Effects of hindlimb unloading on ex vivo growth and osteogenic/adipogenic potentials of bone marrow-derived mesenchymal stem cells in rats

The goal of this study was to determine the effects of hindlimb unloading (HU) on the ex vivo growth and the osteogenic potential of mesenchymal stem cells (MSCs) from the femurs of rats. Microgravity was simulated by 28-day HU in male Sprague-Dawley (SD) rats, and the bone marrow (BM) was collected from hindlimb femurs of HU or control (CTL) rats. MSCs were isolated from BM and cultured for eight passages. Then MSCs at passages 2, 4, and 8 were induced for osteogenesis or adipogenesis. The results revealed that HU decreased the osteogenic potential of MSCs and also decreased the expression of osteoblast gene marker mRNAs in cells induced by osteogenic conditions. Meanwhile, the expression of Runx2 mRNA and the phosphorylation of ERK were also decreased. There were no significant differences of osteoblast gene marker and Runx2 mRNA expression between cells induced from different passages of MSCs in UH rats. Under adipogenic conditions, HU increased both the adipogenic potential of MSCs and the expression of adipocytic gene marker mRNAs in induced cells. HU also increased the expression of PPAR gamma 2 mRNA, but with no effect on the phosphorylation of p38MAPK. The adipogenic potential of MSCs and the expression of adipocytic gene marker mRNAs in induced cells decreased along with cell cultures under normal gravity. This suggests that the normal gravity during in vitro MSC culture and the centrifugal force produced during cell harvest after each passage could decrease the adipogenic potential of MSCs, but could not reverse the effect of HU on the osteogenic potential of MSCs.     

A comprehensive analysis of the dual roles of BMPs in regulating adipogenic and osteogenic differentiation of mesenchymal progenitor cells

Pluripotent mesenchymal stem cells (MSCs) are bone marrow stromal progenitor cells that can differentiate into osteogenic, chondrogenic, adipogenic, and myogenic lineages. Several signaling pathways have been shown to regulate the lineage commitment and terminal differentiation of MSCs. Here, we conducted a comprehensive analysis of the 14 types of bone morphogenetic protein (BMPs) for their abilities to regulate multilineage specific differentiation of MSCs. We found that most BMPs exhibited distinct abilities to regulate the expression of Runx2, Sox9, MyoD, and PPARgamma2. Further analysis indicated that BMP-2, BMP-4, BMP-6, BMP-7, and BMP-9 effectively induced both adipogenic and osteogenic differentiation in vitro and in vivo. BMP-induced commitment to osteogenic or adipogenic lineage was shown to be mutually exclusive. Overexpression of Runx2 enhanced BMP-induced osteogenic differentiation, whereas knockdown of Runx2 expression diminished BMP-induced bone formation with a decrease in adipocyte accumulation in vivo. Interestingly, overexpression of PPARgamma2 not only promoted adipogenic differentiation, but also enhanced osteogenic differentiation upon BMP-2, BMP-6, and BMP-9 stimulation. Conversely, MSCs with PPARgamma2 knockdown or mouse embryonic fibroblasts derived from PPARgamma2(-/-) mice exhibited a marked decrease in adipogenic differentiation, coupled with reduced osteogenic differentiation and diminished mineralization upon BMP-9 stimulation, suggesting that PPARgamma2 may play a role in BMP-induced osteogenic and adipogenic differentiation. Thus, it is important to understand the molecular mechanism behind BMP-regulated lineage divergence during MSC differentiation, as this knowledge could help us to understand the pathogenesis of skeletal diseases and may lead to the development of strategies for regenerative medicine.     

间充质干细胞体外成骨及成脂肪分化中sortilin基因表达的研究

目的:研究间充质干细胞(MSC)体外成骨、成脂肪分化时sortilin基因表达变化。方法:从骨髓中分离培养人间充质干细胞,流式细胞术鉴定其表型,加入成骨和成脂肪诱导剂,RT-PCR检测成骨标志骨桥蛋白(Op)和成脂肪标志脂蛋白脂肪酶(LpL)表达,半定量RT-PCR分析sortilin基因随诱导时间的表达变化。结果:①体外分离培养的人间充质干细胞能向成骨细胞和脂肪细胞分化,分别表达Op和LpL。②在体外成骨分化过程中,sortilin基因表达第1d开始上调,持续约1周后恢复至原水平;在培养3d时,sortilin基因表达明显上调,与未诱导组相比,差异明显(P＜0.01)。③体外成脂肪分化时,sortilin基因表达无明显的改变(P＞0.05)。结论:sortilin基因可能参与间充质干细胞成骨分化的调节,而与成脂肪分化无关,通过调控sortilin基因的表达,有可能为成骨障碍性疾病的治疗,提供新的思想和策略。     

