Paracrine Hypothesis Research Articles

Review article: Paracrine effects of Transplanted Neural stem cells in Ischemic strokes

Ischemic stroke is one of the most common causes of death in the world. Pathophysiologically, ischemic stroke is associated with blood brain barrier disruption, cell loss, inflammation and intense immune reaction which worsen the condition. The Stroke Treatment Academic Industry Roundtable recommends the use of any treatment that has multiple mechanisms of action to restore the neurological function. Growing evidences from researchers to understand the biology of neural stem cells indicated that these cells have crucial role in brain homeostasis and have high therapeutic potential to modify and restore neurological function after neurovascular injury. Contemporarily, Paracrine hypothesis is growing and indicated that neural stem cells transplantation can release several neurotrophic factors which can regenerate, restore, and modulate the neurological diseases by mitigating the inflammatory process, reducing the immune reactions and also can stimulate the angiogenesis and neurogenesis. This, generate a new attitude toward the development of acellular therapy instead of using whole allogenic neural stem cells in the regenerative medicine. This review is to focus on the paracrine effects of transplanted neural stem cells in the brain ischemic injuries which can modulate and improve the neurological outcome after ischemic injury.

Mesenchymal Stem Cells for Coronavirus (COVID-19)-Induced Pneumonia: Revisiting the Paracrine Hypothesis with New Hopes?

Mesenchymal stem cells (MSCs) bear a promising potential for regenerative medicine therapies and they repair damaged tissue through secretion of immune modulatory and anti-inflammatory molecules acting in a paracrine fashion. Coronavirus disease 2019 (COVID-19) has spread all over the world with high morbidity and mortality rates and there is no specific treatment for this infection. A recent study published in the journal reports that MSC infusion is safe and effective in patients suffering from COVID-19 induced pneumonia. In the light of this study and previous reports, we make additional comments about possible therapeutic effects of MSCs in COVID-19 infection.

Cell-Based Therapy in Cardiac Regeneration: An Overview.

Although pioneering preclinical research on the use of cell therapy for cardiac regeneration was conducted in the last quarter of the 20th century,1,2 a preponderance of advances have occurred in the 21st century, making this a relatively young field. In the first important clinical trial of cardiac cell therapy, begun in 2001, Menasche et al3 implanted autologous skeletal myoblasts into postinfarct scar at the time of coronary artery bypass surgery. Although the transplanted cells remained viable and exhibited contraction, they formed the nidus for serious ventricular tachyarrhythmias, which led to premature discontinuation of the trial. Despite this outcome, the trial energized the field, accelerating both preclinical and clinical research, albeit not with skeletal myoblasts. The extensive progress in cardiac regeneration is reviewed in this Compendium, and as occurs frequently in science, important observations have led to more questions and challenges (Table). View this table: Table. Important Challenges to Cell Therapy for Cardiac Regeneration Many cell types have been evaluated as candidates for cardiac regeneration. Among the earliest clinical trials, Zeiher’s group infused autologous bone marrow-derived progenitor cells into the coronary arteries of patients with acute,4 as well as healed myocardial infarction (MI)5 and reported improvements in left ventricular (LV) function. However, these results have not been fully confirmed by later studies, as pointed out in the review in the Compendium by Banarjee, Bolli, and Hare.6 Pittenger et al7 were among the first to direct attention to bone marrow-derived (stromal) mesenchymal stem cells (MSCs), emphasizing that these cells proliferated extensively in culture and suggesting that they could be attractive candidates for transplantation. In 2004, Chen et al8 reported that intracoronary infusion of autologous bone marrow-derived MSCs improved cardiac function. Zimmet and Hare pointed out that MSCs lack histocompatibility type II markers and elude rejection by …

Paracrine Hypothesis and Cardiac Repair

Paracrine Hypothesis and Cardiac Repair

Expanding the Paracrine Hypothesis of Stem Cell-Mediated Repair in the Heart: When the Unconventional Becomes Conventional.

