茂丹通脉片含药血清体外诱导 S 分M化C为 内皮细胞的作用

目的：观察芪丹通脉片含药血清体外诱导大鼠骨髓间充质干细胞（MSCs）向内皮细胞分化的作用。方法：灌胃法制备芪丹通脉片含药血清和对照血清。采用密度梯度离心法分离和培养大鼠MSCs,取第三代MSCs,采用10wg／LVEGF预诱导24h后,分别加入15％芪丹通脉片含药血清与对照血清体外时MSCs诱导分化,至第7天,利用相差显微镜观察细胞形态改变,透射电镜观察细胞超微结构。免疫荧光方法检测内皮细胞特异性表面标志CD31、Ⅷ因子的表达。结果：至第7天,合15％芪丹通脉片合药血清组诱导后的MSCs形态发生明显改变,呈“卵石样”改变,透射电镜下细胞胞浆内可见Weible-Palade小体,共聚焦显微镜下可见CD31、Ⅷ因子阳性细胞。对照血清组MSCs形态仍呈长梭型,电镜下胞浆内无Weible-Palade小体,共聚焦显微镜下无CD31、Ⅷ因子阳性细胞。结论：益气活血复方芪丹通脉片含药血清具有体外诱导大鼠MSCs向内皮细胞定向分化的作用。     

Shear stress during early embryonic stem cell differentiation promotes hematopoietic and endothelial phenotypes

Pluripotent embryonic stem cells (ESCs) are a potential source for cell‐based tissue engineering and regenerative medicine applications, but their translation into clinical use will require efficient and robust methods for promoting differentiation. Fluid shear stress, which can be readily incorporated into scalable bioreactors, may be one solution for promoting endothelial and hematopoietic phenotypes from ESCs. Here we applied laminar shear stress to differentiating ESCs using a 2D adherent parallel plate configuration to systematically investigate the effects of several mechanical parameters. Treatment similarly promoted endothelial and hematopoietic differentiation for shear stress magnitudes ranging from 1.5 to 15 dyne/cm² and for cells seeded on collagen‐, fibronectin‐ or laminin‐coated surfaces. Extension of the treatment duration consistently induced an endothelial response, but application at later stages of differentiation was less effective at promoting hematopoietic phenotypes. Furthermore, inhibition of the FLK1 protein (a VEGF receptor) neutralized the effects of shear stress, implicating the membrane protein as a critical mediator of both endothelial and hematopoietic differentiation by applied shear. Using a systematic approach, studies such as these help elucidate the mechanisms involved in force‐mediated stem cell differentiation and inform scalable bioprocesses for cellular therapies. Biotechnol. Bioeng. 2013; 110: 1231–1242. © 2012 Wiley Periodicals, Inc.     

ARPE-19 conditioned medium promotes neural differentiation of adipose-derived mesenchymal stem cells

