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Background: Smooth muscle cell (SMC) phenotypic reprogramming toward a mixed synthetic-proteolytic state is a central feature of aortic root aneurysm in Marfan syndrome (MFS). Previous work identified Klf4 as a potential mediator of SMC plasticity in MFS. Methods: MFS ( Fbn1 C1041G/+ ) mouse strains with an inducible vascular SMC fluorescent reporter ( MFS SMC ) with or without SMC-specific deletion of Klf4 exons 2 to 3 ( MFS SMC-Klf4Δ ) were generated. Simultaneous SMC tracing and Klf4 loss-of-function ( Klf4Δ mice) was induced at 6 weeks of age. Aneurysm growth was assessed via serial echocardiography (4–24 weeks). Twenty-four-week-old mice were assessed via histology, RNA in situ hybridization, and aortic single-cell RNA sequencing. Results: MFS mice demonstrated progressive aortic root dilatation compared with control (WT SMC ) mice regardless of Klf4 genotype ( P MFS SMC-Klf4Δ versus MFS SMC ( P =0.884). Efficient SMC Klf4 deletion was confirmed via lineage-stratified genotyping, RNA in situ hybridization, and immunohistochemistry. Single-cell RNA sequencing of traced SMCs revealed a highly similar pattern of phenotype modulation marked by loss of contractile markers (eg, Myh11, Cnn1 ) and heightened expression of matrix genes (eg, Col1a1, Fn1 ) between Klf4 genotypes. Pseudotemporal quantitation of SMC dedifferentiation confirmed that Klf4 deletion did not alter the global extent of phenotype modulation, but reduced expression of 23 genes during this phenotype transition in MFS SMC-Klf4Δ mice, including multiple chondrogenic genes expressed by only the most severely dedifferentiated SMCs (eg, Cytl1, Tnfrsf11b ). Conclusions: Klf4 is not required to initiate SMC phenotype modulation in MFS aneurysm but may exert regulatory control over chondrogenic genes expressed in highly dedifferentiated SMCs.

Background: Aortic root smooth muscle cells (SMC) develop from both the second heart field (SHF) and neural crest. Disparate responses to disease-causing Fbn1 variants by these lineages are proposed to promote focal aortic root aneurysm formation in Marfan syndrome (MFS), but lineage-stratified SMC analysis in vivo is lacking. Methods: We generated SHF lineage-traced MFS mice and performed integrated multiomic (single-cell RNA and assay for transposase-accessible chromatin sequencing) analysis stratified by embryological origin. SMC subtypes were spatially identified via RNA in situ hybridization. Response to TWIST1 overexpression was determined via lentiviral transduction in human aortic SMCs. Results: Lineage stratification enabled nuanced characterization of aortic root cells. We identified heightened SHF-derived SMC heterogeneity including a subset of Tnnt2 (cardiac troponin T)-expressing cells distinguished by altered proteoglycan expression. MFS aneurysm-associated SMC phenotypic modulation was identified in both SHF-traced and nontraced (neural crest–derived) SMCs; however, transcriptomic responses were distinct between lineages. SHF-derived modulated SMCs overexpressed collagen synthetic genes and small leucine-rich proteoglycans while nontraced SMCs activated chondrogenic genes. These modulated SMCs clustered focally in the aneurysmal aortic root at the region of SHF/neural crest lineage overlap. Integrated RNA-assay for transposase-accessible chromatin analysis identified enriched Twist1 and Smad2/3/4 complex binding motifs in SHF-derived modulated SMCs. TWIST1 overexpression promoted collagen and SLRP gene expression in vitro, suggesting TWIST1 may drive SHF-enriched collagen synthesis in MFS aneurysm. Conclusions: SMCs derived from both SHF and neural crest lineages undergo phenotypic modulation in MFS aneurysm but are defined by subtly distinct transcriptional responses. Enhanced TWIST1 transcription factor activity may contribute to enriched collagen synthetic pathways SHF-derived SMCs in MFS.