兔骨髓间充质干细胞分化成骨及VEGF表达

目的　研究兔骨髓间充质干细胞 (MSC)诱导培养分化为成骨细胞的功能表面及血管内皮生长因子 (VEGF)的表达。方法　分离、培养新生兔骨髓间充质干细胞 ,体外扩增 ,用含地塞米松、β 甘油磷酸钠和维生素C的条件培养液诱导MSC向成骨细胞分化 ,观察诱导细胞碱性磷酸酶染色、钙化结节形成以及VEGF的表达。结果　MSC增殖能力活跃 ,成骨诱导后 ,细胞碱性磷酸酶呈强阳性染色 ,形成矿化结节 ,且VEGF表达增强。结论　兔MSC可迅速扩增 ,经诱导分化成骨后VEGF表达增强 ,是研究骨组织工程的理想种子细胞     

A Novel Semisynthetic Molecule Icaritin Stimulates Osteogenic Differentiation and Inhibits Adipogenesis of Mesenchymal Stem Cells

Background We previously reported that the constitutional flavonoid glycosides derived from herb Epimedium (EF, composed of seven flavonoid compounds with common nuclear stem) exerted beneficial effects on the bone, including promoting bone formation and inhibiting bone marrow fat deposition. Recent in vivo study showed that Icaritin was a common metabolite of these constitutional flavonoid glycosides, indicating that Icaritin is a bioactive compound. The present study was designed to investigate whether Icaritin could promote osteogenic differentiation and suppress adipogenic differentiation of marrow mesenchymal stem cells (MSCs).Methods Primary MSCs were harvested from adult mice and exposed to Icaritin to evaluate whether it could promote osteogenesis and suppress adipogenesis using the following assays: determination of alkaline phosphatase (ALP) activity and mineralization; mRNA expression of osteogenic differentiation marker Runx2; osteocalcin and bone sialoprotein (BSP) by RT-PCR; quantification of adipocyte-like cells by Oil Red O staining assay and mRNA expression for adipogenic differentiation markers peroxisome proliferator-activated receptor gamma (PPARγ); adipocyte fatty acid binding protein (aP2) and lipoprotein lipase (LPL) by RT-PCR. For the underlying mechanism, glycogen synthase kinase-3beta (GSK3β) and β-catenin were also explored by western blotting.Results Icaritin promoted osteogenic differentiation and maturation of MSCs as indicated by increased mRNA expression for Runx2, osteocalcin and BSP, and enhanced ALP activity and mineralization; Icaritin inhibited adipogenic differentiation, as indicated by decreased mRNA expression for PPARγ, LPL, aP2, and suppressed formation of adipocyte-like cells; Icaritin inactivated GSK3β and suppressed PPARγ expression when promoting osteogenesis and suppressing adipogenesis of MSCs.Conclusion This was the first study demonstrating that the novel semisynthetic molecule Icaritin could stimulate osteogenic differentiation and inhibit adipogenesis of MSCs, which was associated with the suppression of GSK3β and PPARγ.     

人脐血间充质干细胞的生物学特性及其成骨成脂肪分化*

背景：目前有关脐血间充质干细胞的生物学特性及分化能力的研究较少。 目的：观察人脐血间充质干细胞的生物学特性,及其向成骨、成脂肪细胞分化的能力。 方法：从不同胎龄脐血中分离间充质干细胞,对其进行原代和传代培养,并诱导其向成骨及成脂肪细胞分化。 结果与结论：倒置相差显微镜下见分离培养的脐血间充质干细胞贴壁生长,呈成纤维细胞样外观,细胞呈螺旋状排列;透射电镜下可见脐血间充质干细胞胞核比例大,细胞器少,为低分化细胞;原代及传代培养的脐血间充质干细胞生长曲线均呈S型,第3,5代细胞增殖能力最强,低胎龄的脐血间充质干细胞集落形成能力最强。流式细胞仪检测结果显示,脐血间充质干细胞稳定表达间充质干细胞相关抗原CD29,CD44 和CD90,不表达造血细胞标志CD34和CD45。成骨诱导后3 周,碱性磷酸酶染色为强阳性,茜素红染色可见大量钙化基质的形成;成脂诱导3周,油红O染色可检测到胞质中脂滴的形成。提示脐血间充质干细胞具有间充质干细胞的形态特征、生长增殖特点及细胞表面标志物等生物学特性,可向成骨细胞及脂肪细胞分化。     