Recent interest in mechanisms of stem cell–mediated repair in the heart have spawned the paracrine hypothesis, which posits that stem cells release beneficial substances that improve regeneration and function of the injured and diseased myocardium. In support of this hypothesis are studies showing that stem cells release small membranous vesicles called exosomes that deliver beneficial cargo to other cells in the heart. However, in addition to exosomes, which are released by the unconventional secretory pathway, are many other potentially beneficial factors released by the unconventional and the conventional secretory pathways. Therefore, a broader perspective of mechanisms of secretion, as well as an appreciation for the ways in which the secretion of a wide range of different types of molecules can be regulated, will spawn new avenues of thought necessary to move us beyond the exosome-centric view that drives much of the current thinking of those who study of stem cell–mediated repair in the heart. Secretion is what cells do; excretion is what the kidney does. Secretion is an active process by which cells release materials into the surrounding environment. Among the first secretion mechanisms studied were those involved in the regulated release of peptide hormones from endocrine cells. After release, substances can signal to cells afar via the blood stream (endocrine) and to neighboring cells (paracrine), as well as the cell of origin (autocrine). Additionally, some substances signal within the cell of origin (intracrine). Endocrine, paracrine, and autocrine signaling all involve the release of communicator substances directly into the interstitial spaces surrounding the cells of origin. Secretion into a duct, such as salivary or digestive enzyme secretion, is exocrine. Cells secrete many different substances, including proteins, lipids, steroids, nucleic acids, nucleotides, metabolites, and ions. Generally, these substances are secreted to facilitate communication with other cells and to affect the structure …

Paracrine Mechanisms of Intravenous Bone Marrow-Derived Mononuclear Stem Cells in Chronic Ischemic Stroke

Background: The emerging role of stem cell technology and transplantation has helped scientists to study their potential role in neural repair and regeneration. The fate of stem cells is determined by their niche, consisting of surrounding cells and the secreted trophic growth factors. This interim report evaluates the safety, feasibility and efficacy (if any) of bone marrow-derived mononuclear stem cells (BM-MNC) in chronic ischemic stroke by studying the release of serum vascular endothelial growth factor (VEGF) and brain-derived neurotrophic growth factor (BDNF). Methods: Twenty stroke patients and 20 age-matched healthy controls were recruited with the following inclusion criteria: 3 months to 1.5 years from the index event, Medical Research Council (MRC) grade of hand muscles of at least 2, Brunnstrom stage 2-5, conscious, and comprehendible. They were randomized to one group receiving autologous BM-MNC (mean 60-70 million) and to another group receiving saline infusion (placebo). All patients were administered a neuromotor rehabilitation regime for 8 weeks. Clinical assessments [Fugl Meyer scale (FM), modified Barthel index (mBI), MRC grade, Ashworth tone scale] were carried out and serum VEGF and BDNF levels were assessed at baseline and at 8 weeks. Results: No serious adverse events were observed during the study. There was no statistically significant clinical improvement between the groups (FM: 95% CI 15.2-5.35, p = 0.25; mBI: 95% CI 14.3-4.5, p = 0.31). VEGF and BDNF expression was found to be greater in group 1 compared to group 2 (VEGF: 442.1 vs. 400.3 pg/ml, p = 0.67; BDNF: 21.3 vs. 19.5 ng/ml) without any statistically significant difference. Conclusion: Autologous mononuclear stem cell infusion is safe and tolerable by chronic ischemic stroke patients. The released growth factors (VEGF and BDNF) in the microenvironment could be due to the paracrine hypothesis of stem cell niche and neurorehabilitation regime.

Current Trends in Regenerative Medicine: From Cell to Cell-Free Therapy

One of the most promising approaches to stimulate regeneration and angiogenesis in traumatic or ischemic tissue damage is stem cell therapy. Embryonic and fetal stem cells have the greatest potential of differentiation into different cell types; however, at the same time, they carry the highest risk of teratoma formation. Adult stem cells have the potential risk of transformation during prolonged cultivation in vitro, or as a result of genetic changes during gene-cell therapy applications. In this regard, technologies that can reduce the potential risks of cell and gene-cell therapy are of particular interest. According to the paracrine hypothesis, the beneficial effect of stem cell therapy is due to stimulation of resident cells by cell-to-cell contacts, secretion of bioactive molecules, and release of extracellular vesicles. In this review, we discuss the development of regenerative medicine from cell to cell-free therapy based on extracellular vesicles.

