间充质干细胞旁分泌作用的研究进展

间充质干细胞（MSCs）通常利用多分化特性在组织损伤时起到修复功能。然而,近期研究表明,MSCs大多数治疗作用都是通过旁分泌来发挥作用的,其中最受关注的是可溶性蛋白分泌和细胞外膜泡（EVS）。MSCs释放的EVS可反映细胞的来源,能够影响局部微环境中其他细胞的活动。越来越多人提出利用MSCs分泌的各种因子（称为分泌体）替代MSCs细胞治疗的观点。现就MSCs旁分泌特性、分泌体发生和释放机制以及细胞来源对旁分泌影响等方面的研究进展进行综述。     

Activation of cardiac progenitor cells through paracrine effects of mesenchymal stem cells

Mesenchymal stem cells (MSC) transplantation has been proved to be promising strategy to treat the failing heart. The effect of MSC transplantation is thought to be mediated mainly in a paracrine manner. Recent reports have suggested that cardiac progenitor cells (CPC) reside in the heart. In this study, we investigated whether MSC had paracrine effects on CPC in vitro. CPC were isolated from the neonatal rat heart using an explant method. MSC were isolated from the adult rat bone marrow. MSC-derived conditioned medium promoted proliferation of CPC and inhibited apoptosis of CPC induced by hypoxia and serum starvation. Chemotaxis chamber assay demonstrated that MSC-derived conditioned medium enhanced migration of CPC. Furthermore, MSC-derived conditioned medium upregulated expression of cardiomyocyte-related genes in CPC such as β-myosin heavy chain (β-MHC) and atrial natriuretic peptide (ANP). In conclusion, MSC-derived conditioned medium had protective effects on CPC and enhanced their migration and differentiation.     

初级纤毛与Wnt信号通路相关性研究进展

初级纤毛是一类以微管为基础结构的细胞器,其来源于细胞的母中心粒,锚定在细胞膜并如“天线”般突出细胞表面。作为细胞感受器,初级纤毛从环境中接受各种信号,传导至细胞内引起细胞反应。近期的研究表明,初级纤毛对与胚胎发育密切相关的Wnt信号通路的传导起重要作用。纤毛的损害可造成Wnt信号通路的异常,并引起胚胎中多类脏器一系列的病理改变,导致初级纤毛相关疾病的发生。文章主要阐述了初级纤毛与Wnt/β-catenin、Wnt/PCP通路及初级纤毛相关疾病之间的关系,并对初级纤毛相关疾病的治疗进行了初步探讨。对初级纤毛与Wnt信号通路关系的深入研究将有助于人们对该类疾病的进一步诊断和治疗。     

Conditioned medium from osteocytes stimulates the proliferation of bone marrow mesenchymal stem cells and their differentiation into osteoblasts

Osteocytes are the most abundant cells in bone and there is increasing evidence that they control bone remodeling via direct cell-to-cell contacts and by soluble factors. In the present study, we have used the MLO-Y4 cell line to study the effect of osteocytes on the proliferation, differentiation and bone-forming capacity of bone marrow mesenchymal stem cells (MSC). Conditioned media (CM) from osteocytic MLO-Y4 and osteoblastic MC3T3-E1 cell lines were collected and added on mouse bone marrow cultures, in which MSC were induced to osteoblasts. There was a significant increase in alkaline phosphatase activity and osteocalcin expression in the presence of MLO-Y4 CM. No such stimulus could be observed with MC3T3-E1 CM. There was almost 4-fold increase in bone formation and up to 2-fold increase in the proliferation of MSC with MLO-Y4 CM. The highly proliferating bone marrow cells were negative for ALP and OCN, suggesting that they could represent early osteoblast precursors. MLO-Y4 CM did not enhance the viability of mature osteoblasts nor protected them of apoptosis. This is the first study to describe soluble signals between osteocytes and osteoblasts and there most likely are several still unidentified or unknown factors in osteocyte CM. We conclude that osteocytes have an active stimulatory role in controlling bone formation.     

