Mesenchymal stem cells for cardiac cell therapy

Insight in Hypoxia-Mimetic Agents as Potential Tools for Mesenchymal Stem Cell Priming in Regenerative Medicine

Hypoxia-mimetic agents are new potential tools in MSC priming instead of hypoxia incubators or chambers. Several pharmaceutical/chemical hypoxia-mimetic agents can be used to induce hypoxia in the tissues: deferoxamine (DFO), dimethyloxaloylglycine (DMOG), 2,4-dinitrophenol (DNP), cobalt chloride (CoCl2), and isoflurane (ISO). Hypoxia-mimetic agents can increase cell proliferation, preserve or enhance differentiation potential, increase migration potential, and induce neovascularization in a concentration- and stem cell source-dependent manner. Moreover, hypoxia-mimetic agents may increase HIF-1α, changing the metabolism and enhancing glycolysis like hypoxia. So, there is clear evidence that treatment with hypoxia-mimetic agents is beneficial in regenerative medicine, preserving stem cell capacities. These agents are not studied so wildly as hypoxia but, considering the low cost and ease of use, are believed to find application as pretreatment of many diseases such as ischemic heart disease and myocardial fibrosis and promote cardiac and cartilage regeneration. The knowledge of MSC priming is critical in evaluating safety procedures and use in clinics. In this review, similarities and differences between hypoxia and hypoxia-mimetic agents in terms of their therapeutic efficiency are considered in detail. The advantages, challenges, and future perspectives in MSC priming with hypoxia mimetic agents are also discussed.

Extracellular vesicles for tissue repair and regeneration: Evidence, challenges and opportunities

Extracellular vesicles (EVs) are biological nanoparticles naturally secreted by cells, acting as delivery vehicles for molecular messages. During the last decade, EVs have been assigned multiple functions that have established their potential as therapeutic mediators for a variety of diseases and conditions. In this review paper, we report on the potential of EVs in tissue repair and regeneration. The regenerative properties that have been associated with EVs are explored, detailing the molecular cargo they carry that is capable of mediating such effects, the signaling cascades triggered in target cells and the functional outcome achieved. EV interactions and biodistribution in vivo that influence their regenerative effects are also described, particularly upon administration in combination with biomaterials. Finally, we review the progress that has been made for the successful implementation of EV regenerative therapies in a clinical setting.

Combining stem cells in myocardial infarction: The road to superior repair?

Myocardial infarction irreversibly destroys millions of cardiomyocytes in the ventricle, making it the leading cause of heart failure worldwide. Over the past two decades, many progenitor and stem cell types were proposed as the ideal candidate to regenerate the heart after injury. The potential of stem cell therapy has been investigated thoroughly in animal and human studies, aiming at cardiac repair by true tissue replacement, by immune modulation, or by the secretion of paracrine factors that stimulate endogenous repair processes. Despite some successful results in animal models, the outcome from clinical trials remains overall disappointing, largely due to the limited stem cell survival and retention after transplantation. Extensive interest was developed regarding the combinational use of stem cells and various priming strategies to improve the efficacy of regenerative cell therapy. In this review, we provide a critical discussion of the different stem cell types investigated in preclinical and clinical studies in the field of cardiac repair. Moreover, we give an update on the potential of stem cell combinations as well as preconditioning and explore the future promises of these novel regenerative strategies.

Transplantation of Umbilical Cord-Derived Mesenchymal Stem Cells Overexpressing Lipocalin 2 Ameliorates Ischemia-Induced Injury and Reduces Apoptotic Death in a Rat Acute Myocardial Infarction Model

Myocardial infarction (MI) is a leading cause of death worldwide and requires development of efficient therapeutic strategies . Mesenchymal stem cells (MSCs) -based therapy of MI has been promising but inefficient due to undesirable microenvironment of the infarct tissue. Hence, the current study was conducted to fortify MSCs against the unfavorable microenvironment of infarct tissue via overexpression of Lipocalin 2 (Lcn2) as a cytoprotective factor. The engineered cells (Lcn2-MSCs) were transplanted to infarcted heart of a rat model of MI. According to our findings, Lcn2 overexpression resulted in increased MSCs survival in the MI tissue (p < 0.05) compared to non-engineered cells. Furthermore, the infusion of Lcn2-MSCs mitigated Left ventricle (LV) remodeling, decreased fibrosis (p < 0.0001), and reduced apoptotic death of the LVs' cells (p < 0.0001) compared to the control. Our findings suggest a potential novel therapeutic strategy for MI, however, further investigations such as safety and efficacy assessments in large animals followed by clinical trials are required.

Injectable Cell-Laden Hydrogels for Tissue Engineering: Recent Advances and Future Opportunities

Tissue engineering intends to create functionalized tissues/organs for regenerating the injured parts of the body using cells and scaffolds. A scaffold as a supporting substrate affects the cells' fate and behavior, including growth, proliferation, migration, and differentiation. Hydrogel as a biomimetic scaffold plays an important role in cellular behaviors and tissue repair, providing a microenvironment close to the extracellular matrix with adjustable mechanical and chemical features that can provide sufficient nutrients and oxygen. To enhance the hydrogel performance and compatibility with native niche, the cell-laden hydrogel is an attractive choice to mimic the function of the targeted tissue. Injectable hydrogels, due to the injectability, are ideal options for in vivo minimally invasive treatment. Cell-laden injectable hydrogels can be utilized for tissue regeneration in a noninvasive way. This article reviews the recent advances and future opportunities of cell-laden injectable hydrogels and their functions in tissue engineering. It is expected that this strategy allows medical scientists to develop a minimally invasive method for tissue regeneration in clinical settings. Impact statement Cell-laden hydrogels have been vastly utilized in biomedical application, especially tissue engineering. It is expected that this upcoming review article will be a motivation for the community. Although this strategy is still in its early stages, this concept is so alluring that it has attracted all scientists in the community and specialists at academic health centers. Certainly, this approach requires more development, and a bunch of crucial challenges have yet to be solved. In this review, we discuss this various aspects of this approach, the questions that must be answered, the expectations associated with it, and rational restrictions to develop injectable cell-laden hydrogels.

Effect of Autologous Expanded Bone Marrow Mesenchymal Stem Cells or Leukocyte-Poor Platelet-Rich Plasma in Chronic Patellar Tendinopathy (With Gap >3 mm): Preliminary Outcomes After 6 Months of a Double-Blind, Randomized, Prospective Study

BACKGROUND

Patellar tendinopathy is common. The success of traditional management, including isometric or eccentric exercises combined with shockwave therapy and even surgery, is limited. Therefore, it is important to determine whether biological treatments such as ultrasound-guided intratendinous and peritendinous injections of autologous expanded bone marrow mesenchymal stem cells (BM-MSCs) or leukocyte-poor platelet-rich plasma (Lp-PRP) improve clinical outcomes in athletic patients with patellar tendinopathy.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A prospective, double-blinded, randomized, 2-arm parallel group, active controlled, phase 1/2 single-center clinical study was performed in patients who had proximal patellar tendinopathy with a lesion >3 mm. A total of 20 participants (age 18-48 years) with pain for >4 months (mean, 23.6 months) and unresponsive to nonoperative treatments were randomized into 2 groups. Of these, 10 participants were treated with BM-MSC (20 × 10⁶ cells) and 10 with Lp-PRP. Both groups performed the same postintervention rehabilitation protocol. Outcomes included the Victorian Institute of Sport Assessment for pain (VISA-P), self-reported tendon pain during activity (visual analog scale [VAS]), muscle function by dynamometry, tendon thickness and intratendinous vascularity by ultrasonographic imaging and Doppler signal, ultrasound tissue characterization (UTC) echo type changes, and magnetic resonance imaging (MRI) T2-weighted mapping changes. Participants were followed longitudinally for 6 months.

