Pharmacologically preconditioned skeletal myoblasts are resistant to oxidative stress and promote angiomyogenesis via release of paracrine factors in the infarcted heart

Mitochondrial transplantation for cardioprotection and induction of angiogenesis in ischemic heart disease

To date, the regenerative potential of mitochondrial transplantation (MT) has been extensively investigated under several pathologies. Among various cardiovascular diseases, ischemic heart disease (IHD), the most prevalent pathological condition in human medicine, is induced by coronary artery narrowing, or occlusion, leading to bulk necrotic changes and fibrosis within the myocardium. Data associated with the pro-angiogenic activity of mitochondria have not been completely elucidated in terms of cardiac tissue regeneration. Here, we aimed to highlight the recent studies and advantages related to the application of mitochondrial mass in the ischemic myocardium. How and by which mechanisms, mitochondria can reduce aberrant myocardial tissue remodeling via different pathways such as angiogenesis and de novo blood formation was discussed in detail. We hope that data from the current review article help us understand the molecular and cellular mechanisms by which transplanted mitochondria exert their regenerative properties in the ischemic myocardium.

Pretreatment with Notoginsenoside R1 enhances the efficacy of neonatal rat mesenchymal stem cell transplantation in model of myocardial infarction through regulating PI3K/Akt/FoxO1 signaling pathways

BACKGROUND

Although stem cell transplantation is a promising approach for the treatment of myocardial infarction (MI), there are still some problems faced such as the low survival rate of stem cells. Here, we investigated the role of Notoginsenoside R1 (NGR1) pretreatment in improving the effects of neonatal rat bone marrow mesenchymal stem cell (MSC) transplantation for treatment of MI.

METHODS

Cardiac functions were detected by echocardiography and the myocardial infarct size was determined by Masson's trichrome staining in a rat model of MI. The cardioprotective effects of NGR1/LY294002 co-pretreated MSCs was evaluated to explore the underlying mechanism. The angiogenesis was determined by vWF and α-SMA immunofluorescence staining and cell apoptosis was detected by TUNEL. In vitro, the effects of NGR1 on stem cell proliferation was examined by CCK-8 and levels of P-Akt, P-CREB, P-FoxO1 were detected by western blot. Apoptosis, ROS content, and cytokine levels were examined by DAPI and TUNEL staining, a ROS assay kit, and ELISA, respectively.

RESULTS

NGR1 elevated the therapeutic effect of MSC transplantation on infarction by preserving cardiac function, increasing angiogenesis and expressions of IGF-1, VEGF, and SDF-1, and reducing cell apoptosis, whereas the addition of LY294002 prior to NGR1 treatment significantly counteracted the foregoing effects of NGR1. NGR1 pretreatment and SC79 pretreatment were similar in that both significantly increased P-Akt and P-FoxO1 levels in MSC and did not affect P-CREB levels. Besides, both NGR1 and SC79 promoted VEGF, SCF and bFGF levels in MSC cultures, and significantly reduced ROS accumulation and the attenuated cell apoptosis in MSC triggered by H2O2. Similarly, addition of LY294002 before NGR1 treatment significantly counteracted the aforementioned effects of NGR1 in vitro.

CONCLUSIONS

NGR1 pretreatment enhances the effect of MSC transplantation for treatment of MI through paracrine signaling, and the mechanism underlying this effect may be associated with PI3K/Akt/FoxO1 signaling pathways.

Priming mesenchymal stem cells to develop "super stem cells"

The stem cell pre-treatment approaches at cellular and sub-cellular levels encompass physical manipulation of stem cells to growth factor treatment, genetic manipulation, and chemical and pharmacological treatment, each strategy having advantages and limitations. Most of these pre-treatment protocols are non-combinative. This editorial is a continuum of Li et al's published article and Wan et al's editorial focusing on the significance of pre-treatment strategies to enhance their stemness, immunoregulatory, and immunosuppressive properties. They have elaborated on the intricacies of the combinative pre-treatment protocol using pro-inflammatory cytokines and hypoxia. Applying a well-defined multi-pronged combinatorial strategy of mesenchymal stem cells (MSCs), pre-treatment based on the mechanistic understanding is expected to develop "Super MSCs", which will create a transformative shift in MSC-based therapies in clinical settings, potentially revolutionizing the field. Once optimized, the standardized protocols may be used with slight modifications to pre-treat different stem cells to develop "super stem cells" with augmented stemness, functionality, and reparability for diverse clinical applications with better outcomes.

Cellular preconditioning and mesenchymal stem cell ferroptosis

In this editorial, we comment on the article published in the recent issue of the World Journal of Stem Cells. They focus on stem cell preconditioning to prevent ferroptosis by modulating the cystathionine γ-lyase/hydrogen sulfide (H2S) pathway as a novel approach to treat vascular disorders, particularly pulmonary hypertension. Preconditioned stem cells are gaining popularity in regenerative medicine due to their unique ability to survive by resisting the harsh, unfavorable microenvironment of the injured tissue. They also secrete various paracrine factors against apoptosis, necrosis, and ferroptosis to enhance cell survival. Ferroptosis, a regulated form of cell death characterized by iron accumulation and oxidative stress, has been implicated in various pathologies encompassing degenerative disorders to cancer. The lipid peroxidation cascade initiates and sustains ferroptosis, generating many reactive oxygen species that attack and damage multiple cellular structures. Understanding these intertwined mechanisms provides significant insights into developing therapeutic modalities for ferroptosis-related diseases. This editorial primarily discusses stem cell preconditioning in modulating ferroptosis, focusing on the cystathionase gamma/H2S ferroptosis pathway. Ferroptosis presents a significant challenge in mesenchymal stem cell (MSC)-based therapies; hence, the emerging role of H2S/cystathionase gamma/H2S signaling in abrogating ferroptosis provides a novel option for therapeutic intervention. Further research into understanding the precise mechanisms of H2S-mediated cytoprotection against ferroptosis is warranted to enhance the therapeutic potential of MSCs in clinical settings, particularly vascular disorders.

Electrospun Fiber-Coated Human Amniotic Membrane: A Potential Angioinductive Scaffold for Ischemic Tissue Repair

Cardiac patch implantation helps maximize the paracrine function of grafted cells and serves as a reservoir of soluble proangiogenic factors required for the neovascularization of infarcted hearts. We have previously fabricated a cardiac patch, EF-HAM, composed of a human amniotic membrane (HAM) coated with aligned PLGA electrospun fibers (EF). In this study, we aimed to evaluate the biocompatibility and angiogenic effects of EF-HAM scaffolds with varying fiber thicknesses on the paracrine behavior of skeletal muscle cells (SkM). Conditioned media (CM) obtained from SkM-seeded HAM and EF-HAM scaffolds were subjected to multiplex analysis of angiogenic factors and tested on HUVECs for endothelial cell viability, migration, and tube formation analyses. All three different groups of EF-HAM scaffolds demonstrated excellent biocompatibility with SkM. CM derived from SkM-seeded EF-HAM 7 min scaffolds contained significantly elevated levels of proangiogenic factors, including angiopoietin-1, IL-8, and VEGF-C compared to plain CM, which was obtained from SkM cultured on the plain surface. CM obtained from all SkM-seeded EF-HAM scaffolds significantly increased the viability of HUVECs compared to plain CM after five days of culture. However, only EF-HAM 7 min CM induced a higher migration capacity in HUVECs and formed a longer and more elaborate capillary-like network on Matrigel compared with plain CM. Surface roughness and wettability of EF-HAM 7 min scaffolds might have influenced the proportion of skeletal myoblasts and fibroblasts growing on the scaffolds and subsequently potentiated the angiogenic paracrine function of SkM. This study demonstrated the angioinductive properties of EF-HAM composite scaffold and its potential applications in the repair and regeneration of ischemic tissues.

The Paracrine Function of Mesenchymal Stem Cells in Response to Pulsed Focused Ultrasound

We studied the paracrine function of mesenchymal stem cells (MSCs) derived from various sources in response to pulsed focused ultrasound (pFUS). Human adipose tissue (AD), bone marrow (BM), and umbilical cord (UC) derived MSCs were exposed to pFUS at two intensities: 0.45 W/cm² I_SATA (310 kPa PNP) and 1.3 W/cm² I_SATA (540 kPa PNP). Following pFUS, the viability and proliferation of MSCs were assessed using a hemocytometer and confocal microscopy, and their secreted cytokine profile determined using a multiplex ELISA. Our findings showed that pFUS can stimulate the production of immunomodulatory, anti-inflammatory, and angiogenic cytokines from MSCs which was dependent on both the source of MSC being studied and the acoustic intensity employed. These important findings set the foundation for additional mechanistic and validation studies using this novel noninvasive and clinically translatable technology for modulating MSC biology.