WJSC 6th Anniversary Special Issues（2）:Mesenchymal stem cells Enhancing the efficacy of mesenchymal stem cell therapy

Mesenchymal stem cell(MSC)therapy is entering a challenging phase after completion of many preclinical and clinical trials.Among the major hurdles encountered in MSC therapy are inconsistent stem cell potency,poor cell engraftment and survival,and age/disease-related host tissue impairment.The recognition that MSCs primarily mediate therapeutic benefits through paracrine mechanisms independent of cell differentiation provides a promising framework for enhancing stem cell potency and therapeutic benefits.Several MSC priming approaches are highlighted,which will likely allow us to harness the full potential of adult stem cells for their future routine clinical use.     

Role of mesenchymal stem cells in cell life and their signaling

Mesenchymal stem cells(MSCs) have various roles in the body and cellular environment, and the cellular phenotypes of MSCs changes in different conditions. MSCs support the maintenance of other cells, and the capacity of MSCs to differentiate into several cell types makes the cells unique and full of possibilities. The involvement of MSCs in the epithelial-mesenchymal transition is an important property of these cells. In this review, the role of MSCs in cell life, including their application in therapy, is first described, and the signaling mechanism of MSCs is investigated for a further understanding of these cells.     

Role of mesenchymal stem cells in cell life and their signaling简

Mesenchymal stem cells (MSCs) have various roles in the body and cellular environment, and the cellular phenotypes of MSCs changes in different conditions. MSCs support the maintenance of other cells, and the capacity of MSCs to differentiate into several cell types makes the cells unique and full of possibilities. The involvement of MSCs in the epithelial-mesenchymal transition is an important property of these cells. In this review, the role of MSCs in cell life, including their application in therapy, is first described, and the signaling mechanism of MSCs is investigated for a further understanding of these cells.     

Role of mesenchymal stem cells in neurogenesis and nervous system repair

Bone marrow-derived mesenchymal stem cells (MSCs) are attractive candidates for use in regenerative medicine since they are easily accessible and can be readily expanded in vivo, and possess unique immunogenic properties. Moreover, these multipotent cells display intriguing environmental adaptability and secretory capacity. The ability of MSCs to migrate and engraft in a range of tissues has received significant attention. Evidence indicating that MSC transplantation results in functional improvement in animal models of neurological disorders has highlighted exciting potential for their use in neurological cell-based therapies. The manner in which MSCs elicit positive effects in the damaged nervous system remains unclear. Cell fusion and/or ‘transdifferentiation’ phenomena, by which MSCs have been proposed to adopt neural cell phenotypes, occur at very low frequency and are unlikely to fully account for observed neurological improvement. Alternatively, MSC-mediated neural recovery may result from the release of soluble molecules, with MSC-derived growth factors and extracellular matrix components influencing the activity of endogenous neural cells. This review discusses the potential of MSCs as candidates for use in therapies to treat neurological disorders and the molecular and cellular mechanisms by which they are understood to act.     

Oscillatory fluid flow induces the osteogenic lineage commitment of mesenchymal stem cells: The effect of shear stress magnitude,frequency, and duration

A potent regulator of bone anabolism is physical loading. However, it is currently unclear whether physical stimuli such as fluid shear within the marrow cavity is sufficient to directly drive the osteogenic lineage commitment of resident mesenchymal stem cells (MSC). Therefore, the objective of the study is to employ a systematic analysis of oscillatory fluid flow (OFF) parameters predicted to occur in vivo on early MSC osteogenic responses and late stage lineage commitment. MSCs were exposed to OFF of 1 Pa, 2 Pa and 5 Pa magnitudes at frequencies of 0.5 Hz, 1 Hz and 2 Hz for 1 h, 2 h and 4 h of stimulation. Our findings demonstrate that OFF elicits a positive osteogenic response in MSCs in a shear stress magnitude, frequency, and duration dependent manner that is gene specific. Based on the mRNA expression of osteogenic markers Cox2, Runx2 and Opn after short-term fluid flow stimulation, we identified that a regime of 2 Pa shear magnitude and 2 Hz frequency induces the most robust and reliable upregulation in osteogenic gene expression. Furthermore, long-term mechanical stimulation utilising this regime, elicits a significant increase in collagen and mineral deposition when compared to static control demonstrating that mechanical stimuli predicted within the marrow is sufficient to directly drive osteogenesis.     

