Isolation, culture, and osteogenic/chondrogenic differentiation of bone marrow-derived mesenchymal stem cells

Extracellular Vesicles Derived from Osteogenic-Differentiated Human Bone Marrow-Derived Mesenchymal Cells Rescue Osteogenic Ability of Bone Marrow-Derived Mesenchymal Cells Impaired by Hypoxia

In orthopedics, musculoskeletal disorders, i.e., non-union of bone fractures or osteoporosis, can have common histories and symptoms related to pathological hypoxic conditions induced by aging, trauma or metabolic disorders. Here, we observed that hypoxic conditions (2% O2) suppressed the osteogenic differentiation of human bone marrow-derived mesenchymal cells (hBMSC) in vitro and simultaneously increased reactive oxygen species (ROS) production. We assumed that cellular origin and cargo of extracellular vesicles (EVs) affect the osteogenic differentiation capacity of hBMSCs cultured under different oxygen pressures. Proteomic analysis revealed that EVs isolated from osteogenic differentiated hBMSC cultured under hypoxia (hypo-osteo EVs) or under normoxia (norm-osteo EVs) contained distinct protein profiles. Extracellular matrix (ECM) components, antioxidants and pro-osteogenic proteins were decreased in hypo-osteo EVs. The proteomic analysis in our previous study revealed that under normoxic culture conditions, pro-osteogenic proteins and ECM components have higher concentrations in norm-osteo EVs than in EVs derived from naïve hBMSCs (norm-naïve EVs). When selected for further analysis, five anti-hypoxic proteins were significantly upregulated (response to hypoxia) in norm-osteo EVs. Three of them are characterized as antioxidant proteins. We performed qRT-PCR to verify the corresponding gene expression levels in the norm-osteo EVs' and norm-naïve EVs' parent cells cultured under normoxia. Moreover, we observed that norm-osteo EVs rescued the osteogenic ability of naïve hBMSCs cultured under hypoxia and reduced hypoxia-induced elevation of ROS production in osteogenic differentiated hBMSCs, presumably by inducing expression of anti-hypoxic/ antioxidant and pro-osteogenic genes.

Comparison of ligamentization potential between anterior cruciate ligament-derived cells and adipose-derived mesenchymal stem cells reseeded to acellularized tendon allograft

AIMS

To test the hypothesis that reseeded anterior cruciate ligament (ACL)-derived cells have a better ability to survive and integrate into tendon extracellular matrix (ECM) and accelerate the ligamentization process, compared to adipose-derived mesenchymal stem cells (ADMSCs).

METHODS

Acellularized tibialis allograft tendons were used. Tendons were randomly reseeded with ACL-derived cells or ADMSCs. ACL-derived cells were harvested and isolated from remnants of ruptured ACLs during reconstruction surgery and cultured at passage three. Cell suspensions (200 µl) containing 2 × 106 ACL-derived cells or ADMSCs were prepared for the purpose of reseeding. At days 1, 3, and 7 post-reseeding, graft composites were assessed for repopulation with histological and immunohistochemical analysis. Matrix protein contents and gene expression levels were analyzed.

RESULTS

In the graft reseeded with ACL-derived cells, a large number of elongated cells that integrated into the matrix were evident at day 3 and day 7. However, in the graft reseeded with ADMSCs, only a small number of elongated cells were found integrated into the matrix. Immunofluorescence for Ki-67 and type I collagen confirmed the pronounced production of type I collagen by Ki-67-positive ACL-derived cells integrated into the ECM. A messenger RNA (mRNA) expression assay demonstrated significantly higher gene expression levels of types I (p = 0.013) and III (p = 0.050) collagen in the composites reseeded with ACL-derived cells than ADMSCs.

CONCLUSION

ACL-derived cells, when reseeded to acellularized tendon graft, demonstrated earlier better survival and integration in the tendon ECM and resulted in higher gene expression levels of collagen, which may be essential to the normal ligamentization process compared to ADMSCs.Cite this article: Bone Joint Res 2022;11(11):777-786.

Effects of Extracellular Vesicles from Osteogenic Differentiated Human BMSCs on Osteogenic and Adipogenic Differentiation Capacity of Naïve Human BMSCs

Osteoporosis, or steroid-induced osteonecrosis of the hip, is accompanied by increased bone marrow adipogenesis. Such a disorder of adipogenic/osteogenic differentiation, affecting bone-marrow-derived mesenchymal stem cells (BMSCs), contributes to bone loss during aging. Here, we investigated the effects of extracellular vesicles (EVs) isolated from human (h)BMSCs during different stages of osteogenic differentiation on the osteogenic and adipogenic differentiation capacity of naïve (undifferentiated) hBMSCs. We observed that all EV groups increased viability and proliferation capacity and suppressed the apoptosis of naïve hBMSCs. In particular, EVs derived from hBMSCs at late-stage osteogenic differentiation promoted the osteogenic potential of naïve hBMSCs more effectively than EVs derived from naïve hBMSCs (naïve EVs), as indicated by the increased gene expression of COL1A1 and OPN. In contrast, the adipogenic differentiation capacity of naïve hBMSCs was inhibited by treatment with EVs from osteogenic differentiated hBMSCs. Proteomic analysis revealed that osteogenic EVs and naïve EVs contained distinct protein profiles, with pro-osteogenic and anti-adipogenic proteins encapsulated in osteogenic EVs. We speculate that osteogenic EVs could serve as an intercellular communication system between bone- and bone-marrow adipose tissue, for transporting osteogenic factors and thus favoring pro-osteogenic processes. Our data may support the theory of an endocrine circuit with the skeleton functioning as a ductless gland.