RESULTS

The average VAS scores improved in both groups at all time points, and there was a significant reduction in pain during sporting activities (P < .05). In both groups, the average mean VISA-P scores at 6 months were significantly increased compared with baseline (66 BM-MSC group and 72.90 Lp-PRP group), with no significant differences in VAS or VISA-P scores between the groups. There were statistically significant greater improvements in tendon structure on 2-dimensional ultrasound and UTC in the BM-MSC group compared with the Lp-PRP group at 6 months. Similarly, the BM-MSC group demonstrated significant evidence of restoration of tendon structure on MRI compared with the Lp-PRP group at 6 months. Only the participants in the BM-MSC group showed evidence of normalization of tendon structure, with statistically significant differences between the groups on T2-weighted, fat-saturated sagittal and coronal scans and hypersignal in T2-weighted on spin-echo T2-weighted coronal MRI scan. Both treatments were safe, and no significant adverse events were reported in either group.

CONCLUSION

Treatment with BM-MSC or Lp-PRP in combination with rehabilitation in chronic patellar tendinopathy is effective in reducing pain and improving activity levels in active participants. Participants who received BM-MSC treatment demonstrated greater improvement in tendon structure compared with those who received Lp-PRP.

REGISTRATION

2016-001262-28 (EudraCT identifier); NCT03454737 (ClinicalTrials.gov identifier).

Targeted Therapy in Cardiovascular Disease: A Precision Therapy Era

Targeted therapy refers to exploiting the specific therapeutic drugs against the pathogenic molecules (a protein or a gene) or cells. The drug specifically binds to disease-causing molecules or cells without affecting normal tissue, thus enabling personalized and precision treatment. Initially, therapeutic drugs included antibodies and small molecules, (e.g. nucleic acid drugs). With the advancement of the biology technology and immunotherapy, the gene editing and cell editing techniques are utilized for the disease treatment. Currently, targeted therapies applied to treat cardiovascular diseases (CVDs) mainly include protein drugs, gene editing technologies, nucleic acid drugs and cell therapy. Although targeted therapy has demonstrated excellent efficacy in pre-clinical and clinical trials, several limitations need to be recognized and overcome in clinical application, (e.g. off-target events, gene mutations, etc.). This review introduces the mechanisms of different targeted therapies, and mainly describes the targeted therapy applied in the CVDs. Furthermore, we made comparative analysis to clarify the advantages and disadvantages of different targeted therapies. This overview is expected to provide a new concept to the treatment of the CVDs.

Experimental artefacts can lead to misattribution of bioactivity from soluble mesenchymal stem cell paracrine factors to extracellular vesicles

It has been demonstrated that some commonly used Extracellular Vesicle (EV) isolation techniques can lead to substantial contamination with non-EV factors. Whilst it has been established that this impacts the identification of biomarkers, the impact on apparent EV bioactivity has not been explored. Extracellular vesicles have been implicated as critical mediators of therapeutic human mesenchymal stem cell (hMSC) paracrine signalling. Isolated hMSC-EVs have been used to treat multiple in vitro and in vivo models of tissue damage. However, the relative contributions of EVs and non-EV factors have not been directly compared. The dependence of hMSC paracrine signalling on EVs was first established by ultrafiltration of hMSC-conditioned medium to deplete EVs, which led to a loss of signalling activity. Here, we show that this method also causes depletion of non-EV factors, and that when this is prevented proangiogenic signalling activity is fully restored in vitro. Subsequently, we used size-exclusion chromatography (SEC) to separate EVs and soluble proteins to directly and quantitatively compare their relative contributions to signalling. Non-EV factors were found to be necessary and sufficient for the stimulation of angiogenesis and wound healing in vitro. EVs in isolation were found to be capable of potentiating signalling only when isolated by a low-purity method, or when used at comparatively high concentrations. These results indicate a potential for contaminating soluble factors to artefactually increase the apparent bioactivity of EV isolates and could have implications for future studies on the biological roles of EVs.

Isolation and Characterization of Multipotent Canine Urine-Derived Stem Cells

Current cell-based therapies on musculoskeletal tissue regeneration were mostly determined in rodent models. However, a direct translation of those promising cell-based therapies to humans exists a significant hurdle. For solving this problem, canine has been developed as a new large animal model to bridge the gap from rodents to humans. In this study, we reported the isolation and characterization of urine-derived stem cells (USCs) from mature healthy beagle dogs. The isolated cells showed fibroblast-like morphology and had good clonogenicity and proliferation. Meanwhile, these cells positively expressed multiple markers of MSCs (CD29, CD44, CD90, and CD73), but negatively expressed for hematopoietic antigens (CD11b, CD34, and CD45). Additionally, after induction culturing, the isolated cells can be differentiated into osteogenic, adipogenic, chondrogenic, and tenogenic lineages. The successful isolation and verification of USCs from canine were useful for studying cell-based therapies and developing new treatments for musculoskeletal injuries using the preclinical canine model.

Autologous Stem Cells in Achilles Tendinopathy (ASCAT): protocol for a phase IIA, single-centre, proof-of-concept study

INTRODUCTION

Achilles tendinopathy (AT) is a cause of pain and disability affecting both athletes and sedentary individuals. More than 150 000 people in the UK every year suffer from AT.While there is much preclinical work on the use of stem cells in tendon pathology, there is a scarcity of clinical data looking at the use of mesenchymal stem cells to treat tendon disease and there does not appear to be any studies of the use of autologous cultured mesenchymal stem cells (MSCs) for AT. Our hypothesis is that autologous culture expanded MSCs implanted into an area of mid-portion AT will lead to improved pain-free mechanical function. The current paper presents the protocol for a phase IIa clinical study.

METHODS AND ANALYSIS

The presented protocol is for a non-commercial, single-arm, open-label, phase IIa proof-of-concept study. The study will recruit 10 participants and will follow them up for 6 months. Included will be patients aged 18-70 years with chronic mid-portion AT who have failed at least 6 months of non-operative management. Participants will have a bone marrow aspirate collected from the posterior iliac crest under either local or general anaesthetic. MSCs will be isolated and expanded from the bone marrow. Four to 6 weeks after the harvest, participants will undergo implantation of the culture expanded MSCs under local anaesthetic and ultrasound guidance. The primary outcome will be safety as defined by the incidence rate of serious adverse reaction. The secondary outcomes will be efficacy as measured by patient-reported outcome measures and radiological outcome using ultrasound techniques.

ETHICS AND DISSEMINATION

The protocol has been approved by the National Research Ethics Service Committee (London, Harrow; reference 13/LO/1670). Trial findings will be disseminated through peer-reviewed publications and conference presentations.

TRIAL REGISTRATION NUMBER

NCT02064062.

Self-assembling peptide hydrogel enables instant epicardial coating of the heart with mesenchymal stromal cells for the treatment of heart failure

Transplantation of mesenchymal stromal cells (MSCs) is an emerging therapy for the treatment of heart failure. However, the delivery method of MSC is currently suboptimal. The use of self-assembling peptide hydrogels, including PuraMatrix® (PM; 3-D Matrix, Ltd), has been reported for clinical hemostasis and in research models. This study demonstrates the feasibility and efficacy of an advanced approach for MSC-therapy, that is coating of the epicardium with the instantly-produced PM hydrogel incorporating MSCs (epicardial PM-MSC therapy). We optimized the conditions/procedure to produce "instant" 2PM-MSC complexes. After spreading on the epicardium by easy pipetting, the PM-MSC complex promptly and stably adhere to the beating heart. Of note, this treatment achieved more extensive improvement of cardiac function, with greater initial retention and survival of donor MSCs, compared to intramyocardial MSC injection in rat heart failure models. This enhanced efficacy was underpinned by amplified myocardial upregulation of a group of tissue repair-related genes, which led to enhanced repair of the damaged myocardium, i.e. augmented microvascular formation and reduced interstitial fibrosis. These data suggest a potential for epicardial PM-MSC therapy to be a widely-adopted treatment of heart failure. This approach may also be useful for treating diseases in other organs than the heart.

Influence of patient related factors on number of mesenchymal stromal cells reached after in vitro culture expansion for clinical treatment

BACKGROUND

Number of stromal cells injected in patients with ischaemic heart disease (IHD) may be of importance for the treatment efficacy, which in turn may be influenced by various patient-related factors. In this study, we investigate whether patient-related factors influence the number of autologous stromal cells reached after in vitro culture expansion for clinical therapy.

METHODS

Culture expansion data from 111 patients with IHD treated with autologous stromal cells in three clinical trials were used. We correlated the final cell count after two passages of cultivation with different patient factors.

