Mesenchymal stem cell-derived extracellular vesicles in skin wound healing:roles,opportunities and challenges

Skin wounds are characterized by injury to the skin due to trauma,tearing,cuts,or contusions.As such injuries are common to all human groups,they may at times represent a serious socioeconomic burden.Currently,increasing numbers of studies have focused on the role of mesenchymal stem cell(MSC)-derived extracellular vesicles(EVs)in skin wound repair.As a cell-free therapy,MSC-derived EVs have shown significant application potential in the field of wound repair as a more stable and safer option than conventional cell therapy.Treatment based on MSC-derived EVs can significantly promote the repair of damaged substructures,including the regeneration of vessels,nerves,and hair follicles.In addition,MSC-derived EVs can inhibit scar formation by affecting angiogenesis-related and antifibrotic pathways in promoting macrophage polarization,wound angiogenesis,cell proliferation,and cell migration,and by inhibiting excessive extracellular matrix production.Additionally,these structures can serve as a scaffold for components used in wound repair,and they can be developed into bioengineered EVs to support trauma repair.Through the formulation of standardized culture,isolation,purification,and drug delivery strategies,exploration of the detailed mechanism of EVs will allow them to be used as clinical treatments for wound repair.In conclusion,MSCderived EV-based therapies have important application prospects in wound repair.Here we provide a comprehensive overview of their current status,application potential,and associated drawbacks.

The antioxidant trolox inhibits aging and enhances prostaglandin E-2 secretion in mesenchymal stem cells

Mesenchymal stem cells(MSCs)have been widely used in regenerative medicine and clinical therapy due to their capabilities of proliferation,differentiation,and immune regulation.However,during in vitro expansion,MSCs are prone to aging,which largely limits their application.Prostaglandin E-2(PGE-2)is a key effector secreted by MSCs to exert immunomodulatory effects.By screening the compound library for PGE-2 secretion,the antioxidant trolox was verified as a stimulator of MSCs to secrete PGE-2.The effect of antioxidant trolox on biological characteristics of MSCS,including aging,proliferation,and gene expression,was examined.The results demonstrated that trolox can resist aging,promote proliferation,and enhance PGE-2 secretion of MSCs without affecting their surface marker expression.Furthermore,trolox treatment up-regulates miR-17-92 clusters in MSCs and may contribute to its anti-aging effects.Thus,trolox addition might be beneficial for MSCs expansion and their application.

The Osteogenic Capacity of Human Amniotic Membrane Mesenchymal Stem Cell (hAMSC) and Potential for Application in Maxillofacial Bone Reconstruction <i>in Vitro</i>Study

Amniotic membrane of human placenta is a source of abundant mesenchymal stem cell (hAMSC) which makes it a potential source of allogeneic multipotent cell for bone healing. However, much has to be explored about its isolation procedure and the osteogenic differentiation potential. The aims of this study are to establish the procurement procedure of human amniotic membrane, the isolation and culture of hAMSC, the MSC phenotypic characterization, and the in vitro osteogenic differentiation of hAMSC. Results of the study are as follows. The quality of human amniotic membrane would be best if procured from Caesarean operation under highly aseptic condition to avoid fungal and bacterial contamination on the culture. Isolation procedure using modified Soncini protocol yielded large amount of MSC with high proliferative capacity in culture medium. Characterization of hAMSC showed that the majority of the target cells exhibited specific MSC markers (CD105 and CD90) with a small number of these cells expressing CD45, the marker of hematopoeitic cells. The in vitro osteogenic differentiation of hAMSC followed by Alizarin Red staining showed that osteoblastic differentiation was detected in a significantly high number of cells. This study concludes that hAMSCs isolated from human amniotic membrane have the capacity for in vitro osteogenesis which makes them be one of the potential allogeneic stem cells for application in maxillofacial bone reconstruction.