Effects of Different Basal Cell Culture Media upon the Osteogenic Response of hMSCs Evaluated by 99mTc-HDP Labeling

The osteogenic differentiation of mesenchymal stem cells is now a standard procedure in modern bone tissue engineering. As this is a promising field for future clinical applications, many cell culture media exist to promote osteogenic differentiation. Prior to differentiation, cells must be expanded to obtain sufficient numbers for experiments. Little evidence is available regarding the optimal media combination for expansion and differentiation to maximize the osteogenic response. Therefore, human BM-MSCs (n = 6) were expanded in parallel in DMEM (Dulbecco’s Modified Eagle Medium) LG (Low Glucose) and α-MEM (Minimum Essential Media alpha-modification), followed by simultaneous monolayer differentiation toward the osteogenic lineage in: 1. DMEM LG (Low Glucose), 2. DMEM HG (High Glucose), 3. α-MEM, 4. “Bernese medium”, and 5. “Verfaillie medium”, with a corresponding negative control (total 20 groups). As a marker for osteogenic differentiation, hydroxyapatite was accessed using radioactive ^99mTc-HDP labeling and quantitative alizarin red staining. The results indicate that all media except “Bernese medium” are suitable for osteogenic differentiation, while there was evidence that DMEM LG is partly superior when used for expansion and differentiation of BM-hMSCs. Using “Verfaillie medium” after DMEM LG expansion led to the highest grade of osteogenic differentiation. Nevertheless, the difference was not significant. Therefore, we recommend using DMEM LG for robust osteogenic differentiation, as it is highly suitable for that purpose, economical compared to other media, and requires little preparation time.

LRP5-Mediated Lipid Uptake Modulates Osteogenic Differentiation of Bone Marrow Mesenchymal Stromal Cells

Nutritional microenvironment determines the specification of progenitor cells, and lipid availability was found to modulate osteogenesis in skeletal progenitors. Here, we investigated the implications of lipid scarcity in the osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) and the role of low-density lipoprotein receptor-related protein 5 (LRP5), a co-receptor transducing canonical Wnt/beta-catenin signals, in BMSC lipid uptake during osteogenesis. The osteogenic differentiation of murine BMSCs was suppressed by lipid scarcity and partially rescued by additional fatty acid treatment with oleate. The enhancement of osteogenesis by oleate was found to be dosage-dependent, along with the enhanced activation of beta-catenin and Wnt target genes. Conditional knockout (CKO) of Lrp5 gene in murine mesenchymal lineage using Lrp5^fl/fl;Prrx1-cre mice led to decreased bone quality and altered fat distribution in vivo. After Lrp5 ablation using adenoviral Cre-recombinase, the accumulation of lipid droplets in BMSC cytoplasm was significantly reduced, and the osteogenesis of BMSCs was suppressed. Moreover, the impaired osteogenesis due to either lipid scarcity or Lrp5 ablation could be rescued by recombinant Wnt3a protein, indicating that the osteogenesis induced by Wnt/beta-catenin signaling was independent of LRP5-mediated lipid uptake. In conclusion, lipid scarcity suppresses BMSC osteogenic differentiation. LRP5 plays a role in the uptake of lipids in BMSCs and therefore mediates osteogenic specification.

Umbilical cord-derived mesenchymal stem cells promote myeloid-derived suppressor cell enrichment by secreting CXCL1 to prevent graft-versus-host disease after hematopoietic stem cell transplantation

BACKGROUND AIMS

Human mesenchymal stem cells (MSCs) from various tissues have emerged as attractive candidates for the prevention and treatment of graft-versus-host disease (GVHD). However, the molecular machinery that defines and channels the behavior of these cells remains poorly understood.

METHODS

In this study, the authors compared the efficacy of four tissue-derived MSC types in controlling GVHD in a murine model and investigated their immunomodulatory effects.

RESULTS

Human umbilical cord-derived mesenchymal stem cells (hUCMSCs) effectively decreased the incidence and severity of GVHD, which was mediated by the enrichment of myeloid-derived suppressor cells in GVHD target tissues. RNA sequencing results showed that hUCMSCs highly expressed CXCL1.

CONCLUSIONS

These results suggest a novel prophylactic application of hUCMSCs for controlling GVHD after allogeneic hematopoietic stem cell transplantation.

Exosomes derived from bone marrow mesenchymal stem cells reverse epithelial-mesenchymal transition potentially via attenuating Wnt/β-catenin signaling to alleviate silica-induced pulmonary fibrosis

Pulmonary fibrosis induced by silica dust is an irreversible, chronic, and fibroproliferative lung disease with no effective treatment at present. BMSCs-derived exosomes (BMSCs-Exo) possess similar functions to their parent cells. In this study, we investigated the therapeutic potential and underlying molecular mechanism for BMSCs-Exo in the treatment of silica-induced pulmonary fibrosis. The rat model of experimental silicosis pulmonary fibrosis was induced with 1.0 mL of one-off infusing silica suspension using the non-exposed intratracheal instillation (50 mg/mL/rat). In vivo transplantation of BMSCs-Exo effectively alleviated silica-induced pulmonary fibrosis, including a reduction in collagen accumulation, inhibition of TGF-β1, and decreased HYP content. Treatment of BMSCs-Exo increased the expression of epithelial marker proteins including E-cadherin (E-cad) and cytokeratin19 (CK19) and reduced the expression of fibrosis marker proteins including α-Smooth muscle actin (α-SMA) after exposure to silica suspension. Furthermore, we found that BMSCs-Exo inhibited the expression of Wnt/β-catenin pathway components (P-GSK3β, β-catenin, Cyclin D1) in pulmonary fibrosis tissue. BMSCs-Exo is involved in the alleviation of silica-induced pulmonary fibrosis by reducing the level of profibrotic factor TGF-β1 and inhibiting the progression of epithelial-mesenchymal transition (EMT). Additionally, attenuation of the Wnt/β-catenin signaling pathway closely related to EMT may be one of the mechanisms involved in anti-fibrotic effects of exosomes.