RESULTS

There was a significant relation between body mass index (BMI) and the number of adipose derived stromal cells (ASCs) reached after culture expansion and for all patients included into the three studies (r = 0.375, p = .019 and r = 0.200, p = .036, respectively). Moreover, there was a significantly higher number of ASCs reached in patients with hypertension compared to those without hypertension and for all patients overall (68.8 ± 39.6 × 10⁶ vs. 39.1 ± 23.6 × 10⁶, p = .020 and 62.0 ± 55.0 × 10⁶ vs. 29.0 ± 19.3 × 10⁶, p < .001, respectively). The same tendency was seen with bone marrow derived mesenchymal stromal cells (MSCs) in patients with hypertension compared to those without hypertension (58.4 ± 61.8 × 10⁶ vs. 22.6 ± 13.3 × 10⁶, p < .001) and in males compared to females (56.4 ± 61.5 × 10⁶ vs. 30.9 ± 27.9 × 10⁶, p = .041). Moreover, a significant negative correlation between left ventricular ejection fraction and number of MSCs was found (r = -0.287, p = .017).

CONCLUSIONS

Patient related factors such as BMI, hypertension and gender may influence the number of MSCs reached after in vitro culture expansion.

Stretchable Piezoelectric Substrate Providing Pulsatile Mechanoelectric Cues for Cardiomyogenic Differentiation of Mesenchymal Stem Cells

Ex vivo induction of cardiomyogenic differentiation of mesenchymal stem cells (MSCs) before implantation would potentiate therapeutic efficacy of stem cell therapies for ischemic heart diseases because MSCs rarely undergo cardiomyogenic differentiation following implantation. In cardiac microenvironments, electric pulse and cyclic mechanical strain are sequentially produced. However, no study has applied the pulsatile mechanoelectric cues (PMEC) to stimulate cardiomyogenic differentiation of MSCs ex vivo. In this study, we developed a stretchable piezoelectric substrate (SPS) that can provide PMEC to human MSCs (hMSCs) for cardiomyogenic differentiation ex vivo. Our data showed that hMSCs subjected to PMEC by SPS underwent promoted cardiac phenotype development: cell alignment and the expression of cardiac markers (i.e., cardiac transcription factors, structural proteins, ion channel proteins, and gap junction proteins). The enhanced cardiac phenotype development was mediated by the upregulation of cardiomyogenic differentiation-related autocrine factor expression, focal adhesion kinase, and extracellular signal-regulated kinases signaling pathways. Thus, SPS providing electrical and mechanical regulation of stem cells may be utilized to potentiate hMSC therapies for myocardial infarction and provide a tool for the study of stem cell biology.

Extracellular Vesicles: Satellites of Information Transfer in Cancer and Stem Cell Biology

The generation and shedding of extracellular vesicles (EVs), including exosomes and microvesicles (MVs), by cells has emerged as a form of intercellular communication with important roles in several physiological processes and diseases such as cancer. These membrane-enclosed packets can transfer specific proteins, RNA transcripts, microRNAs, and even DNA to target cells, thereby altering their function. Despite the exponential growth of the EV field, a great deal remains unclear about the mechanisms that regulate exosome and MV biogenesis, as well as about how to isolate different classes of EVs and how to best take advantage of them for clinical applications.

Function and Therapeutic Potential of Mesenchymal Stem Cells in Atherosclerosis

Atherosclerosis is a complicated disorder and largely attributable to dyslipidaemia and chronic inflammation. Despite therapeutic advances over past decades, atherosclerosis remains the leading cause of mortality worldwide. Due to their capability of immunomodulation and tissue regeneration, mesenchymal stem cells (MSCs) have evolved as an attractive therapeutic agent in various diseases including atherosclerosis. Accumulating evidences support the protective role of MSCs in all stages of atherosclerosis. In this review, we highlight the current understanding of MSCs including their characteristics such as molecular markers, tissue distribution, migratory property, immune-modulatory competence, etc. We also summarize MSC functions in animal models of atherosclerosis. MSC transplantation is able to modulate cytokine and chemokine secretion, reduce endothelial dysfunction, promote regulatory T cell function, decrease dyslipidemia, and stabilize vulnerable plaques during atherosclerosis development. In addition, MSCs may migrate to lesions where they develop into functional cells during atherosclerosis formation. Finally, the perspectives of MSCs in clinical atherosclerosis therapy are discussed.

Enhanced neuroprotective efficacy of bone marrow mesenchymal stem cells co-overexpressing BDNF and VEGF in a rat model of cardiac arrest-induced global cerebral ischemia

Cardiac arrest-induced global cerebral ischemia injury (CA-GCII) usually leads to a poor neurological outcome without an effective treatment. Bone marrow-derived mesenchymal stem cells (BMMSCs) may provide a potential cell-based therapy against neurologic disorders through induction of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF). To optimize the neuroprotective efficacy of BMMSCs further, in this study we have derived BMMSCs, which co-overexpress both BDNF and VEGF, and tested them for the treatment of CA-GCII in a rat model. Lentiviruses that express rat BDNF exon IV or VEGF-A were created using the bicistronic shuttle vectors of pLVX-IRES-ZsGreen1 and pLVX-IRES-tdTomato, respectively. BMMSCs that were co-transduced with the engineered lentiviruses with co-overexpression of both BDNF and VEGF along with corresponding fluorescent protein reporters were injected via jugular vein of rats that just recovered from a cardiac arrest. Animals were then scored for neurofunctional deficits and examined for brain pathology and gene expression relevant to the engraftment seven days after the treatments. We demonstrate that anchorage of lentiviral vector-transduced BMMSCs, which co-overexpressed both BDNF and VEGF in the hippocampus and temporal cortex along with significantly ameliorated brain pathology and improved neurofunctional performance in CA-GCII rats after transplantation. These findings provide a proof of concept for the further validation of engineered BMMSCs for the treatment of CA-GCII patients in clinical practice in the future.

Nano-Biosensor for Monitoring the Neural Differentiation of Stem Cells

In tissue engineering and regenerative medicine, monitoring the status of stem cell differentiation is crucial to verify therapeutic efficacy and optimize treatment procedures. However, traditional methods, such as cell staining and sorting, are labor-intensive and may damage the cells. Therefore, the development of noninvasive methods to monitor the differentiation status in situ is highly desirable and can be of great benefit to stem cell-based therapies. Toward this end, nanotechnology has been applied to develop highly-sensitive biosensors to noninvasively monitor the neural differentiation of stem cells. Herein, this article reviews the development of noninvasive nano-biosensor systems to monitor the neural differentiation of stem cells, mainly focusing on optical (plasmonic) and eletrochemical methods. The findings in this review suggest that novel nano-biosensors capable of monitoring stem cell differentiation are a promising type of technology that can accelerate the development of stem cell therapies, including regenerative medicine.

Fibroblast-Derived Extracellular Matrix Induces Chondrogenic Differentiation in Human Adipose-Derived Mesenchymal Stromal/Stem Cells in Vitro

Mesenchymal stromal/stem cells (MSCs) represent an area being intensively researched for tissue engineering and regenerative medicine applications. MSCs may provide the opportunity to treat diseases and injuries that currently have limited therapeutic options, as well as enhance present strategies for tissue repair. The cellular environment has a significant role in cellular development and differentiation through cell-matrix interactions. The aim of this study was to investigate the behavior of adipose-derived MSCs (ad-MSCs) in the context of a cell-derived matrix so as to model the in vivo physiological microenvironment. The fibroblast-derived extracellular matrix (fd-ECM) did not affect ad-MSC morphology, but reduced ad-MSC proliferation. Ad-MSCs cultured on fd-ECM displayed decreased expression of integrins α2 and β1 and subsequently lost their multipotency over time, as shown by the decrease in CD44, Octamer-binding transcription factor 4 (OCT4), SOX2, and NANOG gene expression. The fd-ECM induced chondrogenic differentiation in ad-MSCs compared to control ad-MSCs. Loss of function studies, through the use of siRNA and a mutant Notch1 construct, revealed that ECM-mediated ad-MSCs chondrogenesis requires Notch1 and β-catenin signaling. The fd-ECM also showed anti-senescence effects on ad-MSCs. The fd-ECM is a promising approach for inducing chondrogenesis in ad-MSCs and chondrogenic differentiated ad-MSCs could be used in stem cell therapy procedures.