Changes in expression of the antioxidant enzyme SOD3 occur upon differentiation of human bone marrow-derived mesenchymal stem cells in vitro

The discovery that mesenchymal stem cells (MSCs) secrete SOD3 may help explain studies in which MSCs have direct antioxidant activities both in vivo and in vitro. SOD3 is an antioxidant enzyme that dismutes toxic free radicals produced during inflammatory processes. Therefore, MSC production and secretion of active and therapeutically significant levels of SOD3 would further support the use of MSCs as a cellular based antioxidant therapy. The aim of this study was therefore to investigate in vitro if MSC differentiation down the adipogenic, chondrogenic, and osteogenic lineages influences the expression of the antioxidant molecule SOD3. Human bone marrow MSCs and their differentiated progeny were cultured under standard conditions and both the SOD3 gene and protein expression examined. Following adipogenesis, cultures demonstrated that both SOD3 protein and gene expression are significantly increased, and conversely, following chondrogenesis SOD3 protein and gene expression is significantly decreased. Following osteogenesis there were no significant changes in SOD3 protein or gene expression. This in vitro study describes the initial characterization of SOD3 expression and secretion by differentiated MSCs. This should help guide further in vivo work establishing the therapeutic and antioxidative potential of MSC and their differentiated progeny.     

Activation of Sirt1 decreases adipocyte formation during osteoblast differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSC) can differentiate into osteoblasts, adipocytes, chondrocytes and myoblasts. It has been suggested that a reciprocal relationship exists between the differentiation of MSC into osteoblasts and adipocytes. Peroxisome proliferator-activated receptor gamma2 (PPARgamma2) is a key element for the differentiation into adipocytes. Activation of the nuclear protein deacetylase Sirt1 has recently been shown to decrease adipocyte development from preadipocytes via inhibition of PPARgamma2. In vitro, MSC differentiate to osteoblasts when exposed to bone-inducing medium. However, adipocytes are also developed. In the present study we have targeted Sirt1 to control adipocyte development during differentiation of MSC into osteoblasts. The finding that resveratrol and isonicotinamide markedly inhibited adipocyte and promoted osteoblast differentiation demonstrates an interesting alternative to PPARgamma antagonists. These results are important for the evolving field of cell-based tissue engineering, but may also be relevant in the search for new treatments of osteoporosis.     

兔骨髓间充质干细胞定向诱导分化为脂肪细胞及成骨细胞的研究

用密度梯度离心和贴壁法分离和纯化兔骨髓间充干细胞，建立诱导兔MSCs向脂肪细胞及成骨细胞表型转化的方法及条件。在成脂诱导剂或成骨诱导剂作用下，对原代和第2代兔MSCs进行成脂和成骨诱导培养，并鉴定成脂及成骨表型。结果表明：原代及第2代兔MSCs均有一定的成脂、成骨能力，且第2代细胞的分化能力较原代低。在诱导培养条件下，原代及第2代兔MSCs均能分化，成脂诱导21d，75％的兔MSCs转化为脂肪细胞；成骨诱导21d，75％的兔MSCs转化为成骨细胞。兔MSCs在适当的诱导条件下可快速分化为脂肪细胞或成骨细胞。     

Adipogenic Mesenchymal Stromal Cells from Bone Marrow and Their Hematopoietic Supportive Role: Towards Understanding the Permissive Marrow Microenvironment in Acute Myeloid Leukemia

Purpose

The role of bone marrow-derived mesenchymal stem/stromal cells (MSCs) in creating a permissive microenvironment that supports the emergence and progression of acute myeloid leukemia (AML) is not well established. We investigated the extent to which adipogenic differentiation in normal MSCs alters hematopoietic supportive capacity and we undertook an in-depth comparative study of human bone marrow MSCs derived from newly diagnosed AML patients and healthy donors, including an assessment of adipogenic differentiation capacity.

Findings

MSCs from healthy controls with partial induction of adipogenic differentiation, in comparison to MSCs undergoing partial osteogenic differentiation, expressed increased levels of hematopoietic factors and induced greater proliferation, decreased quiescence and reduced in vitro hematopoietic colony forming capacity of CD34⁺ hematopoietic stem and progenitor cells (HSPCs). Moreover, we observed that AML-derived MSCs had markedly increased adipogenic potential and delayed osteogenic differentiation, while maintaining normal morphology and viability. AML-derived MSCs, however, possessed reduced proliferative capacity and decreased frequency of subendothelial quiescent MSCs compared to controls.