BACKGROUND: To delineate the effects of integrin αv signaling in Marfan syndrome (MFS) and examine the potential efficacy of integrin αv blockade as a therapeutic strategy for MFS aneurysms. METHODS: Induced pluripotent stem cells were differentiated into aortic smooth muscle cells (SMCs) of the second heart field (SHF) and neural crest lineages, enabling in vitro modeling of thoracic aortic aneurysm in MFS. Fbn1 C1039G/+ MFS mice treated with integrin αv antagonist (GLPG0187) confirmed the pathological role of integrin αv on aneurysm formation. RESULTS: Induced pluripotent stem cell–derived MFS SHF SMCs overexpress integrin αv relative to MFS neural crest and healthy control SHF cells. Furthermore, downstream targets of integrin αv (FAK [focal adhesion kinase]/Akt Thr308 /mTORC1 [mechanistic target of rapamycin complex 1]) were activated, especially in MFS SHF. Treatment GLPG0187 reduced p-FAK/p-Akt Thr308 /mTORC1 activity in MFS SHF back to control SHF levels. Functionally, MFS SHF SMCs had increased proliferation and migration compared to MFS neural crest and control SMCs, which was then inhibited by GLPG0187 treatment. In the Fbn1 C1039G/+ MFS mouse model, integrin αv, p-Akt Thr308 , and downstream targets of mTORC1 proteins were elevated in the aortic root/ascending segment compared to littermate wild-type control. Mice treated with GLPG0187 (age 6–14 weeks) resulted in reduced aneurysm growth, elastin fragmentation, and normalization of the FAK/Akt Thr308 /mTORC1 pathway. GLPG0187 treatment reduced the amount and severity of SMC modulation assessed by single-cell RNA sequencing. CONCLUSIONS: The integrin αv-FAK-Akt Thr308 signaling pathway is activated in induced pluripotent stem cell SMCs from MFS patients, specifically from the SHF lineage. Mechanistically, this signaling pathway promotes SMC proliferation and migration in vitro. As biological proof of concept, GLPG0187 treatment slowed aneurysm growth and p-Akt Thr308 signaling in Fbn1 C1039G/+ mice. Integrin αv blockade via GLPG0187 may be a promising therapeutic approach to inhibit MFS aneurysmal growth.

Introduction: Heart transplantation provides lifesaving therapy for patients with end-stage heart failure. The longevity of the therapy is limited by Cardiac Graft Dysfunction (CGD), which is an acquired cardiomyopathy affecting transplanted hearts associated with diastolic and/or systolic dysfunction. Some clinical risk factors for CGD have been identified, but none of them are easily modifiable. An unexplored potential contributor to CGD is the choice of immunosuppression agent used despite multiple clinical reports suggesting reduced adverse cardiac remodeling with mammalian target of rapamycin (mTOR) inhibitors compared to calcineurin inhibitors (CNI). This study examines mechanisms of differential cardiac remodeling effects of CNI versus mTOR inhibitors in a human cellular cardiac model. Methods/Results: We utilized 3D cardiac spheres composed of induced pluripotent stem cell-derived cardiomyocytes, cardiac fibroblasts, and endothelial cells (cardiac organoids). Cardiac organoids were treated with 5 days of vehicle, tacrolimus (CNI), or sirolimus (mTOR inhibitor). We did not observe a significant difference in surrogates of systolic or diastolic function in treated cardiac organoids. We pursued single cell-RNA sequencing of drug-treated cardiac organoids and identified gene expression changes consistent with increased extracellular matrix deposition and fibroblast activity in response to CNI treatment. In addition, CNI-treated cardiac organoids cellular composition was notable for increased proportion of fibroblasts and less cardiomyocytes compared to mTOR inhibitor-treated cardiac organoids. To validate gene expression changes observed, we treated cardiac fibroblasts with drugs and observed an increase in collagen production in response to CNI treatment and a reduction in fibroblast number and collagen production in response to mTOR inhibitor treatment. Furthermore, we observed increased ATP production in CNI-treated cardiac fibroblasts, but a reduction in mTOR-treated counterparts. Conclusion: We identify reduced extracellular matrix deposition and cardiac fibroblast proliferation in response to mTOR inhibitor as a potential mechanism for the more favorable remodeling profile observed clinically.