Bioreactors to influence stem cell fate: Augmentation of mesenchymal stem cell signaling pathways via dynamic culture systems

Background

Mesenchymal stem cells (MSCs) are a promising cell source for bone and cartilage tissue engineering as they can be easily isolated from the body and differentiated into osteoblasts and chondrocytes. A cell based tissue engineering strategy using MSCs often involves the culture of these cells on three-dimensional scaffolds; however the size of these scaffolds and the cell population they can support can be restricted in traditional static culture. Thus dynamic culture in bioreactor systems provides a promising means to culture and differentiate MSCs in vitro.

Scope of review

This review seeks to characterize key MSC differentiation signaling pathways and provides evidence as to how dynamic culture is augmenting these pathways. Following an overview of dynamic culture systems, discussion will be provided on how these systems can effectively modify and maintain important culture parameters including oxygen content and shear stress. Literature is reviewed for both a highlight of key signaling pathways and evidence for regulation of these signaling pathways via dynamic culture systems.

Major conclusions

The ability to understand how these culture systems are affecting MSC signaling pathways could lead to a shear or oxygen regime to direct stem cell differentiation. In this way the efficacy of in vitro culture and differentiation of MSCs on three-dimensional scaffolds could be greatly increased.

General significance

Bioreactor systems have the ability to control many key differentiation stimuli including mechanical stress and oxygen content. The further integration of cell signaling investigations within dynamic culture systems will lead to a quicker realization of the promise of tissue engineering and regenerative medicine. This article is part of a Special Issue entitled Biochemistry of Stem Cells.     

间充质干细胞分化为内皮细胞的意义和细胞学基础

间充质干细胞(mesenchymalstemcells,MSCs)主要存在于骨髓中,是多潜能干细胞,在脐血、外周血、脂肪、皮肤等多种组织中也相继分离出MSCs。MSCs具有独特的免疫特性,在异种异体环境内长期存在,使其临床应用前景更为广泛。目前,MSCs的分离培养、诱导分化及鉴定体系已趋成熟,理论上可分化为所有中胚层来源的细胞,内皮细胞来源于中胚层,因此MSCs具有分化为内皮细胞的可能性。本文对MSCs内皮分化意义和细胞学基础及其新近的研究进展作一综述。     

Hedgehog signaling and osteoblast gene expression are regulated by purmorphamine in human mesenchymal stem cells

Several biological events are controlled by Hedgehog (Hh) signaling, including osteoblast phenotype development. This study aimed at evaluating the gene expression profile of human mesenchymal stem cells (hMSCs) treated with the Hh agonist, purmorphamine, focusing on Hh signaling and osteoblast differentiation. hMSCs from bone marrow were cultured in non‐osteogenic medium with or without purmorphamine (2 µM) for periods of up to 14 days. Purmorphamine up‐regulated gene expression of the mediators of Hh pathway, SMO, PTCH1, GLI1, and GLI2. The activation of Hh pathway by purmorphamine increased the expression of several genes (e.g., RUNX2 and BMPs) related to osteogenesis. Our results indicated that purmorphamine triggers Hh signaling pathway in hMSCs, inducing an increase in the expression of a set of genes involved in the osteoblast differentiation program. Thus, we conclude that Hh is a crucial pathway in the commitment of undifferentiated cells to the osteoblast lineage. J. Cell. Biochem. 113: 204–208, 2012. © 2011 Wiley Periodicals, Inc.     

