Mesenchymal stromal cell migration: possibilities to improve cellular therapy

Histone demethylase JMJD3 downregulation protects against aberrant force-induced osteoarthritis through epigenetic control of NR4A1

Osteoarthritis (OA) is a prevalent joint disease with no effective treatment strategies. Aberrant mechanical stimuli was demonstrated to be an essential factor for OA pathogenesis. Although multiple studies have detected potential regulatory mechanisms underlying OA and have concentrated on developing novel treatment strategies, the epigenetic control of OA remains unclear. Histone demethylase JMJD3 has been reported to mediate multiple physiological and pathological processes, including cell differentiation, proliferation, autophagy, and apoptosis. However, the regulation of JMJD3 in aberrant force-related OA and its mediatory effect on disease progression are still unknown. In this work, we confirmed the upregulation of JMJD3 in aberrant force-induced cartilage injury in vitro and in vivo. Functionally, inhibition of JMJD3 by its inhibitor, GSK-J4, or downregulation of JMJD3 by adenovirus infection of sh-JMJD3 could alleviate the aberrant force-induced chondrocyte injury. Mechanistic investigation illustrated that aberrant force induces JMJD3 expression and then demethylates H3K27me3 at the NR4A1 promoter to promote its expression. Further experiments indicated that NR4A1 can regulate chondrocyte apoptosis, cartilage degeneration, extracellular matrix degradation, and inflammatory responses. In vivo, anterior cruciate ligament transection (ACLT) was performed to construct an OA model, and the therapeutic effect of GSK-J4 was validated. More importantly, we adopted a peptide-siRNA nanoplatform to deliver si-JMJD3 into articular cartilage, and the severity of joint degeneration was remarkably mitigated. Taken together, our findings demonstrated that JMJD3 is flow-responsive and epigenetically regulates OA progression. Our work provides evidences for JMJD3 inhibition as an innovative epigenetic therapy approach for joint diseases by utilizing p5RHH-siRNA nanocomplexes.

Insensitivity of dental pulp stem cells migration to substrate stiffness

Dental pulp stem cells (DPSCs) are a promising cell source for regeneration of dental pulp. Migration is a key event but influence of the microenvironment rigidity (5 kPa at the center of dental pulp to 20 GPa for the dentin) is largely unknown. Mechanical signals are transmitted from the extracellular matrix to the cytoskeleton, to the nuclei, and to the chromatin, potentially regulating gene expression. To identify the microenvironmental influence on migration, we analyzed motility on PDMS substrates with stiffness increasing from 1.5 kPa up to 2.5 MPa. We found that migration speed slightly increases as substrate stiffness decreases in correlation with decreasing focal adhesion size. Motility is relatively insensitive to substrate stiffness, even on a bi-rigidity PDMS substrate where DPSCs migrate without preferential direction. Migration is independent of both myosin II activity and YAP translocation after myosin II inhibition. Additionally, inhibition of Arp2/3 complex leads to significant speed decrease for all rigidities, suggesting contribution of the lamellipodia in the migration. Interestingly, the chromatin architecture remains stable after a 7-days exposure on the PDMS substrates for all rigidity. To design scaffold mimicking dental pulp environment, similar DPSCs migration for all rigidity, leaves field open to choose this mechanical parameter.

Cellular therapies for graft-versus-host disease: a tale of tissue repair and tolerance

The success of allogeneic hematopoietic cell transplantation depends heavily on the delicate balance between the activity of the donor immune system against malignant and nonmalignant cells of the recipient. Abrogation of alloreactivity will lead to disease relapse, whereas untamed allo-immune responses will lead to lethal graft-versus-host disease (GVHD). A number of cell types have been identified that can be used to suppress alloreactive immune cells and prevent lethal GVHD in mice. Of those, mesenchymal stromal cells and, to a lesser extent, regulatory T cells have demonstrated efficacy in humans. Ideally, cellular therapy for GVHD will not affect alloreactive immune responses against tumor cells. The importance of tissue damage in the pathophysiology of GVHD rationalizes the development of cells that support tissue homeostasis and repair, such as innate lymphoid cells. We discuss recent developments in the field of cellular therapy to prevent and treat acute and chronic GVHD, in the context of GVHD pathophysiology.

Targeting NR4A Nuclear Receptors to Control Stromal Cell Inflammation, Metabolism, Angiogenesis, and Tumorigenesis

The NR4A1–NR4A3 (Nur77, Nurr1, and Nor-1) subfamily of nuclear receptors is a group of immediate early genes induced by a pleiotropy of stimuli including peptide hormones, growth factors, cytokines, inflammatory, and physiological stimuli, and cellular stress. NR4A receptors function as potent sensors of changes in the cellular microenvironment to control physiological and pathological processes through genomic and non-genomic actions. NR4A receptors control metabolism and cardiovascular and neurological functions and mediate immune cell homeostasis in inflammation and cancer. This receptor subfamily is increasingly recognized as an important molecular connection between chronic inflammation, altered immune cell responses, and cancer development. In this review, we examine how transcriptome analysis identified NR4A1/NR4A2 receptors as transcriptional regulators in mesenchymal stromal cell (MSC) migration, cell cycle progression, and cytokine production to control local immune responses. In chronic inflammatory conditions, such as rheumatoid arthritis, NR4A receptors have been shown to modify the activity of MSC and fibroblast-like stromal cells to regulate synovial tissue hyperplasia, pathological angiogenesis, and cartilage turnover in vivo. Additionally, as NR4A1 has been observed as a major transcriptional regulator in tumor–stromal communication controlling tumorigenesis, we discuss how advances in the pharmacological control of these receptors lead to important new mechanistic insights into understanding the role of the tumor microenvironment in health and disease.

Regulation of neuronal bioenergetics as a therapeutic strategy in neurodegenerative diseases

Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis are a heterogeneous group of debilitating disorders with multifactorial etiologies and pathogeneses that manifest distinct molecular mechanisms and clinical manifestations with abnormal protein dynamics and impaired bioenergetics. Mitochondrial dysfunction is emerging as an important feature in the etiopathogenesis of these age-related neurodegenerative diseases. The prevalence and incidence of these diseases is on the rise with the increasing global population and average lifespan. Although many therapeutic approaches have been tested, there are currently no effective treatment routes for the prevention or cure of these diseases. We present the current status of our knowledge and understanding of the involvement of mitochondrial dysfunction in these diseases and highlight recent advances in novel therapeutic strategies targeting neuronal bioenergetics as potential approach for treating these diseases.

Catharmus tinctorius volatile oil promote the migration of mesenchymal stem cells via ROCK2/Myosin light chain signaling

MSC transplantation has been explored as a new clinical approach to stem cell-based therapies for bone diseases in regenerative medicine due to their osteogenic capability. However, only a small population of implanted MSC could successfully reach the injured areas. Therefore, enhancing MSC migration could be a beneficial strategy to improve the therapeutic potential of cell transplantation. Catharmus tinctorius volatile oil (CTVO) was found to facilitate MSC migration. Further exploration of the underlying molecular mechanism participating in the pro-migratory ability may provide a novel strategy to improve MSC transplantation efficacy. This study indicated that CTVO promotes MSC migration through enhancing ROCK2 mRNA and protein expressions. MSC migration induced by CTVO was blunted by ROCK2 inhibitor, which also decreased myosin light chain (MLC) phosphorylation. Meanwhile, the siRNA for ROCK2 inhibited the effect of CTVO on MSC migration ability and attenuated MLC phosphorylation, suggesting that CTVO may promote BMSC migration via the ROCK2/MLC signaling. Taken together, this study indicates that C. tinctorius volatile oil could enhance MSC migration via ROCK2/MLC signaling in vitro. C. tinctorius volatile oil-targeted therapy could be a beneficial strategy to improve the therapeutic potential of cell transplantation for bone diseases in regenerative medicine.