Stem cells and growth factors-based delivery approaches for chronic wound repair and regeneration: A promise to heal from within

The sophisticated chain of cellular and molecular episodes during wound healing includes cell migration, cell proliferation, deposition of extracellular matrix, and remodelling and are onerous to replicate. Encapsulation of growth factors (GFs) and Stem cell-based (SCs) has been proclaimed to accelerate healing by transforming every phase associated with wound healing to enhance skin regeneration. Therapeutic application of mesenchymal stem cells (MSCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (PSCs) provides aid in wound fixing, tissue integrity restoration and function of impaired tissue. Several scientific studies have established the essential role GFs in wound healing and their reduced degree in the chronic wound. The overall limitation includes half-life, unfriendly microhabitat abundant with protease, and inadequate delivery approaches results in decreased delivery of effective amounts in a suitable time-based fashion. Advancements in the area of reformative medicine as well as tissue engineering have offered techniques competent of dispensing SCs and GFs in site-oriented manner. The progress in nanotechnology-based approaches attracts researcher to study and evaluate the potential of this SCs and GFs based therapy in chronic wounds. These techniques embrace the polymeric regime viz., nano-formulations, hydrogels, liposomes, scaffolds, nanofibers, metallic nanoparticles, lipid-based nanoparticles and dendrimers that have established better retort through targeting tissues when GFs and SCs are transported via these humans made devices. Assumed the current problems, improvements in delivery approaches and difficulties offered by chronic wounds, we hope to show that encapsulation of SCs and GFs loaded nanoformulations therapies is the rational next step in improving wound care.

Facilitating islet transplantation using a three-step approach with mesenchymal stem cells, encapsulation, and pulsed focused ultrasound

BACKGROUND

The aim of this study was to examine the effect of a three-step approach that utilizes the application of adipose tissue-derived mesenchymal stem cells (AD-MSCs), encapsulation, and pulsed focused ultrasound (pFUS) to help the engraftment and function of transplanted islets.

METHODS

In step 1, islets were co-cultured with AD-MSCs to form a coating of AD-MSCs on islets: here, AD-MSCs had a cytoprotective effect on islets; in step 2, islets coated with AD-MSCs were conformally encapsulated in a thin layer of alginate using a co-axial air-flow method: here, the capsule enabled AD-MSCs to be in close proximity to islets; in step 3, encapsulated islets coated with AD-MSCs were treated with pFUS: here, pFUS enhanced the secretion of insulin from islets as well as stimulated the cytoprotective effect of AD-MSCs.

RESULTS

Our approach was shown to prevent islet death and preserve islet functionality in vitro. When 175 syngeneic encapsulated islets coated with AD-MSCs were transplanted beneath the kidney capsule of diabetic mice, and then followed every 3 days with pFUS treatment until day 12 post-transplantation, we saw a significant improvement in islet function with diabetic animals re-establishing glycemic control over the course of our study (i.e., 30 days). In addition, our approach was able to enhance islet engraftment by facilitating their revascularization and reducing inflammation.

CONCLUSIONS

This study demonstrates that our clinically translatable three-step approach is able to improve the function and viability of transplanted islets.

Insight into adipokines to optimize therapeutic effects of stem cell for tissue regeneration

Stem cell therapy is considered as a promising regenerative medicine for repairing and treating damaged tissues and/or preventing various diseases. But there are still some obstacles such as low cell migration, poor stem cell engraftment and decreased cell survival that need to be overcome before transplantation. Therefore, a large body of studies has focused on improving the efficiency of stem cell therapy. For instance, preconditioning of stem cells has emerged as an effective strategy to reinforce therapeutic efficacy. Adipokines are signaling molecules, secreted by adipose tissue, which regulate a variety of biological processes in adipose tissue and other organs including the brain, liver, and muscle. In this review article, we shed light on the biological effects of some adipokines including apelin, oncostatin M, omentin-1 and vaspin on stem cell therapy and the most recent preclinical advances in our understanding of how these functions ameliorate stem cell therapy outcome.

Y-27632 preconditioning enhances transplantation of human-induced pluripotent stem cell-derived cardiomyocytes in myocardial infarction mice

Aims

The effectiveness of cell-based treatments for regenerative myocardial therapy is limited by low rates of cell engraftment. Y-27632 inhibits Rho-associated protein kinase (ROCK), which regulates the cytoskeletal changes associated with cell adhesion, and has been used to protect cultured cells during their passaging. Here, we investigated whether preconditioning of cardiomyocytes, derived from human-induced pluripotent stem cells (hiPSC-CM), with Y-27632 improves their survival and engraftment in a murine model of acute myocardial infarction (MI).

Methods and results

After MI induction, mice were subjected to intramyocardial injections of phosphate-buffered saline, hiPSC-CM cultured under standard conditions (hiPSC-CM-RI), or Y-27632-preconditioned hiPSC-CM (hiPSC-CM+RI). The resulting engraftment rate calculated 4 weeks after implantation was significantly higher and the abundance of apoptotic transplanted cells was significantly lower in hiPSC-CM+RI recipients than in hiPSC-CM-RI animals. In cultured hiPSC-CM, Y-27632-preconditioning reversibly reduced contractile activity and the expression of troponin genes, while increasing their attachment to an underlying mouse cardiomyocyte (HL1) monolayer. Y-27632 preconditioning also increased the expression of N-cadherin and integrin ß1, the two cell junction proteins. hiPSC-CM+RI were also larger in cell area with greater cytoskeletal alignment and a more rod-like shape than hiPSC-CM-RI, both after transplantation (in vivo) and in culture. The effects of Y-27632 preconditioning on contractile activity and morphology of hiPSC-CMs in culture, as well as on their engraftment rate and apoptotic death in MI mouse grafts, could be recapitulated by hiPSC-CM treatment with the L-type calcium-channel blocker verapamil.

Conclusion

Preconditioning with the ROCK inhibitor Y-27632 increased the engraftment of transplanted hiPSC-CM in a murine MI model, while reversibly impairing hiPSC-CM contractility and promoting adhesion.

Mineralocorticoid receptor deficiency improves the therapeutic effects of mesenchymal stem cells for myocardial infarction via enhanced cell survival

The poor survival of stem cells seriously limits their therapeutic efficacy for myocardial infarction (MI). Mineralocorticoid receptor (MR) activation plays an important role in the pathogenesis of multiple cardiovascular diseases. Here, we examined whether MR silencing in bone marrow derived mesenchymal stem cells (MSCs) could improve MSCs’ survival and enhance their cardioprotective effects in MI. MSCs from male Sprague‐Dawley rats were transfected with adenoviral small interfering RNA to silence MR (siRNA‐MR). MR silencing decreased hypoxia‐induced MSCs’ apoptosis, as demonstrated by Annexin V/7‐AAD staining. The mechanisms contributing to the beneficial effects of MR depletion were associated with inhibiting intracellular reactive oxygen species production and increased Bcl‐2/Bax ratio. In vivo study, 1 × 10⁶ of MSCs with or without siRNA‐MR were injected into rat hearts immediately after MI. Depletion of MR could improve the MSCs’ survival significantly in infarcted myocardium, associated with more cardiac function improvement and smaller infarct size. Capillary density were also significantly higher in siRNA group with increased expression of vascular endothelial growth factor. Our study demonstrated that silencing MR promoted MSCs’ survival and repair efficacy in ischaemic hearts. MR might be a potential target for enhancing the efficacy of cell therapy in ischaemic heart disease.

Tissue regeneration: Impact of sleep on stem cell regenerative capacity

The circadian rhythm orchestrates many cellular functions, such as cell division, cell migration, metabolism and numerous intracellular biological processes. The physiological changes during sleep are believed to promote a suitable microenvironment for stem cells to proliferate, migrate and differentiate. These effects are mediated either directly by circadian clock genes or indirectly via hormones and cytokines. Hormones, such as melatonin and cortisol, are secreted in response to neural optic signals and act in harmony to regulate many biological functions during sleep. Herein, we correlate the effects of the main circadian genes on the expression of certain stem cell genes responsible for the regeneration of different tissues, including bone, cartilage, skin, and intestine. We also review the effects of different hormones and cytokines on stem cell activation or suppression and their relationship to the day/night cycle. The correlation of circadian rhythm with tissue regeneration could have implications in understanding the biology of sleep and tissue regeneration and in enhancing the efficacy and timing of surgical procedures.