Rebuilding the Damaged Heart: Mesenchymal Stem Cells, Cell-Based Therapy, and Engineered Heart Tissue

Mesenchymal stem cells (MSCs) are broadly distributed cells that retain postnatal capacity for self-renewal and multilineage differentiation. MSCs evade immune detection, secrete an array of anti-inflammatory and anti-fibrotic mediators, and very importantly activate resident precursors. These properties form the basis for the strategy of clinical application of cell-based therapeutics for inflammatory and fibrotic conditions. In cardiovascular medicine, administration of autologous or allogeneic MSCs in patients with ischemic and nonischemic cardiomyopathy holds significant promise. Numerous preclinical studies of ischemic and nonischemic cardiomyopathy employing MSC-based therapy have demonstrated that the properties of reducing fibrosis, stimulating angiogenesis, and cardiomyogenesis have led to improvements in the structure and function of remodeled ventricles. Further attempts have been made to augment MSCs' effects through genetic modification and cell preconditioning. Progression of MSC therapy to early clinical trials has supported their role in improving cardiac structure and function, functional capacity, and patient quality of life. Emerging data have supported larger clinical trials that have been either completed or are currently underway. Mechanistically, MSC therapy is thought to benefit the heart by stimulating innate anti-fibrotic and regenerative responses. The mechanisms of action involve paracrine signaling, cell-cell interactions, and fusion with resident cells. Trans-differentiation of MSCs to bona fide cardiomyocytes and coronary vessels is also thought to occur, although at a nonphysiological level. Recently, MSC-based tissue engineering for cardiovascular disease has been examined with quite encouraging results. This review discusses MSCs from their basic biological characteristics to their role as a promising therapeutic strategy for clinical cardiovascular disease.

Oxygen cycling to improve survival of stem cells for myocardial repair: A review

Heart disease represents the leading cause of death among Americans. There is currently no clinical treatment to regenerate viable myocardium following myocardial infarction, and patients may suffer progressive deterioration and decreased myocardial function from the effects of remodeling of the necrotic myocardium. New therapeutic strategies hold promise for patients who suffer from ischemic heart disease by directly addressing the restoration of functional myocardium following death of cardiomyocytes. Therapeutic stem cell transplantation has shown modest benefit in clinical human trials with decreased fibrosis and increased functional myocardium. Moreover, autologous transplantation holds the potential to implement these therapies while avoiding the immunomodulation concerns of heart transplantation. Despite these benefits, stem cell therapy has been characterized by poor survival and low engraftment of injected stem cells. The hypoxic tissue environment of the ischemic/infracting myocardium impedes stem cell survival and engraftment in myocardial tissue. Hypoxic preconditioning has been suggested as a viable strategy to increase hypoxic tolerance of stem cells. A number of in vivo and in vitro studies have demonstrated improved stem cell viability by altering stem cell secretion of protein signals and up-regulation of numerous paracrine signaling pathways that affect inflammatory, survival, and angiogenic signaling pathways. This review will discuss both the mechanisms of hypoxic preconditioning as well as the effects of hypoxic preconditioning in different cell and animal models, examining the pitfalls in current research and the next steps into potentially implementing this methodology in clinical research trials.

Enhanced cell survival and paracrine effects of mesenchymal stem cells overexpressing hepatocyte growth factor promote cardioprotection in myocardial infarction

Poor cell survival post transplantation compromises the therapeutic benefits of mesenchymal stem cells (MSCs) in myocardial infarction (MI). Hepatocyte growth factor (HGF) is an important cytokine for angiogenesis, anti-inflammation and anti-apoptosis. This study aimed to evaluate the cardioprotective effects of MSCs overexpressing HGF in a mouse model of MI. The apoptosis of umbilical cord-derived MSCs (UC-MSCs) and HGF-UC-MSCs under normoxic and hypoxic conditions was detected. The conditioned medium (CdM) of UC-MSCs and HGF-UC-MSCs under a hypoxic condition was harvested and its protective effect on neonatal cardiomyocytes (NCMs) exposed to a hypoxic challenge was examined. UC-MSCs and HGF-UC-MSCs were transplanted into the peri-infarct region in mice following MI and heart function assessed 4 weeks post transplantation. The apoptosis of HGF-UC-MSCs under hypoxic conditions was markedly decreased compared with that of UC-MSCs. NCMs treated with HGF-UC-MSC hypoxic CdM (HGF-UC-MSCs-hy-CdM) exhibited less cell apoptosis in response to hypoxic challenge than those treated with UC-MSC hypoxic CdM (UC-MSCs-hy-CdM). HGF-UC-MSCs-hy-CdM released the inhibited p-Akt and lowered the enhanced ratio of Bax/Bcl-2 induced by hypoxia in the NCMs. HGF-UC-MSCs-hy-CdM expressed higher levels of HGF, EGF, bFGF and VEGF than UC-MSCs-hy-CdM. Transplantation of HGF-UC-MSCs or UC-MSCs greatly improved heart function in the mouse model of MI. Compared with UC-MSCs, transplantation of HGF-UC-MSCs was associated with less cardiomyocyte apoptosis, enhanced angiogenesis and increased proliferation of cardiomyocytes. This study may provide a novel therapeutic strategy for MSC-based therapy in cardiovascular disease.

Endoplasmic reticulum stress contributes to arsenic trioxide-induced intrinsic apoptosis in human umbilical and bone marrow mesenchymal stem cells

Arsenic trioxide is an old drug and has been used for a long time in traditional Chinese and Western medicines. However, the cancer treatment of arsenic trioxide has heart and vascular toxicity. The cytotoxic effects of arsenic trioxide and its molecular mechanism in human umbilical mesenchymal stem cells (HUMSC) and human bone marrow-derived mesenchymal stem cells (HMSC-bm) were investigated in this study. Our results showed that arsenic trioxide significantly reduced the viability of HUMSC and HMSC-bm in a concentration- and time-dependent manner. Arsenic trioxide is able to induce apoptotic cell death in HUMSC and HMSC-bm, as shown from the results of morphological examination, flow cytometric analyses, DAPI staining and comet assay. The appearance of arsenic trioxide also led to an increase of intracellular free calcium (Ca(2+) ) concentration and the disruption of mitochondrial membrane potential (ΔΨm). The caspase-9 and caspase-3 activities were time-dependently increased in arsenic trioxide-treated HUMSC and HMSC-bm. In addition, the proteomic analysis and DNA microarray were carried out to investigate the expression level changes of genes and proteins affected by arsenic trioxide treatment in HUMSC. Our results suggest that arsenic trioxide induces a prompt induction of ER stress and mitochondria-modulated apoptosis in HUMSC and HMSC-bm. A framework was proposed for the effect of arsenic trioxide cytotoxicity by targeting ER stress.

Proteomic Analysis of Mesenchymal Stem Cells

Mesenchymal stem or stromal cells (MSCs) are of great interest in biomedical sciences and disease treatment because of their multipotency and wide range of applications for tissue repair and suppression of the immune system. Proteomic analysis of these unique cells has contributed to the identification of important pathways utilized by MSCs to differentiate into distinct tissues as well as important proteins responsible for their special function in vivo and in vitro. However, comparison of proteomic studies in MSCs still suffers from the heterogeneity of MSC preparations. In addition, as proteomics technology advances, several studies can be revisited in order to increase the depth of analysis and, therefore, elucidate more refined mechanisms involved in MSC functionalities. Here, we present detailed protocols to obtain MSCs, as well as protocols to perform in-depth profiling and quantification of alterations in MSC proteomes.

p53-Dependent Senescence in Mesenchymal Stem Cells under Chronic Normoxia Is Potentiated by Low-Dose γ-Irradiation

Mesenchymal stem cells (MSCs) are a source of adult multipotent cells important in tissue regeneration. Murine MSCs are known to proliferate poorly in vitro under normoxia. The aim of this study is to analyze the interaction of nonphysiological high oxygen and low-dose γ-irradiation onto growth, senescence, and DNA damage. Tri-potent bone marrow-derived MSCs from p53 wildtype and p53−/− mice were cultured under either 21% or 2% O₂. Long-term observations revealed a decreasing ability of wildtype mMSCs to proliferate and form colonies under extended culture in normoxia. This was accompanied by increased senescence under normoxia but not associated with telomere shortening. After low-dose γ-irradiation, the normoxic wildtype cells further increased the level of senescence. The number of radiation-induced γH2AX DNA repair foci was higher in mMSCs kept under normoxia but not in p53−/− cells. P53-deficient MSCs additionally showed higher clonogeneity, lower senescence levels, and fewer γH2AX repair foci per cell as compared to their p53 wildtype counterparts irrespective of oxygen levels. These results reveal that oxygen levels together with γ-irradiation and p53 status are interconnected factors modulating growth capacity of BM MSCs in long-term culture. These efforts help to better understand and optimize handling of MSCs prior to their therapeutic use.