Ultrastructural Characteristics of Sheep and Horse Mesenchymal Stem Cells (MSCs)

In the present study, the morphological and ultrastructural characteristics of mesenchymal stem cells (MSCs) induced towards osteogenic, adipogenic, and chondrogenic lineages were investigated. The main objective of this paper was to focus on the differentiation capacity of ovine [oMSCs] and equine MSCs [eMSCs]. Bone marrow [BM] MSCs were isolated from ovine and equine patients, expanded in monolayer culture and induced into osteogenic, adipogenic and chondrogenic differentiation. For chondrogenic differentiation, cells were cultured in micromass culture. Also, their ultrastructural phenotypes were studied by transmission electron microscopy [TEM]. This study was aimed to provide an indepth morphological description of BM-derived ovine and equine MSCs induced towards three lineages, it demonstrated that TEM analysis is useful in elucidating detailed structural information.

Adipose-derived mesenchymal stem cells(MSCs)are a superior cell source for bone tissue engineering

Effective bone regeneration through tissue engineering requires a combination of osteogenic progenitors,osteoinductive biofactors and biocompatible scaffold materials.Mesenchymal stem cells(MSCs)represent the most promising seed cells for bone tissue engineering.As multipotent stem cells that can self-renew and differentiate into multiple lineages including bone and fat,MSCs can be isolated from numerous tissues and exhibit varied differentiation potential.To identify an optimal progenitor cell source for bone tissue engineering,we analyzed the proliferative activity and osteogenic potential of four commonly-used mouse MSC sources,including immortalized mouse embryonic fibroblasts(iMEF),immortalized mouse bone marrow stromal stem cells(imBMSC),immortalized mouse calvarial mesenchymal progenitors(iCAL),and immortalized mouse adipose-derived mesenchymal stem cells(iMAD).We found that iMAD exhibited highest osteogenic and adipogenic capabilities upon BMP9 stimulation in vitro,whereas iMAD and iCAL exhibited highest osteogenic capability in BMP9-induced ectopic osteogenesis and critical-sized calvarial defect repair.Transcriptomic analysis revealed that,while each MSC line regulated a distinct set of target genes upon BMP9 stimulation,all MSC lines underwent osteogenic differentiation by regulating osteogenesis-related signaling including Wnt,TGF-β,PI3K/AKT,MAPK,Hippo and JAK-STAT pathways.Collectively,our results demonstrate that adipose-derived MSCs represent optimal progenitor sources for cell-based bone tissue engineering.

Similarities and differences between mesenchymal stem/progenitor cells derived from various human tissues

BACKGROUND Mesenchymal stromal/stem cells (MSCs) constitute a promising tool in regenerative medicine and can be isolated from different human tissues. However, their biological properties are still not fully characterized. Whereas MSCs from different tissue exhibit many common characteristics, their biological activity and some markers are different and depend on their tissue of origin. Understanding the factors that underlie MSC biology should constitute important points for consideration for researchers interested in clinical MSC application. AIM To characterize the biological activity of MSCs during longterm culture isolated from: bone marrow (BM-MSCs), adipose tissue (AT-MSCs), skeletal muscles (SMMSCs), and skin (SK-MSCs). METHODS MSCs were isolated from the tissues, cultured for 10 passages, and assessed for: phenotype with immunofluorescence and flow cytometry, multipotency with differentiation capacity for osteo-, chondro-, and adipogenesis, stemness markers with qPCR for mRNA for Sox2 and Oct4, and genetic stability for p53 and c-Myc;27 bioactive factors were screened using the multiplex ELISA array, and spontaneous fusion involving a co-culture of SM-MSCs with BM-MSCs or AT-MSCs stained with PKH26 (red) or PKH67 (green) was performed. RESULTS All MSCs showed the basic MSC phenotype;however, their expression decreased during the follow-up period, as confirmed by fluorescence intensity. The examined MSCs express CD146 marker associated with proangiogenic properties;however their expression decreased in AT-MSCs and SM-MSCs, but was maintained in BM-MSCs. In contrast, in SK-MSCs CD146 expression increased in late passages. All MSCs, except BM-MSCs, expressed PW1, a marker associated with differentiation capacity and apoptosis. BM-MSCs and AT-MSCs expressed stemness markers Sox2 and Oct4 in long-term culture. All MSCs showed a stable p53 and c-Myc expression. BM-MSCs and AT-MSCs maintained their differentiation capacity during the follow-up period. In contrast, SK-MSCs and SM-MSCs had a limited ability to differentiate into adipocytes. BM-MSCs and AT-MSCs revealed similarities in phenotype maintenance, capacity for multilineage differentiation, and secretion of bioactive factors. Because AT-MSCs fused with SM-MSCs as effectively as BM-MSCs, AT-MSCs may constitute an alternative source for BM-MSCs. CONCLUSION Long-term culture affects the biological activity of MSCs obtained from various tissues. The source of MSCs and number of passages are important considerations in regenerative medicine.