Sphingosine 1-phosphate promotes mesenchymal stem cell-mediated cardioprotection against myocardial infarction via ERK1/2-MMP-9 and Akt signaling axis

AIMS

The sphingolipid metabolite sphingosine 1‑phosphate (S1P) has emerged as a potential cardioprotective molecule against ischemic heart disease. Moreover, S1P triggers mobilization and homing of bone marrow-derived stem/progenitor cells into the damaged heart. However, it remains elusive whether S1P promotes mesenchymal stem cells (MSCs)-mediated cardioprotection against ischemic heart diseases.

MAIN METHODS

Adipose tissue-derived MSCs (AT-MSCs) were obtained from GFP transgenic mice or C57BL/6J. Myocardial infarction (MI) was induced in C57BL/6J mice by ligation of the left anterior descending coronary artery (LAD). Subsequently, S1P-treated AT-MSCs or vehicle-treated AT-MSCs were intravenously administered for 24 h after induction of MI or sham procedure.

KEY FINDINGS

Pre-conditioning with S1P significantly enhanced the migratory and anti-apoptotic efficacies of AT-MSCs. In MI-induced mice, intravenous administration of S1P-treated AT-MSCs significantly augmented their homing and engraftment in ischemic area. Besides, AT-MSCs with S1P pre-treatment exhibited enhanced potencies to inhibit cardiomyocyte apoptosis and fibrosis, and stimulate angiogenesis and preserve cardiac function. Mechanistic studies revealed that S1P promoted AT-MSCs migration through activation of ERK1/2-MMP-9, and protected AT-MSCs against apoptosis via Akt activation. Further, S1P activated the ERK1/2 and Akt via S1P receptor 2 (S1PR2), but not through S1PR1. S1PR2 knockdown by siRNA, however, significantly attenuated S1P-mediated AT-MSCs migration and anti-apoptosis.

SIGNIFICANCE

The findings of the present study revealed the protective efficacies of S1P pretreatment on the survival/retention and cardioprotection of engrafted MSCs. Pre-conditioning of donor MSCs with S1P is an effective strategy to promote the therapeutic potential of MSCs for ischemic heart diseases.

Fluoxetine pretreatment enhances neurogenic, angiogenic and immunomodulatory effects of MSCs on experimentally induced diabetic neuropathy

Being one of the most debilitating complications among diabetic patients, diabetic polyneuropathy (DPN) is a paramount point of continuous research. Stem cell therapies have shown promising results. However, limited cell survival and paracrine activities hinder its transfer from bench to bedside. We designed this study to evaluate fluoxetine-pretreatment technique of mesenchymal stem cells (MSCs) as an approach to enhance their paracrine and immunomodulatory properties in DPN. Effects of fluoxetine treatment of MSCs were tested in vitro. Forty-two adult Wistar male albino rats were utilized, further subdivided into control, diabetic, MSC-treated and fluoxetine-pretreated MSC groups. Sciatic nerve sections were prepared for light and electron microscope examination and immunohistochemical detection of neurofilament (NF) protein. Also, we assessed in vitro survival and paracrine properties of fluoxetine-pretreated MSCs. Real time PCR of BDNF, VEGF, IL-1β, and IL-10 expression in tissue homogenate was performed. Our results showed restoration of normal neuronal histomorphology and ultrastructure, moreover, immunohistochemical expression of anti-neurofilament protein was significantly elevated in MSC-treated groups compared to the diabetic one. Fluoxetine enhanced the MSC survival and their paracrine properties of MSCs in vitro. Furthermore, the fluoxetine-pretreated MSC group revealed a significant elevation of mRNA expression of BDNF (neurotrophic factor) and VEGF (angiogenic factor), denoting ameliorated MSC paracrine properties. Similarly, improved immunomodulatory functions were evident by a significant reduction of interleukin-1β mRNA expression (pro-inflammatory) and a reciprocal significant increase of interleukin-10 (anti-inflammatory). We concluded that fluoxetine-pretreatment of MSCs boosts their survival, paracrine, and immunomodulatory traits and directly influenced neuronal histomorphology. Hence, it presents a promising intervention of diabetic polyneuropathy. Graphical Abstract.

Tadalafil, a long acting phosphodiesterase inhibitor, promotes bone marrow stem cell survival and their homing into ischemic myocardium for cardiac repair

The aim was to evaluate the tadalafil‐mediated effects at molecular level on bone marrow‐derived mesenchymal stem cells (MSCs) survival and their homing into the infarcted hearts to promote cardiac repair and improve function. MSCs were pretreated in vitro with inhibitors of PKG, MAPK, FasL, nitric oxide synthase (NOS) (L‐NAME), CXCR4 (AMD3100), or miR‐21 inhibitors (+/−luciferase construction +/−Fas) prior to tadalafil treatment for 2 h. These MSCs were then subjected to H₂O₂ stress to assess their injury. Rats were subjected to acute myocardial infarction (AMI), and then followed by injection of saline or 1.5 x 10⁶ MSCs‐treated ± tadalafil into infarcted and peri‐infarcted area. In another group, AMI was performed in 1‐month post‐myelo‐ablated rats and were injected intraperitoneally (IP) with tadalafil ± AMD3100 or L‐NAME for 5 days. Also, in another group, AMI mice were treated with IP ± tadalafil before intravenous injection with ¹¹¹In‐oxine‐MSCs followed by CT/SPECT imaging to locate mobilized MSCs. Cardiac function was assessed by echocardiography. MSCs and heart extracts were analyzed by molecular bioassays. Tadalafil‐treated MSCs had higher expression of cGMP, NOS, SDF‐1α, p‐VASP, p‐Erk1/2, p‐STAT3, p‐Akt, PKG1 and Bcl‐xl; expression of these molecules was reduced with PKG1, MAPK, NOS or FasL inhibitors. Tadalafil inhibited apoptosis through increased miR‐21 expression and improved cell survival by inhibiting Fas (restored by PKG1, MAPK or miR‐21 inhibitors). In vivo, heart function, grafted cell survival, MSCs mobilization and homing were improved in tadalafil‐treated AMI animals versus controls. Conclusions: Tadalafil prolonged MSCs survival via up‐regulation of miR‐21 dependent suppression of Fas, and increased MSCs mobilization and their homing into infarcted myocardium resulting in improved cardiac repair and function.

Nicorandil potentiates sodium butyrate induced preconditioning of neurons and enhances their survival upon subsequent treatment with H2O2

Background

Extensive loss of donor neural stem cell (NSCs) due to ischemic stress and low rate of differentiation at the site of cell graft are two of the major issues that hamper optimal outcome in NSCs transplantation studies. Given that histone deacetylases (HDACs) modulate various cellular processes by deacetylating histones and non-histone proteins, we hypothesized that combined treatment with small molecules, sodium butyrate (NaB; a known HDAC inhibitor) and nicorandil, will enhance the rate neuronal differentiation of NSCs besides their preconditioning to resist oxidative stress.

Methods

NSCs derived from 14-day old Sprague Dawley rat ganglion eminence were characterized for tri-lineage differentiation. Treatment with 1 mM NaB significantly changed their culture characteristics while continuous treatment for 10 days enhanced their neural differentiation. NaB treatment also preconditioned the cells for their resistance to oxidative stress.

Results

The highest rate of neural differentiation and preconditioning effect was achieved when the NSCs were treated concomitantly with NaB and nicorandil. Cell proliferation assay showed that concomitant treatment with NaB and nicorandil retarded their rate of proliferation.

Conclusion

These data conclude that preconditioning of NSCs with NaB and nicorandil effectively enhances their differentiation capacity besides preconditioning the cells to support their survival under ischemic conditions.

Electronic supplementary material

The online version of this article (10.1186/s40035-017-0097-1) contains supplementary material, which is available to authorized users.

