Machine Learning Models for Inverse Design of the Electrochemical Oxidation Process for Water Purification.

In this study, a machine learning (ML) framework is developed toward target-oriented inverse design of the electrochemical oxidation (EO) process for water purification. The XGBoost model exhibited the best performances for prediction of reaction rate (k) based on training the data set relevant to pollutant characteristics and reaction conditions, indicated by Rext2 of 0.84 and RMSEext of 0.79. Based on 315 data points collected from the literature, the current density, pollutant concentration, and gap energy (Egap) were identified to be the most impactful parameters available for the inverse design of the EO process. In particular, adding reaction conditions as model input features allowed provision of more available information and an increase in the sample size of the data set to improve the model accuracy. The feature importance analysis was performed for revealing the data pattern and feature interpretation by using Shapley additive explanations (SHAP). The ML-based inverse design for the EO process was generalized to a random case for tailoring the optimum conditions with phenol and 2,4-dichlorophenol (2,4-DCP) serving as model pollutants. The resulting predicted k values were close to the experimental k values by experimental verification, accounting for the relative error lower than 5%. This study provides a paradigm shift from conventional trial-and-error mode to data-driven mode for advancing research and development of the EO process by a time-saving, labor-effective, and environmentally friendly target-oriented strategy, which makes electrochemical water purification more efficient, more economic, and more sustainable in the context of global carbon peaking and carbon neutrality.

Bmi-1 high-expressing cells enrich cardiac stem/progenitor cells and respond to heart injury.

Bmi-1 gene is well recognized as an oncogene, but has been recently demonstrated to play a role in the self-renewal of tissue-specific stem cells. By using Bmi-1GFP/+ mice, we investigated the role of Bmi-1 in cardiac stem/progenitor cells and myocardial repair. RT-PCR and flow cytometry analysis indicated that the expression of Bmi-1 was significantly higher in cardiac side population than the main population from CD45- Ter119- CD31- heart cells. More Sca-1+ cardiac stem/progenitor cells were found in Bmi-1 GFPhi subpopulation, and these Bmi-1 GFPhi heart cells showed the potential of differentiation into SMM+ smooth muscle-like cells and TnT+ cardiomyocyte-like cells in vitro. The silencing of Bmi-1 significantly inhibited the proliferation and differentiation of heart cells. Otherwise, myocardial infarction induced a significantly increase (2.7-folds) of Bmi-1 GFPhi population, mainly within the infarction and border zones. These preliminary data suggest that Bmi-1hi heart cells are enriched in cardiac stem/progenitor cells and may play a role in myocardial repair.

TroCCL4, a CC chemokine of Trachinotus ovatus, is involved in the antimicrobial immune response.

CC chemokines are a large subfamily of chemokines that play an important role in the innate immune system. To date, several CC chemokines have been identified in fish species; however, the activities and functions of these putative chemokines remain ambiguous in teleosts, especially in the golden pompano, Trachinotus ovatus. Here, we characterized CC chemokine ligand 4 from T. ovatus (TroCCL4) and studied its functions. TroCCL4 contains a 294 bp open reading frame that encodes a putative peptide comprising 97 amino acids. TroCCL4 shares a high amino acid sequence similarity of 31.11%-78.35% with other CC chemokines sequences in humans and teleosts and has four cysteine residues that are conserved among other CC chemokines. TroCCL4 is also related to the macrophage inflammatory protein (MIP) group of CC chemokines. TroCCL4 expression was most abundant in immune organs and significantly upregulated in a time-dependent manner following Edwardsiella tarda infection. Recombinant TroCCL4 (rTroCCL4) induced the migration of peripheral blood leukocytes and the cellular proliferation of head kidney lymphocytes. In addition, rTroCCL4 inhibited the growth of Escherichia coli and E. tarda, indicating an antimicrobial function. Furthermore, the results of in vivo analysis showed that TroCCL4 overexpression in T. ovatus significantly enhanced macrophage activation; upregulated the gene expression of interleukin 1-ß (IL-1ß), interleukin 15 (IL15), interferon-induced Mx protein (Mx), tumor necrosis factor α (TNFα), complement C3, and major histocompatibility complex (MHC) class Iα and class IIα; and protected against bacterial infection in fish tissues. In contrast, knockdown of TroCCL4 expression resulted in increased bacterial dissemination and colonization in fish tissues. Taken together, our results provide evidence indicating that TroCCL4 has the ability to stimulate leukocytes and macrophages and enhance host immunity to defend against bacterial infection.