Overexpression of HOXB4 Promotes Protection of Bone Marrow Mesenchymal Stem Cells Against Lipopolysaccharide-Induced Acute Lung Injury Partially Through the Activation of Wnt/β-Catenin Signaling

Purpose

Pulmonary vascular endothelial cell (EC) injury is recognized as one of the pathological factors of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Bone marrow mesenchymal stem cell (BMSC)-based cytotherapy has attracted substantial attention over recent years as a promising therapeutic approach for ALI/ARDS; however, its use remains limited due to inconsistent efficacy. Currently, gene modification techniques are widely applied to MSCs. In the present study, we aimed to investigate the effect of BMSCs overexpressing Homeobox B4 (HOXB4) on lipopolysaccharide (LPS)-induced EC injury.

Methods

We used LPS to induce EC injury and established EC-BMSC coculture system using transwell chambers. The effect of BMSCs on ECs was explored by detecting EC proliferation, apoptosis, migration, tube formation, and permeability, and determining whether the Wnt/β-catenin pathway is involved in the regulatory mechanism using XAV-939, inhibitor of Wnt/ β-catenin.

Results

As compared to BMSC^WT, BMSC^HOXB4 coculture promoted EC proliferation, migration, and tube formation after LPS stimulation and attenuated LPS-induced EC apoptosis and vascular permeability. Mechanistically, BMSC^HOXB4 coculture prevented LPS-induced EC injury by activating the Wnt/β-catenin pathway, which is partially reversible by XAV-939. When cocultured with BMSC^HOXB4, pro-inflammatory factors were dramatically decreased and anti-inflammatory factors were greatly increased in the EC medium compared to those in the LPS group (P<0.05). Additionally, when compared to BMSC^WT coculture, the BMSC^HOXB4 coculture showed an enhanced modulation of IL-6, TNF-α, and IL-10, but there was no statistically significant effect on IL-1β and IL-4.

Conclusion

Coculturing of BMSC^HOXB4 prevented LPS-induced EC injury by reversing the inactivation of the Wnt/β-catenin signaling pathway. An in vivo study remains warranted to ascertain whether engraftment of BMSC^HOXB4 can be an attractive strategy for the treatment of ALI/ARDS.

Ultrasmall Superparamagnetic Iron Oxide Labeled Silk Fibroin/Hydroxyapatite Multifunctional Scaffold Loaded With Bone Marrow-Derived Mesenchymal Stem Cells for Bone Regeneration

Numerous tissue-engineered constructs have been investigated as bone scaffolds in regenerative medicine. However, it remains challenging to non-invasively monitor the biodegradation and remodeling of bone grafts after implantation. Herein, silk fibroin/hydroxyapatite scaffolds incorporated with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles were successfully synthesized, characterized, and implanted subcutaneously into the back of nude mice. The USPIO labeled scaffolds showed good three-dimensional porous structures and mechanical property, thermal stability for bone repair. After loaded with bone marrow-derived mesenchymal stem cells (BMSCs), the multifunctional scaffolds promoted cell adhesion and growth, and facilitated osteogenesis by showing increased levels of alkaline phosphatase activity and up-regulation of osteoblastic genes. Furthermore, in vivo quantitative magnetic resonance imaging (MRI) results provided valuable information on scaffolds degradation and bone formation simultaneously, which was further confirmed by computed tomography and histological examination. These findings demonstrated that the incorporation of USPIO into BMSCs-loaded multifunctional scaffold system could be feasible to noninvasively monitor bone regeneration by quantitative MRI. This tissue engineering strategy provides a promising tool for translational application of bone defect repair in clinical scenarios.

Safety and Efficacy of Intraventricular Delivery of Bone Marrow-Derived Mesenchymal Stem Cells in Hemorrhagic Stroke Model

External ventricular drain (EVD) is used clinically to relieve intracranial pressure and occasionally to deliver medications following intracerebral hemorrhage (ICH). Mesenchymal stem cell (MSC) therapy has been shown to be neuroprotective and can induce neuroregeneration in stroke models. We evaluated the safety and efficacy of delivering MSCs intraventricularly in a rat hemorrhagic stroke model. Using autologous blood, hemorrhagic stroke was induced at specific coordinates in the right basal ganglia. After 30 minutes, rats were treated with either bone marrow-derived MSCs or a phosphate-buffered saline placebo via direct intraventricular infusion. Three dosages (2 × 10⁵/kg, 5 × 10⁵/kg, and 1 × 10⁶/kg) of MSCs were administered. Forelimb use asymmetry test was employed to evaluate functional improvement after cell therapy. At the end of the experiment, peripheral blood samples and organs were harvested; biochemistry, cytokine, and growth factor analysis and histology evaluations were performed to explore cell toxicity and cell fate, and the effects of MSC therapy on injury volume, anti-inflammation, and neurogenesis. Intraventricular administration of MSCs in ICH rat model showed improved behavior and alleviated brain damage. Additionally, treated ICH rats showed significantly reduced expression of IL-1α, IL-6, and IFN-γ. No obvious cell toxicity was noticed through blood chemistry and histology evaluation. None of the infused MSCs were detected at the end of the experiment. EVD is safe and effective to use as a method of delivering MSCs to treat ICH. Intraventricularly delivered MSCs have anti-inflammatory properties and a capacity to induce neurogenesis and improve function following ICH injury.