Chemical activation of the Piezo1 channel drives mesenchymal stem cell migration via inducing ATP release and activation of P2 receptor purinergic signaling

In this study, we examined the Ca²⁺‐permeable Piezo1 channel, a newly identified mechanosensing ion channel, in human dental pulp‐derived mesenchymal stem cells (MSCs) and hypothesized that activation of the Piezo1 channel regulates MSC migration via inducing ATP release and activation of the P2 receptor purinergic signaling. The Piezo1 mRNA and protein were readily detected in hDP‐MSCs from multiple donors and, consistently, brief exposure to Yoda1, the Piezo1 channel‐specific activator, elevated intracellular Ca²⁺ concentration. Yoda1‐induced Ca²⁺ response was inhibited by ruthenium red or GsMTx4, two Piezo1 channel inhibitors, and also by Piezo1‐specific siRNA. Brief exposure to Yoda1 also induced ATP release. Persistent exposure to Yoda1 stimulated MSC migration, which was suppressed by Piezo1‐specific siRNA, and also prevented by apyrase, an ATP scavenger, or PPADS, a P2 generic antagonist. Furthermore, stimulation of MSC migration induced by Yoda1 as well as ATP was suppressed by PF431396, a PYK2 kinase inhibitor, or U0126, an inhibitor of the mitogen‐activated protein kinase MEK/ERK signaling pathway. Collectively, these results suggest that activation of the Piezo1 channel stimulates MSC migration via inducing ATP release and subsequent activation of the P2 receptor purinergic signaling and downstream PYK2 and MEK/ERK signaling pathways, thus revealing novel insights into the molecular and signaling mechanisms regulating MSC migration. Such findings provide useful information for evolving a full understanding of MSC migration and homing and developing strategies to improve MSC‐based translational applications.

Genetically modified mesenchymal stem cell therapy for acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a devastating hypoxemic respiratory failure, characterized by disruption of the alveolar-capillary membrane barrier. Current management for ARDS remains supportive, including lung-protective ventilation and a conservative fluid strategy. Mesenchymal stem cells (MSCs) have emerged as a potentially attractive candidate for the management of ARDS through facilitating lung tissue regeneration and repair by releasing paracrine soluble factors. Over the last decade, a variety of strategies have emerged to optimize MSC-based therapy. Among these, the strategy using genetically modified MSCs has received increased attention recently due to its distinct advantage, in conferring incremental migratory capacity and, enhancing the anti-inflammatory, immunomodulatory, angiogenic, and antifibrotic effects of these cells in numerous preclinical ARDS models, which may in turn provide additional benefits in the management of ARDS. Here, we provide an overview of recent studies testing the efficacy of genetically modified MSCs using preclinical models of ARDS.

Nuclear shape, protrusive behaviour and in vivo retention of human bone marrow mesenchymal stromal cells is controlled by Lamin-A/C expression

Culture expanded mesenchymal stromal cells (MSCs) are being extensively studied for therapeutic applications, including treatment of graft-versus-host disease, osteogenesis imperfecta and for enhancing engraftment of hematopoietic stem cells after transplantation. Thus far, clinical trials have shown that the therapeutic efficiency of MSCs is variable, which may in part be due to inefficient cell migration. Here we demonstrate that human MSCs display remarkable low migratory behaviour compared to other mesodermal-derived primary human cell types. We reveal that specifically in MSCs the nucleus is irregularly shaped and nuclear lamina are prone to wrinkling. In addition, we show that expression of Lamin A/C is relatively high in MSCs. We further demonstrate that in vitro MSC migration through confined pores is limited by their nuclei, a property that might correlate to the therapeutic inefficiency of administered MSC in vivo. Silencing expression of Lamin A/C in MSCs improves nuclear envelope morphology, promotes the protrusive activity of MSCs through confined pores and enhances their retention in the lung after intravenous administration in vivo. Our findings suggest that the intrinsic nuclear lamina properties of MSCs underlie their limited capacity to migrate, and that strategies that target the nuclear lamina might alter MSC-based cellular therapies.

Targeted Migration of Human Adipose-Derived Stem Cells to Secondary Lymphoid Organs Enhances Their Immunomodulatory Effect and Prolongs the Survival of Allografted Vascularized Composites

The targeted delivery of therapeutic agents to secondary lymphoid organs (SLOs), which are the niches for immune initiation, provides an unprecedented opportunity for immune intolerance induction. The alloimmune rejection postvascularized composite allotransplantation (VCA) is mediated by T lymphocytes. Human adipose-derived stem cells (hASCs) possess the superiority of convenient availability and potent immunoregulatory property, but their therapeutic results in the VCA are unambiguous thus far. Chemokine receptor 7 (CCR7) can specifically guide immune cells migrating into SLOs. There, the genes of CCR7-GFP or GFP alone were introduced into hASCs by lentivirus. hASCs/CCR7 maintained the multidifferentiation and immunoregulatory abilities, but it gained the migration capacity elicited by secondary lymphoid organ chemokine (SCL) (CCR7 ligand) in vitro. Noteworthily, intravenously infused hASCs/CCR7 targetedly relocated in the T-cell aggression area in SLOs. In a rat VCA model, hASCs/GFP transfusion had a rare effect on the allografted vascularized composite. However, hASCs/CCR7 infusion potently prolonged the grafts' survival time. The ameliorated pathologic exhibition and the regulated inflammatory cytokines in the peripheral blood were also observed. The altered axis of Th1/Th2 and Tregs/Th17 in SLOs may underlie the downregulated rejection response. Moreover, the proteomic examination of splenic T lymphocytes also confirmed that hASCs/CCR7 decreased the proteins related to cytokinesis, lymphocyte proliferation, differentiation, and apoptotic process. In conclusion, our present study demonstrated that targeted migration of hASCs/CCR7 to SLOs highly intensifies their in vivo immunomodulatory effect in the VCA model for the first time. We believe this SLO-targeting strategy may improve the clinical therapeutic efficacy of hASC for allogeneic and autogenic immune disease. Stem Cells 2019;37:1581-1594.

Overexpression of CX3CR1 in Adipose-Derived Stem Cells Promotes Cell Migration and Functional Recovery After Experimental Intracerebral Hemorrhage

Stem cell therapy has emerged as a new promising therapeutic strategy for intracerebral hemorrhage (ICH). However, the efficiency of stem cell therapy is partially limited by low retention and engraftment of the delivered cells. Therefore, it’s necessary to improve the migration ability of stem cells to the injured area in order to save the costs and duration of cell preparation. This study aimed to investigate whether overexpression of CX3CR1, the specific receptor of chemokine fractalkine (FKN), in adipose-derived stem cells (ADSCs) can stimulate the cell migration to the injured area in the brain, improve functional recovery and protect against cell death following experimental ICH. ADSCs were isolated from subcutaneous adipose tissues of rats. ICH was induced by means of an injection of collagenase type VII. ELISA showed that the expression levels of fractalkine/FKN were increased at early time points, with a peak at day 3 after ICH. And it was found that different passages of ADSCs could express the chemokine receptor CX3CR1. Besides, the chemotactic movements of ADSCs toward fractalkine have been verified by transwell migration assay. ADSCs overexpressing CX3CR1 were established through lentivirus transfection. We found that after overexpression of CX3CR1 receptor, the migration ability of ADSCs was increased both in vitro and in vivo. In addition, reduced cell death and improved sensory and motor functions were seen in the mice ICH model. Thus, ADSCs overexpression CX3CR1 might be taken as a promising therapeutic strategy for the treatment of ICH.

Forkhead box O1 (FOXO1) controls the migratory response of Toll-like receptor (TLR3)-stimulated human mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) can potently regulate the functions of immune cells and are being investigated for the management of inflammatory diseases. Toll-like receptor 3 (TLR3)-stimulated human MSCs (hMSCs) exhibit increased migration and chemotaxis within and toward damaged tissues. However, the regulatory mechanisms underlying these migratory activities are unclear. Therefore, we analyzed the migration capability and gene expression profiles of TLR3-stimulated hMSCs using RNA-Seq, wound healing, and transwell cell migration assay. Along with increased cell migration, the TLR3 stimulation also increased the expression of cytokines, chemokines, and cell migration-related genes. The promoter regions of the latter showed an enrichment of putative motifs for binding the transcription factors forkhead box O1 (FOXO1), FOXO3, NF-κB (NF-κB1), and RELA proto-oncogene and NF-κB subunit. Of note, FOXO1 inhibition by the FOXO1-selective inhibitor AS1842856 significantly reduced both migration and the expression of migration-related genes. In summary, our results indicate that TLR3 stimulation induces hMSC migration through the expression of FOXO1-activated genes.

