Production Of Mesenchymal Stem Cells Research Articles

Mesenchymal stem cells: biological properties and clinical applications

Importance of the field: In the last decade, knowledge of mesenchymal stem cells (MSCs) has evolved rapidly; their immunomodulatory properties and paracrine interactions with specific cell types in damaged tissues and promising results in some clinical applications have made these cells an attractive option for the treatment of certain diseases.Areas covered in this review: We present some relevant methodological issues and biological properties of MSCs, as well as clinical applications of MSC therapies with particular emphasis in the treatment of graft versus host disease (GVHD), complex perianal fistula and refractory metastatic neuroblastoma. Other topical aspects relevant to the application of cellular therapies such as biosafety studies and cellular production of MSCs are also discussed in this review.What the reader will gain: The growing optimism regarding MSCs research is based on the promising results obtained in in vitro and in vivo studies. The rapid translational research with MSCs necessitated standardization of methodology and terminology and greater focus on other aspects such as biosafety and cellular production, especially for clinical use of MSCs.Take home message: Much has been learned about the biology and applications of MSCs and much remains to be learned.

Mesenchymal stem cell transplantation increases expression of vascular endothelial growth factor in papain-induced emphysematous lungs and inhibits apoptosis of lung cells

Pulmonary emphysema is characterized by loss of alveolar structures. We have found that bone marrow (BM) mesenchymal stem cell (MSC) transplantation ameliorates papain-induced pulmonary emphysema. However, the underlying mechanism is not completely understood. It has been shown that blocking the vascular endothelial growth factor (VEGF) signaling pathway leads to apoptosis of lung cells and pulmonary emphysema, and MSC are capable of secreting VEGF. We hypothesized that MSC transplantation may have a protective effect on pulmonary emphysema by increasing VEGF-A expression and inhibiting apoptosis of lung cells. We examined the morphology and expression of VEGF-A in rat lung after papain treatment and MSC transplantation. We also used a co-culture system in which MSC and cells prepared from papain-treated lungs or control lungs were cultured together. The levels of VEGF-A in cells and culture medium were determined, and apoptosis of cultured lung cells was evaluated. VEGF-A expression in rat lungs was decreased after papain treatment, which was partly rescued by MSC transplantation. MSC production of VEGF-A was increased when MSC were co-cultured with cells prepared from papain-treated lungs. Furthermore, the apoptosis of papain-treated lung cells was inhibited when co-cultured with MSC. The induction of MSC production of VEGF-A by papain-treated lung cells was inhibited by adding anti-tumor necrosis factor (TNF)-alpha antibody to the medium. The protective effect of MSC transplantation on pulmonary emphysema may be partly mediated by increasing VEGF-A expression and inhibiting the apoptosis of lung cells. TNF-alpha released from papain-treated lung cells induces MSC to secret VEGF-A.

Hypoxia increases Sca-1/CD44 co-expression in murine mesenchymal stem cells and enhances their adipogenic differentiation potential

Mesenchymal stem cells (MSCs) are usually cultured under normoxic conditions (21% oxygen). However, in vivo, the physiological "niches" for MSCs have a much lower oxygen tension. Because of their plasticity, stem cells are particularly sensitive to their environments, and oxygen tension is one developmentally important stimulus in stem cell biology and plays a role in the intricate balance between cellular proliferation and commitment towards differentiation. Therefore, we investigated here the effect of hypoxia (2% oxygen) on murine adipose tissue (AT) MSC proliferation and adipogenic differentiation. AT cells were obtained from the omental fat and AT-MSCs were selected for their ability to attach to the plastic dishes, and were grown under normoxic and hypoxic conditions. Prior exposure of MSCs to hypoxia led to a significant reduction of ex vivo expansion time, with significantly increased numbers of Sca-1(+) as well as Sca-1(+)/CD44(+)double-positive cells. Under low oxygen culture conditions, the AT-MSC number markedly increased and their adipogenic differentiation potential was reduced. Notably, the hypoxia-mediated inhibition of adipogenic differentiation was reversible: AT-MSCs pre-exposed to hypoxia when switched to normoxic conditions exhibited significantly higher adipogenic differentiation capacity compared to their pre-exposed normoxic-cultured counterparts. Accordingly, the expression of adipocyte-specific genes, peroxisome proliferator activated receptor gamma (Ppargamma), lipoprotein lipase (Lpl) and fatty acid binding protein 4 (Fabp4) were significantly enhanced in hypoxia pre-exposed AT-MSCs. In conclusion, pre-culturing MSCs under hypoxic culture conditions may represent a strategy to enhance MSC production, enrichment and adipogenic differentiation.