Conclusion

Our results support the notion of a bone marrow microenvironment characterized by increased propensity toward adipogenesis in AML, which may negatively impact normal hematopoiesis. Larger confirmatory studies are needed to understand the impact of various clinical factors. Novel leukemia treatments aimed at normalizing bone marrow niches may enhance the competitive advantage of normal hematopoietic progenitors over leukemia cells.

     

Bioreactor expansion of human adult bone marrow-derived mesenchymal stem cells

Supplementation of mesenchymal stem cells (MSCs) during hematopoietic stem cell (HSC) transplantation alleviates complications such as graft-versus-host disease, leading to a speedy recovery of hematopoiesis. To meet this clinical demand, a fast MSC expansion method is required. In the present study, we examined the feasibility of using a rotary bioreactor system to expand MSCs from isolated bone marrow mononuclear cells. The cells were cultured in a rotary bioreactor with Myelocult medium containing a combination of supplementary factors, including stem cell factor and interleukin-3 and -6. After 8 days of culture, total cell numbers, Stro-1(+)CD44(+)CD34(-) MSCs, and CD34(+)CD44(+)Stro-1(-) HSCs were increased 9-, 29-, and 8-fold, respectively. Colony-forming efficiency-fibroblast per day of the bioreactor-treated cells was 1.44-fold higher than that of the cells without bioreactor treatment. The bioreactor-expanded MSCs showed expression of primitive MSC markers endoglin (SH2) and vimentin, whereas markers associated with lineage differentiation, including osteocalcin (osteogenesis), type II collagen (chondrogenesis), and C/EBP-alpha (CCAAT/enhancer-binding protein-alpha) (adipogenesis), were not detected. Upon induction, the bioreactor-expanded MSCs were able to differentiate into osteoblasts, chondrocytes, and adipocytes. We conclude that the rotary bioreactor with the modified Myelocult medium reported in this study may be used to rapidly expand MSCs.     

致敏小鼠骨髓间充质干细胞体外培养及多向分化功能的测定

目的：评价异基因脾细胞输注致敏的小鼠骨髓源性间充质干细胞(MSCs)的体外培养生长能力及其多向分化功能。方法：应用贴壁培养法体外培养间充质干细胞,流式检测其表面标志以及检测其成骨、成脂和成肌多向分化状况;结果：致敏小鼠骨髓源性MSCs与非致敏小鼠骨髓源性MSCs比较,形态学无差异且均表达CD29+、CD105+、CD44+和Sca-1+ ;CD34-、CD11b-;同时在相应的诱导条件下具有向成骨、成脂、成肌多向分化的能力。结论：异基因脾细胞输注致敏的小鼠,其骨髓源性MSCs的形态学和功能与正常小鼠的MSCs比较评估未见异常。     

膜联蛋白A1在兔骨髓间充质干细胞体外诱导成骨和成脂早期的表达

背景：骨髓间充质干细胞分化过程中膜联蛋白A1表达变化的研究报道各有不同看法。 目的：分析兔骨髓间充质干细胞在体外诱导成骨和成脂过程中膜联蛋白 A1基因的表达变化。 方法：应用全骨髓贴壁法分离培养骨髓间充质干细胞,分别加入含成骨诱导剂、成脂诱导剂及不添加任何诱导剂的培养基进行培养。 结果与结论：膜联蛋白A1基因在成骨诱导过程中与未诱导细胞相比有明显下调趋势,差异有显著性意义(P < 0.01),而在成脂诱导剂中则为上升(P < 0.01)。成骨诱导剂对细胞生长存在抑制作用并增加细胞凋亡(P < 0.01),而成脂诱导剂对细胞生长与凋亡作用较小(P > 0.05)。因此排除了诱导剂对细胞的作用之后,推测膜联蛋白A1基因可能与骨髓间充质干细胞体外向脂肪细胞分化存在一定关系,但尚不能肯定其在成骨分化中的作用。     

Osteogenic differentiation of human marrow-derived mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (MSCs) are adherent cells that differentiate into chondroblasts, osteoblasts and adipocytes. In this short review, we summarize the molecular mechanisms that are known to control osteoblast differentiation and osteogenic potential of MSCs in vitro. We discuss the advances made in gene-based therapy to promote osteogenic differentiation of MSCs and the perspectives for an optimal use of MSCs for bone tissue regeneration or repair. One important challenge at the present time is to identify factors and pathways that promote osteogenic commitment of MSCs in order to use MSCs with functional potential for optimal bone repair in humans. In this context, genomic and proteomic analyses may help to identify molecules that could be used to promote osteogenic differentiation of human MSCs. In the future this may lead to selective therapeutic strategies for tissue engineering application in bone regeneration and repair in humans.