Down-regulation of Wnt signaling could promote bone marrow-derived mesenchymal stem cells to differentiate into hepatocytes

Bone marrow-derived mesenchymal stem cells (BMSCs) have been demonstrated to be able to differentiate into hepatocytes, but the precise mechanisms controlling this process are unclear. Our aim is try to explore the role of Wnt signaling on the differentiation of BMSCs into hepatocytes. Our study demonstrated that BMSCs could successfully differentiate into hepatocytes under in vitro induction of the tissue extract of damaged liver. The mRNA level of Wnt-1, Wnt-5a, Frizzled1, DSH (disheveled), GSK-3β (glycogen synthase kinase 3 beta) and β-catenin on day 21 when the differentiation direction was determined, was lower than that on days 0, 7, and 11. Furthermore, blocking Wnt-1 signaling by treating BMSCs with Dkk1 could induce BMSCs to express albumin earlier and up-regulation of Wnt signaling by treating BMSCs with Wnt-1 could inhibit BMSCs to differentiate into hepatocytes. Above results indicated that inhibition on Wnt signaling can promote BMSCs to differentiate into hepatocytes.     

间充质干细胞在肝脏疾病应用的研究现况

间充质干细胞（MSC）属于成体干细胞的一种,是一类具有自我更新和多向分化能力的多能干细胞。其来源丰富,免疫原性低,目前体内外实验均发现MSC可促进损伤肝脏修复,改善症状,提高存活率。通过调节肝脏局部和全身炎症反应和免疫紊乱发挥治疗作用。本文就MSC治疗肝脏疾病的研究现况进行综述。     

Salvianolic acid B promotes osteogenesis of human mesenchymal stem cells through activating ERK signaling pathway

Salvianolic acid B, a major bioactive component of Chinese medicine herb, Salvia miltiorrhiza, is widely used for treatment of cardiovascular diseases. Our recent studies have shown that Salvianolic acid B can prevent development of osteoporosis. However, the underlying mechanisms are still not clarified clearly. In the present study, we aim to investigate the effects of Salvianolic acid B on viability and osteogenic differentiation of human mesenchymal stem cells (hMSCs). The results showed Salvianolic acid B (Sal B) had no obvious toxic effects on hMSCs, whereas Sal B supplementation (5 μM) increased the alkaline phosphatase activity, osteopontin, Runx2 and osterix expression in hMSCs. Under osteogenic induction condition, Sal B (5 μM) significantly promoted mineralization; and when the extracellular-signal-regulated kinases signaling (ERK) pathway was blocked, the anabolic effects of Sal B were diminished, indicating that Sal B promoted osteogenesis of hMSCs through activating ERK signaling pathway. The current study confirms that Sal B promotes osteogenesis of hMSCs with no cytotoxicity, and it may be used as a potential therapeutic agent for the management of osteoporosis.     

Immunomodulation by mesenchymal stem cells:Interplay between mesenchymal stem cells and regulatory lymphocytes

Mesenchymal stem cells(MSCs) possess immunomodulatory properties, which confer enormous potential for clinical application. Considerable evidence revealed their efficacy on various animal models of autoimmune diseases, such as multiple sclerosis, systemic lupus erythematosus and uveitis. MSCs elicit their immunomodulatory effects by inhibiting lymphocyte activation and proliferation, forbidding the secretion of proinflammatory cytokines, limiting the function of antigen presenting cells, and inducing regulatory T(Treg) and B(Breg) cells. The induction of Treg and Breg cells is of particular interest since Treg and Breg cells have significant roles in maintaining immune tolerance. Several mechanisms have been proposed regarding to the MSCs-mediated induction of Treg and Breg cells. Accordingly, MSCs induce regulatory lymphocytes through secretion of multiple pleiotropic cytokines, cell-to-cell contact with target cells and modulation of antigen-presenting cells. Here, we summarized how MSCs induce Treg and Breg cells to provoke immunosuppression.     

Biological,chemical and mechanical factors regulating migration and homing of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a population of primary and non-specialized cells, which can be isolated from various tissues. Currently, MSCs are key players in cellular therapy and regenerative medicine. However, the possibility of using MSCs in the treatment of many diseases needs to be preceded, though, by in-depth analysis of their properties, especially by determining the mechanism of tissue homing as well as the mechanism, due to which cells contribute to tissue regeneration. This review is intended to present information on recent findings regarding the mechanism of recruitment and tissue homing by MSCs and discuss current hypotheses for how MSCs can reach target tissues.