Therapeutic efficacy of cardiosphere-derived cells in a transgenic mouse model of non-ischaemic dilated cardiomyopathy.

AIM: Cardiosphere-derived cells (CDCs) produce regenerative effects in the post-infarct setting. However, it is unclear whether CDCs are beneficial in non-ischaemic dilated cardiomyopathy (DCM). We tested the effects of CDC transplantation in mice with cardiac-specific Gαq overexpression, which predictably develop progressive cardiac dilation and failure, with accelerated mortality. METHODS AND RESULTS: Wild-type mouse CDCs (10(5) cells) or vehicle only were injected intramyocardially in 6-, 8-, and 11-week-old Gαq mice. Cardiac function deteriorated in vehicle-treated mice over 3 months of follow-up, accompanied by oxidative stress, inflammation and adverse ventricular remodelling. In contrast, CDCs preserved cardiac function and volumes, improved survival, and promoted cardiomyogenesis while blunting Gαq-induced oxidative stress and inflammation in the heart. The mechanism of benefit is indirect, as long-term engraftment of transplanted cells is vanishingly low. CONCLUSIONS: Cardiosphere-derived cells reverse fundamental abnormalities in cell signalling, prevent adverse remodelling, and improve survival in a mouse model of DCM. The ability to impact favourably on disease progression in non-ischaemic heart failure heralds new potential therapeutic applications of CDCs.

Importance of cell-cell contact in the therapeutic benefits of cardiosphere-derived cells.

Cardiosphere-derived cells (CDCs) effect therapeutic regeneration after myocardial infarction (MI) both in animal models and in humans. Here, we test the hypothesis that cell-cell contact plays a role in mediating the observed therapeutic benefits of CDCs, above and beyond conventional paracrine effects. Human CDCs or vehicle were injected into immunodeficient (SCID) mouse hearts during acute MI. CDC transplantation augmented the proportion of cycling (Ki67(+) ) cardiomyocytes and improved ventricular function. CDC-conditioned media only modestly augmented the percentage of Ki67(+) cardiomyocytes (>control but

Cardiospheres reverse adverse remodeling in chronic rat myocardial infarction: roles of soluble endoglin and Tgf-ß signaling.

Self-assembling heart-derived stem cell clusters named cardiospheres (CSps) improve function and attenuate remodeling in rodent models of acute myocardial infarction. The effects of CSps in chronically remodeled myocardium post-MI, and the underlying mechanisms, remain unknown. One month after permanent coronary ligation, rats were randomly assigned to injection of vehicle (controls) or CSps in the peri-infarct area. One month post-injection, CSps increased left ventricular function, reduced scar mass and collagen density, and enhanced vascularity within the infarct zone compared to controls. Immunoblots revealed Tgfß-1/smad cascade downregulation and an increase in soluble endoglin post-CSp injection. Six months post-transplantation, left ventricular function further improved and cardiomyocyte hypertrophy was attenuated in the CSp-treated group. In vitro, co-culture of CSps with fibroblasts recapitulated the suppression of the Tgf-ß1/smad pathway changes, responses which were blunted by neutralizing antibody against endoglin. Thus, cardiosphere transplantation enhances angiogenesis and reduces fibrosis in chronically infarcted myocardium, leading to partial reversal of cardiac dysfunction. The underlying mechanism involves inhibition of Tgf-ß1/smad signaling by CSp-secreted soluble endoglin.

Serine protease inhibitor, SerpinA3n, regulates cardiac remodelling after myocardial infarction.