Differentiation of Mesenchymal Stem Cells Into Dopaminergic Neuron-like Cells in vitro

To explore the way to induce mesenchymal stem cells (MSCs) to differentiate into dopaminergic neurons in vitro. Methods MSCs were obtained from rat bone marrow, cultured and passaged. MSCs used in this experiment had multipotency, which was indirectly proved by being induced to differentiate into chondrocytes and adipocytes. MSCs were cultured in medium containing 0.5 mmol/L IBMX for 2 days. Then the medium was replaced with induction medium, which contained GDNF, IL-1β, mesencephalic glial-cell-conditioned medium and flash-frozen mesencephalic membrane fragments. The surface markers of the differentiated neurons, such as NSE, nestin, MAP-2a, b and TH were detected by immunocytochemistry and Western blot after MSCs were cultured in induction medium for 7 days and 15 days. Results MSCs differentiated into neural progenitors and expressed nestin after MSCs were incubated with medium containing IBMX for 2 d. After the medium was replaced with induction medium containing many inducing agents, MSCs differentiated into neuron-like cells and dopaminergic neuron-like cells and expressed NSE, MAP-2a, b and TH. The percentage of NSE-positive cells, MAP-2a, b-positive cells and TH-positive cells was 30.032±2.489%, 41.580±5.101% and 34.958±5.534%, respectively after MSCs were induced in medium containing GDNF, IL-1β, mesencephalic glial-cell-conditioned medium and flash-frozen mesencephalic membrane fragments for 15 days. Conclusion MSCs can differentiate into dopaminergic neuron-like cells and are a new cell source for the treatment of neurodegeneration diseases and have a great potential for wide application

Optimal time for mesenchymal stem cell transplantation in rats with myocardial infarction

Background:Bone marrow mesenchymal stem cell (MSC) transplantation is a promising strategy in the treatment of myocardial infarction (MI). However, the time for transplanting cells remains controversial. The aim of this study was to find an optimal time point for cell transplantation. Methods: MSCs were isolated and cultured from Sprague-Dawley (SD) rats. MI model was set up in SD rats by permanent ligation of left anterior descending coronary artery. MSCs were directly injected into the infarct border zone at 1 h, 1 week and 2 weeks after MI, respectively. Sham-operated and MI control groups received equal volume of phosphate buffered saline (PBS). At 4 weeks after MI, cardiac function was assessed by echocardiography; vessel density was analyzed on hematoxylin-eosin stained slides by light microscopy; the apoptosis of cardiomyocytes was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay; the expressions of proteins were analyzed by Western blot. Results: MSC transplantation improved cardiac function, reduced the apoptosis of cardiomyocytes and increased vessel density. These benefits were more obvious in 1-week group than in 1-h and 2-week groups. There are more obvious in-creases in the ratio of bcl-2/bax and the expression of vascular endothelial growth factor (VEGF) and more obvious decreases in the expression of cleaved-caspase-3 in 1-week group than those in other two groups. Conclusion: MSC transplantation was beneficial for the recovery of cardiac function. MSC transplantation at 1 week post-MI exerted the best effects on increases of cardiac function, anti-apoptosis and angiogenesis.