Abstract WP146: Intravenous Bone Marrow Derived Mononuclear Stem Cells in Chronic Ischemic Stroke-Paracrine Mechanisms of Recovery

Background: The emerging role of Stem cell technology and transplantation has helped scientists to study its potential role in neural repair and regeneration. The fate of stem cells is determined by its niche, consisting of surrounding cells and the secreted trophic growth factors. This present study evaluates the safety, feasibility and efficacy of bone marrow derived mononuclear stem cells (BM-MNC) in chronic ischemic stroke by studying the release of serum vascular endothelial growth factor (VEGF) and brain derived neurotrophic growth factor (BDNF). Methods: Twenty (n=20) stroke patients recruited with the inclusion criteria as: 3 months to 1.5 years of index event, power of hand muscles atleast 2; Brunnstrom stage: 2-5; conscious and comprehendible, were randomized to study and control groups receiving autologous mean 60-70 million BM-MNC and controls receiving neuromotor rehabilitation regime only for 8 weeks. Clinical assessment (FM, mBI, MRC, Ashworth) and serum VEGF & BDNF were done at baseline and 8 weeks (2 months). Results: No patients exhibited any complication or adverse events during the whole procedure. There was no statistical significant clinical improvement between study and control groups (FM: 95%CI; 15.2 to 5.35, p=0.25; mBI : 95% CI;14.3 to 4.5, p=0.31). VEGF and BDNF were increased after stem cell infusion and exercise training in both the groups (VEGF: 442.1 pg/ml vs 400.3pg/ml; p=0.67; BDNF:95% CI∼15.09 to 4.09, p=0.57), without any statistical significant result. Conclusion: Autologous mononuclear stem cell infusion is safe and tolerable by chronic ischemic stroke. The paracrine hypothesis extends the traditional concept of stem cell niche to study the influence of stem cell released growth factors (VEGF and BDNF) on the microenvironment.

Exosomes isolation protocols: facts and artifacts for cardiac regeneration.

In recent years, exosomes have attracted increasing scientific interest and are no longer considered just as containers for cell waste, but as important mediators of intercellular communication. Among many biomedical research topics, a possible direct role of exosomes in the regenerative medicine field has been underlined in recent studies, including those regarding the so called "paracrine hypothesis". In this perspective, a therapeutic role and/or use of exosomes for tissue regeneration seems to be plausible. However, the majority of the cells isolated and cultured in vitro are exposed to an exogenous exosomes source because of the wide use of foetal bovine serum as cell culture supplement. Bovine serum has been gradually considered as a major biological stimulus, but with still unknown outcome. In this review, we present the state of the art about the role of exosomes in regenerative medicine, particularly for the cardiovascular system. We also analyse the most commonly used exosome isolation techniques that, since their discovery, have undergone continuous development to reach the highest degree of scalability for future clinical translation.

Abstract 109: Characterization of Secretome From C-kit+ Cells Derived From Neonate and Adult Heart Patients

Background: Despite the regenerative benefit reported in recent human clinical trials (SCIPIO trial) using human cardiac stem cells (CSCs) (identified by ckit+CD45-/lin-), low retention and differentiation of transplanted hCSCs into cardiomyocytes are insufficient to explain the myocardial regeneration. This discrepancy has led to the paracrine hypothesis of stem cell action that indicates communication between newly transplanted stem cells and reparative native cells, essentially jumpstarting the repair process. Methods: We derived CSCs from the biopsies of right atrial appendage (RAA) of neonatal human subjects (nCSCs, age < 2 months) and from adult human subjects (aCSCs, age >50 years). CSCs were grown upto 90% confluency and incubated with basal medium (Ham’s/F12) for 72 hours. Conditioned medium (CM) was collected and further analyzed. Results: The expression levels of various key cytokines were analyzed using ELISA and data showed nCSCs secrete higher levels of the angiogenic cytokines like SDF1, VEGF-A, ANG, SCF, PDGB, and FGF2 compared to over 20 other cytokines we examined as compared to aCSCs. CM derived from nCSCs showed more angiogeneic potential as compared to CM derived from aCSCs as analyzed by HuVEC tube assay formation. We also did a comparative analysis of CM from nCSCs and aCSCs using mass spectrometry. Molecular distribution of lead proteins revealed that the yhCSCs has more angiogenic, anti-inflammatory and proliferative proteins while ahCSCs have more of apoptotic proteins Conclusion: These data provide preliminary evidence that there is a difference in the cytokine secretion by the nCSCs as compared to aCSCs and implicates highly expressed cytokines as the key to myocardial recovery.