Assessment of the Immunosuppressive Potential of INF-γ Licensed Adipose Mesenchymal Stem Cells, Their Secretome and Extracellular Vesicles

There is an active search for the ideal strategy to potentialize the effects of Mesenchymal Stem-Cells (MSCs) over the immune system. Also, part of the scientific community is seeking to elucidate the therapeutic potential of MSCs secretome and its extracellular vesicles (EVs), in order to avoid the complexity of a cellular therapy. Here, we investigate the effects of human adipose MSCs (AMSCs) licensing with INF-γ and TLR3 agonist over AMSCs proliferation, migration, as well as the immunomodulatory function. Furthermore, we evaluated how the licensing of AMSCs affected the immunomodulatory function of AMSC derived-secretome, including their EVs. INF-γ licensed-AMSCs presented an elevated expression of indoleamine 2,3-dioxygenase (IDO), accompanied by increased ICAM-1, as well as a higher immunosuppressive potential, compared to unlicensed AMSCs. Interestingly, the conditioned medium obtained from INF-γ licensed-AMSCs also revealed a slightly superior immunosuppressive potential, compared to other licensing strategies. Therefore, unlicensed and INF-γ licensed-AMSCs groups were used to isolate EVs. Interestingly, EVs isolated from both groups displayed similar capacity to inhibit T-cell proliferation. EVs isolated from both groups shared similar TGF-β and Galectin-1 mRNA content but only EVs derived from INF-γ licensed-AMSCs expressed IDO mRNA. In summary, we demonstrated that INF-γ licensing of AMSCs provides an immunosuppressive advantage both from a cell-cell contact-dependent perspective, as well as in a cell-free context. Interestingly, EVs derived from unlicensed and INF-γ licensed-AMSCs have similar ability to control activated T-cell proliferation. These results contribute towards the development of new strategies to control the immune response based on AMSCs or their derived products.

GM-CSF Enhances Mobilization of Bone Marrow Mesenchymal Stem Cells via a CXCR4-Medicated Mechanism

Background

This study was conducted to investigate the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on the mobilization of mesenchymal stem cells (MSCs) from the bone marrow (BM) into the peripheral blood (PB) in rats.

Methods

GM-CSF was administered subcutaneously to rats at 50 μg/kg body weight for 5 consecutive days. The BM and PB of rats were collected at 1, 3, and 5 days during the administration for analysis.

Results

Upon GM-CSF administration, the number of mononuclear cells increased rapidly at day 1 both in the BM and PB. This number decreased gradually over time in the BM to below the initial amount by day 5, but was maintained at a high level in the PB until day 5. The colony-forming unit-fibroblasts were increased in the PB by 10.3-fold at day 5 of GM-CSF administration, but decreased in the BM. Compared to GM-CSF, granulocyte-colony stimulating factor (G-CSF) stimulated lower levels of MSC mobilization from the BM to the PB. Immunohistochemical analysis revealed that GM-CSF induced a hypoxic and proteolytic microenvironment and increased C-X-C chemokine receptor type 4 (CXCR4) expression in the BM. GM-CSF added to BM MSCs in vitro dose-dependently increased CXCR4 expression and cell migration. G-CSF and stromal cell derived factor-1 (SDF-1) showed similar results in these in vitro assays. Know-down of CXCR4 expression with siRNA significantly abolished GM-CSF- and G-CSF-induced MSC migration in vitro, indicating the involvement of the SDF-1-CXCR4 interaction in the mechanism.

Conclusion

These results suggest that GM-CSF is a useful tool for mobilizing BM MSCs into the PB.

Enhanced adhesion and proliferation of bone marrow mesenchymal stem cells on β‑tricalcium phosphate modified by an affinity peptide

Mesenchymal stem cells (MSCs) are often used in orthopedic tissue engineering, and bone marrow-derived mesenchymal stem cells (BMSCs) are currently considered the gold standard. One of the most important issues in MSC-based tissue engineering therapy is the low number of MSCs in pathological tissues. Achieving efficient recruitment of MSCs to defective or damaged tissues in vivo has been a difficult hurdle. The aim of the present study was to construct a biomaterial that can effectively recruit BMSCs to facilitate the repair of pathological tissues. So functional β-tricalcium phosphate (β-TCP) was synthesized using the BMSC affinity peptide DPIYALSWSGMA (DPI) adsorbed onto β-TCP through an adsorption/freeze-drying strategy. C57BL/6 mouse-derived BMSCs were seeded onto the DPI peptide-modified β-TCP (β-TCP-DPI); in vitro experiments demonstrated that β-TCP-DPI enhanced BMSC adhesion and proliferation compared with unmodified β-TCP. Results from the present study indicated that functional β-TCP may be used as an ideal scaffold in tissue engineering and in regenerative medicine.

Mesenchymal Stem Cells Shift Mitochondrial Dynamics and Enhance Oxidative Phosphorylation in Recipient Cells

Mesenchymal stem cells (MSCs) are the most commonly used cells in tissue engineering and regenerative medicine. MSCs can promote host tissue repair through several different mechanisms including donor cell engraftment, release of cell signaling factors, and the transfer of healthy organelles to the host. In the present study, we examine the specific impacts of MSCs on mitochondrial morphology and function in host tissues. Employing in vitro cell culture of inherited mitochondrial disease and an in vivo animal experimental model of low-grade inflammation (high fat feeding), we show human-derived MSCs to alter mitochondrial function. MSC co-culture with skin fibroblasts from mitochondrial disease patients rescued aberrant mitochondrial morphology from a fission state to a more fused appearance indicating an effect of MSC co-culture on host cell mitochondrial network formation. In vivo experiments confirmed mitochondrial abundance and mitochondrial oxygen consumption rates were elevated in host tissues following MSC treatment. Furthermore, microarray profiling identified 226 genes with differential expression in the liver of animals treated with MSC, with cellular signaling, and actin cytoskeleton regulation as key upregulated processes. Collectively, our data indicate that MSC therapy rescues impaired mitochondrial morphology, enhances host metabolic capacity, and induces widespread host gene shifting. These results highlight the potential of MSCs to modulate mitochondria in both inherited and pathological disease states.

Progress in mesenchymal stem cell-based therapy for acute liver failure

Acute liver failure is a life-threatening clinical syndrome characterized by rapid development of hepatocellular necrosis leading to high mortality and resource costs. Numerous treatment strategies for acute liver failure simply prevent complications and decelerate disease progression. The only curative treatment for acute liver failure is liver transplantation, but there are many restrictions on the application of liver transplantation. In recent years, a growing number of studies have shown that stem cells can effectively treat acute liver failure. Several types of stem cells have been used to study liver diseases; mesenchymal stem cells are most commonly used because they are easy to obtain and present no ethical problems. The aims of this article are to review the current knowledge regarding therapeutic mechanisms of mesenchymal stem cells in acute liver failure, to discuss recent advancements in preclinical and clinical studies in the treatment of mesenchymal stem cells, and to summarize the methodological improvement of mesenchymal stem cell transplantation in treating liver failure.

Interferon-Gamma Impairs Maintenance and Alters Hematopoietic Support of Bone Marrow Mesenchymal Stromal Cells

Bone marrow (BM) mesenchymal stromal cells (MSCs) provide microenvironmental support to hematopoietic stem and progenitor cells (HSPCs). Culture-expanded MSCs are interesting candidates for cellular therapies due to their immunosuppressive and regenerative potential which can be further enhanced by pretreatment with interferon-gamma (IFN-γ). However, it remains unknown whether IFN-γ can also influence hematopoietic support by BM-MSCs. In this study, we elucidate the impact of IFN-γ on the hematopoietic support of BM-MSCs. We found that IFN-γ increases expression of interleukin (IL)-6 and stem cell factor by human BM-MSCs. IFN-γ-treated BM-MSCs drive HSPCs toward myeloid commitment in vitro, but impair subsequent differentiation of HSPC. Moreover, IFN-γ-ARE-Del mice with increased IFN-γ production specifically lose their BM-MSCs, which correlates with a loss of hematopoietic stem cells' quiescence. Although IFN-γ treatment enhances the immunomodulatory function of MSCs in a clinical setting, we conclude that IFN-γ negatively affects maintenance of BM-MSCs and their hematopoietic support in vitro and in vivo.