Background: Vascular smooth muscle cell (SMC) phenotype modulation produces a mixed proteolytic/collagen synthetic state in Marfan syndrome (MFS) aortic root aneurysm. While the transcriptomic changes associated with this process are established, upstream regulators governing this plasticity are poorly characterized. Methods/Results: We performed concurrent single-cell RNA sequencing (scRNAseq) and assay for transposase-accessible chromatin using sequencing (scATACseq) on aortic root aneurysm tissue from adult Fbn1 C1041G/+ (MFS) mice and littermate controls. MFS/control scRNAseq data analysis identified four SMC subtypes including MFS-specific ‘modulated’ cells (modSMCs) which enriched for extracellular matrix organization and collagen synthesis pathway activation. These SMC clusters were projected onto the MFS/control scATAC dataset via integrative label transfer to study dynamic chromatin accessibility during SMC phenotype modulation. We compared DNA accessibility in modSMCs versus mature SMCs, finding 336 enriched and 29 suppressed peaks, suggesting increased open chromatin during modulation. Using chromVAR, we identified 242 enriched transcription factor motifs overrepresented in modSMCs. Motifs representing central but nonspecific transcription factor families including numerous AP-1 (FOS/JUN/ATF) heterodimers and TEAD family members showed highest enrichment, while enriched TWIST1, HAND2, and SMAD2:SMAD3:SMAD4 complex motifs suggested more specific functions. To functionally validate these findings, we examined TWIST1 as a potential regulator of SMC modulation in vitro via lentiviral overexpression in MFS patient-derived aortic SMCs.In SMCs with forced TWIST1 overexpression, we found heightened promoter region DNA accessibility (via bulk ATACseq) and increased mRNA expression (via RT-PCR) for specific modSMC markers (e.g., COL1A1 and LUM confirming TWIST1 promotes collagen synthesis. Conclusions: Integrated single-cell transcriptomic/epigenomic analysis permits identification of critical upstream regulatory signals promoting disease-specific cell phenotype changes. TWIST1 is a potential driver of SMC modulation and a target for therapeutic agent design in MFS aortic aneurysm.

Objective: To delineate temporal and spatial dynamics of vascular smooth muscle cell (SMC) transcriptomic changes during aortic aneurysm development in Marfan syndrome (MFS). Approach and Results: We performed single-cell RNA sequencing to study aortic root/ascending aneurysm tissue from Fbn1 C1041G/ + (MFS) mice and healthy controls, identifying all aortic cell types. A distinct cluster of transcriptomically modulated SMCs (modSMCs) was identified in adult Fbn1 C1041G/ + mouse aortic aneurysm tissue only. Comparison with atherosclerotic aortic data (ApoE −/− mice) revealed similar patterns of SMC modulation but identified an MFS-specific gene signature, including plasminogen activator inhibitor-1 ( Serpine1 ) and Kruppel-like factor 4 ( Klf4 ). We identified 481 differentially expressed genes between modSMC and SMC subsets; functional annotation highlighted extracellular matrix modulation, collagen synthesis, adhesion, and proliferation. Pseudotime trajectory analysis of Fbn1 C1041G/ + SMC/modSMC transcriptomes identified genes activated differentially throughout the course of phenotype modulation. While modSMCs were not present in young Fbn1 C1041G/ + mouse aortas despite small aortic aneurysm, multiple early modSMCs marker genes were enriched, suggesting activation of phenotype modulation. modSMCs were not found in nondilated adult Fbn1 C1041G/ + descending thoracic aortas. Single-cell RNA sequencing from human MFS aortic root aneurysm tissue confirmed analogous SMC modulation in clinical disease. Enhanced expression of TGF-β (transforming growth factor beta)-responsive genes correlated with SMC modulation in mouse and human data sets. Conclusions: Dynamic SMC phenotype modulation promotes extracellular matrix substrate modulation and aortic aneurysm progression in MFS. We characterize the disease-specific signature of modSMCs and provide temporal, transcriptomic context to the current understanding of the role TGF-β plays in MFS aortopathy. Collectively, single-cell RNA sequencing implicates TGF-β signaling and Klf4 overexpression as potential upstream drivers of SMC modulation.

Introduction: Aortic dilation and aneurysm formation is common in patients with a bicuspid aortic valve. Hemodynamics and genetics are both believed to cause dilation, but the relative contributions remain controversial. Further, retrospective studies assess hemodynamics when dilation has already set in. We simulate flows through a tricuspid and three bicuspid aortic valves and study their hemodynamics from a baseline non-dilated aorta. Hypothesis: We hypothesize that the bicuspid phenotype determines flow in the ascending aortic, and high velocity jets will correlate with known regions of dilation in patients with bicuspid valves. Methods: Using methods we recently developed, we constructed a tricuspid valve and bicuspid valves with left/right (LR), right/non (RN) and non/left (NL) coronary cusp fusion. To isolate the effect of leaflet fusion phenotype, we use one healthy, patient-specific aortic geometry throughout. Fluid-structure interaction simulations were performed. Results: Dramatic differences in flow occur between all cases. The tricuspid case shows a relatively uniform flow profile, velocities of ~200cm/s, normalized streamwise momentum 300cm/s, normalized streamwise momentum >2.0, normalized tangential flow strength >1.0, >50% transient reverse flow and sustained pressure gradients >18 mmHg. With LR fusion, the jet hugs the outer curvature of the aorta from the sinotubular junction through the ascending aorta. With RN fusion, the jet moves from the inner to outer curvature of the aorta. Conclusions: With LR and RN cusp fusion, high flow rate jets occur at regions that generally correlate with dilation in prior studies, suggesting that hemodynamic factors alone may be sufficient to cause aortic dilation. This hypothesis should be tested in an animal model.