AIMS: Following myocardial infarction (MI), the heart repairs itself via a fibrotic repair response. The degree of fibrosis is determined by the balance between deposition of extracellular matrix (ECM) by activated fibroblasts and breakdown of nascent scar tissue by proteases that are secreted predominantly by inflammatory cells. Excessive proteolytic activity and matrix turnover has been observed in human heart failure, and protease inhibitors in the injured heart regulate matrix breakdown. Serine protease inhibitors (Serpins) represent the largest and the most functionally diverse family of evolutionary conserved protease inhibitors, and levels of the specific Serpin, SerpinA3, have been strongly associated with clinical outcomes in human MI as well as non-ischaemic cardiomyopathies. Yet, the role of Serpins in regulating cardiac remodelling is poorly understood. The aim of this study was to understand the role of Serpins in regulating scar formation after MI. METHODS AND RESULTS: Using a SerpinA3n conditional knockout mice model, we observed the robust expression of Serpins in the infarcted murine heart and demonstrate that genetic deletion of SerpinA3n (mouse homologue of SerpinA3) leads to increased activity of substrate proteases, poorly compacted matrix, and significantly worse post-infarct cardiac function. Single-cell transcriptomics complemented with histology in SerpinA3n-deficient animals demonstrated increased inflammation, adverse myocyte hypertrophy, and expression of pro-hypertrophic genes. Proteomic analysis of scar tissue demonstrated decreased cross-linking of ECM peptides consistent with increased proteolysis in SerpinA3n-deficient animals. CONCLUSION: Our study demonstrates a hitherto unappreciated causal role of Serpins in regulating matrix function and post-infarct cardiac remodelling.

Antiangiogenic activity of rPAI-1(23) promotes vasa vasorum regression in hypercholesterolemic mice through a plasmin-dependent mechanism.

RATIONALE: The antiangiogenic activity of rPAI-1(23), a truncated plasminogen activator inhibitor-1 (PAI-1) protein, induces vasa vasorum collapse and significantly reduces plaque area and plaque cholesterol in hypercholesterolemic low-density lipoprotein receptor-deficient/apolipoprotein B48-deficient mice. OBJECTIVE: The objective of this study was to examine rPAI-1(23)-stimulated mechanisms that cause vasa vasorum collapse. METHODS AND RESULTS: The rPAI-1(23) protein opposed PAI-1 antiproteolytic function by stimulating a 1.6-fold increase in plasmin activity compared with the saline-treated counterpart. The increased proteolytic activity corresponded to increased activity of matrix metalloproteinase-3 and degradation of fibrin(ogen), nidogen, and perlecan in the adventitia of descending aortas. PAI-1 activity was reduced by 48% in response to rPAI-1(23); however, PAI-1 protein expression levels were similar in the rPAI-1(23)- and saline-treated hypercholesterolemic mice. Coimmunoprecipitation assays demonstrated a novel PAI-1-plasminogen complex in protein from the descending aorta of rPAI-1(23)- and saline-treated mice, but complexed PAI-1 was 1.6-fold greater in rPAI-1(23)-treated mice. Biochemical analyses demonstrated that rPAI-1(23) and PAI-1 binding interactions with plasminogen increased plasmin activity and reduced PAI-1 antiproteolytic activity. CONCLUSIONS: We conclude that rPAI-1(23) causes regression or collapse of adventitial vasa vasorum in hypercholesterolemic mice by stimulating an increase in plasmin activity. The rPAI-1(23)-enhanced plasmin activity was achieved through a novel mechanism by which rPAI-1(23) and PAI-1 bound plasminogen in a cooperative manner to increase plasmin activity and reduce PAI-1 activity.

Flow electrochemical inactivation of waterborne bacterial endospores.

Waterborne pathogens have the risk of spreading waterborne diseases and even pandemics. Some Gram-positive bacteria can form endospores, the hardiest known life form that can withstand heat, radiation, and chemicals. Electrochemical inactivation may offer a promising solution, but is hindered by low inactivation efficiencies resulting from limitation of electrode/endospores interaction in terms of electrochemical reaction selectivity and mass transfer. Herein, these issues were addressed through modifying selectivity of active species formation using electroactive ceramic membrane with high oxygen evolution potential, improving mass transfer property by flow-through operation. In this way, inactivation (6.0-log) of Bacillus atrophaeus endospores was achieved. Theoretical and experimental results demonstrated synergistic inactivation to occur through fragmentation of coat via interfacial electron transfer and electro-produced transient radicals (•OH primarily, •Cl and Cl2•- secondarily), thereby increasing cell permeability to facilitate penetration of electro-produced persistent active chlorine for subsequent rupture of intracellular structures. Numbering-up electrode module strategy was proposed to scale up the system, achieving average 5.3-log inactivation of pathogenic Bacillus anthracis endospores for 30 days. This study demonstrates a proof-of-concept manner for effective inactivation of waterborne bacterial endospores, which may provide an appealing strategy for wide-range applications like water disinfection, bio-safety control and defense against biological warfare.