Recovery of Donor Hematopoiesis after Graft Failure and Second Hematopoietic Stem Cell Transplantation with Intraosseous Administration of Mesenchymal Stromal Cells

Multipotent mesenchymal stromal cells (MSCs) participate in the formation of bone marrow niches for hematopoietic stem cells. Donor MSCs can serve as a source of recovery for niches in patients with graft failure (GF) after allogeneic bone marrow (BM) transplantation. Since only few MSCs reach the BM after intravenous injection, MSCs were implanted into the iliac spine. For 8 patients with GF after allo-BMT, another hematopoietic stem cell transplantation with simultaneous implantation of MSCs from their respective donors into cancellous bone was performed. BM was aspirated from the iliac crest of these patients at 1-2, 4-5, and 9 months after the intraosseous injection of donor MSCs. Patients' MSCs were cultivated, and chimerism was determined. In 6 out of 8 patients, donor hematopoiesis was restored. Donor cells (9.4 ± 3.3%) were detected among MSCs. Thus, implanted MSCs remain localized at the site of administration and do not lose the ability to proliferate. These results suggest that MSCs could participate in the restoration of niches for donor hematopoietic cells or have an immunomodulatory effect, preventing repeated rejection of the graft. Perhaps, intraosseous implantation of MSCs contributes to the success of the second transplantation of hematopoietic stem cells and patient survival.

Basic Fibroblast Growth Factor-Anchored Multilayered Mesenchymal Cell Sheets Accelerate Periosteal Bone Formation

Cell-based regenerative therapy has the potential to repair bone injuries or large defects that are recalcitrant to conventional treatment methods, including drugs and surgery. Here, we developed a multilayered cell-based bone formation system using cells coated with fibronectin-gelatin (FN-G) nanofilms. The multilayered mesenchymal cells (MLMCs) were formed after two days of culture and were shown to express higher levels of BMP-2 and VEGF compared to monolayer cultures of MCs. The MLMCs were used as a graft material in combination with a fusion protein consisting of basic fibroblast growth factor (bFGF), polycystic kidney disease (PKD) domain, and the collagen-binding domain (CBD) of Clostridium histolyticum collagenase. In femur sites grafted with the MLMCs, significantly higher levels of callus volume and bone mineral content were observed compared to the sham controls. The callus volume and bone mineral content were further increased in femur sites grafted with bFGF-PKD-CBD/MLMCs. Taken together, these results suggest that bFGF-PKD-CBD/MLMCs, which can be simply and rapidly generated in vitro, have the potential to promote bone repair when grafted into large defect sites.

The Potential of Mesenchymal Stromal Cells as Treatment for Severe Steroid-Refractory Acute Graft-Versus-Host Disease: A Critical Review of the Literature

BACKGROUND

Acute graft-versus-host disease (GvHD) is a major complication after allogeneic hematopoietic stem cell transplantation which causes high morbidity and mortality among patients who do not respond to steroid treatment. Mesenchymal stromal cells (MSCs) have immune modulatory abilities and earned their place in the treatment of GvHD after a pediatric patient remarkably recovered from steroid-refractory acute GvHD with MSC salvage therapy. Large, prospective clinical trials evaluating the potency of MSCs have however not been published.

METHODS

To evaluate the therapeutic potential of MSCs in the treatment of steroid-refractory acute GvHD, we conducted a systematic literature search. We included all studies that focused on MSC treatment of adult allogeneic hematopoietic stem cell transplantation recipients with grades III to IV steroid-refractory acute GvHD and were transparent about their methods and patient selection criteria.

RESULTS

From a total of 255 articles, 9 articles met the quality criteria for this study. The proportion of patients achieving complete resolution of all symptoms (complete response, CR) varied between 8% and 83%. Four of the 9 studies reported CR rates above 50%. The GvHD grade at the time of treatment was identified as a predictor of clinical response. Interestingly, complete response but not partial response to MSCs was associated with overall survival. No serious side effects of MSC therapy were reported.

CONCLUSIONS

MSC treatment does improve the outcome in steroid-refractory acute GvHD patients but well-designed, prospective randomized clinical trials are needed to confirm the potential of MSCs as salvage therapy for steroid-refractory GvHD and to identify those patients that will benefit most.

Microfracture combined with functional pig peritoneum-derived acellular matrix for cartilage repair in rabbit models

Due to avascular and hypocellular nature of cartilage, repair of articular cartilage defects within synovial joints still poses a significant clinical challenge. To promote neocartilage properties, we established a functional scaffold named APM-E7 by conjugating a bone marrow-derived mesenchymal stem cell (BM-MSC) affinity peptide (E7) onto the acellular peritoneum matrix (APM). During in vitro culture, the APM-E7 scaffold can support better proliferation as well as better differentiation into chondrocytes of BM-MSCs. After implanting into cartilage defects in rabbits for 24weeks, compared with microfracture and APM groups, the APM-E7 scaffolds exhibited superior quality of neocartilage without transplant rejection, according to general observations, histological assessment, synovial fluid analysis, magnetic resonance imaging (MRI) and nanomechanical properties. This APM-E7 scaffold provided a scaffold for cell attachment, which was crucial for cartilage regeneration. Overall, the APM-E7 is a promising biomaterial with low immunogenicity for one-step cartilage repair by promoting autologous connective tissue progenitor (CTP) attachment.

STATEMENT OF SIGNIFICANCE

We report the one-step transplantation of functional acellular peritoneum matrix (APM-E7) with specific mesenchymal stem cell recruitment to repair rabbit cartilage injury. The experimental results illustrated that the APM-E7 scaffold was successfully fabricated, which could specifically recruit MSCs and fill the cartilage defects in the femoral trochlear of rabbits at 24weeks post-surgery. The repaired tissue was hyaline cartilage, which exhibited ideal mechanical stability. The APM-E7 biomaterial could provide scaffold for MSCs and improve cell homing, which are two key factors required for cartilage tissue engineering, thereby providing new insights into cartilage tissue engineering.

Highly Efficient In Vitro Reparative Behaviour of Dental Pulp Stem Cells Cultured with Standardised Platelet Lysate Supplementation

Dental pulp is an accessible source of multipotent mesenchymal stromal cells (MSCs). The perspective role of dental pulp stem cells (DPSCs) in regenerative medicine demands an in vitro expansion and in vivo delivery which must deal with the safety issues about animal serum, usually required in cell culture practice. Human platelet lysate (PL) contains autologous growth factors and has been considered as valuable alternative to fetal bovine serum (FBS) in cell cultures. The optimum concentration to be added of such supplement is highly dependent on its preparation whose variability limits comparability of results. By in vitro experiments, we aimed to evaluate a standardised formulation of pooled PL. A low selected concentration of PL (1%) was able to support the growth and maintain the viability of the DPSCs. The use of PL in cell cultures did not impair cell surface signature typically expressed by MSCs and even upregulated the transcription of Sox2. Interestingly, DPSCs cultured in presence of PL exhibited a higher healing rate after injury and are less susceptible to toxicity mediated by exogenous H₂O₂ than those cultured with FBS. Moreover, PL addition was shown as a suitable option for protocols promoting osteogenic and chondrogenic differentiation of DPSCs. Taken together, our results indicated that PL is a valid substitute of FBS to culture and differentiate DPSCs for clinical-grade use.

Hypoxia and low-dose inflammatory stimulus synergistically enhance bone marrow mesenchymal stem cell migration

OBJECTIVES

Cell migration is necessary for numerous physiological cell processes. Although either inflammatory or hypoxic stimuli of certain dose and duration have positive influence on cell migration, their combination has not been shown to result in a synergistic effect.

MATERIALS AND METHODS

In this study, we investigated combined effects of hypoxia and low-dose inflammatory stimulus (one-tenth of that of a previously used concentration) on migration of human bone marrow-derived mesenchymal stem cells (BMMSCs).