Toll-like receptor 2 mediates mesenchymal stem cell-associated myocardial recovery and VEGF production following acute ischemia-reperfusion injury

Toll-like receptor 2 (TLR2), a key component of the innate immune system, is linked to inflammation and myocardial dysfunction after ischemia-reperfusion injury (I/R). Treatment of the heart with mesenchymal stem cells (MSCs) is known to improve myocardial recovery after I/R in part by paracrine factors such as VEGF. However, it is unknown whether TLR2 activation on the MSCs affects MSC-mediated myocardial recovery and VEGF production. We hypothesized that the knockout of TLR2 on the MSCs (TLR2KO MSCs) would 1) improve MSC-mediated myocardial recovery and 2) increase myocardial and MSC VEGF release. With the isolated heart perfusion system, Sprague-Dawley rat hearts were subjected to I/R and received one of three intracoronary treatments: vehicle, male wild-type MSCs (MWT MSCs), or TL2KO MSCs. All treatments were performed immediately before ischemia, and heart function was measured continuously. Postreperfusion, heart homogenates were analyzed for myocardial VEGF production. Contrary to our hypothesis, only MWT MSC treatment significantly improved the recovery of left ventricular developed pressure and the maximal positive and negative values of the first derivative of pressure. In addition, VEGF production was greatest in hearts treated with MWT MSCs. To investigate MSC production of VEGF, MSCs were activated with TNF in vitro and the supernatants collected for ELISA. In vitro basal levels of MSC VEGF production were similar. However, with TNF activation, MWT MSCs produced significantly more VEGF, whereas activated TLR2KO MSC production of VEGF was unchanged. Finally, we observed that MWT MSCs proliferated more rapidly than TLR2KO MSCs. These data indicate that TLR2 may be essential to MSC-mediated myocardial recovery and VEGF production.

PRECONDITIONING MESENCHYMAL STEM CELLS WITH TRANSFORMING GROWTH FACTOR-ALPHA IMPROVES MESENCHYMAL STEM CELL-MEDIATED CARDIOPROTECTION

Mesenchymal stem cells (MSCs) are a promising therapy for acute organ ischemia in part due to their paracrine production of growth factors. However, transplanted cells encounter an inflammatory environment that mitigates their function and survival, and treating the cells with exogenous agents during ex vivo expansion before transplantation is one strategy for overcoming this limitation by enhancing paracrine function. We hypothesized that preconditioning bone marrow MSCs with TGF-alpha would 1) increase MSC production of the critical paracrine factor, vascular endothelial growth factor (VEGF), via a p38 mitogen-activated protein kinase (MAPK)-dependent mechanism and 2) enhance myocardial functional recovery in a rat model of acute myocardial I/R injury. To study this, bone marrow MSCs were harvested from adult male mice (C57BL/6J) and treated in vitro for 24 h according to the following groups: 1) control, 2) TGF-alpha (250 ng mL (-1)), 3) TNF-alpha (50 ng mL (-1)), 4) TGF-alpha + TNF-alpha, 5) hypoxia, and 6) TGF-alpha + hypoxia. For the isolated heart perfusion experiments, adult male Sprague-Dawley rat hearts were isolated, perfused via the Langendorff model, and subjected to I/R. Vehicle or MSCs with or without TGF-alpha preconditioning were infused immediately before ischemia. Mesenchymal stem cells were also treated with TGF-alpha alone or in combination with a p38 MAPK inhibitor (SB202190). In vitro, TGF-alpha increased MSC VEGF production alone (157.9 +/- 1.11 - 291.0 +/- 3.74 pg 10 (-5); P < 0.05) and, to a greater extent, in combination with TNF-alpha or hypoxia (364.5 +/- 0.868 and 342.0 +/- 7.92 pg 10(-5) cells, respectively; P < 0.05 vs. TGF-alpha alone). Postischemic myocardial functional recovery was greater in hearts infused with TGF-alpha-preconditioned MSCs compared with untreated MSCs or vehicle. Myocardial IL-1beta and TNF-alpha production and activation of caspase 3 were significantly decreased after infusion of both cell groups. p38 MAPK inhibition suppressed TGF-alpha-stimulated MSC VEGF production and postischemic myocardial recovery. These results suggest that TGF-alpha stimulates MSC VEGF production in part via a p38 MAPK-dependent mechanism, and preconditioning MSCs with TGF-alpha may enhance their ability to protect myocardium during I/R injury.