Role of angiotensin II in stem cell therapy of cardiac disease

INTRODUCTION

The renin angiotensin system (RAS) is closely related to the cardiovascular system, body fluid regulation and homeostasis.

MATERIALS AND METHODS

Despite common therapeutic methods, stem cell/progenitor cell therapy is daily increasing as a term of regenerative medicine. RAS and its pharmacological inhibitors are not only involved in physiological and pathological aspects of the cardiovascular system, but also affect the different stages of stem cell proliferation, differentiation and function, via interfering cell signaling pathways.

RESULTS

This study reviews the new role of RAS, in particular Ang II distinct from other common roles, by considering its regulating impact on the different signaling pathways involved in the cardiac and endothelial tissue, as well as in stem cell transplantation.

CONCLUSIONS

This review focuses on the impact of stem cell therapy on the cardiovascular system, the role of RAS in stem cell differentiation, and the role of RAS inhibition in cardiac stem cell growth and development.

Intraocular pressure reduction and neuroprotection conferred by bone marrow-derived mesenchymal stem cells in an animal model of glaucoma

INTRODUCTION

Glaucoma is a sight-threatening retinal neuropathy associated with elevated intraocular pressure (IOP) due to degeneration and fibrosis of the trabecular meshwork (TM). Glaucoma medications aim to reduce IOP without targeting the specific TM pathology, Bone-marrow mesenchymal stem cells (MSCs) are used today in various clinical studies. Here, we investigated the potential of MSCs therapy in an glaucoma-like ocular hypertension (OHT) model and decipher in vitro the effects of MSCs on primary human trabecular meshwork cells.

METHODS

Ocular hypertension model was performed by cauterization of 3 episcleral veins (EVC) of Long-Evans male rat eyes. MSCs were isolated from rat bone marrow, amplified in vitro and tagged with quantum dot nanocrystals. Animals were distributed as 1) MSCs group receiving 5.10(5)cells/6μl Minimum Essential Medium and 2) MEM group receiving 6μl MEM (n = 10 each). Injections were performed into the anterior chamber of 20 days-hypertensive eyes and IOP was monitored twice a week for 4 weeks. At the end of experiment, cell distribution in the anterior segment was examined in confocal microscopy on flat mounted corneas. Moreover, we tested in vitro effects of MSCs conditioned medium (MSC-CM) on primary human trabecular meshwork cells (hTM cells) using Akt activation, myosin phosphorylation and TGF-β2-dependent profibrotic phenotype in hTM cells.

RESULTS

We demonstrated a rapid and long-lasting in vivo effect of MSCs transplantation that significantly reduced IOP in hypertensive eyes induced by EVC. MSCs were located to the ciliary processes and the TM. Enumeration of RGCs on whole flat-mounted retina highlighted a protective effect of MSCs on RGCs death. In vitro, MSC-CM promotes: (i) hTM cells survival by activating the antiapoptotic pathway, Akt, (ii) hTM cells relaxation as analyzed by the decrease in myosin phosphorylation and (iii) inhibition of TGF-β2-dependent profibrotic phenotype acquisition in hTM cells.

CONCLUSIONS

MSCs injection in the ocular anterior chamber in a rat model of OHT provides neuroprotective effect in the glaucoma pathophysiology via TM protection. These results demonstrate that MSCs constitute promising tool for treating ocular hypertension and retinal cell degeneration.

Rap1-mediated nuclear factor-kappaB (NF-κB) activity regulates the paracrine capacity of mesenchymal stem cells in heart repair following infarction

Paracrine effect is the major mechanism that underlies mesenchymal stem cells (MSC)-based therapy. This study aimed to examine how Rap1, telomeric repeat-binding factor 2-interacting protein 1 (Terf2IP), which is a novel modulator involved in the nuclear factor-kappaB (NF-κB) pathway, regulates the paracrine effects of MSC-mediated heart repair following infarction. NF-κB activity of stromal cells was increased by Rap1 as measured by pNF-κB-luciferase reporter activity, and this was abolished by IkB-dominant-negative protein. Knockdown of Rap1 with shRap1 resulted in diminished translocation of p65-NF-κB from the cytoplasm to nuclei in response to tumor necrosis factor-α (TNF-α) stimulation. Compared with BM-MSCs, Rap1^−/−-BM-MSCs displayed a significantly reduced ratio of phosphorylated NF-κB to NF-κB-p65 and of Bax to Bcl-2, and increased resistance to hypoxia-induced apoptosis by the terminal deoxynucleotidal transferase-mediated dUTP nick end labeling (TUNEL) assay. In contrast, re-expression of Rap1 in Rap1^−/−-BM-MSCs resulted in loss of resistance to apoptosis in the presence of hypoxia. Moreover, absence of Rap1 in BM-MSCs led to downregulation of NF-κB activity accompanied by reduced pro-inflammatory paracrine cytokines TNF-α, IL (interleukin)-6 and monocyte chemotactic protein-1 in Rap1^−/−-BM-MSCs compared with BM-MSCs. The apoptosis of neonatal cardiomyocytes (NCMCs) induced by hypoxia was significantly reduced when cocultured with Rap1^−/−-BM-MSC hypoxic-conditioned medium (CdM). The increased cardioprotective effects of Rap1^−/−-BM-MSCs were reduced when Rap1^−/−-BM-MSCs were reconstituted with Rap1 re-expression. Furthermore, in vivo study showed that transplantation of Rap1^−/−-BM-MSCs significantly improved heart function, decreased infarct size, prevented cardiomyocyte apoptosis and inhibited inflammation compared with controls and BM-MSCs (P<0.01). This study reveals that Rap1 has a critical role in the regulation of MSC paracrine actions. Compared with BM-MSCs, Rap1^−/−-BM-MSCs decreased NF-κB sensitivity to stress-induced pro-inflammatory cytokine production and reduced apoptosis. Selective inhibition of Rap1 in BM-MSCs may be a novel strategy to enhance MSC-based therapeutic efficacy in myocardial infarction.

Transplantation of placenta-derived mesenchymal stem cells enhances angiogenesis after ischemic limb injury in mice

Mesenchymal stem cell‐based therapy has emerged as a promising approach for the treatment of peripheral arterial disease. The purpose of this study was to examine the potential effects of human placenta‐derived mesenchymal stem cells (PMSCs) on mouse hindlimb ischemia. PMSCs were isolated from human placenta tissue and characterized by flow cytometry. An in vivo surgical ligation‐induced murine limb ischemia model was generated with fluorescent dye (CM‐DiI) labelled PMSCs delivered via intramuscular injection. Our data show that PMSCs treatment significantly enhanced microvessel density, improved blood perfusion and diminished pathologies in ischemic mouse hindlimbs as compared to those in the control group. Further immunostaining studies suggested that injected PMSCs can incorporate into the vasculature and differentiate into endothelial and smooth muscle cells to enhance angiogenesis in ischemic hind limbs. This may in part explain the beneficial effects of PMSCs treatment. Taken together, we found that PMSCs treatment might be an effective treatment modality for treatment of ischemia‐induced injury to mouse hind limbs by enhancement of angiogenesis.