RESULTS

Our results from real-time PCR, Western blot analysis and an immunofluorescence assay, showed that dual stimulation up-regulated CXCR4 expression. Based on tablet scratch experimentation and transwell assay, the dual stimuli exhibited greater positive effects on cell migration than a single inflammatory or hypoxic stimulus. When effects of various pre-treatments on cell proliferation, differentiation and immunosuppression were screened, cells subjected to the hypoxic stimulus or dual stimuli had increased cell proliferation, while short-term inflammatory stimulus and/or hypoxic stimulus had no negative effect on cell differentiation and immunosuppression.

CONCLUSIONS

These findings suggest that the combination of hypoxia and low-dose inflammatory stimuli enhances the potential of BMMSCs to migrate, thus identifying cell pre-treatment conditions that could enhance future stem cell-based therapeutics.

[Investigational Study of Mesenchymal Stem Cells on Lung Cancer Cell Proliferation and Invasion]

背景与目的

间充质干细胞(mesenchymal stem cells, MSC)是来源于中胚层的成体干细胞。有文献报道MSC通过向肿瘤组织的归巢和向间质成分分化，改变肿瘤微环境，影响肿瘤的生长和转移。但MSC在非小细胞肺癌(non-small cell lung cancer, NSCLC)中的作用报道较少，且不一致。本研究旨在探讨MSC向NSCLC细胞的趋化能力，以及其对NSCLC细胞的增殖和侵袭能力的作用。

方法

Transwell法检测MSC向肺癌细胞迁移能力，Thymidine嵌入实验检测MSC条件培养液对肺癌细胞增殖能力的影响，Real-time PCR法检测肺癌/MSC共培养后MSC表达白介素(interleukin-6, IL-6)、胰岛素样生长因子(insulinlike growth factor, IGF-1)、血管内皮生长因子(vascular endothelial growth factor, VEGF)和Dickkopf相关蛋白1(dickkopf-related protein 1, DKK1)的变化。建立人肺癌A549细胞裸鼠皮下荷瘤模型，给予MSC细胞，定期测量肿瘤体积变化。

结果

MSC可以向肺癌细胞趋化运动，其条件培养液可以促进肺癌细胞的增殖能力。肺癌细胞反过来可以促进MSC过表达IL-6、IGF-1、VEGF和DKK1。体内试验显示MSC注射组的肿瘤体积明显大于对照组。

结论

MSC可以向肺癌细胞趋化并促进肺癌的生长。反过来，肺癌细胞可以刺激MSC过表达生长因子进一步促进肿瘤生长。

Secreted trophic factors of mesenchymal stem cells support neurovascular and musculoskeletal therapies

Adult mesenchymal stem cells (MSCs) represent a subject of intense experimental and biomedical interest. Recently, trophic activities of MSCs have become the topic of a number of revealing studies that span both basic and clinical fields. In this review, we focus on recent investigations that have elucidated trophic mechanisms and shed light on MSC clinical efficacy relevant to musculoskeletal applications. Innate differences due to MSC sourcing may play a role in the clinical utility of isolated MSCs. Pain management, osteochondral, nerve, or blood vessel support by MSCs derived from both autologous and allogeneic sources have been examined. Recent mechanistic insights into the trophic activities of these cells point to ultimate regulation by nitric oxide, nuclear factor-kB, and indoleamine, among other signaling pathways. Classic growth factors and cytokines-such as VEGF, CNTF, GDNF, TGF-β, interleukins (IL-1β, IL-6, and IL-8), and C-C ligands (CCL-2, CCL-5, and CCL-23)-serve as paracrine control molecules secreted or packaged into extracellular vesicles, or exosomes, by MSCs. Recent studies have also implicated signaling by microRNAs contained in MSC-derived exosomes. The response of target cells is further regulated by their microenvironment, involving the extracellular matrix, which may be modified by MSC-produced matrix metalloproteinases (MMPs) and tissue inhibitor of MMPs. Trophic activities of MSCs, either resident or introduced exogenously, are thus intricately controlled, and may be further fine-tuned via implant material modifications. MSCs are actively being investigated for the repair and regeneration of both osteochondral and other musculoskeletal tissues, such as tendon/ligament and meniscus. Future rational and effective MSC-based musculoskeletal therapies will benefit from better mechanistic understanding of MSC trophic activities, for example using analytical "-omics" profiling approaches.

Effects of short-term inflammatory and/or hypoxic pretreatments on periodontal ligament stem cells: in vitro and in vivo studies

In this study, we extensively screened the in vitro and in vivo effects of PDLSCs following short-term inflammatory and/or hypoxic pretreatments. We found that the 24-h hypoxic pretreatment of PDLSCs significantly enhanced cell migration and improved cell surface CXCR4 expression. In addition, hypoxia-pretreated PDLSCs exhibited improved cell colony formation and proliferation. Cells that were dually stimulated also formed more colonies compared to untreated cells but their proliferation did not increase. Importantly, the hypoxic pretreatment of PDLSCs enhanced cell differentiation as determined by elevated RUNX-2 and ALP protein expression. In this context, the inflammatory stimulus impaired cell OCN protein expression, while dual stimuli led to decreased RUNX-2 and OCN mRNA levels. Although preconditioning PDLSCs with inflammatory and/or hypoxic pretreatments resulted in no differences in the production of matrix proteins, hypoxic pretreatment led to the generation of thicker cell sheets; the inflammatory stimulus weakened the ability of cells to form sheets. All the resultant cell sheets exhibited clear bone regeneration following ectopic transplantation as well as in periodontal defect models; the amount of new bone formed by hypoxia-preconditioned cells was significantly greater than that formed by inflammatory stimulus- or dual-stimuli-treated cells or by nonpreconditioned cells. The regeneration of new cementum and periodontal ligaments was only identified in the hypoxia-stimulus and no-stimulus cell groups. Our findings suggest that PDLSCs that undergo short-term hypoxic pretreatment show improved cellular behavior in vitro and enhanced regenerative potential in vivo. The preconditioning of PDLSCs via combined treatments or an inflammatory stimulus requires further investigation.

LL-37 stimulates the functions of adipose-derived stromal/stem cells via early growth response 1 and the MAPK pathway

Background

LL-37 is a naturally occurring antimicrobial peptide found in the wound bed and assists wound repair. No published study has characterized the role of LL-37 in the function(s) of human mesenchymal stem cells (MSCs). This study investigated the functions of adipose-derived stromal/stem cells (ASCs) activated by LL-37 by performing both in vitro assays with cultured cells and in vivo assays with C57BL/6 mice with hair loss.

Methods

Human ASCs were isolated from healthy donors with written informed consent. To examine the effects of LL-37 on ASC function, cell proliferation and migration were measured by a cell counting kit (CCK-8) and a Transwell migration assay. Early growth response 1 (EGR1) mRNA expression was determined by microarray and real-time PCR analyses. The protein levels of EGR1 and regenerative factors were analyzed by specific enzyme-linked immunosorbent assays and western blotting.

Results

LL-37 treatment enhanced the proliferation and migration of human ASCs expressing formyl peptide receptor like-1. Microarray and real-time PCR data showed that EGR1 expression was rapidly and significantly increased by LL-37 treatment. LL-37 treatment also enhanced the production of EGR1. Moreover, small interfering RNA-mediated knockdown of EGR1 inhibited LL-37-enhanced ASC proliferation and migration. Activation of mitogen-activated protein kinases (MAPKs) was essential not only for LL-37-enhanced ASC proliferation and migration but also EGR1 expression; treatment with a specific inhibitor of extracellular signal-regulated kinase, p38, or c-Jun N-terminal kinase blocked the stimulatory effect of LL-37. EGR1 has a strong paracrine capability and can influence angiogenic factors in ASCs; therefore, we evaluated the secretion levels of vascular endothelial growth factor, thymosin beta-4, monocyte chemoattractant protein-1, and stromal cell-derived factor-1. LL-37 treatment increased the secretion of these regenerative factors. Moreover, treatment with the conditioned medium of ASCs pre-activated with LL-37 strongly promoted hair growth in vivo.

Conclusions

These findings show that LL-37 increases EGR1 expression and MAPK activation, and that preconditioning of ASCs with LL-37 has a strong potential to promote hair growth in vivo. This study correlates LL-37 with MSC functions (specifically those of ASCs), including cell expansion, cell migration, and paracrine actions, which may be useful in terms of implantation for tissue regeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0313-4) contains supplementary material, which is available to authorized users.