Fibroblasts in heart scar tissue directly regulate cardiac excitability and arrhythmogenesis.

After heart injury, dead heart muscle is replaced by scar tissue. Fibroblasts can electrically couple with myocytes, and changes in fibroblast membrane potential can lead to myocyte excitability, which suggests that fibroblast-myocyte coupling in scar tissue may be responsible for arrhythmogenesis. However, the physiologic relevance of electrical coupling of myocytes and fibroblasts and its impact on cardiac excitability in vivo have never been demonstrated. We genetically engineered a mouse that expresses the optogenetic cationic channel ChR2 (H134R) exclusively in cardiac fibroblasts. After myocardial infarction, optical stimulation of scar tissue elicited organ-wide cardiac excitation and induced arrhythmias in these animals. Complementing computational modeling with experimental approaches, we showed that gap junctional and ephaptic coupling, in a synergistic yet functionally redundant manner, excited myocytes coupled to fibroblasts.

The antiangiogenic activity of rPAI-1(23) inhibits vasa vasorum and growth of atherosclerotic plaque.

Plaque vascularity has been implicated in its growth and stability. However, there is a paucity of information regarding the origin of plaque vasculature and the role of vasa vasorum in plaque growth. To inhibit growth of vasa vasorum in atherogenic mice and assess its effect on plaque growth, we used a truncated plasminogen activator inhibitor (PAI)-1 protein, rPAI-1(23), that has significant antiangiogenic activity. Female LDLR(-/-)ApoB-48-deficient mice fed Paigen's diet without cholate for 20 weeks received rPAI-1(23) treatment (n=21) for the last 6 weeks. Plaque size and vasa vasorum density were compared to 2 controls: mice fed Paigen's diet and treated with saline for the last 6 weeks (n=16) and mice fed Paigen's diet until the onset of treatment (n=14). The rPAI-1(23) treatment significantly reduced plaque area and plaque cholesterol in the descending aorta and plaque area in the innominate artery. Measurements of reconstructed confocal microscopy images of vasa vasorum demonstrate that rPAI-1(23) treatment decreased vasa vasorum area and length, which was supported by microCT images. Confocal images provide evidence for vascularized plaque in the saline-treated group but not in rPAI-1(23)-treated mice. The increased vessel density in saline-treated mice is attributable, in part, to upregulated fibroblast growth factor-2 expression, which is inhibited by rPAI-1(23). In conclusion, rPAI-1(23) inhibits growth of vasa vasorum, as well as vessels within the adjacent plaque and vessel wall, through inhibition of fibroblast growth factor-2, leading to reduced plaque growth in atherogenic female LDLR(-/-)ApoB-48-deficient mice.

Identification of critical residues in Gap3 of Streptococcus parasanguinis involved in Fap1 glycosylation, fimbrial formation and in vitro adhesion.

BACKGROUND: Streptococcus parasanguinis is a primary colonizer of human tooth surfaces and plays an important role in dental plaque formation. Bacterial adhesion and biofilm formation are mediated by long peritrichous fimbriae that are composed of a 200 kDa serine rich glycoprotein named Fap1 (fimbriae-associated protein). Glycosylation and biogenesis of Fap1 are modulated by a gene cluster downstream of the fap1 locus. A gene encoding a glycosylation-associated protein, Gap3, was found to be important for Fap1 glycosylation, long fimbrial formation and Fap1-mediated biofilm formation. RESULTS: Deletion and site-directed mutagenesis were employed to dissect the regions within Gap3 that were important for its function in Fap1 glycosylation and biogenesis. A deletion of 6 consecutive amino acids, PDLPIL, eliminated the production of the mature 200 kDa Fap1 protein and gave rise instead to a 470 kDa Fap1 intermediate that was only partially glycosylated. Site-directed mutagenesis of the 6 amino acids revealed that only three of these amino acids were required. Mutants in these amino acids (L64R, P65R and L67T) produced the premature 470 kDa Fap1 intermediate. Mutants in the remaining amino acids produced the mature form of Fap1. Cell surface expression of the Fap1 precursor among L64R, P65R and L67T mutants was reduced to levels consistent with that of a gap3 insertional mutant. Electron micrographs showed that these 3 mutants lost their long peritrichous fimbriae. Furthermore, their in vitro adhesion ability to saliva-coated hydroxylapatite (SHA) was inhibited. CONCLUSION: Our data suggest that 3 highly conserved, hydrophobic residues L64, P65 and L67 in Gap3 are essential for Gap3 function and are important for complete glycosylation of Fap1, fimbrial formation and bacterial adhesion.