The research progress of MSCs proliferation and differentiation in bone injury according to the TCM theory

Chinese have enjoyed not only quick recovery from but also effective daily prophylaxis of bone injuries. According to the Traditional Chinese Medicine (TCM) theory, Shen (or nephridium) is in charge of the bone, which corresponds to teeth, spine, skull, femur and the like. The function of Shen can be divided into Shen Yin (or negative nephridium) and Shen Yang (or positive nephridium). Bone injury is usually accompanied with blood stasis and loss in microenvironment. Therefore, traditional Chinese doctors had chosen tonifying Shen Yin, invigorating Shen Yang, enriching and activating the blood or even combining the above three strategies for injured bone repairing. Nowadays, researchers are reunderstanding TCM drugs and formulas by studying mesenchymal stem cells (MSCs) proliferation and differentiation in vitro and vivo. This review will introduce some newest articles mainly in China focusing on the growth and differentiation of MSCs, which were treated with a single herb or formulas of those drugs (belonging to the above four classes) to demonstrate the huge potential of TCMs in the future bone-injury-therapeutic production of MSCs.

Design of bioreactors for mesenchymal stem cell tissue engineering

AbstractThere is a growing need for efficient mesenchymal stem cell (MSC) production processes for a wide spectrum of clinical conditions ranging from the treatment of life‐threatening graft‐versus‐host disease to cartilage repair. Development of cell and tissue engineered products derived from MSCs will be enabled by scalable production processes with standards of safety and efficacy similar to those established for the pharmaceutical industry. Many of the bioreactor design principles established for production of biopharmaceuticals can be applied to production of MSC products; however, specific control of the microenvironment is required for MSC expansion and differentiation. We review how porous scaffolds and bioreactor technologies are applied to the study of the MSC microenvironment. Current methods for MSC production are based on growth in tissue culture flasks, which is labour‐intensive and expensive. We suggest that stirred, perfusion or microfluidic bioreactor technologies can more efficiently address the clinical need for large‐scale MSC production. Soft lithography and microfluidic design offer extreme geometric precision to study MSC function as well as defining the microenvironment for tissue engineering at the micron scale. Copyright © 2008 Society of Chemical Industry

Hyaluronidase and IFN-γ from Activated T-Cells Are Key Mediators To Induce Immunosuppressive Activity of Mesenchymal Stem Cells.

Mesenchymal stem cells (MSC) have been shown to suppress T-cell proliferation in vitro and are being clinically applied to treatment for steroid-refractory graft-versus-host disease (GVHD). However, the molecular mechanisms of immunosuppressive activity of MSC have not been fully understood. We have recently reported that nitric oxide (NO) is one of the key molecules for T-cell suppression by MSC (Blood , 2007; 228–34). Inducible NO synthase (iNOS) expression in MSC and NO production were exclusively detected upon interaction with activated T-cells. An inhibitor of NOS restored the proliferation of T-cells. We have also shown that both IFN-γ and NF-κB mediate NO production by MSC (BBRC , 2007; 80–90), however the factor(s) from T-cells that induce immunosuppressive activity of MSC have not been elucidated. In the present study, we focused on hyaluronic acid (HA), a major extracellular matrix component, because1.low molecular weight (LMW) HA is known to play an essential role in regulation of inflammation and infection,2.HA induces NOS in macrophages through a NF-κB-dependent mechanism, and3.T-cells are reported to express hyaluronidase-2 mRNA after activation.A series of such information suggests that activated T-cells regulate immunosuppressive activity of MSC through HA signaling. We investigated the molecular events in the interaction between MSC and activated T-cells, and demonstrated that HA may play an important role in the scenario. First, ELISA showed that MSC produce a large amount of HA. RT-PCR revealed that among three hyaluronic acid synthase (HAS), mRNA for HAS-1 but neither HAS-2 nor HAS-3 is constitutively expressed by MSC. Flow cytometric analysis also showed that MSC express CD44, one of the receptors for HA. In macrophages, either IFN-γ or LMW HA is known to induce NO production. Therefore, we investigated whether IFN-γ or LMW HA can induce NO production via NF-κB signaling in MSC. As a result, only in the presence of IFN-γ, LMW HA but not high molecular weight (HMW) HA induced expression of iNOS in MSC, followed by NO production from MSC. We found that prostaglandin E2 (PGE2), which was previously reported as another immunosuppressive factor of MSC, is also induced by the combination of IFN-γ and LMW HA. Since hyaluronidase activity in activated T-cells has already been reported, these data support a novel hypothesis that HMW HA produced by MSC is digested by hyaluronidase from activated T-cells, and that resultant LMW HA cooperates with IFN-γ from activated T-cells in inducing iNOS expression in MSC. Locally produced NO through the above mechanisms may suppress activated T-cell proliferation. These findings would be important to further potentiate and regulate the immunomodulatory activity of MSC in a variety of applications.