Chinese preparation Xuesaitong promotes the mobilization of bone marrow mesenchymal stem cells in rats with cerebral infarction

After cerebral ischemia, bone marrow mesenchymal stem cells are mobilized and travel from the bone marrow through peripheral circulation to the focal point of ischemia to initiate tissue regeneration. However, the number of bone marrow mesenchymal stem cells mobilized into peripheral circulation is not enough to exert therapeutic effects, and the method by which blood circulation is promoted to remove blood stasis influences stem cell homing. The main ingredient of Xuesaitong capsules is Panax notoginseng saponins, and Xuesaitong is one of the main drugs used for promoting blood circulation and removing blood stasis. We established rat models of cerebral infarction by occlusion of the middle cerebral artery and then intragastrically administered Xuesaitong capsules (20, 40 and 60 mg/kg per day) for 28 successive days. Enzyme-linked immunosorbent assay showed that in rats with cerebral infarction, middle- and high-dose Xuesaitong significantly increased the level of stem cell factors and the number of CD117-positive cells in plasma and bone marrow and significantly decreased the number of CD54- and CD106-positive cells in plasma and bone marrow. The effect of low-dose Xuesaitong on these factors was not obvious. These findings demonstrate that middle- and high-dose Xuesaitong and hence Panax notoginseng saponins promote and increase the level and mobilization of bone marrow mesenchymal stem cells in peripheral blood.

Allogeneic Mesenchymal Stem Cells in Combination with Hyaluronic Acid for the Treatment of Osteoarthritis in Rabbits

Mesenchymal stem cell (MSC)-based therapies may aid in the repair of articular cartilage defects. The purpose of this study was to investigate the effects of intraarticular injection of allogeneic MSCs in an in vivo anterior cruciate ligament transection (ACLT) model of osteoarthritis in rabbits. Allogeneic bone marrow-derived MSCs were isolated and cultured under hypoxia (1% O2). After 8 weeks following ACLT, MSCs suspended in hyaluronic acid (HA) were injected into the knees, and the contralateral knees were injected with HA alone. Additional controls consisted of a sham operation group as well as an untreated osteoarthritis group. The tissues were analyzed by macroscopic examination as well as histologic and immunohistochemical methods at 6 and 12 weeks post-transplantation. At 6 and 12 weeks, the joint surface showed less cartilage loss and surface abrasion after MSC injection as compared to the tissues receiving HA injection alone. Significantly better histological scores and cartilage content were observed with the MSC transplantation. Furthermore, engraftment of allogenic MSCs were evident in surface cartilage. Thus, injection of the allogeneic MSCs reduced the progression of osteoarthritis in vivo.

Morphology and surface chemistry of bicomponent scaffolds in terms of mesenchymal stromal cell viability

Biological interaction between cells and scaffolds is mediated through events at surfaces. Proteins present in the culture medium adsorb on substrates, generating a protein adlayer that triggers further downstream events governing cell adhesion. Polymer blends often combine the properties of the individual components, for example, can provide mechanical as well as surface properties in one fibre. Therefore, mixtures of synthetic polycaprolactone and gelatin as a denatured form of collagen were electrospun at selected conditions and polymer weight ratios. Fibre morphologies and chemical properties of the surfaces were analysed. These scaffolds were seeded with human mesenchymal stromal cells and their viability was studied. Gelatin addition to polycaprolactone leads to a reduction in fibre diameter. A linear increase in gelatin at the fibre surface was observed in function of the weighed polymers, except for polycaprolactone/gelatin fibres incorporating equal weight ratios. Thereby, a depletion of gelatin at the fibre surface is stated for equally mixed polymers. The depletion of gelatin at the fibre surface is most probably due to hydrophobic interactions between hydrophobic segments of polycaprolactone and gelatin, affecting the spinning mechanism and thus fibre structure. Furthermore, polycaprolactone/gelatin blends show enhanced wettability properties compared to pure gelatin, at least partly due to molecular segregation. Results of in vitro studies reveal an increase in cellular viability and proliferation for cells cultivated on nanofibres containing gelatin, caused by the cell-attractive surface composition as well as the hydrophilic nature of the scaffolds. Contact guidance of cells seeded on parallelised fibres is observed, and DNA tests show evidently enhanced cell numbers on nanofibres containing 20 wt% of gelatin.

Autotaxin-LPA axis regulates hMSC migration by adherent junction disruption and cytoskeletal rearrangement via LPAR1/3-dependent PKC/GSK3β/β-catenin and PKC/Rho GTPase pathways

Bioactive molecules and stem cell-based regenerative engineering is emerging a promising approach for regenerating tissues. Autotaxin (ATX) is a key enzyme that regulates lysophosphatidic acid (LPA) levels in biological fluids, which exerts a wide range of cellular functions. However, the biological role of ATX in human umbilical cord blood-derived mesenchymal stem cells (hMSCs) migration remains to be fully elucidated. In this study, we observed that hMSCs, which were stimulated with LPA, accelerated wound healing, and LPA increased the migration of hMSCs into a wound site in a mouse skin wound healing model. In an experiment to investigate the effect of LPA on hMSC migration, ATX and LPA increased hMSC migration in a dose-dependent manner, and LPA receptor 1/3 siRNA transfections inhibited the ATX-induced cell migration. Furthermore, LPA increased Ca(2+) influx and PKC phosphorylation, which were blocked by Gαi and Gαq knockdown as well as by Ptx pretreatment. LPA increased GSK3β phosphorylation and β-catenin activation. LPA induced the cytosol to nuclear translocation of β-catenin, which was inhibited by PKC inhibitors. LPA stimulated the binding of β-catenin on the E-box located in the promoter of the CDH-1 gene and decreased CDH-1 promoter activity. In addition, the ATX and LPA-induced increase in hMSC migration was blocked by β-catenin siRNA transfection. LPA-induced PKC phosphorylation is also involved in Rac1 and CDC42 activation, and Rac1 and CDC42 knockdown abolished LPA-induced F-actin reorganization. In conclusion, ATX/LPA stimulates the migration of hMSCs through LPAR1/3-dependent E-cadherin reduction and cytoskeletal rearrangement via PKC/GSK3β/β-catenin and PKC/Rho GTPase pathways.

Current status of pluripotent stem cells: moving the first therapies to the clinic

Pluripotent stem cells (PSCs) hold great promise for drug discovery and regenerative medicine owing to their ability to differentiate into any cell type in the body. After more than three decades of research, including delays due to the potential tumorigenicity of PSCs and inefficiencies in differentiation methods, the field is at a turning point, with a number of clinical trials across the globe now testing PSC-derived products in humans. Ocular diseases dominate these first-in-man trials, and Phase l/ll results are showing promising safety data as well as possible efficacy. In addition, the advent of induced PSC (iPSC) technology is enabling the development of a wide range of cell-based disease models from genetically predisposed patients, thereby facilitating drug discovery. In this Review, we discuss the recent progress and remaining challenges for the use of PSCs in regenerative medicine and drug development.

Migrational changes of mesenchymal stem cells in response to cytokines, growth factors, hypoxia, and aging

Mesenchymal stem cells (MSCs) are non-immunogenic, multipotent cells with at least trilineage differentiation potential. They promote wound healing, improve regeneration of injured tissue, and mediate numerous other health effects. MSCs migrate to sites of injury and stimulate repair either through direct differentiation or indirectly through the stimulation of endogenous repair mechanisms. Using the in vitro scratch assay, we show that the inflammatory cytokines, chemokines, and growth factors TNF-α, SDF-1, PDGF, and bFGF enhance migration of rat MSCs under normoxic conditions, while TNF-α, IFN-γ, PDGF, and bFGF promote MSC migration under hypoxic conditions. This indicates that the oxygen concentration affects how MSCs will migrate in response to specific factors and, consistent with this, differential expression of cytokines was observed under hypoxic versus normoxic conditions. Using the transwell migration assay, we find that TNF-α, IFN-γ, bFGF, IGF-1, PDGF, and SDF-1 significantly increase transmigration of rat MSCs compared to unstimulated medium. MSCs derived from aged rats exhibited comparable migration to MSCs derived from young rats under hypoxic and normoxic conditions, even after application with specific factors. Similarly, migration in MSCs from aged, human donors did not statistically differ compared to migration in MSCs derived from human umbilical cord tissue or younger donors.