Hypoxic preconditioning of myoblasts implanted in a tissue engineering chamber significantly increases local angiogenesis via upregulation of myoblast vascular endothelial growth factor-A expression and downregulation of miRNA-1, miRNA-206 and angiopoietin-1

Vascularization is a major hurdle for growing three-dimensional tissue engineered constructs. This study investigated the mechanisms involved in hypoxic preconditioning of primary rat myoblasts in vitro and their influence on local angiogenesis postimplantation. Primary rat myoblast cultures were exposed to 90 min hypoxia at <1% oxygen followed by normoxia for 24 h. Real time (RT) polymerase chain reaction evaluation indicated that 90 min hypoxia resulted in significant downregulation of miR-1 and miR-206 (p < 0.05) and angiopoietin-1 (p < 0.05) with upregulation of vascular endothelial growth factor-A (VEGF-A; p < 0.05). The miR-1 and angiopoietin-1 responses remained significantly downregulated after a 24 h rest phase. In addition, direct inhibition of miR-206 in L6 myoblasts caused a significant increase in VEGF-A expression (p < 0.05), further establishing that changes in VEGF-A expression are influenced by miR-206. Of the myogenic genes examined, MyoD was significantly upregulated, only after 24 h rest (p < 0.05). Preconditioned or control myoblasts were implanted with Matrigel™ into isolated bilateral tissue engineering chambers incorporating a flow-through epigastric vascular pedicle in severe combined immunodeficiency mice and the chamber tissue harvested 14 days later. Chambers implanted with preconditioned myoblasts had a significantly increased percentage volume of blood vessels (p = 0.0325) compared with chambers implanted with control myoblasts. Hypoxic preconditioned myoblasts promote vascularization of constructs via VEGF upregulation and downregulation of angiopoietin-1, miR-1 and miR-206. The relatively simple strategy of hypoxic preconditioning of implanted cells - including non-stem cell types - has broad, future applications in tissue engineering of skeletal muscle and other tissues, as a technique to significantly increase implant site angiogenesis.

Optimization of time for neural stem cells transplantation for brain stroke in rats

BACKGROUND

Despite encouraging data in terms of neurological outcome, stem cell based therapy for ischemic stroke in experimental models and human patients is still hampered by multiple as yet un-optimized variables, i.e., time of intervention, that significantly influence the prognosis. The aim of the present study was to delineate the optimum time for neural stem cells (NSCs) transplantation after ischemic stroke.

METHODS

The NSCs were isolated from 14 days embryo rat ganglion eminence and were cultured in NSA medium (neurobasal medium, 2% B27, 1% N2, bFGF 10 ng/mL, EGF 20 ng/mL and 1% pen/strep). The cells were characterized for tri-lineage differentiation by immunocytochemistry for tubulin-III, Olig2 and GFAP expression for neurons, oligodendrocytes and astrocyte respectively. The NSCs at passage 3 were injected intraventricularly in a rodent model of middle-cerebral artery occlusion (MCAO) on stipulated time points of 1 & 12 h, and 1, 3, 5 and 7 days after ischemic stroke. The animals were euthanized on day 28 after their respective treatment.

RESULTS

dUTP nick end labeling (TUNEL) assay and Caspase assay showed significantly reduced number of apoptotic cells on day 3 treated animals as compared to the other treatment groups of animals. The neurological outcome showed that the group which received NSCs 3 days after brain ischemia had the best neurological performance.

CONCLUSIONS

The optimum time for NSCs transplantation was day 3 after ischemic stroke in terms of attenuation of ischemic zone expansion and better preserved neurological performance.

Optimizing stem cells for cardiac repair: Current status and new frontiers in regenerative cardiology

Cell therapy has the potential to improve healing of ischemic heart, repopulate injured myocardium and restore cardiac function. The tremendous hope and potential of stem cell therapy is well understood, yet recent trials involving cell therapy for cardiovascular diseases have yielded mixed results with inconsistent data thereby readdressing controversies and unresolved questions regarding stem cell efficacy for ischemic cardiac disease treatment. These controversies are believed to arise by the lack of uniformity of the clinical trial methodologies, uncertainty regarding the underlying reparative mechanisms of stem cells, questions concerning the most appropriate cell population to use, the proper delivery method and timing in relation to the moment of infarction, as well as the poor stem cell survival and engraftment especially in a diseased microenvironment which is collectively acknowledged as a major hindrance to any form of cell therapy. Indeed, the microenvironment of the failing heart exhibits pathological hypoxic, oxidative and inflammatory stressors impairing the survival of transplanted cells. Therefore, in order to observe any significant therapeutic benefit there is a need to increase resilience of stem cells to death in the transplant microenvironment while preserving or better yet improving their reparative functionality. Although stem cell differentiation into cardiomyocytes has been observed in some instance, the prevailing reparative benefits are afforded through paracrine mechanisms that promote angiogenesis, cell survival, transdifferentiate host cells and modulate immune responses. Therefore, to maximize their reparative functionality, ex vivo manipulation of stem cells through physical, genetic and pharmacological means have shown promise to enable cells to thrive in the post-ischemic transplant microenvironment. In the present work, we will overview the current status of stem cell therapy for ischemic heart disease, discuss the most recurring cell populations employed, the mechanisms by which stem cells deliver a therapeutic benefit and strategies that have been used to optimize and increase survival and functionality of stem cells including ex vivo preconditioning with drugs and a novel “pharmaco-optimizer” as well as genetic modifications.

Platelet-rich plasma ameliorates senescence-like phenotypes in a cellular photoaging model

Platelet-rich plasma (PRP) is a portion of blood plasma enriched with platelets widely investigated for accelerating bone and soft tissue healing.

Modification of Bone Marrow Stem Cells for Homing and Survival During Cerebral Ischemia

Over the last decade, major advances have been made in stem cell-based therapy for ischemic stroke, which is one of the leading causes of death and disability worldwide. Various stem cells from bone marrow, such as mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), and endothelial progenitor cells (EPCs), have shown therapeutic potential for stroke. Concomitant with these exciting findings are some fundamental bottlenecks that must be overcome in order to accelerate their clinical translation, including the low survival and engraftment caused by the harsh microenvironment after transplantation. In this chapter, strategies such as gene modification, hypoxia/growth factor preconditioning, and biomaterial-based methods to improve cell survival and homing are summarized, and the potential strategies for their future application are also discussed.

Quiescence Preconditioned Human Multipotent Stromal Cells Adopt a Metabolic Profile Favorable for Enhanced Survival under Ischemia

A major impediment to the development of therapies with mesenchymal stem cells/multipotent stromal cells (MSC) is the poor survival and engraftment of MSCs at the site of injury. We hypothesized that lowering the energetic demand of MSCs by driving them into a quiescent state would enhance their survival under ischemic conditions. Human MSCs (hMSCs) were induced into quiescence by serum deprivation (SD) for 48 hours. Such preconditioned cells (SD-hMSCs) exhibited reduced nucleotide and protein syntheses compared to unpreconditioned hMSCs. SD-hMSCs sustained their viability and their ATP levels upon exposure to severe, continuous, near-anoxia (0.1% O₂ ) and total glucose depletion for up to 14 consecutive days in vitro, as they maintained their hMSC multipotential capabilities upon reperfusion. Most importantly, SD-hMSCs showed enhanced viability in vivo for the first week postimplantation in mice. Quiescence preconditioning modified the energy-metabolic profile of hMSCs: it suppressed energy-sensing mTOR signaling, stimulated autophagy, promoted a shift in bioenergetic metabolism from oxidative phosphorylation to glycolysis and upregulated the expression of gluconeogenic enzymes, such as PEPCK. Since the presence of pyruvate in cell culture media was critical for SD-hMSC survival under ischemic conditions, we speculate that these cells may utilize some steps of gluconeogenesis to overcome metabolic stress. These findings support that SD preconditioning causes a protective metabolic adaptation that might be taken advantage of to improve hMSC survival in ischemic environments. Stem Cells 2017;35:181-196.

Stem Cell Therapy for Myocardial Infarction 2001-2013 Revisited

Stem cell therapy for ischemic heart disease was an emerging concept in the early 2000s. First hopes were largely overshadowed by rather inconsistent results in human trials conducted in the middle of the decade. We aimed at investigating how the field of stem cell research expanded worldwide over the years using scientometric methods. We performed a PubMed inquiry and screened a total of 2609 publications dealing with stem cell therapy for myocardial infarction in the years 2001-2013. Density equalizing maps were used to visualize important centres of stem cell research worldwide. This systematic bibliometric study revealed an increasing research interest in the field of stem cell research in the context of ischemic heart disease over the last decade. Though some of the large human trials failed to show significant effects of stem cell therapy, especially basic science represents an ever growing field that evolved promising new concepts over the last couple of years. The scientific principle of protective paracrine mediators released from transplanted stem cells seems to bear great potential for future cell-free therapeutic use. However, further mechanistic insights are needed before transition from bench to bedside should be attempted, taking the lessons learned from previous studies into account.