BMP signaling in mesenchymal stem cell differentiation and bone formation

Bone morphogenetic proteins (BMPs) are members of the TGF-β superfamily and have diverse functions during development and organogenesis. BMPs play a major role in skeletal development and bone formation, and disruptions in BMP signaling cause a variety of skeletal and extraskeletal anomalies. Several knockout models have provided insight into the mechanisms responsible for these phenotypes. Proper bone formation requires the differentiation of osteoblasts from mesenchymal stem cell (MSC) precursors, a process mediated in part by BMP signaling. Multiple BMPs, including BMP2, BMP6, BMP7 and BMP9, promote osteoblastic differentiation of MSCs both in vitro and in vivo. BMP9 is one of the most osteogenic BMPs, yet it is a poorly characterized member of the BMP family. Several studies demonstrate that the mechanisms controlling BMP9-mediated osteogenesis differ from other osteogenic BMPs, but little is known about these specific mechanisms. Several pathways critical to BMP9-mediated osteogenesis are also important in the differentiation of other cell lineages, including adipocytes and chondrocytes. BMP9 has also demonstrated translational promise in spinal fusion and bone fracture repair. This review will summarize our current knowledge of BMP-mediated osteogenesis, with a focus on BMP9, by presenting recently completed work which may help us to further elucidate these pathways.

The genomic landscapes of histone H3-Lys9 modifications of gene promoter regions and expression profiles in human bone marrow mesenchymal stem cells

Mesenchymal stem cells （MSCs） of nonembryonic origins possess the proliferation and multi-lineage differentiation potentials. It has been established that epigenetic mechanisms could be critical for determining the fate of stem cells, and MSCs derived from different origins exhibited different expression profiles individually to a certain extent. In this study, ChiP-on-chip was used to generate genome-wide histone H3-Lys9 acetylation and dimethylation profiles at gene promoters in human bone marrow MSCs. We showed that modifications of histone H3-Lys9 at gene promoters correlated well with mRNA expression in human bone marrow MSCs. Functional analysis revealed that many key cellular pathways in human bone marrow MSC self-renewal, such as the canonical signaling pathways, cell cycle pathways and cytokine related pathways may be regulated by H3-Lys9 modifications. These data suggest that gene activation and silencing affected by H3-Lys9 acetylation and dimethylation, respectively, may be essential to the maintenance of human bone marrow MSC self-renewal and multi-potency.

Decreased osteogenesis of adult mesenchymal stem cel s by reactive oxygen species under cyclic stretch: a possible mechanism of age related osteoporosis

Age related defect of the osteogenic differentiation of mesenchymal stem cells（MSCs） plays a key role in osteoporosis. Mechanical loading is one of the most important physical stimuli for osteoblast differentiation.Here, we compared the osteogenic potential of MSCs from young and adult rats under three rounds of 2 h of cyclic stretch of 2.5% elongation at 1 Hz on 3 consecutive days. Cyclic stretch induced a significant osteogenic differentiation of MSCs from young rats, while a compromised osteogenesis in MSCs from the adult rats.Accordingly, there were much more reactive oxygen species（ROS） production in adult MSCs under cyclic stretch compared to young MSCs. Moreover, ROS scavenger N-acetylcysteine rescued the osteogenic differentiation of adult MSCs under cyclic stretch. Gene expression analysis revealed that superoxide dismutase 1（SOD1） was significantly downregulated in those MSCs from adult rats. In summary, our data suggest that reduced SOD1 may result in excessive ROS production in adult MSCs under cyclic stretch, and thus manipulation of the MSCs from the adult donors with antioxidant would improve their osteogenic ability.