Myocyte renewal and therapeutic myocardial regeneration using various progenitor cells

Whereas the demand on effective treatment options for chronic heart failure is dramatically increasing, the recent recognition of physiological and pathological myocyte turnover in the adult human heart provided a fundamental basis for the therapeutic regeneration. Divergent modalities were experimentally introduced to this field, and selected ones have been applied clinically; the history began with skeletal myoblasts and bone-marrow-derived cells, and lately mesenchymal stem/stromal cells and resident cardiac cells joined the repertoire. Among them, autologous transplantation of c-kit-positive cardiac stem cells in patients with chronic ventricular dysfunction resulted in an outstanding outcome with long-lasting effects without increasing major adverse events. To further optimize currently available approaches, we have to consider multiple factors, such as the targeting disease, the cell population and number to be administered, and the timing and the route of cell delivery. Exploration of the consequence of the previous clinical trials would allow us to envision an ideal cellular therapy for various cardiovascular disorders.

Use of mesenchymal stem cells for therapy of cardiac disease

Despite substantial clinical advances over the past 65 years, cardiovascular disease remains the leading cause of death in America. The past 15 years has witnessed major basic and translational interest in the use of stem and precursor cells as a therapeutic agent for chronically injured organs. Among the cell types under investigation, adult mesenchymal stem cells are widely studied, and in early stage, clinical studies show promise for repair and regeneration of cardiac tissues. The ability of mesenchymal stem cells to differentiate into mesoderm- and nonmesoderm-derived tissues, their immunomodulatory effects, their availability, and their key role in maintaining and replenishing endogenous stem cell niches have rendered them one of the most heavily investigated and clinically tested type of stem cell. Accumulating data from preclinical and early phase clinical trials document their safety when delivered as either autologous or allogeneic forms in a range of cardiovascular diseases, but also importantly define parameters of clinical efficacy that justify further investigation in larger clinical trials. Here, we review the biology of mesenchymal stem cells, their interaction with endogenous molecular and cellular pathways, and their modulation of immune responses. Additionally, we discuss factors that enhance their proliferative and regenerative ability and factors that may hinder their effectiveness in the clinical setting.

CXCL14 and MCP1 are potent trophic factors associated with cell migration and angiogenesis leading to higher regenerative potential of dental pulp side population cells

Introduction

The release of trophic factors from mesenchymal stem cells (MSCs) is critical for tissue regeneration. A systematic investigation of the regenerative potential of trophic factors from different MSCs, however, has not been performed. Thus, in the present study, the regenerative potential of conditioned medium (CM) from dental pulp, bone marrow, and adipose tissue-derived CD31⁻ side population (SP) cells from an individual source was compared in an ectopic tooth transplantation model.

Methods

The tooth root transplantation in an ectopic site model was used for investigation of the regenerative potential and trophic effects in vivo. Either pulp CD31⁻ SP cell populations (1×10⁶ cells) at the third to fourth passage or 5 μg/ml of CM from dental pulp, bone marrow, and adipose stem cells from four different individuals were injected into the root with collagen TE. Each root was transplanted subcutaneously in 5-week-old severe combined immunodeficiency mice. Each root with surrounding tissue was harvested for histology on days 7, 21, and 28 and for Western blot analysis and real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis on day 28. Furthermore, the trophic factors responsible for the regenerative potential were identified as the upregulated genes present in pulp CD31⁻ SP cells when compared with the genes in both bone marrow and adipose CD31⁻ SP cells by using microarray analysis, real-time RT-PCR, and Western blot analysis.

Results

Transplantation of pulp CM yielded increased volume of pulp regeneration, more bromodeoxyuridine (BrdU)-positive migrated cells, and fewer caspase 3-positive cells in the regenerated pulp compared with the others. Pulp CM also demonstrated significantly increased cell migration, anti-apoptosis, and angiogenesis in C2C12 cells. Higher expression of CXCL14 and MCP1 in pulp SP cells suggested candidate trophic factors. The stimulatory effects on both migration and angiogenesis of CXCL14 and MCP1 were demonstrated in vitro. In the regenerated tissue, BrdU-positive migrated cells expressed CXCR4 and CCR2, receptors for CXCL14 and MCP1, respectively.

Conclusions

The higher regenerative potential of pulp SP cells may be due to potent trophic factors, including CXCL14 and MCP1, which promote migration and angiogenesis.

Brown adipocytes, cardiac protection and a common adipo- and myogenic stem precursor in aged human hearts

New data on adult stem cells (ASCs) are continuously added by research for use in regenerative medicine. However organ-specific ASC markers are incompletely explored. It was demonstrated that in non-cardiac brown adipose tissue (BAT) CD133+ cells differentiate in cardiomyocytes, and such BAT-derived cells induce bone marrow-derived cells into cardiomyocytes, thus being a promising source for cardiac stem cell therapy. During embryogenesis the subepicardial fat derives from BAT. Although it was not specifically investigated in human adult or aged hearts, it is actually known that metabolically active BAT can be found in many adult humans, is related to antiobesity effects, and it may derive from stem/progenitor cells. Stro-1 can safely identify in situ cardiac stem cells (CSCs) with myogenic and adipogenic potential. It was therefore raised the hypothesis of subepicardial differentiation of CSCs in BAT in adult/aged hearts, which could be viewed, such as in infants, as a mechanism of protection. This could be determined by the reactivation of an embryologic differentiation pattern in which brown adipocytes and muscle cells derive from a common stem ancestor. Such quiescent common stem ancestors could be suggested in adult, or aged, human hearts, when subepicardial BAT is found, and if a Stro-1+/CD133+/Isl-1+ phenotype of CSCs is determined.

Immuno-modification of enhancing stem cells targeting for myocardial repair

Despite the controversy in mechanism, rodent and clinical studies have demonstrated beneficial effects of stem/progenitor cell therapy after myocardial infarction (MI). In a rat ischaemic reperfusion MI model, we investigated the effects of immunomodification of CD 34⁺ cells on heart function and myocardial conduction. Bispecific antibody (BiAb), consisting of an anti-myosin light chain antibody and anti-CD45 antibody, injected intravenously was used to direct human CD34⁺ cells to injured myocardium. Results were compared to echocardiography guided intramyocardial (IM) injection of CD34⁺ cells and PBS injected intravenously. Treatment was administered 2 days post MI. Echocardiography was performed at 5 weeks and 3 months which demonstrated LV dilatation prevention and fractional shortening improvement in both the BiAb and IM injection approaches, with BiAb achieving better results. Histological analyses demonstrated a decrease in infarct size and increase in arteriogenesis in both BiAb and IM injection. Electrophysiological properties were studied 5 weeks after treatments by optical mapping. Conduction velocity (CV), action potential duration (APD) and rise time were significantly altered in the MI area. The BiAb treated group demonstrated a more normalized activation pattern of conduction and normalization of CV at shorter pacing cycle lengths. The ventricular tachycardia inducibility was lowest in the BiAb treatment group. Intravenous administration of BiAb offers an effective means of stem cell delivery for myocardial repair post-acute MI. Such non-invasive approach was shown to offer a distinct advantage to more invasive direct IM delivery.

Endothelial FoxM1 mediates bone marrow progenitor cell-induced vascular repair and resolution of inflammation following inflammatory lung injury

Adult stem cell treatment is a potential novel therapeutic approach for acute respiratory distress syndrome. Given the extremely low rate of cell engraftment, it is believed that these cells exert their beneficial effects via paracrine mechanisms. However, the endogenous mediator(s) in the pulmonary vasculature remains unclear. Using the mouse model with endothelial cell (EC)-restricted disruption of FoxM1 (FoxM1 CKO), here we show that endothelial expression of the reparative transcriptional factor FoxM1 is required for the protective effects of bone marrow progenitor cells (BMPC) against LPS-induced inflammatory lung injury and mortality. BMPC treatment resulted in rapid induction of FoxM1 expression in wild type (WT) but not FoxM1 CKO lungs. BMPC-induced inhibition of lung vascular injury, resolution of lung inflammation, and survival, as seen in WT mice, were abrogated in FoxM1 CKO mice following LPS challenge. Mechanistically, BMPC treatment failed to induce lung EC proliferation in FoxM1 CKO mice, which was associated with impaired expression of FoxM1 target genes essential for cell cycle progression. We also observed that BMPC treatment enhanced endothelial barrier function in WT but not in FoxM1-deficient EC monolayers. Restoration of β-catenin expression in FoxM1-deficient ECs normalized endothelial barrier enhancement in response to BMPC treatment. These data demonstrate the requisite role of endothelial FoxM1 in the mechanism of BMPC-induced vascular repair to restore vascular integrity and accelerate resolution of inflammation, thereby promoting survival following inflammatory lung injury.