Background: Heart-lung transplantation (HLTx) is an effective treatment for patients with advanced cardiopulmonary failure. However, no large multicenter study has focused on the relationship between donor and recipient risk factors and post-HLTx outcomes. Thus, we investigated this issue using data from the United Network for Organ Sharing database. Methods: All adult patients (age ≥18 years) registered in the United Network for Organ Sharing database who underwent HLTx between 1987 and 2017 were included (n=997). We stratified the cohort by patients who were alive without retransplant at 1 year (n=664) and patients who died or underwent retransplant within 1 year of HLTx (n=333). The primary outcome was the influence of donor and recipient characteristics on 1-year post-HLTx recipient death or retransplant. Kaplan-Meier curves were created to assess overall freedom from death or retransplant. To obtain a better effect estimation on hazard and survival time, the parametric Accelerated Failure Time model was chosen to perform time-to-event modeling analyses. Results: Overall graft survival at 1-year post-HLTx was 66.6%. Of donors, 53% were male, and the mean age was 28.2 years. Univariable analysis showed advanced donor age, recipient male sex, recipient creatinine, recipient history of prior cardiac or lung surgery, recipient extracorporeal membrane oxygenation support, transplant year, and transplant center volume were associated with 1-year post-HLTx death or retransplant. On multivariable analysis, advanced donor age (hazard ratio [HR], 1.017; P =0.0007), recipient male sex (HR, 1.701; P =0.0002), recipient extracorporeal membrane oxygenation support (HR, 4.854; P P P =0.0007) remained as significant predictors of death or retransplant. These predictors were incorporated into an equation capable of estimating the preliminary probability of graft survival at 1-year post-HLTx on the basis of preoperative factors alone. Conclusions: HLTx outcomes may be improved by considering the strong influence of donor age, recipient sex, recipient hemodynamic status, and transplant center volume. Marginal donors and recipients without significant factors contributing to poor post-HLTx outcomes may still be considered for transplantation, potentially with less impact on the risk of early postoperative death or retransplant.

The left ventricular assist device (LVAD) is an established treatment for select patients with end-stage heart failure. Some patients recovered and are considered for explantation. Assessing recovery involves exercise testing and echo ramping on full and minimal LVAD support. Combined cardiopulmonary exercise testing with simultaneous echo ramping (CPET-R) has not been well studied. Patients were included if they had CPET within the previous 6 months, were clinically stable, and had an INR >2.0 on the day of examination. Patients had CPET-R on two occasions within 14 days: (a) with LVAD at therapeutic speed and (b) with LVAD at the lowest speed possible. Six patients were between 29 and 75 years (two female). One patient did not complete a turn-down test due to evidence of ischemia on initial CPET-R subsequently confirmed as a significant coronary artery stenosis on angiography. There were no significant differences in CPET or echo metrics between LVAD speeds. Two patients were explanted due to presumed LV recovery and remained event free for 30 and 47 months, respectively. Serial CPET-R seems safe and feasible for the evaluation of LV and global function and may result in improved clinical decision making for LVAD explantation.