Neural cell injury microenvironment induces neural differentiation of human umbilical cord mesenchymal stem cells

This study aimed to investigate the neural differentiation of human umbilical cord mesenchymal stem cells （hUCMSCs） under the induction of injured neural cells. After in vitro isolation and culture, passage 5 hUCMSCs were used for experimentation, hUCMSCs were co-cultured with normal or AI31.4o-injured PC12 cells, PC12 cell supernatant or PC12 cell lysate in a Transwell co-culture system. Western blot analysis and flow cytometry results showed that choline acetyltransferase and microtubule-associated protein 2, a specific marker for neural cells, were expressed in hUCMSCs under various culture conditions, and highest expression was observed in the hUCMSCs co-cultured with injured PC12 cells. Choline acetyltransferase and microtubule-associated protein 2 were not expressed in hUCMSCs cultured alone （no treatment）. Cell Counting Kit-8 assay results showed that hUCMSCs under co-culture conditions promoted the proliferation of injured PC12 cells. These findings suggest that the microenvironment during neural tissue injury can effectively induce neural cell differentiation of hUCMSCs. These differentiated hUCMSCs likely accelerate the repair of injured neural ceils.

BM-MSCs延缓CD8^(+)初始T细胞衰老

目的验证骨髓间充质干细胞(BM-MSCs)缓解免疫衰老的作用,探究其衰老改善的主要免疫细胞群体。方法分离获得小鼠脾淋巴细胞,刺激增殖7d构建复制性衰老细胞模型。利用流式细胞测量术检测年轻对照组、复制性衰老对照组和BM-MSCs共培养组T细胞亚群衰老标志物p16ink4a(p16)和p21cip1(p21)的表达水平。结果T淋巴细胞复制性衰老模型中观察到持续增殖后CD8^(+)T细胞较CD4^(+)T细胞衰老显著,在CD8^(+)T细胞的初始细胞、效应细胞亚群中,效应细胞衰老最显著;BM-MSCs共培养对衰老的效应细胞没有明显影响,主要通过延缓初始T细胞的衰老,达到缓解CD8^(+)T细胞衰老的作用(P<0.01,P<0.001)。结论与BM-MSCs共培养可以缓解T细胞的复制性衰老表型,对CD8^(+)T细胞的抗衰作用更显著,主要通过抑制初始T细胞的衰老实现。

Morphological Properties of Mesenchymal Stem Cells Derived from Bone Marrow of Rhesus Monkeys

To establish an in vitro system for isolating and culturing the mesenchymal stem cells （MSC） of Rhesus monkeys, and to provide research data for its further application, the bone marrow of Rhesus monkeys was collected and separated by gradient centrifugation to discard most of the blood cells. The MSC contained in the monocyte centrifuging layer was obtained and cultured in Dulbecco＇s modified media （low glucose, L-DMEM） supplemented with 10% Fetal bovine serum （FBS） and 1 ng/ml basic fibroblast growth factor （bFGF）. The non-MSC was screened out by continuously renewing the medium. A passage culture was undertaken while the MSC monolayer formed. The spindle-shaped MSC formed a monolayer after 18 days of primary culturing, and the cells appeared in an oriented array with a swirling and irradiating growth trend. In the anaphase of passage culture, the cell proliferation rate was decreased and the morphology changed into triangular, polygon and flat appearance. These results suggested that mesenchymal stem cells （MSC） of the Rhesus monkey can be passaged in vitro with the established optimized culture system.

The therapeutic potential of mesenchymal stem cells in Alzheimer's disease:converging mechanisms

Mesenchymal stem cells （MSCS） are pluripotent stem cells isolated from various tissues, but mostly from bone marrow, adipose tissue, and umbilical cord blood. Well known for their mesenchymal lineages differentiation （e.g., bone, cartilage and fat tissues）, it was suggested that MSCs possess plasticity prop- erties enabling them to differentiate into non-mesenchymal lineages. Indeed, several protocols claimed for differentiating MSCs to neurons in vitro, but concern was raised for the ef- fectiveness and in vivo relevance of such differentiation. Thus, though their neurogenic differentiation properties are still in debate, they were nevertheless, suggested as candidates for treat- ing neurodegenerative disorders such as Parkinson＇s diseases, multiple sclerosis and Alzheimer＇s disease （AD）.