Abstract 158: Assessing the Paracrine Hypothesis in Cardiac Regeneration Through Endogenous c-Kit+ Cells

Multiple studies have shown an innate capacity of the adult mammalian heart to partially regenerate following stress or injuries such as myocardial infarction (MI). However, this modest capacity is insufficient to resolve the significant damage that occurs post-MI, thus efforts have centered on bolstering this regenerative potential by delivery of various stem or progenitor cell types. To-date, over fifty clinical trials have evaluated cell-based therapeutics to induce regeneration in the setting of ischemic heart disease - mostly using bone marrow mononuclear cells (BM-MNCs) although c-Kit + cardiac progenitor cells (CPCs) and mesenchymal stromal cells (MSCs) from bone were also evaluated. Collectively, cell therapy has demonstrated clinical safety; yet overall effectiveness has been questioned, as evidence that transplanted cells differentiate into cardiomyocytes is lacking. Hence, studies showing some functional benefit have ascribed it to enhanced endogenous regeneration via paracrine factors secreted by the implanted cells. One hypothesis is that these factors stimulate resident c-Kit + progenitors to generate new myocardium. We recently developed an inducible genetic system to trace endogenous c-Kit + cells in the murine heart. We now use this system to evaluate whether delivery of different progenitor-like cell types can enhance c-Kit + -derived myocyte or vessel formation in the uninjured heart; using a dual-reporter strategy to differentially fate map transplanted cells versus endogenous c-Kit + cells. We observed that BM-MNCs induced a modest increase in c-Kit + -derived, CD31 + vessels proximal to the site of injection, although no new myocytes were observed. There was no evidence for fusion between BM-MNCs and host myocardium, or for prolonged engraftment, as by 6 weeks virtually all injected cells were cleared. Taken together, this suggests that BM-MNCs are capable of inducing an acute c-Kit + -mediated vascular response in the uninjured heart. We are also currently evaluating CPCs, bone marrow or adipose-derived MSCs, and bone stromal cells for their capacity to stimulate c-Kit + cells, either without injury or after MI. Our goal is to better define the paracrine hypothesis, improving cell-based therapies for application in humans.

MiRNA Expression in Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) express defined patterns of miRNAs which have been shown to be involved in stemness and differentiation processes. Modulation of miRNA expression by MSCs has been shown to change their biological properties. Moreover, in light of the paracrine hypothesis of MSC action, increasing evidence indicates that miRNA transfer between MSCs and injured cells in tissues accounts for the healing properties exhibited by MSCs. Extracellular vesicles (EVs) are candidates for the trafficking of encapsulated miRNAs between cells, as they are able to cross easily biological barriers and protect nucleic acids from degradation. Moreover, EVs, by expressing the same surface receptors of MSCs, may be recruited to the site of injury as well as the cell of origin. These properties of EVs may be exploited for the generation of specially engineered EVs carrying specific miRNAs for therapeutic purposes.