The Therapeutic Effect of Adipose-Derived Mesenchymal Stem Cells for Radiation-Induced Bladder Injury

This study was designed to investigate the protective effect of adipose derived mesenchymal stem cells (AdMSCs) against radiation-induced bladder injury (RIBI). Female rats were divided into 4 groups: (a) controls, consisting of nontreated rats; (b) radiation-treated rats; (c) radiation-treated rats receiving AdMSCs; and (d) radiation-treated rats receiving AdMSCs conditioned medium. AdMSCs or AdMSCs conditioned medium was injected into the muscular layer of bladder 24 h after radiation. Twelve weeks after radiation, urinary bladder tissue was collected for histological assessment and enzyme-linked immunosorbent assay (ELISA) after metabolic cage investigation. At the 1 w, 4 w, and 8 w time points following cells injection, 3 randomly selected rats in RC group and AdMSCs group were sacrificed to track injected AdMSCs. Metabolic cage investigation revealed that AdMSCs showed protective effect for radiation-induced bladder dysfunction. The histological and ELISA results indicated that the fibrosis and inflammation within the bladder were ameliorated by AdMSCs. AdMSCs conditioned medium showed similar effects in preventing radiation-induced bladder dysfunction. In addition, histological data indicated a time-dependent decrease in the number of AdMSCs in the bladder following injection. AdMSCs prevented radiation induced bladder dysfunction and histological changes. Paracrine effect might be involved in the protective effects of AdMSCs for RIBI.

Diazoxide protects L6 skeletal myoblasts from H2O2-induced apoptosis via the phosphatidylinositol-3 kinase/Akt pathway

OBJECTIVES AND DESIGN

Transplanted cell survival might greatly improve the therapeutic efficacy of cell therapy. Diazoxide (DZ), a highly selective mitochondrial ATP-sensitive potassium channel opener, is known to suppress cell apoptosis and protect cells in oxidative stressed ischemic environment. We explored the mechanisms involved in DZ pre-treatment-induced anti-apoptotic effect on L6 skeletal myoblast (SKM).

MATERIALS AND METHODS

L6 SKMs were divided into control group, H2O2 group, DZ + H2O2 group and DZ + LY + H2O2 group. Treatments of 400 μmol/L H2O2 for 24 h alone, or after 200 μmol/L DZ pre-treatment for 30 min, or after DZ and 50 μmol/L LY294002 co-administration for 30 min were performed. The cell apoptosis rates were assessed by flow cytometric analysis. The changes of mitochondrial membrane potential were determined by JC-1 mitochondrial staining. The activation of phosphatidylinositol-3 kinase (PI3K)/Akt, caspase-9 and caspase-3 was detected by western blot.

RESULTS

Compared with the H2O2 group, DZ pre-treatment protected cells from H2O2-induced damage, increased Akt phosphorylation, prevented mitochondrial membrane depolarization as well as the activation of caspase-9 and caspase-3 and decreased the cell apoptosis rate. However, the DZ-induced cytoprotective and anti-apoptosis effects were partly inhibited by co-administration of a PI3K inhibitor, LY294002.

CONCLUSIONS

These data suggest that DZ pre-treatment contributes to protection of L6 SKMs against apoptosis at least partly by activating the PI3K/Akt pathway and subsequently inhibiting the mitochondrial-mediated caspase-dependent apoptotic signalling pathway.

Myoblast cell sheet transplantation enhances the endogenous regenerative abilities of infant hearts in rats with myocardial infarction

The shortage of heart transplantation donors for infants is severe. Regenerative cell therapy has been expected to offer new methods of treatment, and this study was about regenerative cell therapy for infant hearts. The aims of the present study were to clarify the effects of regenerative cell therapy on the infant heart. The heart impairment model and tissue-engineered myoblast cell sheets were used for regenerative cell therapy. Infant rats (n = 54) aged 2 weeks and adult rats aged 12 weeks (n = 35) were used. Myocardial infarction (MI) was induced as the heart impairment model and triple-layer myoblast cell sheets were used for transplantation to MI lesions. Infant rats after MI had better self-regenerative ability in wall thickness, fibrosis and cardiac function and we observed greater numbers of proliferating cardiomyocytes than in adults. Moreover, infant MI rats treated with myoblast cell sheets showed better results in wall thickness, fibrosis and cardiac function than infant MI rats without myoblast cell sheets, because of the positive effect that myoblast cell sheets had on proliferating cardiomyocytes, increasing vascular networks and accumulating c-kit-positive cells. We clarified that regenerative cell therapy enhances the endogenous regenerative ability of infant hearts in rats with MI; moreover, it has a greater therapeutic effect on infant hearts than on adult hearts, because of the ability of infant hearts for cardiomyocyte proliferation. The present paper provides essential new data for clinical therapy in infant patients. Copyright © 2015 John Wiley & Sons, Ltd.

Diazoxide preconditioning of endothelial progenitor cells from streptozotocin-induced type 1 diabetic rats improves their ability to repair diabetic cardiomyopathy

Type 1 diabetes mellitus (DM) is a strong risk factor for the development of diabetic cardiomyopathy (DCM) which is the leading cause of morbidity and mortality in the type 1 diabetic patients. Stem cells may act as a therapeutic agent for the repair of DCM. However, deteriorated functional abilities and survival of stem cells derived from type 1 diabetic subjects need to be overcome for obtaining potential outcome of the stem cell therapy. Diazoxide (DZ) a highly selective mitochondrial ATP-sensitive K(+) channel opener has been previously shown to improve the ability of mesenchymal stem cells for the repair of heart failure. In the present study, we evaluated the effects of DZ preconditioning in improving the ability of streptozotocin-induced type 1 diabetes affected bone marrow-derived endothelial progenitor cells (DM-EPCs) for the repair of DCM in the type 1 diabetic rats. DM-EPCs were characterized by immunocytochemistry, flow cytometry, and reverse transcriptase PCR for endothelial cell-specific markers like vWF, VE cadherin, VEGFR2, PECAM, CD34, and eNOS. In vitro studies included preconditioning of DM-EPCs with 200 μM DZ for 30 min followed by exposure to either 200 μM H2O2 for 2 h (for oxidative stress induction) or 30 mM glucose media (for induction of hyperglycemic stress) for 48 h. Non-preconditioned EPCs with and without exposure to H2O2 and 30 mM high glucose served as controls. These cells were then evaluated for survival (by MTT and XTT cell viability assays), senescence, paracrine potential (by ELISA for VEGF), and alteration in gene expression [VEGF, stromal derived factor-1α (SDF-1α), HGF, bFGF, Bcl2, and Caspase-3]. DZ preconditioned DM-EPCs demonstrated significantly increased survival and VEGF release while reduced cell injury and senescence. Furthermore, DZ preconditioned DM-EPCs exhibited up-regulated expression of prosurvival genes (VEGF, SDF-1α, HGF, bFGF, and Bcl2) on exposure to H2O2, and VEGF and Bcl2 on exposure to hyperglycemia while down regulation of Caspase-3 gene. Eight weeks after type 1 diabetes induction, DZ preconditioned, and non-preconditioned DM-EPCs were transplanted into left ventricle of diabetic rats (at a dose of 2 × 10(6) DM-EPCs/70 μl serum free medium). After 4 weeks, DZ preconditioned DM-EPCs transplantation improved cardiac function as assessed by Millar's apparatus. There was decrease in collagen content estimated by Masson's trichrome and sirius red staining. Furthermore, reduced cell injury was observed as evidenced by decreased expression of Caspase-3 and increased expression of prosurvival genes Bcl2, VEGF, and bFGF by semi-quantitative real-time PCR. In conclusion, the present study demonstrated that DZ preconditioning enhanced EPCs survival under oxidative and hyperglycemic stress and their ability to treat DCM.

Intracellular transduction of TAT-Hsp27 fusion protein enhancing cell survival and regeneration capacity of cardiac stem cells in acute myocardial infarction

Myocardial infarction (MI) results in the substantial loss of functional cardiomyocytes, which frequently leads to intractable heart disorders. Cardiac stem cells (CSCs) that retain the capacity to replace all cardiac cells might be a promising strategy for providing a source of new functional cardiomyocytes; however, the poor survival and engraftment of transplanted CSCs in the hostile environment of MI critically mitigate their therapeutic benefits. To capitalize their therapeutic potential, an ex vivo strategy in which CSCs were introduced to the recombinant heat shock protein 27 (Hsp27) through a TAT protein transduction domain for increasing the viability and engraftment in the infarcted myocardium was designed. A recombinant TAT fused Hsp27 (TAT-Hsp27) was able to enter CSCs in a dose-dependent manner. CSCs transduced with TAT-Hsp27 expressed not only endogenous Hsp27 but externally introduced Hsp27, resulting in substantial increase of their anti-oxidative and anti-apoptotic properties via suppressing reactive oxygen species production, the MAPKs signaling pathway, and caspase activation. TAT-Hsp27 enabled CSCs to be protected from apoptotic- and hypoxic-induced cell death during in vitro cardiomyogenic differentiation. In vivo studies demonstrated that CSCs transduced TAT-Hsp27 significantly increased the survival and engraftment in the acutely infarcted myocardium, which is closely related to caspase activity suppression. Finally, CSCs transduced TAT-Hsp27 improved cardiac function and attenuated cardiac remodeling in comparison with non-transduced CSCs. Overall, our approach, which is based on the ex vivo intracellular transduction of TAT-Hsp27 into CSCs before myocardial delivery, might be effective in treating MI.