BACKGROUNDAdipose-derived stem cells (ASCs) have been increasingly explored for cell-based medicine because of their numerous advantages in terms of easy availability, high proliferation rate, multipotent differentiation ability and low immunogenicity. In this respect, they have been widely investigated in the last two decades to develop therapeutic strategies for a variety of human pathologies including eye disease. In ocular diseases involving the retina, various cell types may be affected, such as Müller cells, astrocytes, photoreceptors and retinal pigment epithelium (RPE), which plays a fundamental role in the homeostasis of retinal tissue, by secreting a variety of growth factors that support retinal cells.AIMTo test ASC neural differentiation using conditioned medium (CM) from an RPE cell line (ARPE-19).METHODSASCs were isolated from adipose tissue, harvested from the subcutaneous region of healthy donors undergoing liposuction procedures. Four ASC culture conditions were investigated: ASCs cultured in basal Dulbecco''s Modified Eagle Medium (DMEM); ASCs cultured in serum-free DMEM; ASCs cultured in serum-free DMEM/F12; and ASCs cultured in a CM from ARPE-19, a spontaneously arising cell line with a normal karyotype derived from a human RPE. Cell proliferation rate and viability were assessed by crystal violet and MTT assays at 1, 4 and 8 d of culture. At the same time points, ASC neural differentiation was evaluated by immunocytochemistry and western blot analysis for typical neuronal and glial markers: Nestin, neuronal specific enolase (NSE), protein gene product (PGP) 9.5, and glial fibrillary acidic protein (GFAP).RESULTSDepending on the culture medium, ASC proliferation rate and viability showed some significant differences. Overall, less dense populations were observed in serum-free cultures, except for ASCs cultured in ARPE-19 serum-free CM. Moreover, a different cell morphology was seen in these cultures after 8 d of treatment, with more elongated cells, often showing cytoplasmic ramifications. Immunofluorescence results and western blot analysis were indicative of ASC neural differentiation. In fact, basal levels of neural markers detected under control conditions significantly increased when cells were cultured in ARPE-19 CM. Specifically, neural marker overexpression was more marked at 8 d. The most evident increase was observed for NSE and GFAP, a modest increase was observed for nestin, and less relevant changes were observed for PGP9.5. CONCLUSIONThe presence of growth factors produced by ARPE-19 cells in tissue culture induces ASCs to express neural differentiation markers typical of the neuronal and glial cells of the retina.     

The rate of fluid shear stress is a potent regulator for the differentiation of mesenchymal stem cells

We have previously demonstrated that the rate of fluid shear stress (ΔSS) can manipulate the fate of mesenchymal stem cells (MSCs) to osteogenic or chondrogenic cells. However, whether ΔSS is comparable to other two means of induction medium and substrate stiffness that have been proven to be potent in differentiation control is unknown. In this study, we subjected MSCs to 1–7 days of osteogenic or chondrogenic chemical induction, or 1–4 days of 37 or 86 kPa of substrate stiffness induction, followed by 20 min of Fast ΔSS (0–0′) or Slow ΔSS (0–2′), which is a laminar FSS that linearly increased from 0 to 10 dyn/cm ² in 0 (Fast) or 2 min (Slow) and maintained at 10 dyn/cm ² for a total of 20 min. We found that 20 min of ΔSS could compete with 5 days' chemical and 2 days' substrate stiffness inductions. Our study confirmed that ΔSS is a powerful tool to control the differentiation of MSCs, which stressed the possible application in MSCs linage specification.     

Conditioned medium from renal tubular epithelial cells initiates differentiation of human mesenchymal stem cells

Objectives: Mesenchymal–epithelial interactions play a pivotal role in tubular morphogenesis and in maintaining the integrity of the kidney. During renal repair, similar mechanisms may regulate cellular reorganization and differentiation. We have hypothesized that soluble factors from proximal tubular epithelial cells (PTC) induce differentiation of adipose-derived adult mesenchymal stem cells (ASC). This hypothesis has been tested using cultured ASC and PTC.
Material and methods: Conditioned medium was prepared from injured PTC and transferred to ASC cultures. ASC proliferation was analysed by a fluorometric and photometric assay. Signal transduction was analysed by phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/ERK2). Grade of ASC differentiation was assessed by morphological analysis and cell expression of characteristic markers.
Results: Conditioned medium significantly induced proliferation and phosphorylation of ERK1/ERK2 of ASC. After 12 days of incubation, cell morphology changed to an epithelial-like monolayer. Expression of cytokeratin 18 was induced by conditioned medium, while α-smooth muscle actin, CD49a and CD90 expression decreased. These alterations strongly indicate onset of the differentiation process to the epithelial lineage. In summary, soluble factors from PTC induce signal transduction and differentiation of ASC.
Conclusions: Our study shows that conditioned medium from renal tubular epithelial cells provides a convenient source of inductive signals to initiate differentiation of ASC towards epithelial lineage. We deduce that these interactions may play an important role during renal repair mechanisms.     

