of mesenchymal tissue, such as chondrocytes, makes them a potential cell source in cartilage tissue engineering. Because of the requirement of high cell amounts for the generation of cartilage implants or for the extensive experimental studies to investigate the culture parameters, the initial cells have to be expanded, which leads to high population doubling numbers. It is known that hMSC can differentiate into chondrocytes at least up to the 15th population doubling. To monitor the differentiation status, the protein MIA (melanoma inhibitory activity), which is only synthesized by malignant melanomas and chondrocytes, can be used. In this study the chondrogenic differentiation potential of hMSC beyond the 15th population doubling was investigated using MIA as a chondrocyte marker. A chondrogenic potential of hMSC at higher population doubling numbers may be of interest due to the requirement of less frequent isolations of cells. Therefore hMSC were cultured in a monolayer until the 37th population doubling. Cells of different passages were cultured as pellets for two weeks in transforming growth factor (TGF)-beta3 containing differentiation medium. The MIA contents in medium on the last three cultivation days were measured for each case using an MIA-ELISA-kit. A significant difference between MIA content in medium of the pellet and nonstimulated monolayer reference cultures was detectable until the 32nd population doubling. In addition, the hMSC were seeded at lower densities to investigate whether the cells may be expanded faster and with less amount of work due to higher population doubling numbers per passage. The reduced inoculation density led to an increased growth rate.     

人胎盘绒毛膜来源间充质干细胞的生物学特性

背景：骨髓是间充质干细胞的主要来源,但骨髓中间充质干细胞数量和质量会随着年龄的增长而逐渐降低。因此,寻找一种新的干细胞来源具有重要意义。 目的：分离研究了一种新的间充质干细胞来源——人绒毛膜来源间充质干细胞,并研究其生物学特性。 方法：将胎盘冲洗干净后,分离出脐带和羊膜组织,将剩余的胎盘组织进行原代和传代培养。通过短串联重复序列分析检测细胞是否来源于绒毛膜,用MTT法检测细胞生长方式,流式细胞仪分析细胞表型及干细胞标记,使用不同的诱导分化培养基检测其多向分化的能力。将该细胞与植物血凝素刺激的外周血单个核细胞共培养,用酶联免疫吸附试验检测上清γ-干扰素的水平。 结果与结论：短串联重复序列分析证明所得到的细胞来源于绒毛膜,这种绒毛膜来源的细胞生长呈典型的成纤维细胞形态。细胞表达常见的间充质干细胞表面标记CD90、CD73、CD105、CD44,不表达CD45,CD11b和CD34。同时,细胞也表达Nestin和Sox-2。在不同的条件培养基培养状态下,细胞可向成骨、成脂方向分化。这些结果证明所得到的细胞为人绒毛膜间充质干细胞。这些绒毛膜间充质干细胞能抑制植物血凝素刺激的人外周血单个核细胞分泌γ-干扰素。可见绒毛膜来源的间充质干细胞具有和传统的骨髓来源间充质干细胞具有相似的生物学特性。