Trophic Effects and Regenerative Potential of Mobilized Mesenchymal Stem Cells from Bone Marrow and Adipose Tissue as Alternative Cell Sources for Pulp/Dentin Regeneration

Dental pulp stem cell (DPSC) subsets mobilized by granulocyte-colony-stimulating factor (G-CSF) are safe and efficacious for complete pulp regeneration. The supply of autologous pulp tissue, however, is very limited in the aged. Therefore, alternative sources of mesenchymal stem/progenitor cells (MSCs) are needed for the cell therapy. In this study, DPSCs, bone marrow (BM), and adipose tissue (AD)-derived stem cells of the same individual dog were isolated using G-CSF-induced mobilization (MDPSCs, MBMSCs, and MADSCs). The positive rates of CXCR4 and G-CSFR in MDPSCs were similar to MADSCs and were significantly higher than those in MBMSCs. Trophic effects of MDPSCs on angiogenesis, neurite extension, migration, and anti-apoptosis were higher than those of MBMSCs and MADSCs. Pulp-like loose connective tissues were regenerated in all three MSC transplantations. Significantly higher volume of regenerated pulp and higher density of vascularization and innervation were observed in response to MDPSCs compared to MBMSC and MADSC transplantation. Collagenous matrix containing dentin sialophosphoprotein ( DSPP)-positive odontoblast-like cells was the highest in MBMSCs and significantly higher in MADSCs compared to MDPSCs. MBMSCs and MADSCs, therefore, have potential for pulp regeneration, although the volume of regenerated pulp tissue, angiogenesis, and reinnervation, were less. Thus, in conclusion, an alternative cell source for dental pulp/dentin regeneration are stem cells from BM and AD tissue.

New Tools in Experimental Cellular Therapy for the Treatment of Liver Diseases

The current standard of care for end stage liver disease is orthotopic liver transplantation (OLT). Through improvement in surgical techniques, immunosuppression, and general medical care, liver transplantation has become an effective treatment over the course of the last half-century. Unfortunately, due to the limited availability of donor organs, there is a finite limit to the number of patients who will benefit from this therapy. This review will discuss current research in experimental cellular therapies for acute, chronic, and metabolic liver failure that may be appropriate when liver transplantation is not an immediate option.

Mesenchymal stem cells from the human umbilical cord ameliorate fulminant hepatic failure and increase survival in mice

BACKGROUND

Cell therapy has been promising for various diseases. We investigated whether transplantation of human umbilical cord mesenchymal stem cells (hUCMSCs) has any therapeutic effects on D-galactosamine/lipopolysaccharide (GalN/LPS)-induced fulminant hepatic failure in mice.

METHODS

hUCMSCs isolated from human umbilical cord were cultured and transplanted via the tail vein into severe combined immune deficiency mice with GalN/LPS-induced fulminant hepatic failure. After transplantation, the localization and differentiation of hUCMSCs in the injured livers were investigated by immunohistochemical and genetic analyses. The recovery of the injured livers was evaluated histologically. The survival rate of experimental animals was analyzed by the Kaplan-Meier method and log-rank test.

RESULTS

hUCMSCs expressed high levels of CD29, CD73, CD13, CD105 and CD90, but did not express CD31, CD79b, CD133, CD34, and CD45. Cultured hUCMSCs displayed adipogenic and osteogenic differentiation potential. Hematoxylin and eosin staining revealed that transplantation of hUCMSCs reduced hepatic necrosis and promoted liver regeneration. Transplantation of hUCMSCs prolonged the survival rate of mice with fulminant hepatic failure. Polymerase chain reaction for human alu sequences showed the presence of human cells in mouse livers. Positive staining for human albumin, human alpha-fetoprotein and human cytokeratin 18 suggested the formation of hUCMSCs-derived hepatocyte-like cells in vivo.

CONCLUSIONS

hUCMSC was a potential candidate for stem cell based therapies. After transplantation, hUCMSCs partially repaired hepatic damage induced by GalN/LPS in mice. hUCMSCs engrafted into the injured liver and differentiated into hepatocyte-like cells.

Dextran-coated fluorapatite crystals doped with Yb3+/Ho3+ for labeling and tracking chondrogenic differentiation of bone marrow mesenchymal stem cells in vitro and in vivo

Upconversion fluorescent nanoparticles are becoming more widely used as imaging contrast agents, owing to their high resolution and penetration depth, and avoidance of tissue auto-fluorescence and photodamage to cells. Here, we synthesized upconversion fluorescent crystals from rare-earth Yb3+ and Ho3+ co-doped fluorapatite (FA:Yb3+/Ho3+) suitable for long-term tracking and monitoring cartilage development (chondrogenesis) in bone marrow mesenchymal stem cells (BMSCs) in vitro and in vivo. We initially determined the structure, morphology and luminescence of the products using X-ray powder diffraction, transmission electron microscopy and two-photon confocal microscopy. When excited at 980 nm, FA:Yb3+/Ho3+ crystals exhibited distinct upconversion fluorescence peaks at 543 nm and 654 nm. We then conjugated FA:Yb3+/Ho3+ crystals with dextran to enhance hydrophilicity, biocompatibility and cell penetration. Next, we employed the dextran-coated FA:Yb3+/Ho3+ crystals in labeling and tracking chondrogenic differentiation processes in BMSCs stably expressing green fluorescent protein (BMSCsGFP) in vitro and in vivo. Labeled BMSCsGFP were shown to reproducibly exhibit chondrogenic differentiation potential in RT-PCR analysis, histological assessment and immunohistochemistry. We observed continuous luminescence from the FA:Yb3+/Ho3+ upconversion crystals at 4 weeks and 12 weeks post transplantation in BMSCsGFP, while GFP fluorescence in both control and crystal-treated groups significantly decreased at 12 weeks after BMSCsGFP transplantation. We therefore demonstrate the high biocompatibility and stability of FA:Yb3+/Ho3+ crystals in tracking and monitoring BMSCs chondrogenesis in vitro and in vivo, highlighting their excellent cell labeling potential in cartilage tissue engineering.

Dexamethasone and azathioprine promote cytoskeletal changes and affect mesenchymal stem cell migratory behavior

Glucocorticoids and immunosuppressive drugs are commonly used to treat inflammatory disorders, such as inflammatory bowel disease (IBD), and despite a few improvements, the remission of IBD is still difficult to maintain. Due to their immunomodulatory properties, mesenchymal stem cells (MSCs) have emerged as regulators of the immune response, and their viability and activation of their migratory properties are essential for successful cell therapy. However, little is known about the effects of immunosuppressant drugs used in IBD treatment on MSC behavior. The aim of this study was to evaluate MSC viability, nuclear morphometry, cell polarity, F-actin and focal adhesion kinase (FAK) distribution, and cell migratory properties in the presence of the immunosuppressive drugs azathioprine (AZA) and dexamethasone (DEX). After an initial characterization, MSCs were treated with DEX (10 μM) or AZA (1 μM) for 24 hrs or 7 days. Neither drug had an effect on cell viability or nuclear morphometry. However, AZA treatment induced a more elongated cell shape, while DEX was associated with a more rounded cell shape (P < 0.05) with a higher presence of ventral actin stress fibers (P < 0.05) and a decrease in protrusion stability. After 7 days of treatment, AZA improved the cell spatial trajectory (ST) and increased the migration speed (24.35%, P < 0.05, n = 4), while DEX impaired ST and migration speed after 24 hrs and 7 days of treatment (-28.69% and -25.37%, respectively; P < 0.05, n = 4). In conclusion, our data suggest that these immunosuppressive drugs each affect MSC morphology and migratory capacity differently, possibly impacting the success of cell therapy.