The Paracrine Effect of Skeletal Myoblasts Is Cardioprotective Against Oxidative Stress and Involves EGFR-ErbB4 Signaling, Cystathionase, and the Unfolded Protein Response

Therapeutic effects of skeletal myoblast transplantation into the myocardium are mediated via paracrine factors. We investigated the ability of myoblast-derived soluble mediators to protect cardiomyocytes from oxidative stress. Fetal rat cardiac cells were treated with conditioned medium from cultures of myoblasts or cardiac fibroblasts, and oxidative stress was induced with H2O2. Myoblast-derived factors effectively prevented oxidative stress-induced cardiac cell death and loss of mitochondrial membrane potential. This protective effect was mediated via epidermal growth factor (EGF) receptor and c-Met signaling, and mimicked by neuregulin 1 but not EGF. Microarray analysis of cardiac cells treated with myoblast versus cardiac fibroblast-derived mediators revealed differential regulation of genes associated with antioxidative effects: cystathionine-γ-lyase (cst), xanthine oxidase, and thioredoxin-interacting protein as well as tribbles homolog 3 (trib3). Cardiac cell pretreatment with tunicamycin, an inducer of trib3, also protected them against H2O2-induced cell death. Epicardial transplantation of myoblast sheets in a rat model of acute myocardial infarction was used to evaluate the expression of CST and trib3 as markers of myoblasts' paracrine effect in vivo. Myoblast sheets induced expression of the CST as well as trib3 in infarcted myocardium. CST localized around blood vessels, suggesting smooth muscle cell localization. Our results provide a deeper molecular insight into the therapeutic mechanisms of myoblast-derived paracrine signaling in cardiac cells and suggest that myoblast transplantation therapy may prevent oxidative stress-induced cardiac deterioration and progression of heart failure.

In vitro ischemia decreases histone H4K16 acetylation in neural cells

Inhibitors of histone deacetylases are frequently used against ischemia-induced injury, but the specific mechanisms of their action are poorly understood. Here, we report that following a 5-7-h oxygen-glucose deprivation (OGD) acetylation of histone H4 at residue K16 (H4K16Ac) decreases by 40-80% in both PC12 cells and primary neurons. This effect can be reverted by treatment with trichostatin A, or by supplementation with acetyl-CoA. A decrease in H4K16Ac levels can affect the expression of mitochondrial uncoupling protein 2 (UCP2), huntingtin-interacting protein 1 (HIP1) and Notch-pathway genes in a cell-specific manner. Thus, H4K16 acetylation is important for responses to ischemia and cell energy stress, and depends on both cytosolic and mitochondrial acetyl-CoA.

Preconditioning of bone marrow mesenchymal stem cells by prolyl hydroxylase inhibition enhances cell survival and angiogenesis in vitro and after transplantation into the ischemic heart of rats

INTRODUCTION

Poor cell survival and limited functional benefits have restricted the efficacy of bone marrow mesenchymal stem cells (BMSCs) in the treatment of myocardial infarction. We showed recently that hypoxia preconditioning of BMSCs and neural progenitor cells before transplantation can enhance the survival and therapeutic properties of these cells in the ischemic brain and heart. The present investigation explores a novel strategy of preconditioning BMSCs using the Hypoxia-inducible factor 1α (HIF-α) prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG) to enhance their survival and therapeutic efficacy after transplantation into infarcted myocardium.

METHODS

BMSCs from green fluorescent protein transgenic rats were cultured with or without 1 mM DMOG for 24 hours in complete culture medium before transplantation. Survival and angiogenic factors were evaluated in vitro by trypan blue staining, Western blotting, and tube formation test. In an ischemic heart model of rats, BMSCs with and without DMOG preconditioning were intramyocardially transplanted into the peri-infarct region 30 minutes after permanent myocardial ischemia. Cell death was measured 24 hours after engraftment. Heart function, angiogenesis and infarct size were measured 4 weeks later.

RESULTS

In DMOG preconditioned BMSCs (DMOG-BMSCs), the expression of survival and angiogenic factors including HIF-1α, vascular endothelial growth factor, glucose transporter 1 and phospho-Akt were significantly increased. In comparison with control cells, DMOG-BMSCs showed higher viability and enhanced angiogenesis in both in vitro and in vivo assays. Transplantation of DMOG-BMSCs reduced heart infarct size and promoted functional benefits of the cell therapy.

CONCLUSIONS

We suggest that DMOG preconditioning enhances the survival capability of BMSCs and paracrine effects with increased differentiation potential. Prolyl hydroxylase inhibition is an effective and feasible strategy to enhance therapeutic efficacy and efficiency of BMSC transplantation therapy after heart ischemia.

Preconditioning strategy in stem cell transplantation therapy

Stem cell transplantation therapy has emerged as a promising regenerative medicine for ischemic stroke and other neurodegenerative disorders. However, many issues and problems remain to be resolved before successful clinical applications of the cell-based therapy. To this end, some recent investigations have sought to benefit from well-known mechanisms of ischemic/hypoxic preconditioning. Ischemic/hypoxic preconditioning activates endogenous defense mechanisms that show marked protective effects against multiple insults found in ischemic stroke and other acute attacks. As in many other cell types, a sub-lethal hypoxic exposure significantly increases the tolerance and regenerative properties of stem cells and progenitor cells. So far, a variety of preconditioning triggers have been tested on different stem cells and progenitor cells. Preconditioned stem cells and progenitors generally show much better cell survival, increased neuronal differentiation, enhanced paracrine effects leading to increased trophic support, and improved homing to the lesion site. Transplantation of preconditioned cells helps to suppress inflammatory factors and immune responses, and promote functional recovery. Although the preconditioning strategy in stem cell therapy is still an emerging research area, accumulating information from reports over the last few years already indicates it as an attractive, if not essential, prerequisite for transplanted cells. It is expected that stem cell preconditioning and its clinical applications will attract more attention in both the basic research field of preconditioning as well as in the field of stem cell translational research. This review summarizes the most important findings in this active research area, covering the preconditioning triggers, potential mechanisms, mediators, and functional benefits for stem cell transplant therapy.

Transplantation of SIRT1-engineered aged mesenchymal stem cells improves cardiac function in a rat myocardial infarction model

BACKGROUND

Previous studies have demonstrated that biological aging has a negative influence on the therapeutic effects of mesenchymal stem cells (MSCs)-based therapy. Using a rat myocardial infarction (MI) model, we tested the hypothesis that silent mating type information regulation 2 homolog 1 (SIRT1) may ameliorate the phenotype and improve the function of aged MSCs and thus enhance the efficacy of aged MSCs-based therapy.

METHODS

Sixty female rats underwent left anterior descending coronary artery ligation and were randomly assigned to receiving: intramyocardial injection of cell culture medium (DMEM group); SIRT1 overexpression vector-treated aged MSCs (SIRT1-aged MSCs group) obtained from aged male SD rats or empty vector-treated aged MSCs (vector-aged MSCs group). Another 20 sham-operated rats that underwent open-chest surgery without coronary ligation or any other intervention served as controls.

RESULTS

SIRT1-aged MSC group exhibited enhanced blood vessel density in the border zone of MI hearts, which was associated with reduced cardiac remodeling, leading to improved cardiac performance. Consistent with the in vivo data, our in vitro experiments also demonstrated that SIRT1 overexpression ameliorated aged MSCs senescent phenotype and recapitulated the pro-angiogenesis property of MSCs and conferred the anti-stress response capabilities, as indicated by increases in pro-angiogenic factors, angiopoietin 1 (Ang1) and basic fibroblast growth factor (bFGF), expressions and a decrease in anti-angiogenic factor thrombospondin-1 (TBS1) at mRNA levels, and increases in Bcl-2/Bax ratio at protein level.