Comparison of human olfactory and skeletal MSCs using osteogenic nanotopography to demonstrate bone-specific bioactivity of the surfaces

Recently we identified a novel population of mesenchymal stem cells (MSCs) from human olfactory mucosa (OM-MSCs), a tissue which promotes neurogenesis throughout life, and demonstrated that they promoted CNS myelination to a greater extent than bone marrow-derived (BM)-MSCs. Previous data demonstrated that nanotopographies with a degree of disorder induce BM-MSC osteogenic differentiation. Thus, using biomaterials as non-chemical tools, we investigated if MSCs from a completely different cellular niche could be induced to differentiate similarly to nanoscale cues alone. Both MSCs differentiated into bone when cultured on nanotopographically embossed polycaprolactone (PCL) with a disordered pattern and heights but not on a "smooth" non-embossed PCL control substrate, but OM-MSC changes were at lower expression levels. Both MSCs showed similar increases in differentiation markers at the protein and mRNA level when plated on the two patterned surfaces. Thus, topographical cues from substrates with disordered patterns can up-regulate several MSC resident genes in both BM-MSCs and OM-MSCs. Moreover, antibody purified BM-MSCs had similar properties to non-purified BM-MSCs. These data suggest that MSCs from a neural cellular niche express similar bone-induced cues to BM-MSCs, suggesting that MSCs that inherently support nervous tissue can differentiate along the bone lineage in a similar manner to MSCs from a skeletal environment.

The secretome of induced pluripotent stem cells reduces lung fibrosis in part by hepatocyte growth factor

Introduction

Idiopathic pulmonary fibrosis (IPF) is a progressive and irreversible fibrotic lung disease, resulting in respiratory insufficiency and reduced survival. Pulmonary fibrosis is a result of repeated alveolar epithelial microinjuries, followed by abnormal regeneration and repair processes in the lung. Recently, stem cells and their secretome have been investigated as a novel therapeutic approach in pulmonary fibrosis. We evaluated the potential of induced pluripotent stem cells (iPSC) conditioned media (iPSC-cm) to regenerate and repair the alveolar epithelium in vitro and improve bleomycin induced lung injury in vivo.

Methods

IPSC-cm was collected from cultured iPSC derived from human foreskin fibroblasts and its biological effects on alveolar epithelial wound repair was studied in an alveolar wound healing assay in vitro. Furthermore, iPSC-cm was intratracheally instilled 7 days after bleomycin induced injury in the rat lungs and histologically and biochemically assessed 7 days after instillation.

Results

iPSC-cm increased alveolar epithelial wound repair in vitro compared with medium control. Intratracheal instillation of iPSC-cm in bleomycin-injured lungs reduced the collagen content and improved lung fibrosis in the rat lung in vivo. Profibrotic TGFbeta1 and α-smooth muscle actin (α-sma) expression were markedly reduced in the iPSC-cm treated group compared with control. Antifibrotic hepatocyte growth factor (HGF) was detected in iPSC-cm in biologically relevant levels, and specific inhibition of HGF in iPSC-cm attenuated the antifibrotic effect of iPSC-cm, indicating a central role of HGF in iPSC-cm.

Conclusion

iPSC-cm increased alveolar epithelial wound repair in vitro and attenuated bleomycin induced fibrosis in vivo, partially due to the presence of HGF and may represent a promising novel, cell free therapeutic option against lung injury and fibrosis.

Electronic supplementary material

The online version of this article (doi:10.1186/scrt513) contains supplementary material, which is available to authorized users.

Evidence for Transfer of Membranes from Mesenchymal Stem Cells to HL-1 Cardiac Cells

This study examined the interaction of mouse bone marrow mesenchymal stem cells (MSC) with cardiac HL-1 cells during coculture by fluorescent dye labeling and then flow cytometry. MSC were layered onto confluent HL-1 cell cultures in a 1 : 4 ratio. MSC gained gap junction permeant calcein from HL-1 cells after 4 hours which was partially reduced by oleamide. After 20 hours, 99% MSC gained calcein, unaffected by oleamide. Double-labeling HL-1 cells with calcein and the membrane dye DiO resulted in transfer of both calcein and DiO to MSC. When HL-1 cells were labeled with calcein and MSC with DiO, MSC gained calcein while HL-1 cells gained DiO. Very little fusion was observed since more than 90% Sca-1 positive MSC gained DiO from HL-1 cells while less than 9% gained gap junction impermeant CMFDA after 20 hours with no Sca-1 transfer to HL-1 cells. Time dependent transfer of membrane DiD was observed from HL-1 cells to MSC (100%) and vice versa (50%) after 20 hours with more limited transfer of CMFDA. These results demonstrate that MSC and HL-1 cells exchange membrane components which may account for some of the beneficial effect of MSC in the heart after myocardial infarction.

Endothelial cells direct mesenchymal stem cells toward a smooth muscle cell fate

Under defined conditions, mesenchymal stem cells can differentiate into unique cell types, making them attractive candidates for cell-based disease therapies. Ischemic diseases would greatly benefit from treatments that include the formation of new blood vessels from mesenchymal stem cells. However, blood vessels are complex structures composed of endothelial cells and smooth muscle cells, and their assembly and function in a diseased environment is reliant upon joining with the pre-existing vasculature. Although endothelial cell/smooth muscle cell interactions are well known, how endothelial cells may influence mesenchymal stem cells and facilitate their differentiation has not been defined. Therefore, we sought to explore how endothelial cells might drive mesenchymal stem cells toward a smooth muscle fate. Our data show that cocultured endothelial cells induce smooth muscle cell differentiation in mesenchymal stem cells. Endothelial cells can promote a contractile phenotype, reduce proliferation, and enhance collagen synthesis and secretion. Our data show that Notch signaling is essential for endothelial cell-dependent differentiation, and this differentiation pathway is largely independent of growth factor signaling mechanisms.

Intramyocardial transplantation of cardiac mesenchymal stem cells reduces myocarditis in a model of chronic Chagas disease cardiomyopathy

Introduction

New therapeutic options are necessary for patients with chronic Chagas disease, a leading cause of heart failure in Latin American countries. Stem cell therapy focused on improving cardiac function is a promising approach for treating heart disease. Here, we evaluated the therapeutic effects of cardiac mesenchymal stem cells (CMSCs) in a mouse model of chronic Chagas disease.

Methods

CMSCs were isolated from green fluorescent protein (GFP) transgenic C57BL/6 mouse hearts and tested for adipogenic, osteogenic, chondrogenic, endothelial, and cardiogenic differentiation potentials evaluated by histochemical and immunofluorescence techniques. A lymphoproliferation assay was performed to evaluate the immunomodulatory activity of CMSCs. To investigate the therapeutic potential of CMSCs, C57BL/6 mice chronically infected with Trypanosoma cruzi were treated with 10⁶ CMSCs or saline (control) by echocardiography-guided injection into the left ventricle wall. All animals were submitted to cardiac histopathological and immunofluorescence analysis in heart sections from chagasic mice. Analysis by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) was performed in the heart to evaluate the expression of cytokines involved in the inflammatory response.

Results

CMSCs demonstrated adipogenic, osteogenic, and chondrogenic differentiation potentials. Moreover, these cells expressed endothelial cell and cardiomyocyte features upon defined stimulation culture conditions and displayed immunosuppressive activity in vitro. After intramyocardial injection, GFP⁺ CMSCs were observed in heart sections of chagasic mice one week later; however, no observed GFP⁺ cells co-expressed troponin T or connexin-43. Histopathological analysis revealed that CMSC-treated mice had a significantly decreased number of inflammatory cells, but no reduction in fibrotic area, two months after treatment. Analysis by qRT-PCR demonstrated that cell therapy significantly decreased tumor necrosis factor-alpha expression and increased transforming growth factor-beta in heart samples.

Conclusions

We conclude that the CMSCs exert a protective effect in chronic chagasic cardiomyopathy primarily through immunomodulation.