The Development of Stem Cell-Derived Exosomes as a Cell-Free Regenerative Medicine

A successful strategy in regenerative medicine over the last decade has been the translation of stem cell therapy to repair diseased or damaged tissue in a wide range of indications, despite limited evidence attributing any therapeutic benefit to cell survival or differentiation. Recent findings, however, have demonstrated that the conditioned media from stem cell cultures can produce similar efficacious effects compared to those observed for cells. This has led to the stem cell paracrine hypothesis, proposing that secreted factors released from the stem cells contribute significantly to their beneficial effects. It has been well documented that stem cells have the ability to release a range of growth factors, cytokines and chemokines relevant to their function; however, these factors are released at levels too low to account for the reported therapeutic effects. Further purification of the conditioned media has since identified that not only are small molecules released by the stem cells, but so too are a large quantity of membrane-bound vesicles, including exosomes, in a functionally relevant manner. In this review, we present our current understanding and explore the evidence supporting the development of stem cell-derived exosomes as a cell-free regenerative medicine.

The stem cell secretome and its role in brain repair

Compelling evidence exists that non-haematopoietic stem cells, including mesenchymal (MSCs) and neural/progenitor stem cells (NPCs), exert a substantial beneficial and therapeutic effect after transplantation in experimental central nervous system (CNS) disease models through the secretion of immune modulatory or neurotrophic paracrine factors.This paracrine hypothesis has inspired an alternative outlook on the use of stem cells in regenerative neurology. In this paradigm, significant repair of the injured brain may be achieved by injecting the biologics secreted by stem cells (secretome), rather than implanting stem cells themselves for direct cell replacement. The stem cell secretome (SCS) includes cytokines, chemokines and growth factors, and has gained increasing attention in recent years because of its multiple implications for the repair, restoration or regeneration of injured tissues.Thanks to recent improvements in SCS profiling and manipulation, investigators are now inspired to harness the SCS as a novel alternative therapeutic option that might ensure more efficient outcomes than current stem cell-based therapies for CNS repair.This review discusses the most recent identification of MSC- and NPC-secreted factors, including those that are trafficked within extracellular membrane vesicles (EVs), and reflects on their potential effects on brain repair. It also examines some of the most convincing advances in molecular profiling that have enabled mapping of the SCS.

The birth of ‘regenerative pharmacology’: a clinical perspective

Since the seminal paper by Orlic and colleagues in 2001, which demonstrated that local injection of bone marrow-derived stem cells leads to an improvement in cardiac function in a mouse model of myocardial infarction (MI; Orlic et al., 2001), there has been considerable debate with regard to the mechanism by which cardiac repair is achieved. The results in the original paper suggested that the bone marrow-derived allogeneic cells underwent transdifferentiation into cardiomyocytes, thereby repairing the infarcted myocardium. Since then, other groups have shown that bone marrow-derived cells can affect cardiac repair, but no formation of new cardiomyocytes has been observed (Murry et al., 2004; Nygren et al., 2004; Balsam and Robbins, 2005). In order to reconcile these observations, several hypotheses have been proposed to explain cardiac repair in the absence of regeneration and are summarized in Figure 1 (Lovell and Mathur, 2010). Although all of the proposed mechanisms are based on associated evidence, the ‘paracrine effect’ appears to have the most data supporting it, irrespective of the cell type used (Kinnaird et al., 2004; Gnecchi et al., 2005; Xu et al., 2007; Korf-Klingebiel et al., 2008; Ratajczak et al., 2012). The paracrine effect proposes that cells delivered to the site of organ injury (in this case MI) secrete a factor or a combination of factors that have a beneficial effect on cardiac function that is achieved either by enhancing surviving myocyte function, by preventing cell loss as a result of the ischaemic insult (e.g. activation of survival pathways) or stimulating ‘resident’ stem cell niches. The potential identification of individual factors as part of this hypothesis immediately raises the possibility of understanding the ligand–receptor interaction and hence the development of new pharmacological targets in the field of regenerative medicine. The development of an off-the-shelf drug that is capable of myocardial repair and can easily be applied to ‘all comers’ has clinical appeal and would revolutionize the application of regenerative medicine. Although considerable obstacles need to be overcome, more evidence is accumulating to bring the field closer to understanding whether the mechanisms of cell-derived therapy can be dissected down to the ‘basic pharmacology’ that controls them. The role that pharmacology plays as an adjunct to current approaches to cell therapy should also not be overlooked and demonstrates a significant partnership between the two fields. Below, this partnership will be explored using the clinical trials that have targeted cardiovascular disease as an example. Factors that have been identified as part of the paracrine hypothesis will be discussed and the potential for the development of a purely pharmacological approach considered. Figure 1 Potential mechanisms of stem cell therapy. Although initial research was focused on whether stem cells transdifferentiate into functioning cardiomyocytes, subsequent research has supported the existence of other mechanisms including the paracrine hypothesis. ...