Mitogen activated protein kinase signaling pathways participate in the active principle region of Buyang Huanwu decoction-induced differentiation of bone marrow mesenchymal stem cells

Our preliminary studies confirmed that an active principle region of Buyang Huanwu decoction, comprising alkaloid, polysaccharide, aglycon, glucoside and volatile oil, can induce bone marrow mesenchymal stem cell differentiation into neurons. Mitogen-activated protein kinase signaling was identified as one of the key pathways underlying this differentiation process. The present study shows phosphorylated extracellular signal-regulated protein kinase and phosphorylated p38 protein expression was increased after differentiation. Cellular signaling pathway blocking agents, PD98059 and SB203580, inhibited extracellular signal-regulated protein kinase and p38 in mitogen-activated protein kinase signaling pathways respectively, mRNA and protein expression of the neuronal marker, neuron specific enolase, and neural stem cell marker, nestin, were decreased in bone marrow mesenchymal stem cells after treatment with the active principle region of Buyang Huanwu decoction. Experimental findings indicate that, extracellular signal-regulated protein kinase and p38 in mitogen-activated protein kinase signaling pathways participate in bone marrow mesenchymal stem cell differentiation into neuron-like cells, induced by the active principle region of Buyang Huanwu decoction.

骨免疫学视角下绝经后骨质疏松症防治新靶点:MΦ-BMSCs串扰

绝经后骨质疏松症(postmenopausal osteoporosis,PMOP)是以骨量下降、骨结构破坏、易发生骨折为特征的代谢性骨病。PMOP已严重威胁女性健康,制约社会经济发展。近年来雌激素缺乏引起PMOP相关机制研究取得进展,但仍未得到充分阐明。骨免疫学研究显示PMOP病理过程伴随着慢性炎症和免疫系统的参与。巨噬细胞(macrophage,MΦ)是重要的免疫细胞,被报道在骨稳态和再生中发挥作用。巨噬细胞的耗竭能加重OVX小鼠的骨丢失,减少骨髓间充质干细胞(bone mesenchymal stem cells,BMSCs)数量,降低BMSCs成骨分化能力。巨噬细胞的缺失对骨形成的影响似乎超过了其对破骨细胞活性的影响,MΦ与BMSCs之间的串扰可能在这一环节发挥着重要作用。本文基于骨免疫学理论对MΦ-BMSCs串扰和PMOP的相关性进行综述,旨在为PMOP的防治研究提供新思路。

Mesenchymal Stromal Cells Derived from Human Embryonic Stem Cells, Fetal Limb and Bone Marrow Share a Common Phenotype but Are Transcriptionally and Biologically Different

Mesenchymal stromal cells (MSCs) can be obtained from several sources and the significant differences in their properties make it crucial to investigate the differentiation potential of MSCs from different sources to determine the optimal source of MSCs. We investigated if this biological heterogeneity in MSCs from different sources results in different mechanisms for their differentiation. In this study, we compared the gene expression patterns of phenotypically defined MSCs derived from three ontogenically different sources: Embryonic stem cells (hES-MSCs), Fetal limb (Flb-MSCs) and Bone Marrow (BM-MSCs). Differentially expressed genes between differentiated cells and undifferentiated controls were compared across the three MSC sources. We found minimal overlap (5% - 16%) in differentially expressed gene sets among the three sources. Flb-MSCs were similar to BM-MSCs based on differential gene expression patterns. Pathway analysis of the differentially expressed genes using Ingenuity Pathway Analysis (IPA) revealed a large variation in the canonical pathways leading to MSC differentiation. The similar canonical pathways among the three sources were lineage specific. The Flb-MSCs showed maximum overlap of canonical pathways with the BM-MSCs, indicating that the Flb-MSCs are an intermediate source between the less specialised hES-MSC source and the more specialised BM-MSC source. The source specific pathways prove that MSCs from the three ontogenically different sources use different biological pathways to obtain similar differentiation outcomes. Thus our study advocates the understanding of biological pathways to obtain optimal sources of MSCs for various clinical applications.