Effects of shear stress on differentiation of stem cells into endothelial cells

Stem cell transplantation is an appealing potential therapy for vascular diseases and an indispensable key step in vascular tissue engineering. Substantial effort has been made to differentiate stem cells toward vascular cell phenotypes, including endothelial cells (ECs) and smooth muscle cells. The microenvironment of vascular cells not only contains biochemical factors that influence differentiation but also exerts hemodynamic forces, such as shear stress and cyclic strain. More recently, studies have shown that shear stress can influence the differentiation of stem cells toward ECs. A deep understanding of the responses and underlying mechanisms involved in this process is essential for clinical translation. This review highlights current data supporting the role of shear stress in stem cell differentiation into ECs. Potential mechanisms and signaling cascades for transducing shear stress into a biological signal are proposed. Further study of stem cell responses to shear stress will be necessary to apply stem cells for pharmacological applications and cardiovascular implants in the realm of regenerative medicine.     

Effects of an endothelial cell-conditioned medium on the hematopoietic and endothelial differentiation of embryonic stem cells

We have examined the effect of mouse bone marrow endothelial cell-conditioned medium (mEC-CM) on hematopoietic and endothelial differentiation of mouse embryonic stem cells (mESCs). mEC-CM can efficiently promote the differentiation of mESCs into Flk⁺ cells and hematopoietic colony-forming cells. mEC-CM proved to be as potent as a cytokine cocktail comprised of VEGF, bFGF, IGF and EGF. After inducing mESCs with mEC-CM, cobblestone-like cells were mechanically selected and identified which had the ability to incorporate DiI-Ac-LDL. DiI-Ac-LDL-positive cells were endothelial-like cells due to their expression of CD31 and Flk1, ability to bind to UEA1 and capacity to form capillary-like tube structures on matrigel. In conclusion, mEC-CM can efficiently promote the differentiation of mESCs into endothelial cells and hematopoietic colony-forming cells. The differentiated endothelial-like cells can be isolated by using DiI-Ac-LDL labeling and mechanical selection.     

Angiotensin II induces vascular endothelial growth factor synthesis in mesenchymal stem cells

Mesenchymal stem cells (MSCs) transplantation has been proposed as a promising means for ischemic heart disease. Vascular endothelial growth factor (VEGF) has been demonstrated to play an important role in MSCs transplantation. Angiotensin II (AngII), the most important effector peptide of the renin-angiotensin system (RAS), is also an angiogenesis factor. However, the effects of AngII on VEGF expression in MSCs and the related signaling cascades were unknown. In this experiment, we first demonstrated that incubation of MSCs with AngII-induced a rapid increase in VEGF mRNA expression and protein synthesis. However, these effects were abolished by prior treatment with AngII type 1 (AT₁) receptor antagonist losartan while not AngII type 2 (AT₂) receptor antagonist PD123319. The addition of either the extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor U0126 or Akt inhibitor LY294002 also led to a marked inhibition of the AngII-induced VEGF mRNA and protein production. Taken together, these results suggested that AngII stimulated the synthesis of VEGF in MSCs through ERK1/2 and Akt pathway via AT₁ receptor.     

Transforming growth factor-beta1 enhanced vascular endothelial growth factor synthesis in mesenchymal stem cells

Angiogenesis is essential for transplantation of mesenchymal stem cells (MSCs). Vascular endothelial growth factor (VEGF) is one of the most potent angiogenic factors identified to date. Elevated VEGF levels in MSCs correlate with the potential of MSCs transplantation. As an indirect angiogenic agent, transforming growth factor-β1 (TGF-β1) plays a pivotal role in the regulation of vasculogenesis and angiogenesis. However, the effect of TGF-β1 on VEGF synthesis in MSCs is still unknown. Besides, the intracellular signaling mechanism by which TGF-β1 stimulates this process remains poorly understood. In this article, we demonstrated that exposure of MSCs to TGF-β1 stimulated the synthesis of VEGF. Meanwhile, TGF-β1 stimulated the phosphorylation of Akt and extracellular signal-regulated kinase 1/2 (ERK1/2). Moreover, Ly 294002, a specific inhibitor of phosphatidylinositol-3-kinase (PI3K)/Akt significantly attenuated the VEGF synthesis stimulated by TGF-β1. Additionally, U0126, a specific inhibitor of ERK1/2, also significantly attenuated the TGF-β1-stimulated VEGF synthesis. These results indicated that TGF-β1 enhanced VEGF synthesis in MSCs, and the Akt and ERK1/2 activation were involved in this process.     