Role of mesenchymal stem cell-derived microvesicles in tissue repair

Results from recent studies suggest that the beneficial effect of stem cell-based therapy is mainly dependent on a paracrine effect. The paracrine hypothesis implicates the ability of stem cells to limit injury or coordinate repair through the release of soluble factors. Among these factors microvesicles (MVs) have emerged as a mechanism through which stem cells may reprogram injured cells. In fact, MVs released from stem cells may deliver proteins, bio-active lipids and nucleic acids to injured cells. In particular, the transfer of transcripts derived from stem cells may induce phenotypic and functional changes in the recipient cells that promote the activation of regenerative programs.

Ultrastructural Evidence of Exosome Secretion by Progenitor Cells in Adult Mouse Myocardium and Adult Human Cardiospheres

The demonstration of beneficial effects of cell therapy despite the persistence of only few transplanted cells in vivo suggests secreted factors may be the active component of this treatment. This so-called paracrine hypothesis is supported by observations that culture media conditioned by progenitor cells contain growth factors that mediate proangiogenic and cytoprotective effects. Cardiac progenitor cells in semi-suspension culture form spherical clusters (cardiospheres) that deliver paracrine signals to neighboring cells. A key component of paracrine secretion is exosomes, membrane vesicles that are stored intracellularly in endosomal compartments and are secreted when these structures fuse with the cell plasma membrane. Exosomes have been identified as the active component of proangiogenic effects of bone marrow CD34+ stem cells in mice and the regenerative effects of embryonic mesenchymal stem cells in infarcted hearts in pigs and mice. Here, we provide electron microscopic evidence of exosome secretion by progenitor cells in mouse myocardium and human cardiospheres. Exosomes are emerging as an attractive vector of paracrine signals delivered by progenitor cells. They can be stored as an “off-the-shelf” product. As such, exosomes have the potential for circumventing many of the limitations of viable cells for therapeutic applications in regenerative medicine.