CONCLUSIONS

Up-regulating SIRT1 expression could enhance the efficacy of aged MSCs-based therapy for MI as it relates to the amelioration of senescent phenotype and hence improved biological function of aged MSCs.

SIRT1 ameliorates age-related senescence of mesenchymal stem cells via modulating telomere shelterin

Mesenchymal stem cells (MSCs) senescence is an age-related process that impairs the capacity for tissue repair and compromises the clinical use of autologous MSCs for tissue regeneration. Here, we describe the effects of SIRT1, a NAD⁺-dependent deacetylase, on age-related MSCs senescence. Knockdown of SIRT1 in young MSCs induced cellular senescence and inhibited cell proliferation whereas overexpression of SIRT1 in aged MSCs reversed the senescence phenotype and stimulated cell proliferation. These results suggest that SIRT1 plays a key role in modulating age-induced MSCs senescence. Aging-related proteins, P16 and P21 may be downstream effectors of the SIRT1-mediated anti-aging effects. SIRT1 protected MSCs from age-related DNA damage, induced telomerase reverse transcriptase (TERT) expression and enhanced telomerase activity but did not affect telomere length. SIRT1 positively regulated the expression of tripeptidyl peptidase 1 (TPP1), a component of the shelterin pathway that protects chromosome ends from DNA damage. Together, the results demonstrate that SIRT1 quenches age-related MSCs senescence by mechanisms that include enhanced TPP1 expression, increased telomerase activity and reduced DNA damage.

Co-treating mesenchymal stem cells with IL‑1β and TNF-α increases VCAM-1 expression and improves post-ischemic myocardial function

Inflammatory mediators are released by the myocardium following myocardial ischemia as a response to tissue injury, and contribute to cardiac repair and adaptive responses. Treating mesenchymal stem cells (MSCs) with various inflammatory factors activates a series of biological processes that enhance cell-mediated cardioprotection following myocardial infarction (MI). The present study was designed to examine the effect of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) treatment on vascular cell adhesion molecule-1 (VCAM-1) expression in MSCs, and to identify whether cytokine-treated MSCs improve post-ischemic myocardial function in a rat model. MSCs were stimulated with IL-1β and/or TNF-α for 24 h, the production of vascular cell adhesion molecule-1 (VCAM-1) and the adhesion ability of MSCs were assessed by flow cytometry, adhesion assays, quantitative polymerase chain reaction and western blot analysis. The cardiac function was examined by two-dimensional echocardiography. The results demonstrated that in treated MSCs, the secretion of VCAM-1 and the cell adhesion ability were significantly increased, thus markedly improving cardiac function compared with that of the control group (P<0.01). Of all the groups, the rats stimulated with a combination of IL-1β and TNF-α exhibited the greatest cardiac improvements. However, there was no significant difference between the 10 and 20 ng/ml groups which were stimulated with one of the cytokines alone (P>0.05). In conclusion, stimulating MSCs with IL-1β and TNF-α promoted the expression of VCAM-1 and improved post-ischemic cardiac function recovery. Treating MSCs with two cytokines in combination may be a useful method to maximize the potential of cell-based therapy for MI.

Melatonin regulates mesenchymal stem cell differentiation: a review

Among the numerous functions of melatonin, the control of survival and differentiation of mesenchymal stem cells (MSCs) has been recently proposed. MSCs are a heterogeneous population of multipotent elements resident in tissues such as bone marrow, muscle, and adipose tissue, which are primarily involved in developmental and regeneration processes, gaining thus increasing interest for tissue repair and restoration therapeutic protocols. Receptor-dependent and receptor-independent responses to melatonin are suggested to occur in these cells. These involve antioxidant or redox-dependent functions of this indolamine as well as secondary effects resulting from autocrine and paracrine responses. Inflammatory cytokines and adipokines, proangiogenic/mitogenic stimuli, and other mediators that influence the differentiation processes may affect the survival and functional integrity of these mesenchymal precursor cells. In this scenario, melatonin seems to regulate signaling pathways that drive commitment and differentiation of MSC into osteogenic, chondrogenic, adipogenic, or myogenic lineages. Common pathways suggested to be involved as master regulators of these processes are the Wnt/β-catenin pathway, the MAPKs and the, TGF-β signaling. In this respect melatonin emerges a novel and potential modulator of MSC lineage commitment and adipogenic differentiation. These and other aspects of the physiological and pharmacological effects of melatonin as regulator of MSC are discussed in this review.

Small molecules for cell reprogramming and heart repair: progress and perspective

Regenerative medicine for heart failure seeks to replace lost cardiomyocytes. Chemical approaches for producing ample supplies of cells, such as pluripotent stem cells and cardiomyocytes, hold promise as practical means to achieve safe, facile cell-based therapy for cardiac repair and regenerative medicine. In this review, we describe recent advances in the application of small molecules to improve the generation and maintenance of pluripotent stem cells. We also describe new directions in heart repair and regeneration in which chemical approaches may find their application.

Cell based therapies for ischemic stroke: from basic science to bedside

Cell therapy is emerging as a viable therapy to restore neurological function after stroke. Many types of stem/progenitor cells from different sources have been explored for their feasibility and efficacy for the treatment of stroke. Transplanted cells not only have the potential to replace the lost circuitry, but also produce growth and trophic factors, or stimulate the release of such factors from host brain cells, thereby enhancing endogenous brain repair processes. Although stem/progenitor cells have shown a promising role in ischemic stroke in experimental studies as well as initial clinical pilot studies, cellular therapy is still at an early stage in humans. Many critical issues need to be addressed including the therapeutic time window, cell type selection, delivery route, and in vivo monitoring of their migration pattern. This review attempts to provide a comprehensive synopsis of preclinical evidence and clinical experience of various donor cell types, their restorative mechanisms, delivery routes, imaging strategies, future prospects and challenges for translating cell therapies as a neurorestorative regimen in clinical applications.

Preconditioning of Human Skeletal Myoblast with Stromal Cell-derived Factor-1α Promotes Cytoprotective Effects against Oxidative and Anoxic Stress

BACKGROUND AND OBJECTIVES

The incidence of human autologous transplanted skeletal myoblast (SkM) cell death in ischemic myocardium was higher in the first few days after cell therapy. We proposed that human SkM treated by human stromal cell-derived factor (SDF-1α) protein or tranfected by SDF-1α, precondition them against oxidative or anoxic injury.

METHODS AND RESULTS

The purification of human SkM (80∼90%) culture was assessed for desmin and CXCR4 expression using immunostaining and flow cytometry respectively. Cells were transfected to overexpress SDF-1α or treated with rSDF-1α (10∼200 ng/ml, 1∼4 h) were either exposed to anoxia or treated with 100μM H2O2 for different time periods (1∼6 h anoxia) (1∼3 h H2O2). Optimized conditions for transfection of SDF-1α gene into human SkM were achieved, using FuGene(TM)6/phSDF-1α(3：2 v/w, 4 h transfection) with 125μ M ZnCl2 (p＜ 0.001), up to 7 days post-transfection as compared with transfected SkM without ZnCl2 and non-transfected control cells. Transfection efficiency was assessed by immunostaining, ELISA, western blots and PCR. LDH analysis showed significant decrease in release of LDH after exposure to 6 h anoxia or 100μ M H2O2 for 2 h as compared with the normal un-treated or un-transfected SkM (p＜ 0.001). In western blots assay, SDF-1α over-expressing human SkM or treated with rSDF-1α induced marked expression of total Akt (1.2-fold) and phospho-Akt (2.7-fold), Bcl2 (1.6-fold) and VEGF (5.8-fold) after exposure to 6 h anoxia as compared with human SkM controls.

CONCLUSIONS

The preconditioning of donor transplanted human SkM with SDF-1α increased cell survival and promoted cytoprotective effect against oxidative or anoxic injury that may be an innovative approach for clinical application.

Diabetes-associated macrovascular complications: cell-based therapy a new tool?

Diabetes mellitus and its ongoing macrovascular complications represent one of the major health problems around the world. Rise in obesity and population ages correlate with the increased incidence of diabetes. This highlights the need for novel approaches to prevent and treat this pandemic. The discovery of a reservoir of stem/progenitors in bone marrow and in mesenchymal tissue has attracted interest of both biologists and clinicians. A number of preclinical and clinical trials were developed to explore their potential clinical impact, as target or vehicle, in different clinical settings, including diabetes complications. Currently, bone marrow, peripheral blood, mesenchymal, and adipose tissues have been used as stem/progenitor cell sources. However, evidences have been provided that both bone marrow and circulating progenitor cells are dysfunctional in diabetes. These observations along with the growing advantages in genetic manipulation have spurred researchers to exploit ex vivo manipulated cells to overcome these hurdles. In this article, we provide an overview of data relevant to stem-progenitors potential clinical application in revascularization and/or vascular repair. Moreover, the hurdles at using progenitor cells in diabetic patients will be also discussed.