Fluid-flow-induced mesenchymal stem cell migration: role of focal adhesion kinase and RhoA kinase sensors

The study of mesenchymal stem cell (MSC) migration under flow conditions with investigation of the underlying molecular mechanism could lead to a better understanding and outcome in stem-cell-based cell therapy and regenerative medicine. We used peer-reviewed open source software to develop methods for efficiently and accurately tracking, measuring and processing cell migration as well as morphology. Using these tools, we investigated MSC migration under flow-induced shear and tested the molecular mechanism with stable knockdown of focal adhesion kinase (FAK) and RhoA kinase (ROCK). Under steady flow, MSCs migrated following the flow direction in a shear stress magnitude-dependent manner, as assessed by root mean square displacement and mean square displacement, motility coefficient and confinement ratio. Silencing FAK in MSCs suppressed morphology adaptation capability and reduced cellular motility for both static and flow conditions. Interestingly, ROCK silencing significantly increased migration tendency especially under flow. Blocking ROCK, which is known to reduce cytoskeletal tension, may lower the resistance to skeletal remodelling during the flow-induced migration. Our data thus propose a potentially differential role of focal adhesion and cytoskeletal tension signalling elements in MSC migration under flow shear.

Inflammatory Chemokines MIP-1δ and MIP-3α Are Involved in the Migration of Multipotent Mesenchymal Stromal Cells Induced by Hepatoma Cells

In vivo, bone marrow-derived multipotent mesenchymal stromal cells (MSC) have been identified at sites of tumors, suggesting that specific signals mobilize and activate MSC to migrate to areas surrounding tumors. The signals and migratory mechanisms that guide MSC are not well understood. Here, we investigated the migration of human MSC induced by conditioned medium of Huh-7 hepatoma cells (Huh-7 CM). Using a transwell migration system, we showed that human MSC migration was increased in the presence of Huh-7 CM. Using a human cytokine antibody array, we detected increased levels of MIP-1δ and MIP-3α in Huh-7 CM. Recombinant chemokines MIP-1δ and MIP-3α induced MSC migration. Anti-MIP-1δ and anti-MIP-3α antibodies added to Huh-7 CM decreased MSC migration, further suggesting that MIP-1δ and MIP-3α were implicated in the Huh-7 CM-induced MSC migration. By real-time polymerase chain reaction, we observed an absence of chemokine receptors CCR2 and CXCR2 and low expression of CCR1, CCR5, and CCR6 in MSC. Expression of these chemokine receptors was not regulated by Huh-7 CM. Furthermore, matrix metalloproteinase 1 (MMP-1) expression was strongly increased in MSC after incubation with Huh-7 CM, suggesting that MSC migration depends on MMP-1 activity. The signaling pathway MAPK/ERK was activated by Huh-7 CM but its inhibition by PD98059 did not impair Huh-7 CM-induced MSC migration. Further, long-term incubation of MSC with MIP-1δ increased α-smooth muscle actin expression, suggesting its implication in the Huh-7 CM-induced evolvement of MSC into myofibroblasts. In conclusion, we report that two inflammatory cytokines, MIP-1δ and MIP-3α, are able to increase MSC migration in vitro. These cytokines might be responsible for migration and evolvement of MSC into myofibroblasts around tumors.

NR4A1 promotes PDGF-BB-induced cell colony formation in soft agar

The fibroblast mitogen platelet-derived growth factor -BB (PDGF-BB) induces a transient expression of the orphan nuclear receptor NR4A1 (also named Nur77, TR3 or NGFIB). The aim of the present study was to investigate the pathways through which NR4A1 is induced by PDGF-BB and its functional role. We demonstrate that in PDGF-BB stimulated NIH3T3 cells, the MEK1/2 inhibitor CI-1040 strongly represses NR4A1 expression, whereas Erk5 downregulation delays the expression, but does not block it. Moreover, we report that treatment with the NF-κB inhibitor BAY11-7082 suppresses NR4A1 mRNA and protein expression. The majority of NR4A1 in NIH3T3 was found to be localized in the cytoplasm and only a fraction was translocated to the nucleus after continued PDGF-BB treatment. Silencing NR4A1 slightly increased the proliferation rate of NIH3T3 cells; however, it did not affect the chemotactic or survival abilities conferred by PDGF-BB. Moreover, overexpression of NR4A1 promoted anchorage-independent growth of NIH3T3 cells and the glioblastoma cell lines U-105MG and U-251MG. Thus, whereas NR4A1, induced by PDGF-BB, suppresses cell growth on a solid surface, it increases anchorage-independent growth.

Sphingosine-1-phosphate/S1P receptors signaling modulates cell migration in human bone marrow-derived mesenchymal stem cells

The recruitment of bone marrow-derived mesenchymal stem cells (BMSCs) to damaged tissues and sites of inflammation is an essential step for clinical therapy. However, the signals regulating the motility of these cells are still not fully understood. Sphingosine-1-phosphate (S1P), a bioactive sphingolipid metabolite, is known to have a variety of biological effects on various cells. Here, we investigated the roles of S1P and S1P receptors (S1PRs) in migration of human BMSCs. We found that S1P exerted a powerful migratory action on human BMSCs. Moreover, by employing RNA interference technology and pharmacological tools, we demonstrated that S1PR1 and S1PR3 are responsible for S1P-induced migration of human BMSCs. In contrast, S1PR2 mediates the inhibition of migration. Additionally, we explored the downstream signaling pathway of the S1P/S1PRs axis and found that activation of S1PR1 or S1PR3 increased migration of human BMSCs through a G i /extracellular regulated protein kinases 1/2- (ERK1/2-) dependent pathway, whereas activation of S1PR2 decreased migration through the Rho/Rho-associated protein kinase (ROCK) pathway. In conclusion, we reveal that the S1P/S1PRs signaling axis regulates the migration of human BMSCs via a dual-directional mechanism. Thus, selective modulation of S1PR's activity on human BMSCs may provide an effective approach to immunotherapy or tissue regeneration.

Allogenic cardiomyoblasts raised from human mesenchymal stem cells in the therapy of radiation cardiomyopathy and pericarditis: case report

The use of triple systemic transplantation of cardiomyoblasts raised from the culture of allogenic bone marrow mesenchymal stem cells of a healthy donor according to the new medical technology licensed by Federal Service on Surveillance in Healthcare in the therapy of a patient with late radiation cardiomyopathy and radiation exudative pericarditis developed 45 years after radiation therapy for Hodgkin lymphoma. High efficiency of systemic transplantation of mesenchymal stem cells partially differentiated towards cardiomyocytes was demonstrated. The therapeutic effect persists for more than 2 years. Possible mechanisms of the therapeutic effect of this type of stem cells and the prospects of using cell therapy in the treatment of late radiation injuries of vital organs and tissues are discussed.

“Ins” and “Outs” of mesenchymal stem cell osteogenesis in regenerative medicine

Repair and regeneration of bone requires mesenchymal stem cells that by self-renewal, are able to generate a critical mass of cells with the ability to differentiate into osteoblasts that can produce bone protein matrix (osteoid) and enable its mineralization. The number of human mesenchymal stem cells (hMSCs) diminishes with age and ex vivo replication of hMSCs has limited potential. While propagating hMSCs under hypoxic conditions may maintain their ability to self-renew, the strategy of using human telomerase reverse transcriptase (hTERT) to allow for hMSCs to prolong their replicative lifespan is an attractive means of ensuring a critical mass of cells with the potential to differentiate into various mesodermal structural tissues including bone. However, this strategy must be tempered by the oncogenic potential of TERT-transformed cells, or their ability to enhance already established cancers, the unknown differentiating potential of high population doubling hMSCs and the source of hMSCs (e.g., bone marrow, adipose-derived, muscle-derived, umbilical cord blood, etc.) that may provide peculiarities to self-renewal, differentiation, and physiologic function that may differ from non-transformed native cells. Tissue engineering approaches to use hMSCs to repair bone defects utilize the growth of hMSCs on three-dimensional scaffolds that can either be a base on which hMSCs can attach and grow or as a means of sequestering growth factors to assist in the chemoattraction and differentiation of native hMSCs. The use of whole native extracellular matrix (ECM) produced by hMSCs, rather than individual ECM components, appear to be advantageous in not only being utilized as a three-dimensional attachment base but also in appropriate orientation of cells and their differentiation through the growth factors that native ECM harbor or in simulating growth factor motifs. The origin of native ECM, whether from hMSCs from young or old individuals is a critical factor in “rejuvenating” hMSCs from older individuals grown on ECM from younger individuals.