Introduction: Right ventricular failure (RVF) is a common complication following LVAD implantation and a significant driver of post-LVAD mortality. dP/dt max , the maximum rate of rise in ventricular pressure, is a validated hemodynamic parameter of ventricular contractility that, when indexed to CVP, accounts for loading conditions. This parameter has not, however, been studied in the context of post-LVAD RVF. We therefore evaluated the relationship between dP/dt max /CVP and post-LVAD RVF in a cohort of LVAD recipients at Stanford. Methods: We conducted a retrospective, single-center analysis of patients who underwent continuous-flow LVAD implant at Stanford between January 2010 and June 2019. Preoperative RV dP/dt max /CVP values were extracted from right heart catheterization (RHC) reports. For cases in which dP/dt max /CVP was not reported, preoperative RA and RV pressure tracings were utilized to manually calculate the index. We then performed unpaired t-tests to evaluate for the presence of associations between dP/dt max /CVP and early post-LVAD RVF, defined as the prolonged (>7 days) requirement for inotropic or pulmonary vasodilator therapy or the need for RVAD support, and between dP/dt max /CVP and severe post-LVAD RVF, defined only by the requirement for RVAD support. Results: This cohort included 202 LVAD recipients who had available preoperative RHC data. Of these, 14.4% (n = 29) required an RVAD and 50.5% (n = 102) experienced early post-LVAD RVF. Mean values of dP/dt max /CVP amongst patients with and without early post-LVAD RV failure were 94.9 ± 128.5 s -1 and 105.6 ± 125.5 s -1 (p = 0.56), respectively, while mean values of dP/dt max /CVP amongst those who did and did not require an RVAD were 53.2± 42.0 s -1 and 108.2 ± 129.5 s -1 (p = 4.2 х 10 -5 ), respectively. Conclusion: In continuous-flow LVAD recipients, low preoperative RV dP/dt max /CVP is strongly associated with severe post-LVAD RVF requiring RVAD support but not early post-LVAD RVF more generally.

Introduction: We have previously shown that the exogenously injected chemokines induce robust myocardial recovery and angiogenesis after a myocardial infarction (MI). Angiogenesis, however, is a late response, and the acute cellular drivers of chemokine induced recovery remain elusive. Recently it has been shown that an acute macrophage response is central to post-MI recovery after stem-cell injections. As many chemokines act as immunomodulators, we hypothesized that both angiogenic chemokines (SDF-1) and non-angiogenic chemokines of viral origin (vMIP-II) can similarly elicit a macrophage response. Methods: MI was surgically induced in 39 male and female C57BL/6 mice (6-8 weeks old) by ligation of the left anterior descending coronary artery. Mice were randomly assigned to receive intramyocardial injections of PBS (saline), SDF-1, or vMIP-II. Two hearts from each treatment group were explanted at post-operative day 3 (P3) for single cell suspension preparation. Viable cells were used for single cell RNA sequencing (scRNAseq). Echocardiography was performed for all remaining mice at P7 to assess for functional recovery, and hearts were explanted for histology at P14. Results: Treatment with both SDF-1 and vMIP-II led to significant functional recovery assessed via echocardiography at P7, one week in advance of arteriolar collateralization (Ejection Fraction 0.38 ± 0.14 and 0.50 ± 0.15 in SDF-1 and vMIP respectively; 0.27 ± 0.13 in PBS; t-test adjusted p = 0.023). scRNAseq of 7918 captured cells showed a robust acute inflammatory macrophage response at P3 across treatment groups. A robust expansion of Arginase-1 (Arg1+) macrophages - a known M2 anti-inflammatory subtype - was seen specifically in chemokine treated mice at P3 (9% in PBS vs 16.5% in both SDF-1 and vMIP-II). Conclusions: We show that vMIP-II triggers myocardial recovery similar to SDF-1. Furthermore, we show a robust and consistent Arg1+ macrophage response present in both treatment groups.

Introduction: Post-operative right ventricular failure (RV failure) is the single largest contributor to short-term mortality in patients with left ventricular assist devices (LVAD); yet predicting which patient is at risk of developing this complication in the pre-operative setting has remained beyond the abilities of experts in the field. We hypothesized that deep artificial intelligence (AI) driven characterization of subtle pre-operative myocardial motion features, could predict post-operative RV failure in LVAD patients. Methods: We developed a novel echocardiography AI system using an improved dense trajectory algorithm that tracks motion vectors in an unsupervised fashion, and a 3-dimensional convolutional neural network that tracks spatiotemporal features from videos. We used pre-operative ECHO videos from a 536 patient multicenter echocardiographic and clinical dataset, and via a standard 10-fold cross validation, trained and validated the AI system to predict severe or higher grades of post-operative RV failure at the time of index hospitalization. Finally, we independently benchmarked our AI system against clinicians equipped with contemporary clinical risk scores to predict post-operative RV failure (Penn and CRITT score) and manually derived echocardiographic metrics of RV function. Results: 173 (32%) patients were adjudicated to have severe post-operative RV failure. The area under the receiver operator characteristic curve (AUC ROC) for the AI system was 0.86 (95% CI 0.824-0.896). The performance of our AI system exceeded that of both the best performing clinical risk score and manually derived echocardiographic metric by a significant margin (ΔAUC +0.30, 95% CI 0.27 - 0.33 and ΔAUC +0.24, 95% CI 0.21 - 0.27; both p &lt 0.0001). Conclusions: A novel ECHO AI system trained and validated on a multicenter dataset outperformed clinical experts equipped with both contemporary risk scores and manually calculated echocardiographic metrics.