The therapeutic effects of bone marrow-derived mesenchymal stromal cells in the acute lung injury induced by sulfur mustard

Background

Sulfur mustard (SM) is a notorious chemical warfare agent that can cause severe acute lung injury (ALI), in addition to other lesions. Currently, effective medical countermeasures for SM are lacking. Bone marrow-derived mesenchymal stromal cells (BMSCs) possess self-renewal and multipotent differentiation capacity. BMSCs can also migrate to inflammation and injury sites and exert anti-inflammatory and tissue repair functions. Here, we report the curative effect of BMSCs on SM-induced ALI in a mouse model.

Methods

Mice BMSCs were injected into mice via the tail vein 24 h after SM exposure. The distribution of BMSCs in mice was detected by fluorescence imaging. The therapeutic potential of BMSCs was evaluated by the calculating survival rate. The effects of BMSCs on lung tissue injury and repair assessment were examined by staining with H&E and measuring the lung wet/dry weight ratio, BALF protein level, and respiratory function. The effects of BMSCs on the infiltration and phenotypic alteration of inflammatory cells were analyzed by immunohistochemistry and flow cytometry. The levels of chemokines and inflammatory cytokines were examined using the Luminex Performance Assay and ELISA. RNA interference, western blotting, and ELISA were applied to explore the role of the TLR4 signaling pathway in the anti-inflammatory effects of BMSCs. The extent of tissue repair was analyzed by ELISA, western blotting, and immunohistochemistry.

Results

Fluorescence imaging indicated that the lung is the major target organ of BMSCs after injection. The injection of BMSCs significantly improved the survival rate (p < 0.05), respiratory function, and related lung damage indexes (wet/dry weight ratio, total proteins in BALF, etc.) in mice. BMSC administration also reduced the level of pro-inflammatory cytokines, chemokines, and inflammatory cell infiltration, as well as affected the balances of M1/M2 and Th17/Treg. Furthermore, solid evidence regarding the effects of BMSCs on the increased secretion of various growth factors, the differentiation of alveolar epithelial cells, and the enhancement of cell barrier functions was also observed.

Conclusion

BMSCs displayed protective effects against SM-induced ALI by alleviating inflammation and promoting tissue repair. The present study provides a strong experimental basis in a mouse model and suggests possible application for future cell therapy.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1189-x) contains supplementary material, which is available to authorized users.

Conditioned Medium Enhances Osteogenic Differentiation of Induced Pluripotent Stem Cell-Derived Mesenchymal Stem Cells

Background

Recent studies have shown that induced pluripotent stem cells (iPSCs) could be differentiated into mesenchymal stem cells (MSCs) with notable advantages over iPSCs per se. In order to promote the application of iPSC-MSCs for osteoregenerative medicine, the present study aimed to assess the ability of murine iPSC-MSCs to differentiate into osteoblast phenotype.

Methods

Osteogenic differentiation medium, blending mouse osteoblast-conditioned medium (CM) with basic medium (BM) at ratio 3:7, 5:5 and 7:3, were administered to iPSC-MSCs, respectively. After 14 days, differentiation was evaluated by lineage-specific morphology, histological stain, quantitative reverse transcription-polymerase chain reaction and immunostaining.

Results

The osteogenesis-related genes, alp, runx2, col1 and ocn expressions suggest that culture medium consisting of CM:BM at the ratio of 3:7 enhanced the osteogenic differentiation more than other concentrations that were tested. In addition, the alkaline phosphatase activity and osteogenic marker Runx2 expression demonstrate that the combination of CM and BM significantly enhanced the osteogenic differentiation of iPSC-MSCs.

Conclusion

In summary, this study has shown that osteoblast-derived CM can dramatically enhance osteogenic differentiation of iPSC-MSCs toward osteoblasts. Results from this work will contribute to optimize the osteogenic induction conditions of iPSC-MSCs and will assist in the potential application of iPSC-MSCs for bone tissue engineering.

Bone marrow mesenchymal stromal cells attenuate silica-induced pulmonary fibrosis potentially by attenuating Wnt/β-catenin signaling in rats

BACKGROUND

Pulmonary fibrosis induced by silica dust is an irreversible, chronic, and fibroproliferative lung disease with no effective treatment at present. Previous studies have shown that early intervention with bone marrow mesenchymal stem/stromal cells (BMSCs) has positive effect on anti-pulmonary fibrosis caused by silica dust. However, early intervention using BMSCs is not practical, and the therapeutic effects of BMSCs advanced intervention on pulmonary fibrosis have rarely been reported. In this study, we investigated the effects of advanced transplantation (on the 28th day after exposure to silica suspension) of BMSCs on an established rat model of pulmonary fibrosis.

METHODS

Sprague Dawley (SD) rats were randomly divided into four groups including (1) control group (n = 6) which were normally fed, (2) silica model group (n = 6) which were exposed to silica suspension (1 mL of 50 mg/mL/rat), (3) BMSC transplantation group (n = 6) which received 1 mL BMSC suspension (2 × 10⁶ cells/mL) by tail vein injection on the 28th day after exposure to silica suspension, and (4) BMSC-CM (conditioned medium) transplantation group (n = 6) which received CM from the same cell number by tail vein injection on the 28th day after exposure to silica suspension. On the 56th day after exposure to silica suspension, we used computed tomography (CT), hematoxylin and eosin (H&E), and Masson's trichrome staining to evaluate the changes in lung tissue. We examined the expression of epithelial-mesenchymal transition (EMT) and Wnt/β-catenin pathway-related proteins in lung tissue using immunohistochemistry and western blotting.