Cardiosphere-derived cells reverse heart failure with preserved ejection fraction (HFpEF) in rats by decreasing fibrosis and inflammation.

BACKGROUND: The pathogenesis of HFpEF is unclear, but fibrosis, inflammation and hypertrophy have been put forth as likely contributors. CDCs are heart-derived cell products with anti-fibrotic and anti-inflammatory properties. OBJECTIVES: We questioned whether allogeneic rat CDCs might be able to decrease manifestations of HFpEF in hypertensive rats. METHODS: Starting at 7 weeks of age, Dahl salt-sensitive rats were fed a high-salt diet for 6-7 weeks and randomized to receive intracoronary CDCs or placebo. Dahl rats fed normal chow served as controls. RESULTS: High-salt rats developed hypertension, left ventricular (LV) hypertrophy and diastolic dysfunction, without impairment of ejection fraction. Four weeks after treatment, diastolic dysfunction resolved in CDC-treated rats but not in placebo. The improved LV relaxation was associated with lower LV end-diastolic pressure, decreased lung congestion and enhanced survival in CDC-treated rats. Histology and echocardiography revealed no decrease in cardiac hypertrophy after CDC treatment, consistent with the finding of sustained, equally-elevated blood pressure in CDC- and placebo-treated rats. Nevertheless, CDC treatment decreased LV fibrosis and inflammatory infiltrates. Serum inflammatory cytokines were likewise decreased after CDC treatment. Whole-transcriptome analysis revealed major HFpEF-related, CDC-reversed changes in numerous transcripts, including many involved in inflammation and/or fibrosis. CONCLUSION: CDCs normalized LV relaxation and LV diastolic pressure while improving survival in a rat model of HFpEF. The benefits of CDCs occurred despite persistent hypertension and cardiac hypertrophy. By selectively reversing inflammation and fibrosis, CDCs may be beneficial in the treatment of HFpEF.

Repeated transplantation of allogeneic cardiosphere-derived cells boosts therapeutic benefits without immune sensitization in a rat model of myocardial infarction.

BACKGROUND: A single dose of allogeneic cardiosphere-derived cells (CDCs) improves cardiac function and reduces scarring, and increases viable myocardium in the infarcted rat and pig heart without eliciting a detrimental immune response. Clinical trials using single doses of allogeneic human CDCs are underway. It is unknown whether repeat dosing confers additional benefit or if it elicits an immune response. METHODS: Wistar-Kyoto rats underwent coronary artery ligation and intramyocardial injection of CDCs, with a second thoracotomy and repeat CDC injection 3 weeks later. Treatment permutations included 2 doses of allogeneic Brown-Norway CDCs (n = 24), syngeneic Wistar-Kyoto CDCs (n = 24), xenogeneic human CDCs (n = 24) or saline (n = 8). Cardiac function was assessed by transthoracic echocardiography, infarct size and inflammatory infiltration by histology, and cellular and humoral immune responses by lymphocyte proliferation and alloantibody assays. RESULTS: Repeat dosing of allogeneic and syngeneic CDCs improved ejection fraction by 5.2% (95% CI 2.1 to 8.3) and 6.8% (95% CI 3.8 to 9.8) after the first dose, and by 3.4% (95% CI 0.1% to 6.8%) and 6.4% (95% CI 4.2% to 8.6%) after the second dose. Infarct size was equally reduced with repeat dosing of syngeneic and allogeneic CDCs relative to xenogeneic and control treatments (p < 0.0001). Significant rejection-like infiltrates were present only in the xenogeneic group; likewise, lymphocyte proliferation and antibody assays were positive in the xenogeneic and negative in syngeneic and allogeneic groups. CONCLUSIONS: Repeat dosing of allogeneic CDCs in immunocompetent rats is safe and effective, consistent with the known immunomodulatory and anti-inflammatory properties of CDCs. These findings motivate clinical testing of repeatedly dosed CDCs for chronic heart disease.