Background— Experimentally, exogenous administration of recombinant stromal cell–derived factor-1α (SDF) enhances neovasculogenesis and cardiac function after myocardial infarction. Smaller analogs of SDF may provide translational advantages including enhanced stability and function, ease of synthesis, lower cost, and potential modulated delivery via engineered biomaterials. In this study, computational protein design was used to create a more efficient evolution of the native SDF protein. Methods and Results— Protein structure modeling was used to engineer an SDF polypeptide analog (engineered SDF analog [ESA]) that splices the N-terminus (activation and binding) and C-terminus (extracellular stabilization) with a diproline segment designed to limit the conformational flexibility of the peptide backbone and retain the relative orientation of these segments observed in the native structure of SDF. Endothelial progenitor cells (EPCs) in ESA gradient, assayed by Boyden chamber, showed significantly increased migration compared with both SDF and control gradients. EPC receptor activation was evaluated by quantification of phosphorylated AKT, and cells treated with ESA yielded significantly greater phosphorylated AKT levels than SDF and control cells. Angiogenic growth factor assays revealed a distinct increase in angiopoietin-1 expression in the ESA- and SDF-treated hearts. In addition, CD-1 mice (n=30) underwent ligation of the left anterior descending coronary artery and peri-infarct intramyocardial injection of ESA, SDF-1α, or saline. At 2 weeks, echocardiography demonstrated a significant gain in ejection fraction, cardiac output, stroke volume, and fractional area change in mice treated with ESA compared with controls. Conclusions— Compared with native SDF, a novel engineered SDF polypeptide analog (ESA) more efficiently induces EPC migration and improves post–myocardial infarction cardiac function and thus offers a more clinically translatable neovasculogenic therapy.

Background— Myocardial ischemia causes cardiomyocyte death, adverse ventricular remodeling, and ventricular dysfunction. Endothelial progenitor cells (EPCs) have been shown to ameliorate this process, particularly when activated with stromal cell-derived factor-1α (SDF), known to be the most potent EPC chemokine. We hypothesized that implantation of a tissue-engineered extracellular matrix (ECM) scaffold seeded with EPCs primed with SDF could induce borderzone neovasculogenesis, prevent adverse geometric remodeling, and preserve ventricular function after myocardial infarction. Methods and Results— Lewis rats (n=82) underwent left anterior descending artery ligation to induce myocardial infarction. EPCs were isolated, characterized, and cultured on a vitronectin/collagen scaffold and primed with SDF to generate the activated EPC matrix (EPCM). EPCM was sutured to the anterolateral left ventricular wall, which included the region of ischemia. Control animals received sutures but no EPCM. Additional groups underwent application of the ECM alone, ECM primed with SDF (ECM+SDF), and ECM seeded with EPCs but not primed with SDF (ECM+SDF). At 4 weeks, borderzone myocardial tissue demonstrated increased levels of vascular endothelial growth factor in the EPCM group. When compared to controls, Vessel density as assessed by immunohistochemical microscopy was significantly increased in the EPCM group (4.1 versus 6.2 vessels/high-powered field; P P =0.04). Comparisons to additional groups also showed a significantly improved vasculogenic response in the EPCM group. Ventricular geometry and scar fraction assessed by digital planimetric analysis of sectioned hearts exhibited significantly preserved left ventricular internal diameter (9.7 mm versus 8.6 mm; P =0.005) and decreased infarct scar formation expressed as percent of total section area (16% versus 7%; P =0.002) when compared with all other groups. In addition, EPCM animals showed a significant preservation of function as measured by echocardiography, pressure-volume conductance, and Doppler flow. Conclusions— Extracellular matrix seeded with EPCs primed with SDF induces borderzone neovasculogenesis, attenuates adverse ventricular remodeling, and preserves ventricular function after myocardial infarction.

METHODS: 103 patients with degenerative mitral regurgitation (MR) underwent single-suture repair of the mitral valve through a 3-cm right chest incision from May 2007 through December 2012. The prolapsed segment of the mitral valve was imbricated with a double running CV 5 Gore-Tex suture, resulting in a smooth plane of coaptation. Preoperative and perioperative echocardiograms as well as patient outcomes were analyzed and compared to patients undergoing minimally invasive isolated mitral valve repair using quadrangular resection at the same institution during the same time period.