RESULTS

Successful construction of a pulmonary fibrosis model was confirmed by H&E and Masson's trichrome staining on the 28th day after exposure to silica suspension. On the 56th day after exposure, pulmonary CT examination showed a relieving effect of BMSCs on silica-induced pulmonary fibrosis which was confirmed by H&E and Masson's trichrome staining. Treatment of BMSCs increased the expression of epithelial marker proteins including E-cadherin (E-cad) and cytokeratin19 (CK19) and reduced the expression of fibrosis marker proteins including Vimentin (Vim) and α-Smooth actin (α-SMA) after exposure to silica suspension. Furthermore, we found that Wnt/β-catenin signaling pathway is abnormally activated in silica-induced pulmonary fibrosis, and exogenous transplantation of BMSCs may attenuate their expression.

CONCLUSIONS

BMSC transplantation inhibits the EMT to alleviate silica-induced pulmonary fibrosis in rats and the anti-fibrotic effect potentially by attenuating Wnt/β-catenin signaling. ᅟ: ᅟ.

Extracellular matrix dynamics during mesenchymal stem cells differentiation

Mesenchymal stem cells (MSCs) are stromal cells that display self-renewal and multipotent differentiation capacity. The repertoire of mature cells generated ranges but is not restricted to: fat, bone and cartilage. Their potential importance for both cell therapy and maintenance of in vivo homeostasis is indisputable. Nonetheless, both their in vivo identity and use in cell therapy remain elusive. A drawback generated by this fact is that little is known about the MSC niche and how it impacts differentiation and homeostasis maintenance. Hence, the roles played by the extracellular matrix (ECM) and its main regulators namely: the Matrix Metalloproteinases (MMPs) and their counteracting inhibitors (TIMPs and RECK) upon stem cells differentiation are only now beginning to be unveiled. Here, we will focus on mesenchymal stem cells and review the main mechanisms involved in adipo, chondro and osteogenesis, discussing how the extracellular matrix can impact not only lineage commitment, but, also, their survival and potentiality. This review critically analyzes recent work in the field in an effort towards a better understanding of the roles of Matrix Metalloproteinases and their inhibitors in the above-cited events.

Magnesium enhances the chondrogenic differentiation of mesenchymal stem cells by inhibiting activated macrophage-induced inflammation

Magnesium deficiency increases the generation of pro-inflammatory cytokines, which is consistently accompanied by the sensitization of cells such as neutrophils, macrophages and endothelial cells. We investigated the potential of magnesium to regulate macrophage polarization and macrophage-induced inflammation with or without lipopolysaccharide (LPS) and interferon-γ (IFN-γ) activation and further elucidated whether these effects impact the inhibitory functions of activated macrophage-induced inflammation on cartilage regeneration. The results showed that magnesium inhibited the activation of macrophages, as indicated by a significant reduction in the percentage of CCR7-positive cells, while the percentage of CD206-positive cells decreased to a lesser degree. After activation, both pro-inflammatory and anti-inflammatory cytokines were down-regulated at the mRNA level and certain cytokines (IL-1β, IL-6 and IL-10) were decreased in the cell supernatant with the addition of magnesium. Moreover, magnesium decreased the nuclear translocation and phosphorylation of nuclear factor-κB (NF-κB) to impede its activation. A modified micromass culture system was applied to assess the effects of activated macrophage-conditioned medium with or without magnesium treatment on the chondrogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). Magnesium enhanced the chondrogenic differentiation of hBMSCs by reversing the adverse effects of activated macrophage-induced inflammation.

Toward the clinical use of circulating biomarkers predictive of bone union

Current methods for diagnosis of bone healing after treatment of trauma injuries rely on clinical findings and the use of imaging methodologies that provide conclusive results but only at mid/long-term post-intervention. In this Perspective we present and discuss incipient evidence on biomarkers that may serve for monitoring the progression of bone healing as well as predicting eventual nonunion outcomes.

Dynamic changes of epigenetic signatures during chondrogenic and adipogenic differentiation of mesenchymal stem cells

Extensive studies have been performed to clarify the processes during which mesenchymal stem cells (MSCs) differentiate into their lineage fates. In vitro differentiation of MSCs into distinct lineages have attracted the focus of a large number of clinical investigations. Although the gene expression profiling during differentiation of MSC toward bone, cartilage, and adipocytes is well established, the master regulators by which MSC fate can be controlled are not entirely determined. During differentiation of MSCs into a special cell fate, epigenetic mechanisms considered as the primary mediators that suppress the irrelevant genes and activate the genes required for a specific cell lineage. This review dedicated to addressing the changes of various epigenetic mechanisms, including DNA methylation, histone modifications, and micro-RNAs during chondrogenic and adipogenic differentiation of MSC.

Genetic modification of H2AX renders mesenchymal stromal cell-derived dopamine neurons more resistant to DNA damage and subsequent apoptosis

BACKGROUND AIMS

Aberrant production of reactive oxygen species (ROS) and its impact on the integrity of genomic DNA have been considered one of the major risk factors for the loss of dopaminergic neurons in Parkinson's disease (PD). Stem cell transplantation as a strategy to replenish new functional neurons has great potential for PD treatment. However, limited survival of stem cells post-transplantation has always been an obstacle ascribed to the existence of neurotoxic environment in PD patients.

METHODS

To improve the survival of transplanted stem cells for PD treatment, we explored a new strategy based on the function of the H2AX gene (H2A histone family, member X) in determination of DNA repair and cell apoptosis. We introduced a mutant form Y142F of H2AX into dopamine (DA) neuron-like cells differentiated from bone marrow-derived mesenchymal stromal cells (BMSCs).

RESULTS

Expression of H2AX(Y142F) renders DA neuron-like cells more resistant to DNA damage and subsequent cell death induced by ultraviolet irradiation and 1-methyl-4-phenylpyridinium (MPP+) treatment.