Macrophages mediate cardioprotective cellular postconditioning in acute myocardial infarction.

Ischemic injury in the heart induces an inflammatory cascade that both repairs damage and exacerbates scar tissue formation. Cardiosphere-derived cells (CDCs) are a stem-like population that is derived ex vivo from cardiac biopsies; they confer both cardioprotection and regeneration in acute myocardial infarction (MI). While the regenerative effects of CDCs in chronic settings have been studied extensively, little is known about how CDCs confer the cardioprotective process known as cellular postconditioning. Here, we used an in vivo rat model of ischemia/reperfusion (IR) injury-induced MI and in vitro coculture assays to investigate how CDCs protect stressed cardiomyocytes. Compared with control animals, animals that received CDCs 20 minutes after IR had reduced infarct size when measured at 48 hours. CDCs modified the myocardial leukocyte population after ischemic injury. Specifically, introduction of CDCs reduced the number of CD68+ macrophages, and these CDCs secreted factors that polarized macrophages toward a distinctive cardioprotective phenotype that was not M1 or M2. Systemic depletion of macrophages with clodronate abolished CDC-mediated cardioprotection. Using both in vitro coculture assays and a rat model of adoptive transfer after IR, we determined that CDC-conditioned macrophages attenuated cardiomyocyte apoptosis and reduced infarct size, thereby recapitulating the beneficial effects of CDC therapy. Together, our data indicate that CDCs limit acute injury by polarizing an effector macrophage population within the heart.

Angiogenesis, cardiomyocyte proliferation and anti-fibrotic effects underlie structural preservation post-infarction by intramyocardially-injected cardiospheres.

OBJECTIVE: We sought to understand the cellular and tissue-level changes underlying the attenuation of adverse remodeling by cardiosphere transplantation in acute myocardial infarction (MI). BACKGROUND: Cardiospheres (CSps) are heart-derived multicellular clusters rich in stemness and capable of multilineage differentiation. Post-MI CSp transplantation improves left ventricular (LV) function and attenuates remodeling in both small and large animal studies. However, the mechanisms of benefit have not yet been fully elucidated. METHODS: Four groups were studied: 1) "Sham" (Wistar Kyoto rats with thoracotomy and ligature without infarction); 2) "MI" (proximal LAD ligation with peri-infarct injection of vehicle); 3) "MI+CSp" (MI with cardiospheres injected in the peri-infarct area); 4) "Small MI" (mid-LAD ligation only). RESULTS: In vivo 1 week after CSp transplantation, LV functional improvement was associated with an increase in cardiomyocyte proliferation. By 3 weeks, microvessel formation was enhanced, while cardiomyocyte hypertrophy and regional fibrosis were attenuated. Collagen deposition was reduced, collagen degradation was enhanced, and MMPs were upregulated. The beneficial effects of CSp transplantation were not observed in the Small MI group, indicating that the effects are not solely due to CSp-induced cardioprotection. In vitro, CSp-conditioned media reduced collagen production in coculture with fibroblasts and triggered neoangiogenesis in an ex vivo aortic ring assay. CONCLUSION: Cardiospheres enhance cardiomyocyte proliferation and angiogenesis, and attenuate hypertrophy and fibrosis, in the ischemic myocardium. These synergistic effects underlie the attenuation of adverse remodeling by cardiospheres.

Relative roles of CD90 and c-kit to the regenerative efficacy of cardiosphere-derived cells in humans and in a mouse model of myocardial infarction.