Arterial-venous endothelial cell fate is related to vascular endothelial growth factor and Notch status during human bone mesenchymal stem cell differentiation

Human bone mesenchymal stem cells (hMSCs) can differentiate into endothelial cells (ECs), so we aimed to investigate whether hMSCs could also differentiate into a specific arterial or venous ECs. hMSCs were induced to differentiate into ECs using vascular endothelial growth factor (VEGF). Low VEGF concentration (50ng/ml) upregulated the venous marker gene EphB4, however high concentration (100ng/ml) upregulated the arterial marker genes ephrinB2, Dll4 and Notch4, and downregulated the venous marker genes EphB4 and COUP-TFll. This VEGF dose-dependent induction was largely blocked by inhibition of the Notch pathway in hMSCs treated with gamma-secretase inhibitor. Therefore, differentiation of hMSCs into arterial- or venous-specific ECs depends on VEGF and is regulated by the Notch pathway.     

mTOR and the differentiation of mesenchymal stem cells

The mammalian target of rapamycin (mTOR), an evolutionarily conserved serine-threonine protein kinase, belongs to the phosphoinositide 3-kinase (PI3K)-related kinase family, which contains a lipid kinase-like domain within their C-terminal region. Recent studies have revealed that mTOR as a critical intracellular molecule can sense the extracellular energy status and regulate the cell growth and proliferation in a variety of cells and tissues. This review summarizes our current understanding about the effects of mTOR on cell differentiation and tissue development, with an emphasis on the lineage determination of mesenchymal stem cells. mTOR can promote adipogenesis in white adipocytes, brown adipocytes, and muscle satellite cells, while rapamycin inhibits the adipogenic function of mTOR. mTOR signaling may function to affect osteoblast proliferation and differentiation, however, rapamycin has been reported to either inhibit or promote osteogenesis. Although the precise mechanism remains unclear, mTOR is indispensable for myogenesis. Depending on the cell type, rapamycin has been reported to inhibit, promote, or have no effect on myogenesis.     

人骨髓间充质干细胞向血管内皮细胞诱导分化的研究

目的:分析人骨髓间充质干细胞(hMSCs)和脐静脉内皮细胞(hUVECs)的基因表达差异,探讨体外基因转染诱导内皮分化的可行性以及作为血管组织工程种子细胞来源的应用前景。方法:分别从人骨髓和脐静脉分离间充质干细胞(hMSCs)和内皮细胞(hUVECs),扩增培养后进行流式细胞仪、免疫细胞化学,免疫荧光鉴定和超微结构观察。通过BiostarH-40S表达谱芯片分析,选择两者的差异表达基因,导入hMSCs,经RT-PCR、ELISA鉴定该基因的转染和表达,并分析hMSCs的内皮分化程度。结果:hMSCs表达内皮细胞的多种特异性mRNA,经VEGFl65基因瞬时转染后RT-PCR有明显条带,ELISA定量检测VEGF165蛋白表达为(707.9±11.3)ng/L,同时CD44表达明显下调38.80%,CD31则明显上调达56.82%,FI-1,FVⅢAg和CD34的表达也有不同程度升高。结论:hMSCs具有内皮分化潜能,体外基因转染诱导hMSCs产生功能性内皮细胞和组织工程化血管具有广阔前景。     

Vascular endothelial growth factor promotes cardiomyocyte differentiation of embryonic stem cells