In This Issue

HomeCirculation ResearchVol. 109, No. 7In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn This Issue Originally published16 Sep 2011https://doi.org/10.1161/RES.0b013e31823377bfCirculation Research. 2011;109:715Exosomes and Paracrine Effects of CD34+ Cells (p 724)Exosomes are responsible for the angiogenic effects of CD34+ stem cells, report Losordo and colleagues.Download figureDownload PowerPointAlthough stem cell transplantation improves the function of injured hearts, the mechanism of their salubrious effects remains mysterious. Too few of these cells are incorporated into the injured tissue to account for the remarkable functional and physiological benefits that are observed. To account for this discrepancy, some investigators have suggested that stem cells secrete trophic factors that promote the growth of new blood vessels or new cells within the injured tissue (paracrine hypothesis). In an effort to explain the paracrine effect of stem cells, Losordo et al collected exosomes secreted by CD34+ stem cells, shown previously to reduce angina and lower the rates of amputation in patients with critical limb ischemia. They report that these exosomes were just as potent as the CD34+ cells in promoting the growth of endothelial cells in culture and in stimulating angiogenesis in vivo. Exosomes from non-CD34+ cells were ineffective. How stem cell–derived exosomes stimulate angiogenesis remains a mystery, but the authors suggest that the role of angiogenic microRNAs (miR-126 and miR-130), sequestered within these vesicles, is one mechanism to explore in future studies.Peroxiredoxin 2 Ameliorates Atherosclerosis (p 739)Park et al uncover a unique role of peroxiredoxin 2 in preventing atherosclerotic lesion formation.Download figureDownload PowerPointAtherosclerotic lesions preferentially develop in areas where blood vessels are branched or curved. Turbulent blood flow in these areas stimulates the production of reactive oxygen species (ROS), which promote leukocyte adhesion to the vessel wall and stimulate the development of atherosclerotic plaques. Park et al show that vascular areas exposed to turbulent flow express high levels of the hydrogen peroxide–removing enzyme peroxiredoxin 2 (Prdx2) and that deletion of this enzyme increases vascular adhesion and the formation of atherosclerotic lesions in apoE-null mice. They report that loss of Prdx2 increases infiltration of immune cells into plaques and that the absence of this enzyme, either in vascular or immune cells, is equally atherogenic. Significantly, deletion of other peroxide-removing enzymes such as glutathione peroxidase and catalase was less harmful than Prdx2 deficiency, suggesting that Prdx-2 has a unique role in removing peroxides from sites at which they can cause the most damage. Such specificity of action may also explain the limited success of attempts to inhibit atherosclerosis by global antioxidant interventions.Redox Regulation of ATP Synthase (p 750)Van Eyk and associates identify a mitochondrial redox sensor in failing hearts.Download figureDownload PowerPointBecause of conduction defects, heart failure results in discoordinate contraction of the myocardium. Resynchronization of contraction by biventricular stimulation improves heart function and enhances long-term survival of patients with heart failure. Cardiac resynchronization therapy (CRT) also improves the energetic efficiency of the heart, but the molecular and cellular basis for this improvement remains unknown. In their previous work, Van Eyk et al had found that heart failure in dogs results in partial inhibition of mitochondrial ATP synthase and that this activity could be restored by CRT. They also found that CRT affects several mitochondrial proteins involved in energy production and redox regulation. They now link these two phenomena together, demonstrating that dyssynchronous heart failure results in the formation of disulfide bonds between the α- and the γ-subunits of ATP synthase as well as S-glutathiolation of the α-subunit. These changes were reversed by CRT, which induced S-nitrosation of the protein. The authors suggest that a uniquely reactive cysteine residue (Cys-294), located within the α-subunit of ATP synthase, functions as a redox switch that is able to sense the redox state and adjust energy production accordingly.Written by Aruni Bhatnagar. Previous Back to top Next FiguresReferencesRelatedDetails September 16, 2011Vol 109, Issue 7 Advertisement Article InformationMetrics © 2011 American Heart Association, Inc.https://doi.org/10.1161/RES.0b013e31823377bf Originally publishedSeptember 16, 2011 PDF download Advertisement

Stem and progenitor cells for neurological repair: Minor issues, major hurdles, and exciting opportunities for paracrine‐based therapeutics

The transplantation of cultured stem and progenitor cells is a key element in the rapidly growing field of regenerative medicine. Based on their ability to rescue and/or repair injured tissue and partially restore organ function, multiple types of stem/progenitor cells have already entered into clinical trials. However, despite several decades of intense research, the goal to apply culture-expanded stem/progenitor cells in a manner that can effectively replace cells after injury has yet to be realized. Many sources of potentially useful cells are available, but something is clearly missing. In addition, recent studies suggest that paracrine effects of secreted or released factors are responsible for most of the benefits observed after cell transplantation, rather than direct cell replacement. These data call into question the need for cell transplantation for many types of therapy, in particular for acute injuries such as myocardial infarction and stroke. In this review, we examine current progress in the area of cell transplantation and minor issues and major hurdles regarding the clinical application of different cell types. We discuss the "paracrine hypothesis" for the action of transplanted stem/progenitor cells as an opportunity to identify defined combinations of biomolecules to rescue and/or repair tissues after injury. Although many of the concepts in this review will apply to multiple injury/repair systems, we will focus primarily on stem/progenitor cell-based treatments for neurological disorders and stroke.