DISCUSSION

This is a meaningful attempt to improve the sustainability of BMSC-derived dopamine neurons under a brain neurotoxic environment. Further studies are needed to evaluate the implications of our findings in stem cell therapy for PD and related diseases.

Induced Pluripotent Stem Cells as a new Strategy for Osteogenesis and Bone Regeneration

Induced pluripotent stem (iPS) cells, possess high proliferation and differentiation ability, are now considered an attractive option for osteogenic differentiation and bone regeneration. In fact, recent discoveries have demonstrated that iPS cells can be differentiated into osteoblasts, suggesting that iPS cells have the potential to advance future bone regenerative therapies. Herein, we provide an overview of the recent findings on osteogenic characteristics and differentiation potential of iPS cells. In addition, we discuss current methods for inducing their specification towards osteogenic phenotype as well as in vivo evidence supporting the therapeutic benefit of iPS-derived osteoblasts. Finally, we describe recent findings regarding the use of iPS-derived cells for osteogenic differentiation and bone regeneration, which have indicated that these pluripotent cells represent an ideal tool for regenerative cell therapies and might contribute to the development of future bone tissue engineering.

Activation of Notch1 signalling promotes multi-lineage differentiation of c-Kit(POS)/NKX2.5(POS) bone marrow stem cells: implication in stem cell translational medicine

Introduction

Transplantation of bone marrow mesenchymal stem cells (BMSCs) can repair injured hearts. However, whether BMSC populations contain cells with cardiac stem cell characteristics is ill-defined. We report here that Notch signalling can promote differentiation of c-Kit^POS/NKX2.5^POS BMSCs into cardiomyocyte-like cells.

Methods

Total BMSCs were isolated from Sprague–Dawley rat femurs and c-Kit^POS cells were purified. c-Kit^POS/NKX2.5^POS cells were isolated by single-cell cloning, and the presence of cardiomyocyte, smooth muscle cell (SMC), and endothelial cell differentiation markers assessed by immunofluorescence staining and semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR) analysis. Levels of c-Kit and Notch1–4 in total BMSCs and c-Kit^POS/NKX2.5^POS BMSCs were quantitated by flow cytometry. Following infection with an adenovirus over-expressing Notch1 intracellular domain (NICD), total BMSCs and c-Kit^POS/NKX2.5^POS cells were assessed for differentiation to cardiomyocyte, SMC, and endothelial cell lineages by immunofluorescence staining and real-time quantitative RT-PCR. Total BMSCs and c-Kit^POS/NKX2.5^POS cells were treated with the Notch1 ligand Jagged1 and markers of cardiomyocyte, SMC, and endothelial cell differentiation were examined by immunofluorescence staining and real-time quantitative RT-PCR analysis.

Results

c-Kit^POS/NKX2.5^POS cells were present among total BMSC populations, and these cells did not express markers of adult cardiomyocyte, SMC, or endothelial cell lineages. c-Kit^POS/NKX2.5^POS BMSCs exhibited a multi-lineage differentiation potential similar to total BMSCs. Following sorting, the c-Kit level in c-Kit^POS/NKX2.5^POS BMSCs was 84.4%. Flow cytometry revealed that Notch1 was the predominant Notch receptor present in total BMSCs and c-Kit^POS/NKX2.5^POS BMSCs. Total BMSCs and c-Kit^POS/NKX2.5^POS BMSCs overexpressing NICD had active Notch1 signalling accompanied by differentiation into cardiomyocyte, SMC, and endothelial cell lineages. Treatment of total BMSCs and c-Kit^POS/NKX2.5^POS BMSCs with exogenous Jagged1 activated Notch1 signalling and drove multi-lineage differentiation, with a tendency towards cardiac lineage differentiation in c-Kit^POS/NKX2.5^POS BMSCs.

Conclusions

c-Kit^POS/NKX2.5^POS cells exist in total BMSC pools. Activation of Notch1 signalling contributed to multi-lineage differentiation of c-Kit^POS/NKX2.5^POS BMSCs, favouring differentiation into cardiomyocytes. These findings suggest that modulation of Notch1 signalling may have potential utility in stem cell translational medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0085-2) contains supplementary material, which is available to authorized users.

Osseointegrative properties of electrospun hydroxyapatite-containing nanofibrous chitosan scaffolds

Our long-term goal is to develop smart biomaterials that can facilitate regeneration of critical-size craniofacial lesions. In this study, we tested the hypothesis that biomimetic scaffolds electrospun from chitosan (CTS) will promote tissue repair and regeneration in a critical size calvarial defect. To test this hypothesis, we first compared in vitro ability of electrospun CTS scaffolds crosslinked with genipin (CTS-GP) to those of mineralized CTS-GP scaffolds containing hydroxyapatite (CTS-HA-GP), by assessing proliferation/metabolic activity and alkaline phosphatase (ALP) levels of murine mesenchymal stem cells (mMSCs). The cells' metabolic activity exhibited a biphasic behavior, indicative of initial proliferation followed by subsequent differentiation for all scaffolds. ALP activity of mMSCs, a surrogate measure of osteogenic differentiation, increased over time in culture. After 3 weeks in maintenance medium, ALP activity of mMSCs seeded onto CTS-HA-GP scaffolds was approximately two times higher than that of cells cultured on CTS-GP scaffolds. The mineralized CTS-HA-GP scaffolds were also osseointegrative in vivo, as inferred from the enhanced bone regeneration in a murine model of critical size calvarial defects. Tissue regeneration was evaluated over a 3 month period by microCT and histology (Hematoxylin and Eosin and Masson's Trichrome). Treatment of the lesions with CTS-HA-GP scaffolds induced a 38% increase in the area of de novo generated mineralized tissue area after 3 months, whereas CTS-GP scaffolds only led to a 10% increase. Preseeding with mMSCs significantly enhanced the regenerative capacity of CTS-GP scaffolds (by ∼3-fold), to 35% increase in mineralized tissue area after 3 months. CTS-HA-GP scaffolds preseeded with mMSCs yielded 45% new mineralized tissue formation in the defects. We conclude that the presence of HA in the CTS-GP scaffolds significantly enhances their osseointegrative capacity and that mineralized chitosan-based scaffolds crosslinked with genipin may represent a unique biomaterial with possible clinical relevance for the repair of critical calvarial bone defects.