The beneficial effects of intracoronary autologous bone marrow stem cell transfer as an adjunct to percutaneous coronary intervention in patients with acute myocardial infarction

The efficacy of post-percutaneous coronary intervention (PCI) intracoronary injection with bone marrow mesenchymal stem cells (BMSCs) in patients with acute myocardial infarction (AMI) remains controversial. Here, 58 patients with AMI undergoing PCI were randomly divided into two groups: BMSC and control groups. Autologous BSMCs were then generated in vitro from the BMSC patients. After transplantation, left ventricular ejection fraction (LVEF), left ventricular end-diastolic dimensions (LVDd), and infarct size (IS) were evaluated in both groups. LVEF, LVDd, and IS improved after BMSC transplantation but the changes were not significantly different from those in the controls. The number of adverse events and rehospitalization rates after 1 month were significantly higher in the control group than in the BMSC group. BMSC transplantation thus benefits patients by decreasing the number of adverse events and reducing the rehospitalization rate in the early stages following PCI.

Magnetic Nanoparticle Based Nonviral MicroRNA Delivery into Freshly Isolated CD105(+) hMSCs

Genetic modifications of bone marrow derived human mesenchymal stem cells (hMSCs) using microRNAs (miRs) may be used to improve their therapeutic potential and enable innovative strategies in tissue regeneration. However, most of the studies use cultured hMSCs, although these can lose their stem cell characteristics during expansion. Therefore, we aimed to develop a nonviral miR carrier based on polyethylenimine (PEI) bound to magnetic nanoparticles (MNPs) for efficient miR delivery in freshly isolated hMSCs. MNP based transfection is preferable for genetic modifications in vivo due to improved selectivity, safety of delivery, and reduced side effects. Thus, in this study different miR/PEI and miR/PEI/MNP complex formulations were tested in vitro for uptake efficiency and cytotoxicity with respect to the influence of an external magnetic field. Afterwards, optimized magnetic complexes were selected and compared to commercially available magnetic vectors (Magnetofectamine, CombiMag). We found that all tested transfection reagents had high miR uptake rates (yielded over 60%) and no significant cytotoxic effects. Our work may become crucial for virus-free introduction of therapeutic miRs as well as other nucleic acids in vivo. Moreover, in the field of targeted stem cell therapy nucleic acid delivery prior to transplantation may allowfor initial cell modulation in vitro.

Changes in the composition of the extracellular matrix accumulated by mesenchymal stem cells during in vitro expansion

One of the approaches to preserve the properties of mesenchymal stem cells (MSCs) during in vitro expansion is to use cell culture substrates. MSCs are known to generate the extracellular matrix (ECM) proper to preserve their proliferative capacity in vitro, but extensive expansion is considered to deprive MSCs of the capacity to prepare such ECM. In order to examine the features of ECM proper that is required to preserve the proliferative capacity of MSCs, we analyzed the changes in the composition of ECM accumulated by MSCs during in vitro expansion. Biochemical and immunological analysis showed that collagen and laminin content decreased during expansion. Immunofluorescence and ultrastructural analyses showed that the ECM structure changed from a dynamic fibrous, porous and steric structure to a static, crammed, and planar one. The results of Western blotting analysis suggested loose intermolecular association in ECM molecules accumulated by extensively proliferated MSCs. The ECM prepared by extensively proliferated MSCs was less effective to recover their proliferative capacity than that prepared by less proliferated cells. Our results suggest that a cell culture substrate to expand MSCs requires abundance in collagen and basement membrane components, and steric, porous and fibrous structure in which ECM molecules are tightly associated.

Transplantation of mesenchymal stem cells carrying the human receptor activity-modifying protein 1 gene improves cardiac function and inhibits neointimal proliferation in the carotid angioplasty and myocardial infarction rabbit model

Although transplanting mesenchymal stem cells (MSCs) can improve cardiac function and contribute to endothelial recovery in a damaged artery, natural MSCs may induce neointimal hyperplasia by directly or indirectly acting on vascular smooth muscle cells (VSMCs). Receptor activity-modifying protein 1 (RAMP1) is the component and the determinant of ligand specificity of calcitonin gene-related peptide (CGRP). It is recently reported that CGRP and its receptor involve the proliferation and the apoptosis in vivo and in vitro, and the exogenous RAMP1 enhances the antiproliferation effect of CGRP in VSMCs. Here, we investigated the effects of MSCs overexpressing the human receptor activity-modifying protein 1 (hRAMP1) on heart function and artery repair in rabbit models of myocardial infarction (MI) reperfusion and carotid artery injury. MSCs transfected with a recombinant adenovirus containing the hRAMP1 gene (EGFP-hRAMP1-MSCs) were injected into the rabbit models via the ear vein at 24 h after carotid artery injury and MI 7 days post-EGFP-hRAMP1-MSC transplantation. The cells that expressed both enhance green fluorescent protein (EGFP) and CD31 were detected in the neointima of the damaged artery via immunofluorescence. EGFP-hRAMP1 expression was observed in the injured artery and infarcted myocardium by western blot analysis, confirming that the engineered MSCs targeted the injured artery and infarcted myocardium and expressed hRAMP1 protein. Compared with the EGFP-MSCs group, the EGFP-hRAMP1-MSCs group had a significantly smaller infarcted area and improved cardiac function by 28 days after cell transplantation, as detected by triphenyltetrazolium chloride staining and echocardiography. Additionally, arterial hematoxylin-eosin staining revealed that the area of the neointima and the area ratio of intima/media were significantly decreased in the EGFP-hRAMP1-MSCs group. An immunohistological study showed that the expression of α-smooth muscle antigen and proliferating cell nuclear antigen in the neointima cells of the carotid artery of the EGFP-hRAMP1-MSCs group was approximately 50% lower than that of the EGFP-MSCs group, suggesting that hRAMP1 expression may inhibit VSMCs proliferation within the neointima. Therefore, compared with natural MSCs, EGFP-hRAMP1-engineered MSCs improved infarcted heart function and endothelial recovery from artery injury more efficiently, which will provide valuable information for the development of MSC-based therapy.

Chemokine contribution in stem cell engraftment into the infarcted myocardium

Modern life styles have made cardiovascular disease the leading cause of morbidity and mortality worldwide. Although current treatments substantially ameliorate patients’ prognosis after MI, they cannot restore the affected tissue or entirely re-establish organ function. Therefore, the main goal of modern cardiology should be to design strategies to reduce myocardial necrosis and optimize cardiac repair following MI. Cell-based therapy was considered a novel and potentially new strategy in regenerative medicine; however, its clinical implementation has not yielded the expected results. Chemokines seem to increase the efficiency of cell-therapy and may represent a reliable method to be exploited in the future. This review surveys current knowledge of cell therapy and highlights key insights into the role of chemokines in stem cell engraftment in infarcted myocardium and their possible clinical implications.

Injection of Sca-1+/CD45+/CD31+ mouse bone mesenchymal stromal-like cells improves cardiac function in a mouse myocardial infarct model

The objective of this study was to screen mouse bone marrow mesenchymal stromal cells (BMSCs) according to expression of cardiac stem cell (CSC) surface antigens and to assess the effects of resulting BMSC-like subsets on cardiac function after injection in a mouse myocardial infarct model. BMSCs were sorted by magnetic beads according to the expression of differentiation antigens on the surface of mouse CSCs, and four subsets were identified on the basis of CD45 and CD31 expression: stem cell antigen-1+ (Sca-1+)/CD45-/CD31-, Sca-1+/CD45-/CD31+, Sca-1+/CD45+/CD31-, and Sca-1+/CD45+/CD31+. When co-cultured with myocardial stem cells and 5-aza-2'-deoxycytidine for 14 days, each subset showed expression of cardiac markers α-actin, connexin 43, desmin, and cardiac troponin I; however, expression was greatest in Sca-1+/CD45+/CD31+ cells. To assess the ability of these cells to improve cardiac function, each subset was injected separately into mice with myocardial infarct induced by ligation of the left anterior descending coronary artery, and in vivo cardiac dual inversion recovery (DIR) imaging and Doppler echocardiography were performed 48 h, 96 h, and 7 days after injection. Results indicated that Sca-1+/CD45+/CD31+ cells were superior in improving cardiac function compared with the other subsets and with unsorted BMSCs. These results suggest that mouse BMSC cells are polyclonal and that the BMSC-like Sca-1+/CD45+/CD31+ subset was effective in directing cardiac differentiation and improving cardiac function in mice with myocardial infarcts.