BACKGROUND: The regenerative potential of cardiosphere-derived cells (CDCs) for ischemic heart disease has been demonstrated in mice, rats, pigs, and a recently completed clinical trial (CADUCEUS). CDCs are CD105(+) stromal cells of intrinsic cardiac origin, but the antigenic characteristics of the active fraction remain to be defined. CDCs contain a small minority of c-kit(+) cells, which have been argued to be cardiac progenitors, and a variable fraction of CD90(+) cells whose bioactivity is unclear. METHODS: We performed a retrospective analysis of data from the CADUCEUS trial and a prospective mouse study to elucidate the roles of c-kit(+) and CD90(+) cells in human CDCs. Here, we show, surprisingly, that c-kit expression has no relationship to CDCs' therapeutic efficacy in humans, and depletion of c-kit(+) cells does not undermine the structural and functional benefits of CDCs in a mouse model of myocardial infarction (MI). In contrast, CD90 expression negatively correlates with the therapeutic benefit of CDCs in humans (ie, higher CD90 expression associated with lower efficacy). Depletion of CD90(+) cells augments the functional potency of CDCs in murine MI. CD90(-) CDCs secrete lower levels of inflammatory cytokines and can differentiate into cardiomyocytes in vitro and in vivo. CONCLUSION: The majority population of CDCs (CD105(+)/CD90(-)/c-kit(-)) constitutes the active fraction, both in terms of therapeutic efficacy and in the ability to undergo cardiomyogenic differentiation. The c-kit(+) fraction is neither necessary for, nor contributory to, the regenerative efficacy of CDCs.

Magnetic antibody-linked nanomatchmakers for therapeutic cell targeting.

Stem cell transplantation is a promising strategy for therapeutic cardiac regeneration, but current therapies are limited by inefficient interaction between potentially beneficial cells (either exogenously transplanted or endogenously recruited) and the injured tissue. Here we apply targeted nanomedicine to achieve in vivo cell-mediated tissue repair, imaging and localized enrichment without cellular transplantation. Iron nanoparticles are conjugated with two types of antibodies (one against antigens on therapeutic cells and the other directed at injured cells) to produce magnetic bifunctional cell engager (MagBICE). The antibodies link the therapeutic cells to the injured cells, whereas the iron core of MagBICE enables physical enrichment and imaging. We treat acute myocardial infarction by targeting exogenous bone marrow-derived stem cells (expressing CD45) or endogenous CD34-positive cells to injured cardiomyocytes (expressing myosin light chain. Targeting can be further enhanced by magnetic attraction, leading to augmented functional benefits. MagBICE represents a generalizable platform technology for regenerative medicine.

Stimulation of endogenous cardioblasts by exogenous cell therapy after myocardial infarction.

Controversy surrounds the identity, origin, and physiologic role of endogenous cardiomyocyte progenitors in adult mammals. Using an inducible genetic labeling approach to identify small non-myocyte cells expressing cardiac markers, we find that activated endogenous cardioblasts are rarely evident in the normal adult mouse heart. However, myocardial infarction results in significant cardioblast activation at the site of injury. Genetically labeled isolated cardioblasts express cardiac transcription factors and sarcomeric proteins, exhibit spontaneous contractions, and form mature cardiomyocytes in vivo after injection into unlabeled recipient hearts. The activated cardioblasts do not arise from hematogenous seeding, cardiomyocyte dedifferentiation, or mere expansion of a preformed progenitor pool. Cell therapy with cardiosphere-derived cells amplifies innate cardioblast-mediated tissue regeneration, in part through the secretion of stromal cell-derived factor 1 by transplanted cells. Thus, stimulation of endogenous cardioblasts by exogenous cells mediates therapeutic regeneration of injured myocardium.

Cardiac BIN1 folds T-tubule membrane, controlling ion flux and limiting arrhythmia.

Cardiomyocyte T tubules are important for regulating ion flux. Bridging integrator 1 (BIN1) is a T-tubule protein associated with calcium channel trafficking that is downregulated in failing hearts. Here we find that cardiac T tubules normally contain dense protective inner membrane folds that are formed by a cardiac isoform of BIN1. In mice with cardiac Bin1 deletion, T-tubule folding is decreased, which does not change overall cardiomyocyte morphology but leads to free diffusion of local extracellular calcium and potassium ions, prolonging action-potential duration and increasing susceptibility to ventricular arrhythmias. We also found that T-tubule inner folds are rescued by expression of the BIN1 isoform BIN1+13+17, which promotes N-WASP-dependent actin polymerization to stabilize the T-tubule membrane at cardiac Z discs. BIN1+13+17 recruits actin to fold the T-tubule membrane, creating a 'fuzzy space' that protectively restricts ion flux. When the amount of the BIN1+13+17 isoform is decreased, as occurs in acquired cardiomyopathy, T-tubule morphology is altered, and arrhythmia can result.