Norepinephrine inhibition of mesenchymal stem cell and chondrogenic progenitor cell chondrogenesis and acceleration of chondrogenic hypertrophy

OBJECTIVE

Mesenchymal progenitor cell chondrogenesis is the biologic platform for the generation or regeneration of cartilage, but the external influence of the sympathetic nervous system on this process is not yet known. Sympathetic nerve fibers are present in articular tissue, and the sympathetic nervous system influences the musculoskeletal system by, for example, increasing osteoclastogenesis. This study was initiated to explore the role of the sympathetic neurotransmitter norepinephrine (NE) in mesenchymal stem cell (MSC)-dependent and cartilage progenitor cell (CPC)-dependent chondrogenesis.

METHODS

Using human MSCs or CPCs, chondrogenic differentiation was induced in the presence of NE, the specific β-adrenergic receptor (β-AR) agonist isoproterenol, and the specific β-AR antagonist nadolol. We studied sympathetic nerve fibers, tyrosine hydroxylase (TH) expression, catecholamine biosynthesis, and synovial fluid levels in human joints, as well as cartilage-specific matrix deposition during differentiation.

RESULTS

TH+ sympathetic nerve fibers were present in the synovial tissue, meniscus, and subchondral bone marrow. In addition, synovial fluid from patients with knee trauma demonstrated high concentrations of NE. During MSC or CPC chondrogenesis, β-AR were expressed. Chondrogenic aggregates treated with NE or isoproterenol synthesized lower amounts of type II collagen and glycosaminoglycans. NE and isoproterenol treatment dose-dependently increased the levels of cartilage hypertrophy markers (type X collagen and matrix metalloproteinase 13). Nadolol reversed the inhibition of chondrogenesis and the up-regulation of cartilage hypertrophy.

CONCLUSION

Our findings demonstrate NE-dependent inhibition of chondrogenesis and acceleration of hypertrophic differentiation. By inhibiting cartilage repair, these sympathetic influences can be important after joint trauma. These findings may be a basis for novel neurochondrogenic therapeutic options.

Comprehensive characterization of four different populations of human mesenchymal stem cells as regards their immune properties, proliferation and differentiation

In the present study, we compared mesenchymal stem cells (MSCs) derived from 4 different sources, human bone marrow (BM), adipose tissue (AT), umbilical cord Wharton's Jelly (WJ) and the placenta (PL), in order to determine which population of MSCs displayed the most prominent immunosuppressive effects on phytohemagglutinin-induced T cell proliferation, and which one had the highest proliferative and differentiation potential. MSC and T lymphocyte co-culture (mixed culture) was used to determine whether the MSCs inhibit T cell proliferation, as well as which population of MSCs has the strongest inhibitory ability. The expression of immune-related genes was analyzed by RT-PCR and RT-qPCR. The proliferation and differentiation potential of the MSCs were determined using standard methods. Following MSC and T cell co-culture, mitogen-induced T cell proliferation was effectively suppressed by all 4 populations of MSCs. This occurred through soluble factors rather than direct contact inhibition. Among the 4 populations of MSCs, the WJ-MSC has the strongest suppression effects. On immune related genes, WJ-MSC has the weakest expression of MHC II genes, TLR4, TLR3, JAG1, NOTCH2 and NOTCH3. To compare the proliferation potential, WJ-MSCs showed the most rapid growth rate followed by the AT-, PL- and BM-MSCs. As regards differentiation potential, the WJ-MSCs had the strongest osteogenetic ability followed by PL, AT and BM-MSC. AT-MSC has the strongest adipogenetic ability followed by the WJ-, BM- and PL-MSCs. These data indicated that the WJ-MSCs had the strongest immunomodulatory and immunosuppressive potential. In light of these observations, we suggest that WJ-MSCs are the most attractive cell population for use in immune cellular therapy when immunosuppressive action is required.

Mechanism of mesenchymal stem cell-induced neuron recovery and anti-inflammation

BACKGROUND AIMS

After ischemic or hemorrhagic stroke, neurons in the penumbra surrounding regions of irreversible injury are vulnerable to delayed but progressive damage as a result of ischemia and hemin-induced neurotoxicity. There is no effective treatment to rescue such dying neurons. Mesenchymal stem cells (MSCs) hold promise for rescue of these damaged neurons. In this study, we evaluated the efficacy and mechanism of MSC-induced neuro-regeneration and immune modulation.

METHODS

Oxygen-glucose deprivation (OGD) was used in our study. M17 neuronal cells were subjected to OGD stress then followed by co-culture with MSCs. Rescue effects were evaluated using proliferation and apoptosis assays. Cytokine assay and quantitative polymerase chain reaction were used to explore the underlying mechanism. Antibody and small molecule blocking experiments were also performed to further understand the mechanism.

RESULTS

We showed that M17 proliferation was significantly decreased and the rate of apoptosis increased after exposure to OGD. These effects could be alleviated via co-culture with MSCs. Tumor necrosis factor-α was found elevated after OGD stress and was back to normal levels after co-culture with MSCs. We believe these effects involve interleukin-6 and vascular endothelial growth factor signaling pathways.