Lipocalin-2-mediated upregulation of various antioxidants and growth factors protects bone marrow-derived mesenchymal stem cells against unfavorable microenvironments

Despite many advantages of mesenchymal stem cells (MSCs) that make them suitable for cell therapy purposes, their therapeutic application has been limited due to their susceptibility to several stresses (e.g., nutrient-poor environment, oxidative stress, and hypoxic and masses of cytotoxic factors) to which they are exposed during their preparation and following transplantation. Hence, reinforcing MSCs against these stresses is a challenge for both basic and clinician scientists. Recently, much attention has been directed toward equipping MSCs with cytoprotective factors to strengthen them against unfavorable microenvironments. Here, we engineered MSCs with lipocalin 2 (Lcn2), a cytoprotective factor that is naturally induced following exposure of cells to stresses imposed by the microenvironment. Lcn2 overexpression not only did not interfere with the multidifferentiation capacity of the MSCs but also granted many protective properties to them. Lcn2 potentiated MSCs to withstand oxidative, hypoxia, and serum deprivation (SD) conditions via antagonizing their induced cytotoxicity and apoptosis. Adhesion rate of MSCs to coated culture plates was also enhanced by Lcn2 overexpression. In addition, Lcn2 induced antioxidants and upregulated some growth factors in MSCs. Our findings suggested a new strategy for prevention of graft cell death in MSC-based cell therapy.

Improving survival and efficacy of pluripotent stem cell-derived cardiac grafts

Human embryonic stem cells (hESCs) can be differentiated into structurally and electrically functional myocardial tissue and have the potential to regenerate large regions of infarcted myocardium. One of the key challenges that needs to be addressed towards full-scale clinical application of hESCs is enhancing survival of the transplanted cells within ischaemic or scarred, avascular host tissue. Shortly after transplantation, most hESCs are lost as a result of multiple mechanical, cellular and host factors, and a large proportion of the remaining cells undergo apoptosis or necrosis shortly thereafter, as a result of loss of adhesion-related signals, ischaemia, inflammation or immunological rejection. Blocking the apoptotic signalling pathways of the cells, using pro-survival cocktails, conditioning hESCs prior to transplant, promoting angiogenesis, immunosuppressing the host and using of bioengineered matrices are among the emerging techniques that have been shown to optimize cell survival. This review presents an overview of the current strategies for optimizing cell and host tissue to improve the survival and efficacy of cardiac cells derived from pluripotent stem cells.

Cardiac stem cells with electrical stimulation improve ischaemic heart function through regulation of connective tissue growth factor and miR-378

AIMS

In this study, we investigated whether pre-conditioning (PC) by electrical stimulation (EleS) induces cytoprotective effect on cardiac stem cells (CSCs) and determined its underlying molecular mechanisms.

METHODS AND RESULTS

Sca-1(+) CSCs were isolated from male C57BL6 mice (12 weeks) hearts. PC of CSCs with EleS ((EleS)CSCs) was carried out for 3 h at 1.5 V followed by exposure to 300 µM H2O2 for 5 h. Cytoprotective effects and cell adhesion ability were significantly increased by EleS as evaluated by transferase-mediated dUTP nick-end labelling (TUNEL), lactate dehydrogenase (LDH) release assay, and adhesion assay. EleS increased phosphorylation of AKT, focal adhesion kinase (FAK), and glycogen synthase kinase (GSK3β), as well as decreased caspase-3 cleavage. Interestingly, inhibition of AKT or FAK abolished the pro-survival effects of EleS. We found that connective tissue growth factor (Ctgf) was responsible for EleS-induced CSC survival and adhesion.The survival rate of (EleS)CSCs after transplantation in the infarcted myocardium was significantly increased together with improvement in cardiac function. Importantly, knockdown of Ctgf abolished EleS-induced cytoprotective effects and recovery of cardiac function. Furthermore, we identified miR-378 as a potential Ctgf regulator in (EleS)CSCs.

CONCLUSION

EleS enhanced CSC survival in vitro and in vivo as well as functional recovery of the ischaemic heart through an AKT/FAK/CTGF signalling pathway. It is suggested that Ctgf and miR-378 are novel therapeutic targets for stem cell-based therapy.

Transplantation of bone marrow-derived mesenchymal stem cells after regional hepatic irradiation ameliorates thioacetamide-induced liver fibrosis in rats

BACKGROUND

Recent studies have demonstrated that bone marrow-derived mesenchymal stem cells (BM-MSCs) can potentially revert liver fibrosis, but it is not known if preparative hepatic irradiation (HIR) contributes to the therapeutic effect of transplanted BM-MSCs. In this study, we investigate the effects of HIR on transplanted BM-MSCs in cirrhotic rats and the underlying mechanism by which mesenchymal stem cells (MSCs) relieve liver fibrosis.

MATERIALS AND METHODS

The BM-MSCs from male rats were labeled with CM-Dil and injected via portal vein into two groups of thioacetamide-induced cirrhotic rats, and the controls were injected with the same volume of saline. The right hemiliver of one cirrhotic rat group was irradiated (15 Gy) 4 d before transplantation. Liver function tests and histologic experiments were performed, and the liver population of BM-MSCs was estimated.

RESULTS

The transplantation of MSCs alleviated liver fibrosis and reduced expression of transforming growth factor-β1, Smad2, collagen type I, and α-SMA. HIR preconditioning promoted homing and repopulation of MSCs and resulted in better treatment outcomes.

CONCLUSIONS

HIR preconditioning enhances the effect of BM-MSCs in improving thioacetamide-induced liver fibrosis in rats by promoting their homing and repopulation. BM-MSCs may function by inhibiting transforming growth factor-β1-Smad signaling pathway in the liver.

Priming adult stem cells by hypoxic pretreatments for applications in regenerative medicine

The efficiency of regenerative medicine can be ameliorated by improving the biological performances of stem cells before their transplantation. Several ex-vivo protocols of non-damaging cell hypoxia have been demonstrated to significantly increase survival, proliferation and post-engraftment differentiation potential of stem cells. The best results for priming cultured stem cells against a following, otherwise lethal, ischemic stress have been obtained with brief intermittent episodes of hypoxia, or anoxia, and reoxygenation in accordance with the extraordinary protection afforded by the conventional maneuver of ischemic preconditioning in severely ischemic organs. These protocols of hypoxic preconditioning can be rather easily reproduced in a laboratory; however, more suitable pharmacological interventions inducing stem cell responses similar to those activated in hypoxia are considered among the most promising solutions for future applications in cell therapy. Here we want to offer an up-to-date review of the molecular mechanisms translating hypoxia into beneficial events for regenerative medicine. To this aim the involvement of epigenetic modifications, microRNAs, and oxidative stress, mainly activated by hypoxia inducible factors, will be discussed. Stem cell adaptation to their natural hypoxic microenvironments (niche) in healthy and neoplastic tissues will be also considered.

Overexpression of CXCL12 chemokine up-regulates connexin and integrin expression in mesenchymal stem cells through PI3K/Akt pathway

Mesenchymal stem cells offer several potential advantages over other types of stem cells for cardiac repair. Nevertheless, poor survival of donor cells is one of the major concerns that hampers a better prognosis. Integrins, which involved in cell/extracellular matrix (ECM) interaction and connexins (Cxs), with a dual role as an anti-apoptotic and gap-junctional protein, can effectively resolve this issue. CXCL12, a member of the chemokine CXC subfamily, may play a role in stem cell survival and proliferation. CXCL12 activates several signaling pathways in stem cells, particularly the survival kinase, PI3K/Akt, which is also an important mediator of integrins and Cxs. Based on these characteristics of CXCL12, we investigated the potential of CXCL12 overexpression to induce integrin and connexin expression via PI3K/Akt pathway. Mesenchymal stem cells were transfected with adenovirus for increasing CXCL12 secretion. Membranous integrin and Cx expression as well as Akt expression levels were evaluated using Western blot analysis. Transfection resulted in increased CXCL12 in situ. Increased CXCL12 elevated membrane Cx43, Cx45, and integrin αVβ3 expression, as well as Cx phosphorylaton, which was activated by PI3K/Akt pathway. This mechanism may serve to improve mesenchymal stem cell viability in host tissue.