STAT3 mediates bone marrow mesenchymal stem cell VEGF production

The mechanisms by which mesenchymal stem cells (MSCs) may protect native tissue are incompletely understood. Understanding the mechanisms by which these cells release factors such as vascular endothelial growth factor (VEGF), may lead to enhanced protection. We hypothesized that stress, in the form of hypoxia or TNF, activates MSCs to release VEGF by STAT3 and p38 MAPK dependent mechanisms. Mouse MSCs from wild type (WT) and STAT3 knockout mice (STAT3KO) were harvested and purified by a single-step method using adhesion. The release of VEGF was analyzed by using MSC conditioned media under hypoxia or TNF stimulation with or without p38 MAPK inhibition. Activation of STAT3 and p38 MAPK was determined by analysis of cell lysates. MSCs released VEGF under normoxia, which was associated with constitutive STAT3 activity. STAT3 deficiency resulted in decreased MSC production of VEGF. In response to hypoxia or TNF, MSCs produced more VEGF, which was correlated with hypoxia or TNF activated p38 MAPK and STAT3. The p38 MAPK inhibitor significantly decreased hypoxia-induced or TNF-stimulated VEGF production in WT. Additionally, STAT3 ablation neutralized hypoxia-induced MSC release of VEGF. No effect of p38 MAPK inhibitor alone was observed on MSC release of VEGF in WT. However, inhibition of p38 MAPK blocked release of VEGF in STAT3KO MSCs. MSCs are a potent source of VEGF, the production of which is mediated by STAT3 under normoxia partly; however, following hypoxia or TNF exposure, MSC release of VEGF is mediated by both STAT3 and p38 MAPK.

Toll-Like Receptor-Stimulated CD14+ Monocytes Induce Soluble Factors That Activate Human Mesenchymal Stem Cells To Inhibit T-Cell Alloreactivity.

Human mesenchymal stem cells (MSCs) produce soluble factors that inhibit T-cell proliferation and alloreactivity. We have previously shown that MSCs require activation by CD14+ monocytes in cell culture. Toll-like receptors (TLRs) critically modulate antigen-presenting cell (APC) activation, maturation and function. Therefore, we aimed to determine whether TLR agonists could enhance CD14-mediated MSC activation and subsequent MSC-mediated T-cell inhibition. TLR agonists and human IL-1β were used to stimulate CD14+ cells isolated from peripheral blood of normal donors. TLR agonists included formalin-fixed Staphylococcus aureus Cowan A strain (SAC, TLR-2), Pam3CysSerLys4 (Pam3Cys, TLR-2), Salmonella enteriditis lipopolysaccharide (LPS, TLR-4), and R848 (Resiquimod, TLR7/8) in complete RPMI media (heat-inactivated FBS, glutamine, and antibiotics). TLR-stimulated CD14+ cells and supernatants from TLR-stimulated CD14+ cells were then used to stimulate third- and fourth-passage human MSCs (CD45−CD105+CD90+CD80−CD73+HLA-I+) expanded from normal volunteer bone marrow aspirate specimens. After a 24-hour culture with stimulant cells or supernatants, stimuli were removed, MSCs were washed twice with sterile PBS, and then were cultured for an additional 24 h in FBS-free RPMI media. Supernatants from TLR-stimulated CD14+ cell cultures and from washed MSC cultures were used to measure cytokine and chemokine production and to inhibit T-cell alloreactivity using an established mixed lymphocyte reaction (MLR) IFN-γ ELISPOT. MLR was also performed in the presence of TLR agonists and media alone. TLR stimulation resulted in high-level soluble factor induction (IL-1β, IL-6, TNF-α, and RANTES) from CD14+ cells. For example, levels of inducible IL-6 measured in CD14+ cell culture supernatants following LPS, SAC and R848 stimulation were 5.2 (70.3 ± 26.2 ng/ml), 4.7 (64.1 ± 16.3 ng/ml), and 4.6 (63.4 ± 13.1 ng/ml)-fold higher than after IL-1β stimulation (13.7 ± 4.0 ng/ml) (Mean ± SEM, 4 independent experiments). Supernatants of TLR-stimulated CD14+ cells induced higher levels of soluble factors from MSCs than stimulation with CD14+ cells themselves, suggesting that soluble factors from CD14+ cells activate MSCs. Not all supernatants of TLR-stimulated CD14+ cells were similar in their capacity to activate MSC-mediated inhibition of T-cell alloreactivity. For example, supernatants of Pam3Cys-, R848- and SAC-stimulated CD14+ cells all induced high levels of TNF-α in washed MSC cultures; but only supernatant from Pam3Cys-stimulated CD14+ cells resulted in MSC-mediated inhibition of T-cell alloreactivity (63.7 ± 12.9 % inhibition, Mean ± SEM, 4 independent ELISPOTs). Ongoing studies are being performed to define these immunomodulatory factors. Together, these results suggest that ex vivo TLR stimulation enhances soluble factor production from CD14+ cells, which, in turn, increases MSC production of immunomodulatory factors that mediate inhibition of T-cell alloreactivity.