DISCUSSION

Our studies have shown that MSCs have anti-inflammatory properties and the capacity to rescue injured neurons.

Mesenchymal stem cells do not prevent antibody responses against human α-L-iduronidase when used to treat mucopolysaccharidosis type I

Mucopolysaccharidosis type I (MPSI) is an autosomal recessive disease that leads to systemic lysosomal storage, which is caused by the absence of α-L-iduronidase (IDUA). Enzyme replacement therapy is recognized as the best therapeutic option for MPSI; however, high titers of anti-IDUA antibody have frequently been observed. Due to the immunosuppressant properties of MSC, we hypothesized that MSC modified with the IDUA gene would be able to produce IDUA for a long period of time. Sleeping Beauty transposon vectors were used to modify MSC because these are basically less-immunogenic plasmids. For cell transplantation, 4×10⁶ MSC-KO-IDUA cells (MSC from KO mice modified with IDUA) were injected into the peritoneum of KO-mice three times over intervals of more than one month. The total IDUA activities from MSC-KO-IDUA before cell transplantation were 9.6, 120 and 179 U for the first, second and third injections, respectively. Only after the second cell transplantation, more than one unit of IDUA activity was detected in the blood of 3 mice for 2 days. After the third cell transplantation, a high titer of anti-IDUA antibody was detected in all of the treated mice. Anti-IDUA antibody response was also detected in C57Bl/6 mice treated with MSC-WT-IDUA. The antibody titers were high and comparable to mice that were immunized by electroporation. MSC-transplanted mice had high levels of TNF-alpha and infiltrates in the renal glomeruli. The spreading of the transplanted MSC into the peritoneum of other organs was confirmed after injection of ¹¹¹In-labeled MSC. In conclusion, the antibody response against IDUA could not be avoided by MSC. On the contrary, these cells worked as an adjuvant that favored IDUA immunization. Therefore, the humoral immunosuppressant property of MSC is questionable and indicates the danger of using MSC as a source for the production of exogenous proteins to treat monogenic diseases.

The effect of bone allografts combined with bone marrow stromal cells on the healing of segmental bone defects in a sheep model

Background

The repair of large bone defects is a major orthopedic challenge because autologous bone grafts are not available in large amounts and because harvesting is often associated with donor-site morbidity. Considering that bone marrow stromal cells (BMSC) are responsible for the maintenance of bone turnover throughout life, we investigated bone repair at a site of a critically sized segmental defect in sheep tibia treated with BMSCs loaded onto allografts. The defect was created in the mid-portion of the tibial diaphysis of eight adult sheep, and the sheep were treated with ex-vivo expanded autologous BMSCs isolated from marrow aspirates and loaded onto cortical allografts (n = 4). The treated sheep were compared with control sheep that had been treated with cell-free allografts (n = 4) obtained from donors of the same breed as the receptor sheep.

Results

The healing response was monitored by radiographs monthly and by computed tomography and histology at six, ten, fourteen, and eighteen weeks after surgery. For the cell-loaded allografts, union was established more rapidly at the interface between the host bone and the allograft, and the healing process was more conspicuous. Remodeling of the allograft was complete at 18 weeks in the cell-treated animals. Histologically, the marrow cavity was reestablished, with intertrabecular spaces being filled with adipose marrow and with evidence of focal hematopoiesis.

Conclusions

Allografts cellularized with AOCs (allografts of osteoprogenitor cells) can generate great clinical outcomes to noncellularized allografts to consolidate, reshape, structurally and morphologically reconstruct bone and bone marrow in a relatively short period of time. These features make this strategy very attractive for clinical use in orthopedic bioengineering.

Repair of mandibular defects by bone marrow stromal cells expressing the basic fibroblast growth factor transgene combined with multi-pore mineralized Bio-Oss

The aim of the present study was to evaluate the effect of combining Bio‑Oss with bone marrow stromal cells (BMSCs) transfected with the basic fibroblast growth factor (bFGF) gene on bone regeneration during mandibular distraction of rabbits. BMSCs obtained from rabbits were transfected with bFGF gene‑encoding plasmids and proliferation rate and the differentiation marker alkaline phosphatase activity were measured. Following seeding into Bio‑Oss collagen and 9‑day culture in vitro, the surface morphology of the Bio‑Oss was assessed using scanning electron microscopy analysis. Three mandibular defects were induced in the lower border of the bilateral mandibular ramus in each New Zealand white rabbit (total n=6). Three scaffolds, group A (seeded with BMSCs/bFGF), B (seeded with BMSCs/pVAX1) and C (cell‑free), which had been cultured in vitro under standard cell culture conditions for 18 days, were implanted into mandibular defects under sterile conditions. Animals were sacrificed by anesthesia overdose 12 weeks following surgery and the scaffolds were extracted for bone mineral density and histological analyses. Results indicate that bFGF was successfully transfected into BMSCs. Proliferation and osteoblast differentiation of BMSCs were stimulated by bFGF in vitro. No differences were identified in surface morphology for Bio‑Oss loaded with variable groups of cells. At week 12 following implantation of Bio‑Oss scaffolds, mineralization of BMSCs in Bio‑Oss scaffolds was observed to be increased by bFGF. New bone and cartilage formation was revealed in hematoxylin and eosin‑stained sections in Bio‑Oss scaffolds and was most abundant in group A (BMSCs transfected with bFGF). In the current study, the bFGF gene was transfected into BMSCs and expressed successfully. bFGF promoted proliferation and differentiation of BMSCs in vitro and implantation of bFGF‑expressing BMSCs combined with Bio‑Oss enhanced new bone regeneration more effectively than traditional methods.