Embryonic stem cells (ESCs) overexpressing the vascular endothelial growth factor (VEGF) improve cardiac function in mouse models of myocardial ischemia and infarction by mechanisms that are poorly understood. Here we studied the effects of VEGF on cardiomyocyte differentiation of mouse ESCs in vitro. We used flow cytometry to determine the expression of alpha-myosin heavy chain (alpha-MHC), cardiac troponin I (cTn-I), and Nkx2.5 in differentiated ESCs. VEGF (20 ng/ml) significantly enhanced alpha-MHC, cTn-I, and Nkx2.5 expression in differentiated ESCs. Western blot analysis confirmed these findings. We found that VEGF receptor FMS-like tyrosine kinase-1 (Flt-1) and fetal liver kinase-1 (Flk-1) expression increased during ESC differentiation. Antibodies against Flk-1 totally blocked and against Flt-1 partially blocked VEGF-induced NKx2.5-positive-stained cells. The ERK inhibitor PD-098059 abolished VEGF-induced cardiomyocyte differentiation of ESCs. Our results suggest that VEGF promotes cardiomyocyte differentiation predominantly by ERK-mediated Flk-1 activation and, to a lesser extent, by Flt-1 activation. These findings may be of significance for stem cell and growth factor therapies to regenerate failing cardiomyocytes.     

Hepatogenic differentiation of mesenchymal stem cells induced by insulin like growth factor-I

AIM:To improve hepatic differentiation of human mesenchymal stem cell(MSC)using insulin growth factor 1(IGF-Ⅰ),which has important role in liver development,hepatocyte differentiation and function.METHODS:Bone marrow of healthy donors was aspirated from the iliac crest.The adherent cells expanded rapidly and were maintained with periodic passages until a relatively homogeneous population was established.The identification of these cells was carried out by immunophenotype analysis and differentiation potential into osteocytes and adipocytes.To effectively induce hepatic differentiation,we designed a protocol based on a combination of IGF-Ⅰ and liver specificfactors(hepatocyte growth factor,oncostatin M and dexamethasone).Morphological features,hepatic functions and cytological staining were assessed to evaluate transdifferentiation of human marrow-derived MSCs.RESULTS:Flow cytometric analysis and the differentiation potential into osteoblasts and adipocytes showed that more than 90% of human MSCs which were isolated and expanded were positive by specif ic markers and functional tests.Morphological assessment and evaluation of glycogen storage,albumin and α-feto protein expression,as well as albumin and urea secretion revealed a statistically signif icant difference between the experimental groups and control.CONCLUSION:In vitro differentiated MSCs using IGF-Ⅰwere able to display advanced liver metabolic functions,supporting the possibility of developing them as potential alternatives to primary hepatocytes.     

Trafficking and differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a heterogeneous population of stem/progenitor cells with pluripotent capacity to differentiate into mesodermal and non‐mesodermal cell lineages, including osteocytes, adipocytes, chondrocytes, myocytes, cardiomyocytes, fibroblasts, myofibroblasts, epithelial cells, and neurons. MSCs reside primarily in the bone marrow, but also exist in other sites such as adipose tissue, peripheral blood, cord blood, liver, and fetal tissues. When stimulated by specific signals, these cells can be released from their niche in the bone marrow into circulation and recruited to the target tissues where they undergo in situ differentiation and contribute to tissue regeneration and homeostasis. Several characteristics of MSCs, such as the potential to differentiate into multiple lineages and the ability to be expanded ex vivo while retaining their original lineage differentiation commitment, make these cells very interesting targets for potential therapeutic use in regenerative medicine and tissue engineering. The feasibility for transplantation of primary or engineered MSCs as cell‐based therapy has been demonstrated. In this review, we summarize the current knowledge on the signals that control trafficking and differentiation of MSCs. J. Cell. Biochem. 106: 984–991, 2009. © 2009 Wiley‐Liss, Inc.