Human UCB CD133+ Cell Infusion In NOD-SCID Mice with Acute Hind Limb Ischemia Improves Reperfusion of An Ischemic Bed

AbstractAbstract 4697Clinical trials have shown intracoronary or intramuscular injections of hematopoietic stem cells (HSC) ameliorate vascular ischemia. HSCs are isolated from bone marrow (BM), umbilical cord blood (UCB), and adult peripheral blood (AB). Critical limb ischemia patients, injected with autologous HSC into ischemic tissue had improved perfusion and reduced amputations. However, autologous HSC effectiveness declines with age. We hypothesized that UCB CD133+ HSCs' are more efficacious than autologous HSC at revascularization for an ischemic bed.Immune reactive surface antigens on UCB CD133+ cells were determined using multi-parameter flow cytometry. UCB CD133+ allogeneic immune responses from 72 h co-cultures were analyzed using a mixed lymphocyte culture (MLR) proliferation assays, and induced cytokine production found using TH1(inflammatory)/TH2(anti-inflammatory) cytometric bead assays (CBA) (BD Biosciences (San Jose, CA). In vivo studies were done using NOD/SCID mice treated with low-dose irradiation (200cGy) then femoral ligation. Study mice were divided into 3 treatment groups and underwent intracoronary infusions of; 1×106 UCB CD133+, 0.5×106 UCB mononuclear cells (MNCs), or EGM media alone. Day 3 post-ligation and cell infusion, quadriceps from 3 mice in each group were harvested, total RNA isolated using Trizol™ and RNA for each treatment group pooled. Pooled RNA was converted to cDNA then assayed using mouse ABI Affymetrix™ Gene chip. Computational pathway analyzes were run for significant transcriptome changes. Gene array data was confirmed on select genes using quantitative reverse transcriptase real time PCR (qPCR). Treated mice were followed for ischemic bed reperfusion by Laser Doppler imaging for 28 days post-ligation. UCB CD133+ cells express MHC class I and II, but lack CD80 and CD86. Allogeneic MLR assays using UCB and AB MNCs showed UCB CD133+ cells were stimulatory to MNC proliferation. The MNCs alloresponse to UCB CD133+ cells produced high concentration of interleukin 4 (IL-4) and IL-10 indicative of a TH2 response. These results show allogeneic UCB CD133+ cells induce a TH2 immune response due to an absence of co-stimulation of immune cells. To verify whether the results are recapitulated in vivo, we treated acute limb ischemia in NOD/SCID mice with human UCB CD133+ cells and monitored revascularization by blood flow and Affymetrix mouse gene array. Computational analysis of Affymetrix mouse gene arrays from comparing all 3 treatment protocols indicated that ischemic quadriceps treated with UCB CD133+ cells exhibited a significant enrichment of anti-angiogeneic, chemotaxic, cytokine, and immune response genes. UCB CD133+ treated mice had increase expression of anti-inflammatory, and anti-angiogeneic genes versus controls. Conversely media and UCB MNC treated mice had equal to or higher pro-inflammatory gene expression. The anti-inflammatory gene response was confirmed for 2 of the 3 genes, arginase 1, CXCL7, and tumor growth factor beta binding protein 2 (TGFβBP2) comparing CD133+ treated mice to UCB MNC treated mice. TGFβBP2 was not observed to change in vivo. UCB CD133+ cells treated mice also had improved blood perfusion of the ischemic bed at 28 days post-ligation versus control protocols. The in vivo mouse model supports the in vitro observation, but demonstrates improved reperfusion over controls.Currently there are 2 non-exclusive hypotheses for the function of CD133+ cells in revascularization. First the CD133+ cells integrate and differentiate into new vascular endothelial cells and the second is that the CD133+ cells augment revascularization via a paracrine effect which does not require integration into the host tissue. In vitro studies suggest that UCB CD133+ cells promote an allogeneic TH2 type response because of a lack of co-stimulatory immune surface antigens, resulting in high concentrations of IL-4 and IL-10. This skewed TH2 response inhibits inflammation, the subsequent tissue damage, and may augment revascularization. Although these studies cannot exclude a role for UCB CD133+ cellular integration, results support the paracrine hypothesis as infusion of selected CD133+ cells appears to promote an anti-inflammatory, anti-angiogenic profile at day 3 post-ligation and at 1 month improved reperfusion compared with non-selected MNC. Disclosures:No relevant conflicts of interest to declare.